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<div class="section" id="module-torch.autograd">
<span id="automatic-differentiation-package-torch-autograd"></span><h1>Automatic differentiation package - torch.autograd<a class="headerlink" href="#module-torch.autograd" title="Permalink to this heading">¶</a></h1>
<p><code class="docutils literal notranslate"><span class="pre">torch.autograd</span></code> provides classes and functions implementing automatic
differentiation of arbitrary scalar valued functions. It requires minimal
changes to the existing code - you only need to declare <code class="xref py py-class docutils literal notranslate"><span class="pre">Tensor</span></code> s
for which gradients should be computed with the <code class="docutils literal notranslate"><span class="pre">requires_grad=True</span></code> keyword.
As of now, we only support autograd for floating point <code class="xref py py-class docutils literal notranslate"><span class="pre">Tensor</span></code> types (
half, float, double and bfloat16) and complex <code class="xref py py-class docutils literal notranslate"><span class="pre">Tensor</span></code> types (cfloat, cdouble).</p>
<table class="autosummary longtable docutils colwidths-auto align-default">
<tbody>
<tr class="row-odd"><td><p><p id="torch.autograd.backward"/><a class="reference internal" href="generated/torch.autograd.backward.html#torch.autograd.backward" title="torch.autograd.backward"><code class="xref py py-obj docutils literal notranslate"><span class="pre">backward</span></code></a></p></td>
<td><p>Computes the sum of gradients of given tensors with respect to graph leaves.</p></td>
</tr>
<tr class="row-even"><td><p><p id="torch.autograd.grad"/><a class="reference internal" href="generated/torch.autograd.grad.html#torch.autograd.grad" title="torch.autograd.grad"><code class="xref py py-obj docutils literal notranslate"><span class="pre">grad</span></code></a></p></td>
<td><p>Computes and returns the sum of gradients of outputs with respect to the inputs.</p></td>
</tr>
</tbody>
</table>
<div class="section" id="forward-mode-automatic-differentiation">
<span id="forward-mode-ad"></span><h2>Forward-mode Automatic Differentiation<a class="headerlink" href="#forward-mode-automatic-differentiation" title="Permalink to this heading">¶</a></h2>
<div class="admonition warning">
<p class="admonition-title">Warning</p>
<p>This API is in beta. Even though the function signatures are very unlikely to change, improved
operator coverage is planned before we consider this stable.</p>
</div>
<p>Please see the <a class="reference external" href="https://pytorch.org/tutorials/intermediate/forward_ad_usage.html">forward-mode AD tutorial</a>
for detailed steps on how to use this API.</p>
<table class="autosummary longtable docutils colwidths-auto align-default">
<tbody>
<tr class="row-odd"><td><p><a class="reference internal" href="generated/torch.autograd.forward_ad.dual_level.html#torch.autograd.forward_ad.dual_level" title="torch.autograd.forward_ad.dual_level"><code class="xref py py-obj docutils literal notranslate"><span class="pre">forward_ad.dual_level</span></code></a></p></td>
<td><p>Context-manager for forward AD, where all forward AD computation must occur within the <code class="docutils literal notranslate"><span class="pre">dual_level</span></code> context.</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="generated/torch.autograd.forward_ad.make_dual.html#torch.autograd.forward_ad.make_dual" title="torch.autograd.forward_ad.make_dual"><code class="xref py py-obj docutils literal notranslate"><span class="pre">forward_ad.make_dual</span></code></a></p></td>
<td><p>Associate a tensor value with its tangent to create a "dual tensor" for forward AD gradient computation.</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="generated/torch.autograd.forward_ad.unpack_dual.html#torch.autograd.forward_ad.unpack_dual" title="torch.autograd.forward_ad.unpack_dual"><code class="xref py py-obj docutils literal notranslate"><span class="pre">forward_ad.unpack_dual</span></code></a></p></td>
<td><p>Unpack a "dual tensor" to get both its Tensor value and its forward AD gradient.</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="generated/torch.autograd.forward_ad.enter_dual_level.html#torch.autograd.forward_ad.enter_dual_level" title="torch.autograd.forward_ad.enter_dual_level"><code class="xref py py-obj docutils literal notranslate"><span class="pre">forward_ad.enter_dual_level</span></code></a></p></td>
<td><p>Enter a new forward grad level.</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="generated/torch.autograd.forward_ad.exit_dual_level.html#torch.autograd.forward_ad.exit_dual_level" title="torch.autograd.forward_ad.exit_dual_level"><code class="xref py py-obj docutils literal notranslate"><span class="pre">forward_ad.exit_dual_level</span></code></a></p></td>
<td><p>Exit a forward grad level.</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="generated/torch.autograd.forward_ad.UnpackedDualTensor.html#torch.autograd.forward_ad.UnpackedDualTensor" title="torch.autograd.forward_ad.UnpackedDualTensor"><code class="xref py py-obj docutils literal notranslate"><span class="pre">forward_ad.UnpackedDualTensor</span></code></a></p></td>
<td><p>Namedtuple returned by <code class="xref py py-func docutils literal notranslate"><span class="pre">unpack_dual()</span></code> containing the primal and tangent components of the dual tensor.</p></td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="functional-higher-level-api">
<span id="functional-api"></span><h2>Functional higher level API<a class="headerlink" href="#functional-higher-level-api" title="Permalink to this heading">¶</a></h2>
<div class="admonition warning">
<p class="admonition-title">Warning</p>
<p>This API is in beta. Even though the function signatures are very unlikely to change, major
improvements to performances are planned before we consider this stable.</p>
</div>
<p>This section contains the higher level API for the autograd that builds on the basic API above
and allows you to compute jacobians, hessians, etc.</p>
<p>This API works with user-provided functions that take only Tensors as input and return
only Tensors.
If your function takes other arguments that are not Tensors or Tensors that don’t have requires_grad set,
you can use a lambda to capture them.
