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<div class="section" id="kvstore-api">
<span id="kvstore-api"></span><h1>KVStore API<a class="headerlink" href="#kvstore-api" title="Permalink to this headline"></a></h1>
<div class="section" id="basic-push-and-pull">
<span id="basic-push-and-pull"></span><h2>Basic Push and Pull<a class="headerlink" href="#basic-push-and-pull" title="Permalink to this headline"></a></h2>
<p>Provides basic operation over multiple devices (GPUs) on a single device.</p>
<div class="section" id="initialization">
<span id="initialization"></span><h3>Initialization<a class="headerlink" href="#initialization" title="Permalink to this headline"></a></h3>
<p>Let’s consider a simple example. It initializes
a (<code class="docutils literal"><span class="pre">int</span></code>, <code class="docutils literal"><span class="pre">NDArray</span></code>) pair into the store, and then pulls the value out.</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">kv</span> <span class="o">=</span> <span class="n">mx</span><span class="o">.</span><span class="n">kv</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="s1">'local'</span><span class="p">)</span> <span class="c1"># create a local kv store.</span>
<span class="gp">>>> </span><span class="n">shape</span> <span class="o">=</span> <span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">init</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">ones</span><span class="p">(</span><span class="n">shape</span><span class="p">)</span><span class="o">*</span><span class="mi">2</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">a</span> <span class="o">=</span> <span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">zeros</span><span class="p">(</span><span class="n">shape</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">pull</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="n">out</span> <span class="o">=</span> <span class="n">a</span><span class="p">)</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">a</span><span class="o">.</span><span class="n">asnumpy</span><span class="p">()</span>
<span class="go">[[ 2. 2. 2.]</span>
<span class="go"> [ 2. 2. 2.]]</span>
</pre></div>
</div>
</div>
<div class="section" id="push-aggregation-and-updater">
<span id="push-aggregation-and-updater"></span><h3>Push, Aggregation, and Updater<a class="headerlink" href="#push-aggregation-and-updater" title="Permalink to this headline"></a></h3>
<p>For any key that’s been initialized, you can push a new value with the same shape to the key, as follows:</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">push</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">ones</span><span class="p">(</span><span class="n">shape</span><span class="p">)</span><span class="o">*</span><span class="mi">8</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">pull</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="n">out</span> <span class="o">=</span> <span class="n">a</span><span class="p">)</span> <span class="c1"># pull out the value</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">a</span><span class="o">.</span><span class="n">asnumpy</span><span class="p">()</span>
<span class="go">[[ 8. 8. 8.]</span>
<span class="go"> [ 8. 8. 8.]]</span>
</pre></div>
</div>
<p>The data that you want to push can be stored on any device. Furthermore, you can push multiple
values into the same key, where KVStore first sums all of these
values, and then pushes the aggregated value, as follows:</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">gpus</span> <span class="o">=</span> <span class="p">[</span><span class="n">mx</span><span class="o">.</span><span class="n">gpu</span><span class="p">(</span><span class="n">i</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">4</span><span class="p">)]</span>
<span class="gp">>>> </span><span class="n">b</span> <span class="o">=</span> <span class="p">[</span><span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">ones</span><span class="p">(</span><span class="n">shape</span><span class="p">,</span> <span class="n">gpu</span><span class="p">)</span> <span class="k">for</span> <span class="n">gpu</span> <span class="ow">in</span> <span class="n">gpus</span><span class="p">]</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">push</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="n">b</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">pull</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="n">out</span> <span class="o">=</span> <span class="n">a</span><span class="p">)</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">a</span><span class="o">.</span><span class="n">asnumpy</span><span class="p">()</span>
<span class="go">[[ 4. 4. 4.]</span>
<span class="go"> [ 4. 4. 4.]]</span>
</pre></div>
</div>
<p>For each push command, KVStore applies the pushed value to the value stored by an
<code class="docutils literal"><span class="pre">updater</span></code>. The default updater is <code class="docutils literal"><span class="pre">ASSIGN</span></code>. You can replace the default to
control how data is merged.</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="k">def</span> <span class="nf">update</span><span class="p">(</span><span class="n">key</span><span class="p">,</span> <span class="nb">input</span><span class="p">,</span> <span class="n">stored</span><span class="p">):</span>
