session.html



<!DOCTYPE html>
<!--[if IE 8]><html class="no-js lt-ie9" lang="en" > <![endif]-->
<!--[if gt IE 8]><!--> <html class="no-js" lang="en" > <!--<![endif]-->
<head>
  <meta charset="utf-8">
  
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  
  <title>Design Doc: Session &mdash; PaddlePaddle  documentation</title>
  

    <link rel="stylesheet" href="../../_static/css/theme.css" type="text/css" />
  

        <link rel="index" title="Index"
              href="../../genindex.html"/>
        <link rel="search" title="Search" href="../../search.html"/>
    <link rel="top" title="PaddlePaddle  documentation" href="../../index.html"/> 

  <link rel="stylesheet" href="https://cdn.jsdelivr.net/perfect-scrollbar/0.6.14/css/perfect-scrollbar.min.css" type="text/css" />
  <link rel="stylesheet" href="../../_static/css/override.css" type="text/css" />
  <script>
  var _hmt = _hmt || [];
  (function() {
    var hm = document.createElement("script");
    hm.src = "//hm.baidu.com/hm.js?b9a314ab40d04d805655aab1deee08ba";
    var s = document.getElementsByTagName("script")[0]; 
    s.parentNode.insertBefore(hm, s);
  })();
  </script>

  
  <script src="../../_static/js/modernizr.min.js"></script>

</head>

<body class="wy-body-for-nav" role="document">

  
  <header class="site-header">
    <div class="site-logo">
      <a href="/"><img src="../../_static/images/PP_w.png"></a>
    </div>
    <div class="site-nav-links">
      <div class="site-menu">
        <a class="fork-on-github" href="https://github.com/PaddlePaddle/Paddle" target="_blank"><i class="fa fa-github"></i>Fork me on Github</a>
        <div class="language-switcher dropdown">
          <a type="button" data-toggle="dropdown">
            <span>English</span>
            <i class="fa fa-angle-up"></i>
            <i class="fa fa-angle-down"></i>
          </a>
          <ul class="dropdown-menu">
            <li><a href="/doc_cn">中文</a></li>
            <li><a href="/doc">English</a></li>
          </ul>
        </div>
        <ul class="site-page-links">
          <li><a href="/">Home</a></li>
        </ul>
      </div>
      <div class="doc-module">
        
        <ul>
<li class="toctree-l1"><a class="reference internal" href="../../getstarted/index_en.html">GET STARTED</a></li>
<li class="toctree-l1"><a class="reference internal" href="../../howto/index_en.html">HOW TO</a></li>
<li class="toctree-l1"><a class="reference internal" href="../../api/index_en.html">API</a></li>
<li class="toctree-l1"><a class="reference internal" href="../../mobile/index_en.html">MOBILE</a></li>
</ul>

        
<div role="search">
  <form id="rtd-search-form" class="wy-form" action="../../search.html" method="get">
    <input type="text" name="q" placeholder="Search docs" />
    <input type="hidden" name="check_keywords" value="yes" />
    <input type="hidden" name="area" value="default" />
  </form>
</div>        
      </div>
    </div>
  </header>
  