For example, for a function <code class="docutils literal notranslate"><span class="pre">f</span></code> that takes three inputs, a Tensor for which we want the jacobian, another
tensor that should be considered constant and a boolean flag as <code class="docutils literal notranslate"><span class="pre">f(input,</span> <span class="pre">constant,</span> <span class="pre">flag=flag)</span></code>
you can use it as <code class="docutils literal notranslate"><span class="pre">functional.jacobian(lambda</span> <span class="pre">x:</span> <span class="pre">f(x,</span> <span class="pre">constant,</span> <span class="pre">flag=flag),</span> <span class="pre">input)</span></code>.</p>
<table class="autosummary longtable docutils colwidths-auto align-default">
<tbody>
<tr class="row-odd"><td><p><a class="reference internal" href="generated/torch.autograd.functional.jacobian.html#torch.autograd.functional.jacobian" title="torch.autograd.functional.jacobian"><code class="xref py py-obj docutils literal notranslate"><span class="pre">functional.jacobian</span></code></a></p></td>
<td><p>Compute the Jacobian of a given function.</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="generated/torch.autograd.functional.hessian.html#torch.autograd.functional.hessian" title="torch.autograd.functional.hessian"><code class="xref py py-obj docutils literal notranslate"><span class="pre">functional.hessian</span></code></a></p></td>
<td><p>Compute the Hessian of a given scalar function.</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="generated/torch.autograd.functional.vjp.html#torch.autograd.functional.vjp" title="torch.autograd.functional.vjp"><code class="xref py py-obj docutils literal notranslate"><span class="pre">functional.vjp</span></code></a></p></td>
<td><p>Compute the dot product between a vector <code class="docutils literal notranslate"><span class="pre">v</span></code> and the Jacobian of the given function at the point given by the inputs.</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="generated/torch.autograd.functional.jvp.html#torch.autograd.functional.jvp" title="torch.autograd.functional.jvp"><code class="xref py py-obj docutils literal notranslate"><span class="pre">functional.jvp</span></code></a></p></td>
<td><p>Compute the dot product between the Jacobian of the given function at the point given by the inputs and a vector <code class="docutils literal notranslate"><span class="pre">v</span></code>.</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="generated/torch.autograd.functional.vhp.html#torch.autograd.functional.vhp" title="torch.autograd.functional.vhp"><code class="xref py py-obj docutils literal notranslate"><span class="pre">functional.vhp</span></code></a></p></td>
<td><p>Compute the dot product between vector <code class="docutils literal notranslate"><span class="pre">v</span></code> and Hessian of a given scalar function at a specified point.</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="generated/torch.autograd.functional.hvp.html#torch.autograd.functional.hvp" title="torch.autograd.functional.hvp"><code class="xref py py-obj docutils literal notranslate"><span class="pre">functional.hvp</span></code></a></p></td>
<td><p>Compute the dot product between the scalar function's Hessian and a vector <code class="docutils literal notranslate"><span class="pre">v</span></code> at a specified point.</p></td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="locally-disabling-gradient-computation">
<span id="locally-disable-grad"></span><h2>Locally disabling gradient computation<a class="headerlink" href="#locally-disabling-gradient-computation" title="Permalink to this heading">¶</a></h2>
<p>See <a class="reference internal" href="notes/autograd.html#locally-disable-grad-doc"><span class="std std-ref">Locally disabling gradient computation</span></a> for more information on the differences
between no-grad and inference mode as well as other related mechanisms that
may be confused with the two. Also see <a class="reference internal" href="torch.html#torch-rst-local-disable-grad"><span class="std std-ref">Locally disabling gradient computation</span></a>
for a list of functions that can be used to locally disable gradients.</p>
</div>
<div class="section" id="default-gradient-layouts">
<span id="default-grad-layouts"></span><h2>Default gradient layouts<a class="headerlink" href="#default-gradient-layouts" title="Permalink to this heading">¶</a></h2>
<p>When a non-sparse <code class="docutils literal notranslate"><span class="pre">param</span></code> receives a non-sparse gradient during
<a class="reference internal" href="generated/torch.autograd.backward.html#torch.autograd.backward" title="torch.autograd.backward"><code class="xref py py-func docutils literal notranslate"><span class="pre">torch.autograd.backward()</span></code></a> or <a class="reference internal" href="generated/torch.Tensor.backward.html#torch.Tensor.backward" title="torch.Tensor.backward"><code class="xref py py-func docutils literal notranslate"><span class="pre">torch.Tensor.backward()</span></code></a>
<code class="docutils literal notranslate"><span class="pre">param.grad</span></code> is accumulated as follows.</p>
<p>If <code class="docutils literal notranslate"><span class="pre">param.grad</span></code> is initially <code class="docutils literal notranslate"><span class="pre">None</span></code>:</p>
<ol class="arabic simple">
<li><p>If <code class="docutils literal notranslate"><span class="pre">param</span></code>’s memory is non-overlapping and dense, <code class="docutils literal notranslate"><span class="pre">.grad</span></code> is
created with strides matching <code class="docutils literal notranslate"><span class="pre">param</span></code> (thus matching <code class="docutils literal notranslate"><span class="pre">param</span></code>’s
layout).</p></li>
<li><p>Otherwise, <code class="docutils literal notranslate"><span class="pre">.grad</span></code> is created with rowmajor-contiguous strides.</p></li>
</ol>
<p>If <code class="docutils literal notranslate"><span class="pre">param</span></code> already has a non-sparse <code class="docutils literal notranslate"><span class="pre">.grad</span></code> attribute:</p>
<ol class="arabic simple" start="3">
<li><p>If <code class="docutils literal notranslate"><span class="pre">create_graph=False</span></code>, <code class="docutils literal notranslate"><span class="pre">backward()</span></code> accumulates into <code class="docutils literal notranslate"><span class="pre">.grad</span></code>
in-place, which preserves its strides.</p></li>
<li><p>If <code class="docutils literal notranslate"><span class="pre">create_graph=True</span></code>, <code class="docutils literal notranslate"><span class="pre">backward()</span></code> replaces <code class="docutils literal notranslate"><span class="pre">.grad</span></code> with a
new tensor <code class="docutils literal notranslate"><span class="pre">.grad</span> <span class="pre">+</span> <span class="pre">new</span> <span class="pre">grad</span></code>, which attempts (but does not guarantee)
matching the preexisting <code class="docutils literal notranslate"><span class="pre">.grad</span></code>’s strides.</p></li>
</ol>
<p>The default behavior (letting <code class="docutils literal notranslate"><span class="pre">.grad</span></code>s be <code class="docutils literal notranslate"><span class="pre">None</span></code> before the first
<code class="docutils literal notranslate"><span class="pre">backward()</span></code>, such that their layout is created according to 1 or 2,
and retained over time according to 3 or 4) is recommended for best performance.