<span class="gp">>>> </span> <span class="k">print</span> <span class="s2">"update on key: </span><span class="si">%d</span><span class="s2">"</span> <span class="o">%</span> <span class="n">key</span>
<span class="gp">>>> </span> <span class="n">stored</span> <span class="o">+=</span> <span class="nb">input</span> <span class="o">*</span> <span class="mi">2</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">_set_updater</span><span class="p">(</span><span class="n">update</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">pull</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="n">out</span><span class="o">=</span><span class="n">a</span><span class="p">)</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">a</span><span class="o">.</span><span class="n">asnumpy</span><span class="p">()</span>
<span class="go">[[ 4. 4. 4.]</span>
<span class="go"> [ 4. 4. 4.]]</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">push</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">ones</span><span class="p">(</span><span class="n">shape</span><span class="p">))</span>
<span class="go">update on key: 3</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">pull</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="n">out</span><span class="o">=</span><span class="n">a</span><span class="p">)</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">a</span><span class="o">.</span><span class="n">asnumpy</span><span class="p">()</span>
<span class="go">[[ 6. 6. 6.]</span>
<span class="go"> [ 6. 6. 6.]]</span>
</pre></div>
</div>
</div>
<div class="section" id="pull">
<span id="pull"></span><h3>Pull<a class="headerlink" href="#pull" title="Permalink to this headline"></a></h3>
<p>You’ve already seen how to pull a single key-value pair. Similar to the way that you use the push command, you can
pull the value into several devices with a single call.</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">b</span> <span class="o">=</span> <span class="p">[</span><span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">ones</span><span class="p">(</span><span class="n">shape</span><span class="p">,</span> <span class="n">gpu</span><span class="p">)</span> <span class="k">for</span> <span class="n">gpu</span> <span class="ow">in</span> <span class="n">gpus</span><span class="p">]</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">pull</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="n">out</span> <span class="o">=</span> <span class="n">b</span><span class="p">)</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">b</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">asnumpy</span><span class="p">()</span>
<span class="go">[[ 6. 6. 6.]</span>
<span class="go"> [ 6. 6. 6.]]</span>
</pre></div>
</div>
</div>
</div>
<div class="section" id="list-key-value-pairs">
<span id="list-key-value-pairs"></span><h2>List Key-Value Pairs<a class="headerlink" href="#list-key-value-pairs" title="Permalink to this headline"></a></h2>
<p>All of the operations that we’ve discussed so far are performed on a single key. KVStore also provides
the interface for generating a list of key-value pairs. For a single device, use the following:</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">keys</span> <span class="o">=</span> <span class="p">[</span><span class="mi">5</span><span class="p">,</span> <span class="mi">7</span><span class="p">,</span> <span class="mi">9</span><span class="p">]</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">init</span><span class="p">(</span><span class="n">keys</span><span class="p">,</span> <span class="p">[</span><span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">ones</span><span class="p">(</span><span class="n">shape</span><span class="p">)]</span><span class="o">*</span><span class="nb">len</span><span class="p">(</span><span class="n">keys</span><span class="p">))</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">push</span><span class="p">(</span><span class="n">keys</span><span class="p">,</span> <span class="p">[</span><span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">ones</span><span class="p">(</span><span class="n">shape</span><span class="p">)]</span><span class="o">*</span><span class="nb">len</span><span class="p">(</span><span class="n">keys</span><span class="p">))</span>
<span class="go">update on key: 5</span>
<span class="go">update on key: 7</span>
<span class="go">update on key: 9</span>
<span class="gp">>>> </span><span class="n">b</span> <span class="o">=</span> <span class="p">[</span><span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">zeros</span><span class="p">(</span><span class="n">shape</span><span class="p">)]</span><span class="o">*</span><span class="nb">len</span><span class="p">(</span><span class="n">keys</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">pull</span><span class="p">(</span><span class="n">keys</span><span class="p">,</span> <span class="n">out</span> <span class="o">=</span> <span class="n">b</span><span class="p">)</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">b</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">asnumpy</span><span class="p">()</span>
<span class="go">[[ 3. 3. 3.]</span>
<span class="go"> [ 3. 3. 3.]]</span>
</pre></div>
</div>