  <div class="main-content-wrap">

    
    <nav class="doc-menu-vertical" role="navigation">
        
          
          <ul>
<li class="toctree-l1"><a class="reference internal" href="../../getstarted/index_en.html">GET STARTED</a><ul>
<li class="toctree-l2"><a class="reference internal" href="../../getstarted/build_and_install/index_en.html">Install and Build</a><ul>
<li class="toctree-l3"><a class="reference internal" href="../../getstarted/build_and_install/pip_install_en.html">Install PaddlePaddle Using pip</a></li>
<li class="toctree-l3"><a class="reference internal" href="../../getstarted/build_and_install/docker_install_en.html">PaddlePaddle in Docker Containers</a></li>
<li class="toctree-l3"><a class="reference internal" href="../../getstarted/build_and_install/build_from_source_en.html">Build PaddlePaddle from Sources</a></li>
</ul>
</li>
</ul>
</li>
<li class="toctree-l1"><a class="reference internal" href="../../howto/index_en.html">HOW TO</a><ul>
<li class="toctree-l2"><a class="reference internal" href="../../howto/usage/cmd_parameter/index_en.html">Set Command-line Parameters</a><ul>
<li class="toctree-l3"><a class="reference internal" href="../../howto/usage/cmd_parameter/use_case_en.html">Use Case</a></li>
<li class="toctree-l3"><a class="reference internal" href="../../howto/usage/cmd_parameter/arguments_en.html">Argument Outline</a></li>
<li class="toctree-l3"><a class="reference internal" href="../../howto/usage/cmd_parameter/detail_introduction_en.html">Detail Description</a></li>
</ul>
</li>
<li class="toctree-l2"><a class="reference internal" href="../../howto/usage/cluster/cluster_train_en.html">PaddlePaddle Distributed Training</a></li>
<li class="toctree-l2"><a class="reference internal" href="../../howto/usage/k8s/k8s_en.html">Paddle On Kubernetes</a></li>
<li class="toctree-l2"><a class="reference internal" href="../../howto/usage/k8s/k8s_aws_en.html">Distributed PaddlePaddle Training on AWS with Kubernetes</a></li>
<li class="toctree-l2"><a class="reference internal" href="../../howto/dev/build_en.html">Build PaddlePaddle from Source Code and Run Unit Test</a></li>
<li class="toctree-l2"><a class="reference internal" href="../../howto/dev/new_layer_en.html">Write New Layers</a></li>
<li class="toctree-l2"><a class="reference internal" href="../../howto/dev/contribute_to_paddle_en.html">Contribute Code</a></li>
<li class="toctree-l2"><a class="reference internal" href="../../howto/deep_model/rnn/index_en.html">RNN Models</a><ul>
<li class="toctree-l3"><a class="reference internal" href="../../howto/deep_model/rnn/rnn_config_en.html">RNN Configuration</a></li>
</ul>
</li>
<li class="toctree-l2"><a class="reference internal" href="../../howto/optimization/gpu_profiling_en.html">Tune GPU Performance</a></li>
</ul>
</li>
<li class="toctree-l1"><a class="reference internal" href="../../api/index_en.html">API</a><ul>
<li class="toctree-l2"><a class="reference internal" href="../../api/v2/model_configs.html">Model Configuration</a><ul>
<li class="toctree-l3"><a class="reference internal" href="../../api/v2/config/activation.html">Activation</a></li>
<li class="toctree-l3"><a class="reference internal" href="../../api/v2/config/layer.html">Layers</a></li>
<li class="toctree-l3"><a class="reference internal" href="../../api/v2/config/evaluators.html">Evaluators</a></li>
<li class="toctree-l3"><a class="reference internal" href="../../api/v2/config/optimizer.html">Optimizer</a></li>
<li class="toctree-l3"><a class="reference internal" href="../../api/v2/config/pooling.html">Pooling</a></li>
<li class="toctree-l3"><a class="reference internal" href="../../api/v2/config/networks.html">Networks</a></li>
<li class="toctree-l3"><a class="reference internal" href="../../api/v2/config/attr.html">Parameter Attribute</a></li>
</ul>
</li>
<li class="toctree-l2"><a class="reference internal" href="../../api/v2/data.html">Data Reader Interface and DataSets</a><ul>
<li class="toctree-l3"><a class="reference internal" href="../../api/v2/data/data_reader.html">Data Reader Interface</a></li>
<li class="toctree-l3"><a class="reference internal" href="../../api/v2/data/image.html">Image Interface</a></li>
<li class="toctree-l3"><a class="reference internal" href="../../api/v2/data/dataset.html">Dataset</a></li>
</ul>
</li>
<li class="toctree-l2"><a class="reference internal" href="../../api/v2/run_logic.html">Training and Inference</a></li>
</ul>
</li>
<li class="toctree-l1"><a class="reference internal" href="../../mobile/index_en.html">MOBILE</a><ul>
<li class="toctree-l2"><a class="reference internal" href="../../mobile/cross_compiling_for_android_en.html">Build PaddlePaddle for Android</a></li>
<li class="toctree-l2"><a class="reference internal" href="../../mobile/cross_compiling_for_raspberry_en.html">Build PaddlePaddle for Raspberry Pi</a></li>
</ul>
</li>
</ul>

        
    </nav>
    
    <section class="doc-content-wrap">

      
<div role="navigation" aria-label="breadcrumbs navigation">
  <ul class="wy-breadcrumbs">
      
    <li>Design Doc: Session</li>
  </ul>
</div>
      
      <div class="wy-nav-content" id="doc-content">
        <div class="rst-content">
          <div role="main" class="document" itemscope="itemscope" itemtype="http://schema.org/Article">
           <div itemprop="articleBody">
            