Calls to <code class="docutils literal notranslate"><span class="pre">model.zero_grad()</span></code> or <code class="docutils literal notranslate"><span class="pre">optimizer.zero_grad()</span></code> will not affect <code class="docutils literal notranslate"><span class="pre">.grad</span></code>
layouts.</p>
<p>In fact, resetting all <code class="docutils literal notranslate"><span class="pre">.grad</span></code>s to <code class="docutils literal notranslate"><span class="pre">None</span></code> before each
accumulation phase, e.g.:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="k">for</span> <span class="n">iterations</span><span class="o">...</span>
<span class="o">...</span>
<span class="k">for</span> <span class="n">param</span> <span class="ow">in</span> <span class="n">model</span><span class="o">.</span><span class="n">parameters</span><span class="p">():</span>
<span class="n">param</span><span class="o">.</span><span class="n">grad</span> <span class="o">=</span> <span class="kc">None</span>
<span class="n">loss</span><span class="o">.</span><span class="n">backward</span><span class="p">()</span>
</pre></div>
</div>
<p>such that they’re recreated according to 1 or 2 every time,
is a valid alternative to <code class="docutils literal notranslate"><span class="pre">model.zero_grad()</span></code> or <code class="docutils literal notranslate"><span class="pre">optimizer.zero_grad()</span></code>
that may improve performance for some networks.</p>
<div class="section" id="manual-gradient-layouts">
<h3>Manual gradient layouts<a class="headerlink" href="#manual-gradient-layouts" title="Permalink to this heading">¶</a></h3>
<p>If you need manual control over <code class="docutils literal notranslate"><span class="pre">.grad</span></code>’s strides,
assign <code class="docutils literal notranslate"><span class="pre">param.grad</span> <span class="pre">=</span></code> a zeroed tensor with desired strides
before the first <code class="docutils literal notranslate"><span class="pre">backward()</span></code>, and never reset it to <code class="docutils literal notranslate"><span class="pre">None</span></code>.
3 guarantees your layout is preserved as long as <code class="docutils literal notranslate"><span class="pre">create_graph=False</span></code>.
4 indicates your layout is <em>likely</em> preserved even if <code class="docutils literal notranslate"><span class="pre">create_graph=True</span></code>.</p>
</div>
</div>
<div class="section" id="in-place-operations-on-tensors">
<h2>In-place operations on Tensors<a class="headerlink" href="#in-place-operations-on-tensors" title="Permalink to this heading">¶</a></h2>
<p>Supporting in-place operations in autograd is a hard matter, and we discourage
their use in most cases. Autograd’s aggressive buffer freeing and reuse makes
it very efficient and there are very few occasions when in-place operations
actually lower memory usage by any significant amount. Unless you’re operating
under heavy memory pressure, you might never need to use them.</p>
<div class="section" id="in-place-correctness-checks">
<h3>In-place correctness checks<a class="headerlink" href="#in-place-correctness-checks" title="Permalink to this heading">¶</a></h3>
<p>All <code class="xref py py-class docutils literal notranslate"><span class="pre">Tensor</span></code> s keep track of in-place operations applied to them, and
if the implementation detects that a tensor was saved for backward in one of
the functions, but it was modified in-place afterwards, an error will be raised
once backward pass is started. This ensures that if you’re using in-place
functions and not seeing any errors, you can be sure that the computed
gradients are correct.</p>
</div>
</div>
<div class="section" id="variable-deprecated">
<h2>Variable (deprecated)<a class="headerlink" href="#variable-deprecated" title="Permalink to this heading">¶</a></h2>
<div class="admonition warning">
<p class="admonition-title">Warning</p>
<p>The Variable API has been deprecated: Variables are no longer necessary to
use autograd with tensors. Autograd automatically supports Tensors with
<code class="docutils literal notranslate"><span class="pre">requires_grad</span></code> set to <code class="docutils literal notranslate"><span class="pre">True</span></code>. Below please find a quick guide on what
has changed:</p>
<ul class="simple">
<li><p><code class="docutils literal notranslate"><span class="pre">Variable(tensor)</span></code> and <code class="docutils literal notranslate"><span class="pre">Variable(tensor,</span> <span class="pre">requires_grad)</span></code> still work as expected,
but they return Tensors instead of Variables.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">var.data</span></code> is the same thing as <code class="docutils literal notranslate"><span class="pre">tensor.data</span></code>.</p></li>
<li><p>Methods such as <code class="docutils literal notranslate"><span class="pre">var.backward(),</span> <span class="pre">var.detach(),</span> <span class="pre">var.register_hook()</span></code> now work on tensors
with the same method names.</p></li>
</ul>
<p>In addition, one can now create tensors with <code class="docutils literal notranslate"><span class="pre">requires_grad=True</span></code> using factory
methods such as <a class="reference internal" href="generated/torch.randn.html#torch.randn" title="torch.randn"><code class="xref py py-func docutils literal notranslate"><span class="pre">torch.randn()</span></code></a>, <a class="reference internal" href="generated/torch.zeros.html#torch.zeros" title="torch.zeros"><code class="xref py py-func docutils literal notranslate"><span class="pre">torch.zeros()</span></code></a>, <a class="reference internal" href="generated/torch.ones.html#torch.ones" title="torch.ones"><code class="xref py py-func docutils literal notranslate"><span class="pre">torch.ones()</span></code></a>, and others
like the following:</p>
<p><code class="docutils literal notranslate"><span class="pre">autograd_tensor</span> <span class="pre">=</span> <span class="pre">torch.randn((2,</span> <span class="pre">3,</span> <span class="pre">4),</span> <span class="pre">requires_grad=True)</span></code></p>
</div>
</div>
<div class="section" id="tensor-autograd-functions">
<h2>Tensor autograd functions<a class="headerlink" href="#tensor-autograd-functions" title="Permalink to this heading">¶</a></h2>
<table class="autosummary longtable docutils colwidths-auto align-default">
<tbody>
<tr class="row-odd"><td><p><code class="xref py py-obj docutils literal notranslate"><span class="pre">torch.Tensor.grad</span></code></p></td>
<td><p>This attribute is <code class="docutils literal notranslate"><span class="pre">None</span></code> by default and becomes a Tensor the first time a call to <a class="reference internal" href="generated/torch.autograd.backward.html#torch.autograd.backward" title="torch.autograd.backward"><code class="xref py py-func docutils literal notranslate"><span class="pre">backward()</span></code></a> computes gradients for <code class="docutils literal notranslate"><span class="pre">self</span></code>.</p></td>
</tr>
<tr class="row-even"><td><p><code class="xref py py-obj docutils literal notranslate"><span class="pre">torch.Tensor.requires_grad</span></code></p></td>
<td><p>Is <code class="docutils literal notranslate"><span class="pre">True</span></code> if gradients need to be computed for this Tensor, <code class="docutils literal notranslate"><span class="pre">False</span></code> otherwise.</p></td>
</tr>
<tr class="row-odd"><td><p><code class="xref py py-obj docutils literal notranslate"><span class="pre">torch.Tensor.is_leaf</span></code></p></td>
<td><p>All Tensors that have <code class="xref py py-attr docutils literal notranslate"><span class="pre">requires_grad</span></code> which is <code class="docutils literal notranslate"><span class="pre">False</span></code> will be leaf Tensors by convention.</p></td>
</tr>
<tr class="row-even"><td><p><code class="xref py py-obj docutils literal notranslate"><span class="pre">torch.Tensor.backward</span></code>([gradient, ...])</p></td>
<td><p>Computes the gradient of current tensor wrt graph leaves.</p></td>
</tr>
<tr class="row-odd"><td><p><code class="xref py py-obj docutils literal notranslate"><span class="pre">torch.Tensor.detach</span></code></p></td>
<td><p>Returns a new Tensor, detached from the current graph.</p></td>
</tr>
<tr class="row-even"><td><p><code class="xref py py-obj docutils literal notranslate"><span class="pre">torch.Tensor.detach_</span></code></p></td>
<td><p>Detaches the Tensor from the graph that created it, making it a leaf.</p></td>
</tr>
<tr class="row-odd"><td><p><code class="xref py py-obj docutils literal notranslate"><span class="pre">torch.Tensor.register_hook</span></code>(hook)</p></td>
<td><p>Registers a backward hook.</p></td>
</tr>
<tr class="row-even"><td><p><code class="xref py py-obj docutils literal notranslate"><span class="pre">torch.Tensor.register_post_accumulate_grad_hook</span></code>(hook)</p></td>
<td><p>Registers a backward hook that runs after grad accumulation.</p></td>
</tr>
<tr class="row-odd"><td><p><code class="xref py py-obj docutils literal notranslate"><span class="pre">torch.Tensor.retain_grad</span></code>()</p></td>
<td><p>Enables this Tensor to have their <a class="reference internal" href="generated/torch.autograd.grad.html#torch.autograd.grad" title="torch.autograd.grad"><code class="xref py py-attr docutils literal notranslate"><span class="pre">grad</span></code></a> populated during <a class="reference internal" href="generated/torch.autograd.backward.html#torch.autograd.backward" title="torch.autograd.backward"><code class="xref py py-func docutils literal notranslate"><span class="pre">backward()</span></code></a>.</p></td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="function">
<h2><span class="hidden-section">Function</span><a class="headerlink" href="#function" title="Permalink to this heading">¶</a></h2>
<dl class="py class">
<dt class="sig sig-object py" id="torch.autograd.Function">
<em class="property"><span class="pre">class</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">torch.autograd.</span></span><span class="sig-name descname"><span class="pre">Function</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="o"><span class="pre">*</span></span><span class="n"><span class="pre">args</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">**</span></span><span class="n"><span class="pre">kwargs</span></span></em><span class="sig-paren">)</span><a class="reference internal" href="_modules/torch/autograd/function.html#Function"><span class="viewcode-link"><span class="pre">[source]</span></span></a><a class="headerlink" href="#torch.autograd.Function" title="Permalink to this definition">¶</a></dt>
<dd><p>Base class to create custom <cite>autograd.Function</cite>.</p>
<p>To create a custom <cite>autograd.Function</cite>, subclass this class and implement
the <a class="reference internal" href="generated/torch.autograd.Function.forward.html#torch.autograd.Function.forward" title="torch.autograd.Function.forward"><code class="xref py py-meth docutils literal notranslate"><span class="pre">forward()</span></code></a> and <a class="reference internal" href="generated/torch.autograd.backward.html#torch.autograd.backward" title="torch.autograd.backward"><code class="xref py py-meth docutils literal notranslate"><span class="pre">backward()</span></code></a> static methods. Then, to use your custom
op in the forward pass, call the class method <code class="docutils literal notranslate"><span class="pre">apply</span></code>. Do not call
<a class="reference internal" href="generated/torch.autograd.Function.forward.html#torch.autograd.Function.forward" title="torch.autograd.Function.forward"><code class="xref py py-meth docutils literal notranslate"><span class="pre">forward()</span></code></a> directly.</p>
<p>To ensure correctness and best performance, make sure you are calling the
correct methods on <code class="docutils literal notranslate"><span class="pre">ctx</span></code> and validating your backward function using
<a class="reference internal" href="#module-torch.autograd.gradcheck" title="torch.autograd.gradcheck"><code class="xref py py-func docutils literal notranslate"><span class="pre">torch.autograd.gradcheck()</span></code></a>.</p>
<p>See <a class="reference internal" href="notes/extending.html#extending-autograd"><span class="std std-ref">Extending torch.autograd</span></a> for more details on how to use this class.</p>
<p>Examples:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="k">class</span> <span class="nc">Exp</span><span class="p">(</span><span class="n">Function</span><span class="p">):</span>
<span class="gp">>>> </span> <span class="nd">@staticmethod</span>
<span class="gp">>>> </span> <span class="k">def</span> <span class="nf">forward</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="n">i</span><span class="p">):</span>
<span class="gp">>>> </span> <span class="n">result</span> <span class="o">=</span> <span class="n">i</span><span class="o">.</span><span class="n">exp</span><span class="p">()</span>
<span class="gp">>>> </span> <span class="n">ctx</span><span class="o">.</span><span class="n">save_for_backward</span><span class="p">(</span><span class="n">result</span><span class="p">)</span>
<span class="gp">>>> </span> <span class="k">return</span> <span class="n">result</span>
<span class="go">>>></span>
<span class="gp">>>> </span> <span class="nd">@staticmethod</span>
<span class="gp">>>> </span> <span class="k">def</span> <span class="nf">backward</span><span class="p">(</span><span class="n">ctx</span><span class="p">,</span> <span class="n">grad_output</span><span class="p">):</span>
<span class="gp">>>> </span> <span class="n">result</span><span class="p">,</span> <span class="o">=</span> <span class="n">ctx</span><span class="o">.</span><span class="n">saved_tensors</span>
<span class="gp">>>> </span> <span class="k">return</span> <span class="n">grad_output</span> <span class="o">*</span> <span class="n">result</span>
<span class="go">>>></span>
<span class="gp">>>> </span><span class="c1"># Use it by calling the apply method:</span>
<span class="gp">>>> </span><span class="n">output</span> <span class="o">=</span> <span class="n">Exp</span><span class="o">.</span><span class="n">apply</span><span class="p">(</span><span class="nb">input</span><span class="p">)</span>
</pre></div>
</div>
</dd></dl>
<table class="autosummary longtable docutils colwidths-auto align-default">
<tbody>