  <div class="section" id="design-doc-session">
<span id="design-doc-session"></span><h1>Design Doc: Session<a class="headerlink" href="#design-doc-session" title="Permalink to this headline">¶</a></h1>
<div class="section" id="abstract">
<span id="abstract"></span><h2>Abstract<a class="headerlink" href="#abstract" title="Permalink to this headline">¶</a></h2>
<p>The <em>session</em> object encapsulates the environment in which the
computation graph is executed.</p>
<p>We will have the <em>local</em> session and <em>remote</em> session, they offer the
same <a class="reference external" href="#interface">interface</a>. The local session encapsulates the local
runtime environment and the remote session encapsulates the cluster
runtime environment.</p>
<p>The local runtime environment contains:</p>
<ol class="simple">
<li>computation devices (i.e., CPU, GPU) handles, and</li>
<li>the <a class="reference internal" href="../scope.html"><span class="doc">scope</span></a> which holds all variables.</li>
</ol>
<p>The remote runtime environment contains:</p>
<ol class="simple">
<li>computation devices (i.e., CPU and GPU on node 0, 1) in a cluster,
and</li>
<li>the distributed <a class="reference internal" href="../scope.html"><span class="doc">scope</span></a> in a cluster which holds all
variables.</li>
</ol>
<p>The user can create a remote session on Paddle Cloud and evaluate the
computation graph with it. In this way, the user can control the
remote computation resource in a cluster from his local computer.</p>
</div>
<div class="section" id="background">
<span id="background"></span><h2>Background<a class="headerlink" href="#background" title="Permalink to this headline">¶</a></h2>
<p>The current design has an implicit global session in which
<code class="docutils literal"><span class="pre">paddle.eval()</span></code> is executed. The pain point is:</p>
<p>Since the user is not able to explicitly switch between runtime
environments, the user cannot run a topology in two independent
environments.</p>
<p>For example, in reinforcement learning, the user may want to have a
stale model for inference and a fresh model for training, and only
replace the stale model with the fresh model periodically.</p>
<p>Furthermore, we have no concept that encapsulates a remote environment
that executes a computation graph.</p>
<p>We need the session object to address above issues.</p>
</div>
<div class="section" id="session">
<span id="session"></span><h2>Session<a class="headerlink" href="#session" title="Permalink to this headline">¶</a></h2>
<p>A session is an object that owns the runtime environment. All
computations are executed through <code class="docutils literal"><span class="pre">session.eval()</span></code>.</p>
<div class="section" id="interface">
<span id="interface"></span><h3>Interface<a class="headerlink" href="#interface" title="Permalink to this headline">¶</a></h3>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="nb">eval</span><span class="p">(</span>
    <span class="n">targets</span><span class="p">,</span>
    <span class="n">feed_dict</span><span class="o">=</span><span class="bp">None</span><span class="p">,</span>
<span class="p">)</span>
</pre></div>
</div>
<p>Evaluates the target Operations or Variables in <code class="docutils literal"><span class="pre">targets</span></code>.</p>
<ul>
<li><p class="first"><em>targets</em>: the evaluation targets. Can be a single Operation or
Variable, or a list with the Operations or Variables as
elements. The value returned by <code class="docutils literal"><span class="pre">eval()</span></code> has the same shape as the
<code class="docutils literal"><span class="pre">target</span></code> argument.</p>
<p>The PaddlePaddle program is represented by
the <a class="reference external" href="design/design/program.md">ProgramDesc</a>, <code class="docutils literal"><span class="pre">eval()</span></code> will infer the
ProgramDesc from the given targets and run the PaddlePaddle
program. Please
see
<a class="reference external" href="/design/refactor/distributed_architecture.html#local-training-architecture">this graph</a> for
the detailed illustration for the local session
and
<a class="reference external" href="/design/refactor/distributed_architecture.html#distributed-training-architecture">this graph</a> for
the detailed illustration for the remote session.</p>
</li>
<li><p class="first"><em>feed_dict</em>: a dictionary that contains the tensors which override
the edges of the computation graph.</p>
<p>feed_dict not only can provide the input data, it can override any
OP&#8217;s input as well:</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="n">a</span> <span class="o">=</span> <span class="n">pd</span><span class="o">.</span><span class="n">constant</span><span class="p">(</span><span class="mf">2.0</span><span class="p">,</span> <span class="n">name</span><span class="o">=</span><span class="s2">&quot;a&quot;</span><span class="p">)</span>
<span class="n">b</span> <span class="o">=</span> <span class="n">pd</span><span class="o">.</span><span class="n">variable</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s2">&quot;b&quot;</span><span class="p">)</span>
<span class="n">c</span> <span class="o">=</span> <span class="n">pd</span><span class="o">.</span><span class="n">mul</span><span class="p">(</span><span class="n">a</span><span class="p">,</span><span class="n">b</span><span class="p">)</span>
<span class="n">sess</span><span class="o">.</span><span class="n">eval</span><span class="p">(</span><span class="n">targets</span><span class="o">=</span><span class="n">c</span><span class="p">,</span> <span class="n">feed_dict</span><span class="o">=</span><span class="p">{</span><span class="s2">&quot;b&quot;</span><span class="p">:</span><span class="mf">3.0</span><span class="p">})</span> <span class="c1"># returns 6.0</span>
</pre></div>
</div>
</li>
</ul>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="n">close</span><span class="p">()</span>
</pre></div>
</div>
<p>Closes the session and releases the scope that the session owns.</p>
</div>
<div class="section" id="create-a-local-session">
<span id="create-a-local-session"></span><h3>Create a Local Session<a class="headerlink" href="#create-a-local-session" title="Permalink to this headline">¶</a></h3>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="n">session</span><span class="p">(</span>