<tr class="row-odd"><td><p><a class="reference internal" href="generated/torch.autograd.Function.forward.html#torch.autograd.Function.forward" title="torch.autograd.Function.forward"><code class="xref py py-obj docutils literal notranslate"><span class="pre">Function.forward</span></code></a></p></td>
<td><p>Define the forward of the custom autograd Function.</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="generated/torch.autograd.Function.backward.html#torch.autograd.Function.backward" title="torch.autograd.Function.backward"><code class="xref py py-obj docutils literal notranslate"><span class="pre">Function.backward</span></code></a></p></td>
<td><p>Define a formula for differentiating the operation with backward mode automatic differentiation.</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="generated/torch.autograd.Function.jvp.html#torch.autograd.Function.jvp" title="torch.autograd.Function.jvp"><code class="xref py py-obj docutils literal notranslate"><span class="pre">Function.jvp</span></code></a></p></td>
<td><p>Define a formula for differentiating the operation with forward mode automatic differentiation.</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="generated/torch.autograd.Function.vmap.html#torch.autograd.Function.vmap" title="torch.autograd.Function.vmap"><code class="xref py py-obj docutils literal notranslate"><span class="pre">Function.vmap</span></code></a></p></td>
<td><p>Define the behavior for this autograd.Function underneath <a class="reference internal" href="generated/torch.vmap.html#torch.vmap" title="torch.vmap"><code class="xref py py-func docutils literal notranslate"><span class="pre">torch.vmap()</span></code></a>.</p></td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="context-method-mixins">
<span id="id1"></span><h2>Context method mixins<a class="headerlink" href="#context-method-mixins" title="Permalink to this heading">¶</a></h2>
<p>When creating a new <a class="reference internal" href="#torch.autograd.Function" title="torch.autograd.Function"><code class="xref py py-class docutils literal notranslate"><span class="pre">Function</span></code></a>, the following methods are available to <cite>ctx</cite>.</p>
<table class="autosummary longtable docutils colwidths-auto align-default">
<tbody>
<tr class="row-odd"><td><p><a class="reference internal" href="generated/torch.autograd.function.FunctionCtx.mark_dirty.html#torch.autograd.function.FunctionCtx.mark_dirty" title="torch.autograd.function.FunctionCtx.mark_dirty"><code class="xref py py-obj docutils literal notranslate"><span class="pre">function.FunctionCtx.mark_dirty</span></code></a></p></td>
<td><p>Mark given tensors as modified in an in-place operation.</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="generated/torch.autograd.function.FunctionCtx.mark_non_differentiable.html#torch.autograd.function.FunctionCtx.mark_non_differentiable" title="torch.autograd.function.FunctionCtx.mark_non_differentiable"><code class="xref py py-obj docutils literal notranslate"><span class="pre">function.FunctionCtx.mark_non_differentiable</span></code></a></p></td>
<td><p>Mark outputs as non-differentiable.</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="generated/torch.autograd.function.FunctionCtx.save_for_backward.html#torch.autograd.function.FunctionCtx.save_for_backward" title="torch.autograd.function.FunctionCtx.save_for_backward"><code class="xref py py-obj docutils literal notranslate"><span class="pre">function.FunctionCtx.save_for_backward</span></code></a></p></td>
<td><p>Save given tensors for a future call to <a class="reference internal" href="generated/torch.autograd.Function.backward.html#torch.autograd.Function.backward" title="torch.autograd.Function.backward"><code class="xref py py-func docutils literal notranslate"><span class="pre">backward()</span></code></a>.</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="generated/torch.autograd.function.FunctionCtx.set_materialize_grads.html#torch.autograd.function.FunctionCtx.set_materialize_grads" title="torch.autograd.function.FunctionCtx.set_materialize_grads"><code class="xref py py-obj docutils literal notranslate"><span class="pre">function.FunctionCtx.set_materialize_grads</span></code></a></p></td>
<td><p>Set whether to materialize grad tensors.</p></td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="custom-function-utilities">
<h2>Custom Function utilities<a class="headerlink" href="#custom-function-utilities" title="Permalink to this heading">¶</a></h2>
<p>Decorator for backward method.</p>
<table class="autosummary longtable docutils colwidths-auto align-default">
<tbody>
<tr class="row-odd"><td><p><a class="reference internal" href="generated/torch.autograd.function.once_differentiable.html#torch.autograd.function.once_differentiable" title="torch.autograd.function.once_differentiable"><code class="xref py py-obj docutils literal notranslate"><span class="pre">function.once_differentiable</span></code></a></p></td>
<td><p></p></td>
</tr>
</tbody>
</table>
<p>Base custom <a class="reference internal" href="#torch.autograd.Function" title="torch.autograd.Function"><code class="xref py py-class docutils literal notranslate"><span class="pre">Function</span></code></a> used to build PyTorch utilities</p>
<table class="autosummary longtable docutils colwidths-auto align-default">
<tbody>
<tr class="row-odd"><td><p><a class="reference internal" href="generated/torch.autograd.function.BackwardCFunction.html#torch.autograd.function.BackwardCFunction" title="torch.autograd.function.BackwardCFunction"><code class="xref py py-obj docutils literal notranslate"><span class="pre">function.BackwardCFunction</span></code></a></p></td>
<td><p>This class is used for internal autograd work.</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="generated/torch.autograd.function.InplaceFunction.html#torch.autograd.function.InplaceFunction" title="torch.autograd.function.InplaceFunction"><code class="xref py py-obj docutils literal notranslate"><span class="pre">function.InplaceFunction</span></code></a></p></td>
<td><p>This class is here only for backward compatibility reasons.</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="generated/torch.autograd.function.NestedIOFunction.html#torch.autograd.function.NestedIOFunction" title="torch.autograd.function.NestedIOFunction"><code class="xref py py-obj docutils literal notranslate"><span class="pre">function.NestedIOFunction</span></code></a></p></td>
<td><p>This class is here only for backward compatibility reasons.</p></td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="module-torch.autograd.gradcheck">
<span id="numerical-gradient-checking"></span><span id="grad-check"></span><h2>Numerical gradient checking<a class="headerlink" href="#module-torch.autograd.gradcheck" title="Permalink to this heading">¶</a></h2>
<table class="autosummary longtable docutils colwidths-auto align-default">
<tbody>
<tr class="row-odd"><td><p><p id="torch.autograd.gradcheck.gradcheck"/><a class="reference internal" href="generated/torch.autograd.gradcheck.gradcheck.html#torch.autograd.gradcheck.gradcheck" title="torch.autograd.gradcheck.gradcheck"><code class="xref py py-obj docutils literal notranslate"><span class="pre">gradcheck</span></code></a></p></td>