    <span class="n">devices</span><span class="o">=</span><span class="bp">None</span>
<span class="p">)</span>
</pre></div>
</div>
<p>Creates a new session. One session owns one global scope, so creating
multiple sessions will create different scopes.</p>
<ul class="simple">
<li><em>devices</em>: a single <code class="docutils literal"><span class="pre">string</span></code> or a list of <code class="docutils literal"><span class="pre">string</span></code> of device names,
the corresponding devices will be the computation devices for
<code class="docutils literal"><span class="pre">eval()</span></code>. If not specified, all available devices (e.g., all GPUs)
will be used. The user doesn&#8217;t need to specify the CPU device since
it will be always used. Multiple sessions can use the same device.</li>
</ul>
<div class="section" id="example">
<span id="example"></span><h4>Example<a class="headerlink" href="#example" title="Permalink to this headline">¶</a></h4>
<div class="highlight-Python"><div class="highlight"><pre><span></span><span class="n">a</span> <span class="o">=</span> <span class="n">paddle</span><span class="o">.</span><span class="n">constant</span><span class="p">(</span><span class="mf">1.0</span><span class="p">)</span>
<span class="n">b</span> <span class="o">=</span> <span class="n">paddle</span><span class="o">.</span><span class="n">constant</span><span class="p">(</span><span class="mf">2.0</span><span class="p">)</span>
<span class="n">c</span> <span class="o">=</span> <span class="n">a</span> <span class="o">+</span> <span class="n">b</span>
<span class="n">sess</span> <span class="o">=</span> <span class="n">paddle</span><span class="o">.</span><span class="n">session</span><span class="p">(</span><span class="n">devices</span><span class="o">=</span><span class="p">[</span><span class="s2">&quot;gpu:0&quot;</span><span class="p">,</span> <span class="s2">&quot;gpu:1&quot;</span><span class="p">,</span> <span class="s2">&quot;fpga:0&quot;</span><span class="p">])</span>
<span class="n">sess</span><span class="o">.</span><span class="n">eval</span><span class="p">(</span><span class="n">c</span><span class="p">)</span>
<span class="n">sess</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
</pre></div>
</div>
</div>
</div>
<div class="section" id="create-a-remote-session">
<span id="create-a-remote-session"></span><h3>Create a Remote Session<a class="headerlink" href="#create-a-remote-session" title="Permalink to this headline">¶</a></h3>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="n">create_cloud_job</span><span class="p">(</span>
    <span class="n">name</span><span class="p">,</span>
    <span class="n">num_trainer</span><span class="p">,</span>
    <span class="n">mem_per_trainer</span><span class="p">,</span>
    <span class="n">gpu_per_trainer</span><span class="p">,</span>
    <span class="n">cpu_per_trainer</span><span class="p">,</span>
    <span class="n">num_ps</span><span class="p">,</span>
    <span class="n">mem_per_ps</span><span class="p">,</span>
    <span class="n">cpu_per_ps</span><span class="p">,</span>
<span class="p">)</span>
</pre></div>
</div>
<p>Creates a Paddle Cloud job. Fails if the job name exists.</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="n">get_cloud_job</span><span class="p">(</span>
    <span class="n">name</span>
<span class="p">)</span>
</pre></div>
</div>
<p>Gets a Paddle Cloud job.</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="n">remote_session</span><span class="p">(</span>
    <span class="n">job</span>
<span class="p">)</span>
</pre></div>
</div>
<ul class="simple">
<li><em>job</em>: the Paddle Cloud job.</li>
</ul>
<div class="section" id="example">
<span id="id1"></span><h4>Example<a class="headerlink" href="#example" title="Permalink to this headline">¶</a></h4>
<div class="highlight-Python"><div class="highlight"><pre><span></span><span class="n">reader</span> <span class="o">=</span> <span class="n">paddle</span><span class="o">.</span><span class="n">reader</span><span class="o">.</span><span class="n">recordio</span><span class="p">(</span><span class="s2">&quot;/pfs/home/peter/mnist-train-*&quot;</span><span class="p">)</span> <span class="c1"># data stored on Paddle Cloud</span>
<span class="n">image</span> <span class="o">=</span> <span class="n">reader</span><span class="o">.</span><span class="n">column</span><span class="p">(</span><span class="mi">0</span><span class="p">)</span>
<span class="n">label</span> <span class="o">=</span> <span class="n">reader</span><span class="o">.</span><span class="n">column</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
<span class="n">fc1</span> <span class="o">=</span> <span class="n">paddle</span><span class="o">.</span><span class="n">op</span><span class="o">.</span><span class="n">fc</span><span class="p">(</span><span class="n">image</span><span class="p">,</span> <span class="n">size</span><span class="o">=</span><span class="mi">256</span><span class="p">,</span> <span class="n">act</span><span class="o">=</span><span class="s2">&quot;sigmoid&quot;</span><span class="p">)</span>
<span class="n">fc2</span> <span class="o">=</span> <span class="n">paddle</span><span class="o">.</span><span class="n">op</span><span class="o">.</span><span class="n">fc</span><span class="p">(</span><span class="n">fc1</span><span class="p">,</span> <span class="n">size</span><span class="o">=</span><span class="mi">10</span><span class="p">,</span> <span class="n">act</span><span class="o">=</span><span class="s2">&quot;softmax&quot;</span><span class="p">)</span>
<span class="n">cost</span> <span class="o">=</span> <span class="n">paddle</span><span class="o">.</span><span class="n">op</span><span class="o">.</span><span class="n">cross_entropy</span><span class="p">(</span><span class="n">fc2</span><span class="p">,</span> <span class="n">label</span><span class="p">)</span>
<span class="n">opt</span> <span class="o">=</span> <span class="n">paddle</span><span class="o">.</span><span class="n">optimizer</span><span class="o">.</span><span class="n">sgd</span><span class="p">(</span><span class="n">cost</span><span class="p">)</span>