<td><p>Check gradients computed via small finite differences against analytical gradients wrt tensors in <code class="xref py py-attr docutils literal notranslate"><span class="pre">inputs</span></code> that are of floating point or complex type and with <code class="docutils literal notranslate"><span class="pre">requires_grad=True</span></code>.</p></td>
</tr>
<tr class="row-even"><td><p><p id="torch.autograd.gradcheck.gradgradcheck"/><a class="reference internal" href="generated/torch.autograd.gradcheck.gradgradcheck.html#torch.autograd.gradcheck.gradgradcheck" title="torch.autograd.gradcheck.gradgradcheck"><code class="xref py py-obj docutils literal notranslate"><span class="pre">gradgradcheck</span></code></a></p></td>
<td><p>Check gradients of gradients computed via small finite differences against analytical gradients wrt tensors in <code class="xref py py-attr docutils literal notranslate"><span class="pre">inputs</span></code> and <code class="xref py py-attr docutils literal notranslate"><span class="pre">grad_outputs</span></code> that are of floating point or complex type and with <code class="docutils literal notranslate"><span class="pre">requires_grad=True</span></code>.</p></td>
</tr>
<tr class="row-odd"><td><p><p id="torch.autograd.gradcheck.GradcheckError"/><a class="reference internal" href="generated/torch.autograd.gradcheck.GradcheckError.html#torch.autograd.gradcheck.GradcheckError" title="torch.autograd.gradcheck.GradcheckError"><code class="xref py py-obj docutils literal notranslate"><span class="pre">GradcheckError</span></code></a></p></td>
<td><p>Error raised by <a class="reference internal" href="generated/torch.autograd.gradcheck.gradcheck.html#torch.autograd.gradcheck.gradcheck" title="torch.autograd.gradcheck.gradcheck"><code class="xref py py-func docutils literal notranslate"><span class="pre">gradcheck()</span></code></a> and <a class="reference internal" href="generated/torch.autograd.gradcheck.gradgradcheck.html#torch.autograd.gradcheck.gradgradcheck" title="torch.autograd.gradcheck.gradgradcheck"><code class="xref py py-func docutils literal notranslate"><span class="pre">gradgradcheck()</span></code></a>.</p></td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="profiler">
<h2>Profiler<a class="headerlink" href="#profiler" title="Permalink to this heading">¶</a></h2>
<p>Autograd includes a profiler that lets you inspect the cost of different
operators inside your model - both on the CPU and GPU. There are three modes
implemented at the moment - CPU-only using <a class="reference internal" href="#torch.autograd.profiler.profile" title="torch.autograd.profiler.profile"><code class="xref py py-class docutils literal notranslate"><span class="pre">profile</span></code></a>.
nvprof based (registers both CPU and GPU activity) using
<a class="reference internal" href="#torch.autograd.profiler.emit_nvtx" title="torch.autograd.profiler.emit_nvtx"><code class="xref py py-class docutils literal notranslate"><span class="pre">emit_nvtx</span></code></a>.
and vtune profiler based using
<a class="reference internal" href="#torch.autograd.profiler.emit_itt" title="torch.autograd.profiler.emit_itt"><code class="xref py py-class docutils literal notranslate"><span class="pre">emit_itt</span></code></a>.</p>
<dl class="py class">
<dt class="sig sig-object py" id="torch.autograd.profiler.profile">
<em class="property"><span class="pre">class</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">torch.autograd.profiler.</span></span><span class="sig-name descname"><span class="pre">profile</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">enabled</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">True</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">*</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">use_cuda</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">use_device</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">record_shapes</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">with_flops</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">profile_memory</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">with_stack</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">with_modules</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">use_kineto</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">use_cpu</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">True</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">use_mtia</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">experimental_config</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="reference internal" href="_modules/torch/autograd/profiler.html#profile"><span class="viewcode-link"><span class="pre">[source]</span></span></a><a class="headerlink" href="#torch.autograd.profiler.profile" title="Permalink to this definition">¶</a></dt>
<dd><p>Context manager that manages autograd profiler state and holds a summary of results.</p>
<p>Under the hood it just records events of functions being executed in C++ and
exposes those events to Python. You can wrap any code into it and it will
only report runtime of PyTorch functions.
Note: profiler is thread local and is automatically propagated into the async tasks</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters</dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>enabled</strong> (<a class="reference external" href="https://docs.python.org/3/library/functions.html#bool" title="(in Python v3.12)"><em>bool</em></a><em>, </em><em>optional</em>) – Setting this to False makes this context manager a no-op.</p></li>
<li><p><strong>use_cuda</strong> (<a class="reference external" href="https://docs.python.org/3/library/functions.html#bool" title="(in Python v3.12)"><em>bool</em></a><em>, </em><em>optional</em>) – Enables timing of CUDA events as well
using the cudaEvent API. (will be deprecated)</p></li>
<li><p><strong>use_device</strong> (<a class="reference external" href="https://docs.python.org/3/library/stdtypes.html#str" title="(in Python v3.12)"><em>str</em></a><em>, </em><em>optional</em>) – Enables timing of device events.
Adds approximately 4us of overhead to each tensor operation when use cuda.
The valid devices options are ‘cuda’, ‘xpu’ and ‘privateuseone’.</p></li>
<li><p><strong>record_shapes</strong> (<a class="reference external" href="https://docs.python.org/3/library/functions.html#bool" title="(in Python v3.12)"><em>bool</em></a><em>, </em><em>optional</em>) – If shapes recording is set, information
about input dimensions will be collected. This allows one to see which
dimensions have been used under the hood and further group by them
using prof.key_averages(group_by_input_shape=True). Please note that
shape recording might skew your profiling data. It is recommended to
use separate runs with and without shape recording to validate the timing.
Most likely the skew will be negligible for bottom most events (in a case
of nested function calls). But for higher level functions the total
self cpu time might be artificially increased because of the shape
collection.</p></li>
<li><p><strong>with_flops</strong> (<a class="reference external" href="https://docs.python.org/3/library/functions.html#bool" title="(in Python v3.12)"><em>bool</em></a><em>, </em><em>optional</em>) – If with_flops is set, the profiler will estimate
the FLOPs (floating point operations) value using the operator’s input shape.
This allows one to estimate the hardware performance. Currently,
this option only works for the matrix multiplication and 2D convolution operators.</p></li>
<li><p><strong>profile_memory</strong> (<a class="reference external" href="https://docs.python.org/3/library/functions.html#bool" title="(in Python v3.12)"><em>bool</em></a><em>, </em><em>optional</em>) – track tensor memory allocation/deallocation.</p></li>
<li><p><strong>with_stack</strong> (<a class="reference external" href="https://docs.python.org/3/library/functions.html#bool" title="(in Python v3.12)"><em>bool</em></a><em>, </em><em>optional</em>) – record source information (file and line number) for the ops.</p></li>
<li><p><strong>with_modules</strong> (<a class="reference external" href="https://docs.python.org/3/library/functions.html#bool" title="(in Python v3.12)"><em>bool</em></a>) – record module hierarchy (including function names)
corresponding to the callstack of the op. e.g. If module A’s forward call’s
module B’s forward which contains an aten::add op,
then aten::add’s module hierarchy is A.B
Note that this support exist, at the moment, only for TorchScript models
and not eager mode models.</p></li>
<li><p><strong>use_kineto</strong> (<a class="reference external" href="https://docs.python.org/3/library/functions.html#bool" title="(in Python v3.12)"><em>bool</em></a><em>, </em><em>optional</em>) – experimental, enable profiling with Kineto profiler.</p></li>
<li><p><strong>use_cpu</strong> (<a class="reference external" href="https://docs.python.org/3/library/functions.html#bool" title="(in Python v3.12)"><em>bool</em></a><em>, </em><em>optional</em>) – profile CPU events; setting to <code class="docutils literal notranslate"><span class="pre">False</span></code> requires
<code class="docutils literal notranslate"><span class="pre">use_kineto=True</span></code> and can be used to lower the overhead for GPU-only profiling.</p></li>
<li><p><strong>experimental_config</strong> (<em>_ExperimentalConfig</em>) – A set of experimental options
used by profiler libraries like Kineto. Note, backward compatibility is not guaranteed.</p></li>
</ul>
</dd>
</dl>
<p class="rubric">Example</p>
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">x</span> <span class="o">=</span> <span class="n">torch</span><span class="o">.</span><span class="n">randn</span><span class="p">((</span><span class="mi">1</span><span class="p">,</span> <span class="mi">1</span><span class="p">),</span> <span class="n">requires_grad</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
<span class="gp">>>> </span><span class="k">with</span> <span class="n">torch</span><span class="o">.</span><span class="n">autograd</span><span class="o">.</span><span class="n">profiler</span><span class="o">.</span><span class="n">profile</span><span class="p">()</span> <span class="k">as</span> <span class="n">prof</span><span class="p">:</span>
<span class="gp">>>> </span> <span class="k">for</span> <span class="n">_</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">100</span><span class="p">):</span> <span class="c1"># any normal python code, really!</span>
<span class="gp">>>> </span> <span class="n">y</span> <span class="o">=</span> <span class="n">x</span> <span class="o">**</span> <span class="mi">2</span>
<span class="gp">>>> </span> <span class="n">y</span><span class="o">.</span><span class="n">backward</span><span class="p">()</span>
<span class="gp">>>> </span><span class="c1"># NOTE: some columns were removed for brevity</span>
<span class="gp">>>> </span><span class="nb">print</span><span class="p">(</span><span class="n">prof</span><span class="o">.</span><span class="n">key_averages</span><span class="p">()</span><span class="o">.</span><span class="n">table</span><span class="p">(</span><span class="n">sort_by</span><span class="o">=</span><span class="s2">"self_cpu_time_total"</span><span class="p">))</span>
<span class="go">----------------------------------- --------------- --------------- ---------------</span>
<span class="go">Name Self CPU total CPU time avg Number of Calls</span>
<span class="go">----------------------------------- --------------- --------------- ---------------</span>
<span class="go">mul 32.048ms 32.048ms 200</span>
<span class="go">pow 27.041ms 27.041ms 200</span>
<span class="go">PowBackward0 9.727ms 55.483ms 100</span>
<span class="go">torch::autograd::AccumulateGrad 9.148ms 9.148ms 100</span>
<span class="go">torch::autograd::GraphRoot 691.816us 691.816us 100</span>
<span class="go">----------------------------------- --------------- --------------- ---------------</span>
</pre></div>
</div>
</dd></dl>
<table class="autosummary longtable docutils colwidths-auto align-default">
<tbody>
<tr class="row-odd"><td><p><a class="reference internal" href="generated/torch.autograd.profiler.profile.export_chrome_trace.html#torch.autograd.profiler.profile.export_chrome_trace" title="torch.autograd.profiler.profile.export_chrome_trace"><code class="xref py py-obj docutils literal notranslate"><span class="pre">profiler.profile.export_chrome_trace</span></code></a></p></td>
<td><p>Export an EventList as a Chrome tracing tools file.</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="generated/torch.autograd.profiler.profile.key_averages.html#torch.autograd.profiler.profile.key_averages" title="torch.autograd.profiler.profile.key_averages"><code class="xref py py-obj docutils literal notranslate"><span class="pre">profiler.profile.key_averages</span></code></a></p></td>
<td><p>Averages all function events over their keys.</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="generated/torch.autograd.profiler.profile.self_cpu_time_total.html#torch.autograd.profiler.profile.self_cpu_time_total" title="torch.autograd.profiler.profile.self_cpu_time_total"><code class="xref py py-obj docutils literal notranslate"><span class="pre">profiler.profile.self_cpu_time_total</span></code></a></p></td>
<td><p>Returns total time spent on CPU.</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="generated/torch.autograd.profiler.profile.total_average.html#torch.autograd.profiler.profile.total_average" title="torch.autograd.profiler.profile.total_average"><code class="xref py py-obj docutils literal notranslate"><span class="pre">profiler.profile.total_average</span></code></a></p></td>
<td><p>Averages all events.</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="generated/torch.autograd.profiler.parse_nvprof_trace.html#torch.autograd.profiler.parse_nvprof_trace" title="torch.autograd.profiler.parse_nvprof_trace"><code class="xref py py-obj docutils literal notranslate"><span class="pre">profiler.parse_nvprof_trace</span></code></a></p></td>
<td><p></p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="generated/torch.autograd.profiler.EnforceUnique.html#torch.autograd.profiler.EnforceUnique" title="torch.autograd.profiler.EnforceUnique"><code class="xref py py-obj docutils literal notranslate"><span class="pre">profiler.EnforceUnique</span></code></a></p></td>
<td><p>Raises an error if a key is seen more than once.</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="generated/torch.autograd.profiler.KinetoStepTracker.html#torch.autograd.profiler.KinetoStepTracker" title="torch.autograd.profiler.KinetoStepTracker"><code class="xref py py-obj docutils literal notranslate"><span class="pre">profiler.KinetoStepTracker</span></code></a></p></td>
<td><p>Provides an abstraction for incrementing the step count globally.</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="generated/torch.autograd.profiler.record_function.html#torch.autograd.profiler.record_function" title="torch.autograd.profiler.record_function"><code class="xref py py-obj docutils literal notranslate"><span class="pre">profiler.record_function</span></code></a></p></td>