<span class="n">job</span> <span class="o">=</span> <span class="n">paddle</span><span class="o">.</span><span class="n">create_cloud_job</span><span class="p">(</span><span class="s2">&quot;test&quot;</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="s2">&quot;1G&quot;</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="mi">2</span><span class="p">,</span> <span class="s2">&quot;1G&quot;</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span>
<span class="n">sess</span> <span class="o">=</span> <span class="n">paddle</span><span class="o">.</span><span class="n">remote_ession</span><span class="p">(</span><span class="n">job</span><span class="p">)</span>
<span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">1000</span><span class="p">):</span>
    <span class="n">sess</span><span class="o">.</span><span class="n">eval</span><span class="p">(</span><span class="n">opt</span><span class="p">)</span>
<span class="n">sess</span><span class="o">.</span><span class="n">close</span><span class="p">()</span>
</pre></div>
</div>
</div>
</div>
</div>
</div>


           </div>
          </div>
          <footer>
  

  <hr/>

  <div role="contentinfo">
    <p>
        &copy; Copyright 2016, PaddlePaddle developers.

    </p>
  </div>
  Built with <a href="http://sphinx-doc.org/">Sphinx</a> using a <a href="https://github.com/snide/sphinx_rtd_theme">theme</a> provided by <a href="https://readthedocs.org">Read the Docs</a>. 

</footer>

        </div>
      </div>

    </section>

  </div>
  

    <script type="text/javascript">
        var DOCUMENTATION_OPTIONS = {
            URL_ROOT:'../../',
            VERSION:'',
            COLLAPSE_INDEX:false,
            FILE_SUFFIX:'.html',
            HAS_SOURCE:  true,
            SOURCELINK_SUFFIX: ".txt",
        };
    </script>
      <script type="text/javascript" src="../../_static/jquery.js"></script>
      <script type="text/javascript" src="../../_static/underscore.js"></script>
      <script type="text/javascript" src="../../_static/doctools.js"></script>
      <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.0/MathJax.js?config=TeX-AMS-MML_HTMLorMML"></script>
       
  
    <script type="text/javascript" src="../../_static/js/theme.js"></script>
  
  
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js" integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" crossorigin="anonymous"></script>
  <script src="https://cdn.jsdelivr.net/perfect-scrollbar/0.6.14/js/perfect-scrollbar.jquery.min.js"></script>
  <script src="../../_static/js/paddle_doc_init.js"></script> 

</body>
</html>