<td><p>Context manager/function decorator that adds a label to a code block/function when running autograd profiler.</p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="generated/torch.autograd.profiler_util.Interval.html#torch.autograd.profiler_util.Interval" title="torch.autograd.profiler_util.Interval"><code class="xref py py-obj docutils literal notranslate"><span class="pre">profiler_util.Interval</span></code></a></p></td>
<td><p></p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="generated/torch.autograd.profiler_util.Kernel.html#torch.autograd.profiler_util.Kernel" title="torch.autograd.profiler_util.Kernel"><code class="xref py py-obj docutils literal notranslate"><span class="pre">profiler_util.Kernel</span></code></a></p></td>
<td><p></p></td>
</tr>
<tr class="row-odd"><td><p><a class="reference internal" href="generated/torch.autograd.profiler_util.MemRecordsAcc.html#torch.autograd.profiler_util.MemRecordsAcc" title="torch.autograd.profiler_util.MemRecordsAcc"><code class="xref py py-obj docutils literal notranslate"><span class="pre">profiler_util.MemRecordsAcc</span></code></a></p></td>
<td><p>Acceleration structure for accessing mem_records in interval.</p></td>
</tr>
<tr class="row-even"><td><p><a class="reference internal" href="generated/torch.autograd.profiler_util.StringTable.html#torch.autograd.profiler_util.StringTable" title="torch.autograd.profiler_util.StringTable"><code class="xref py py-obj docutils literal notranslate"><span class="pre">profiler_util.StringTable</span></code></a></p></td>
<td><p></p></td>
</tr>
</tbody>
</table>
<dl class="py class">
<dt class="sig sig-object py" id="torch.autograd.profiler.emit_nvtx">
<em class="property"><span class="pre">class</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">torch.autograd.profiler.</span></span><span class="sig-name descname"><span class="pre">emit_nvtx</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">enabled</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">True</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">record_shapes</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">False</span></span></em><span class="sig-paren">)</span><a class="reference internal" href="_modules/torch/autograd/profiler.html#emit_nvtx"><span class="viewcode-link"><span class="pre">[source]</span></span></a><a class="headerlink" href="#torch.autograd.profiler.emit_nvtx" title="Permalink to this definition">¶</a></dt>
<dd><p>Context manager that makes every autograd operation emit an NVTX range.</p>
<p>It is useful when running the program under nvprof:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">nvprof</span> <span class="o">--</span><span class="n">profile</span><span class="o">-</span><span class="n">from</span><span class="o">-</span><span class="n">start</span> <span class="n">off</span> <span class="o">-</span><span class="n">o</span> <span class="n">trace_name</span><span class="o">.</span><span class="n">prof</span> <span class="o">--</span> <span class="o"><</span><span class="n">regular</span> <span class="n">command</span> <span class="n">here</span><span class="o">></span>
</pre></div>
</div>
<p>Unfortunately, there’s no way to force nvprof to flush the data it collected
to disk, so for CUDA profiling one has to use this context manager to annotate
nvprof traces and wait for the process to exit before inspecting them.
Then, either NVIDIA Visual Profiler (nvvp) can be used to visualize the timeline, or
<a class="reference internal" href="generated/torch.autograd.profiler.load_nvprof.html#torch.autograd.profiler.load_nvprof" title="torch.autograd.profiler.load_nvprof"><code class="xref py py-func docutils literal notranslate"><span class="pre">torch.autograd.profiler.load_nvprof()</span></code></a> can load the results for inspection
e.g. in Python REPL.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters</dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>enabled</strong> (<a class="reference external" href="https://docs.python.org/3/library/functions.html#bool" title="(in Python v3.12)"><em>bool</em></a><em>, </em><em>optional</em>) – Setting <code class="docutils literal notranslate"><span class="pre">enabled=False</span></code> makes this context manager a no-op.
Default: <code class="docutils literal notranslate"><span class="pre">True</span></code>.</p></li>
<li><p><strong>record_shapes</strong> (<a class="reference external" href="https://docs.python.org/3/library/functions.html#bool" title="(in Python v3.12)"><em>bool</em></a><em>, </em><em>optional</em>) – If <code class="docutils literal notranslate"><span class="pre">record_shapes=True</span></code>, the nvtx range wrapping
each autograd op will append information about the sizes of Tensor arguments received
by that op, in the following format:
<code class="docutils literal notranslate"><span class="pre">[[arg0.size(0),</span> <span class="pre">arg0.size(1),</span> <span class="pre">...],</span> <span class="pre">[arg1.size(0),</span> <span class="pre">arg1.size(1),</span> <span class="pre">...],</span> <span class="pre">...]</span></code>
Non-tensor arguments will be represented by <code class="docutils literal notranslate"><span class="pre">[]</span></code>.
Arguments will be listed in the order they are received by the backend op.
Please note that this order may not match the order in which those arguments were passed
on the Python side. Also note that shape recording may increase the overhead of nvtx range creation.
Default: <code class="docutils literal notranslate"><span class="pre">False</span></code></p></li>
</ul>
</dd>
</dl>
<p class="rubric">Example</p>
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="k">with</span> <span class="n">torch</span><span class="o">.</span><span class="n">cuda</span><span class="o">.</span><span class="n">profiler</span><span class="o">.</span><span class="n">profile</span><span class="p">():</span>
<span class="gp">... </span> <span class="n">model</span><span class="p">(</span><span class="n">x</span><span class="p">)</span> <span class="c1"># Warmup CUDA memory allocator and profiler</span>
<span class="gp">... </span> <span class="k">with</span> <span class="n">torch</span><span class="o">.</span><span class="n">autograd</span><span class="o">.</span><span class="n">profiler</span><span class="o">.</span><span class="n">emit_nvtx</span><span class="p">():</span>
<span class="gp">... </span> <span class="n">model</span><span class="p">(</span><span class="n">x</span><span class="p">)</span>
</pre></div>
</div>
<p><strong>Forward-backward correlation</strong></p>
<p>When viewing a profile created using <a class="reference internal" href="#torch.autograd.profiler.emit_nvtx" title="torch.autograd.profiler.emit_nvtx"><code class="xref py py-class docutils literal notranslate"><span class="pre">emit_nvtx</span></code></a> in the Nvidia Visual Profiler,
correlating each backward-pass op with the corresponding forward-pass op can be difficult.
To ease this task, <a class="reference internal" href="#torch.autograd.profiler.emit_nvtx" title="torch.autograd.profiler.emit_nvtx"><code class="xref py py-class docutils literal notranslate"><span class="pre">emit_nvtx</span></code></a> appends sequence number information to the ranges it
generates.</p>
<p>During the forward pass, each function range is decorated with <code class="docutils literal notranslate"><span class="pre">seq=<N></span></code>. <code class="docutils literal notranslate"><span class="pre">seq</span></code> is a running
counter, incremented each time a new backward Function object is created and stashed for backward.