<p>For multiple devices:</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">b</span> <span class="o">=</span> <span class="p">[[</span><span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">ones</span><span class="p">(</span><span class="n">shape</span><span class="p">,</span> <span class="n">gpu</span><span class="p">)</span> <span class="k">for</span> <span class="n">gpu</span> <span class="ow">in</span> <span class="n">gpus</span><span class="p">]]</span> <span class="o">*</span> <span class="nb">len</span><span class="p">(</span><span class="n">keys</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">push</span><span class="p">(</span><span class="n">keys</span><span class="p">,</span> <span class="n">b</span><span class="p">)</span>
<span class="go">update on key: 5</span>
<span class="go">update on key: 7</span>
<span class="go">update on key: 9</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">pull</span><span class="p">(</span><span class="n">keys</span><span class="p">,</span> <span class="n">out</span> <span class="o">=</span> <span class="n">b</span><span class="p">)</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">b</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="o">.</span><span class="n">asnumpy</span><span class="p">()</span>
<span class="go">[[ 11. 11. 11.]</span>
<span class="go"> [ 11. 11. 11.]]</span>
</pre></div>
</div>
</div>
<div class="section" id="api-reference">
<span id="api-reference"></span><h2>API Reference<a class="headerlink" href="#api-reference" title="Permalink to this headline"></a></h2>
<script src="../../_static/js/auto_module_index.js" type="text/javascript"></script><span class="target" id="module-mxnet.kvstore"></span><p>Key value store interface of MXNet for parameter synchronization.</p>
<dl class="class">
<dt id="mxnet.kvstore.KVStore">
<em class="property">class </em><code class="descclassname">mxnet.kvstore.</code><code class="descname">KVStore</code><span class="sig-paren">(</span><em>handle</em><span class="sig-paren">)</span><a class="headerlink" href="#mxnet.kvstore.KVStore" title="Permalink to this definition"></a></dt>
<dd><p>A key-value store for synchronization of values, over multiple devices.</p>
<dl class="method">
<dt id="mxnet.kvstore.KVStore.init">
<code class="descname">init</code><span class="sig-paren">(</span><em>key</em>, <em>value</em><span class="sig-paren">)</span><a class="headerlink" href="#mxnet.kvstore.KVStore.init" title="Permalink to this definition"></a></dt>
<dd><p>Initializes a single or a sequence of key-value pairs into the store.</p>
<p>For each key, one must <cite>init</cite> it before calling <cite>push</cite> or <cite>pull</cite>.
When multiple workers invoke <cite>init</cite> for the same key, only
the value supplied by worker with rank <cite>0</cite> is used. This function returns
after data has been initialized successfully.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name"/>
<col class="field-body"/>
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first last simple">
<li><strong>key</strong> (<em>str or sequence of str</em>) – The keys.</li>
<li><strong>value</strong> (<em>NDArray or sequence of NDArray</em>) – Values corresponding to the keys.</li>
</ul>
</td>
</tr>
</tbody>
</table>
<p class="rubric">Examples</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="c1"># init a single key-value pair</span>
<span class="gp">>>> </span><span class="n">shape</span> <span class="o">=</span> <span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">kv</span> <span class="o">=</span> <span class="n">mx</span><span class="o">.</span><span class="n">kv</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="s1">'local'</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">init</span><span class="p">(</span><span class="s1">'3'</span><span class="p">,</span> <span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">ones</span><span class="p">(</span><span class="n">shape</span><span class="p">)</span><span class="o">*</span><span class="mi">2</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">a</span> <span class="o">=</span> <span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">zeros</span><span class="p">(</span><span class="n">shape</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">pull</span><span class="p">(</span><span class="s1">'3'</span><span class="p">,</span> <span class="n">out</span><span class="o">=</span><span class="n">a</span><span class="p">)</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">a</span><span class="o">.</span><span class="n">asnumpy</span><span class="p">()</span>
<span class="go">[[ 2. 2. 2.]</span>
<span class="go">[ 2. 2. 2.]]</span>
</pre></div>
</div>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="c1"># init a list of key-value pairs</span>
<span class="gp">>>> </span><span class="n">keys</span> <span class="o">=</span> <span class="p">[</span><span class="s1">'5'</span><span class="p">,</span> <span class="s1">'7'</span><span class="p">,</span> <span class="s1">'9'</span><span class="p">]</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">init</span><span class="p">(</span><span class="n">keys</span><span class="p">,</span> <span class="p">[</span><span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">ones</span><span class="p">(</span><span class="n">shape</span><span class="p">)]</span><span class="o">*</span><span class="nb">len</span><span class="p">(</span><span class="n">keys</span><span class="p">))</span>
</pre></div>
</div>
</dd></dl>
<dl class="method">
<dt id="mxnet.kvstore.KVStore.push">
<code class="descname">push</code><span class="sig-paren">(</span><em>key</em>, <em>value</em>, <em>priority=0</em><span class="sig-paren">)</span><a class="headerlink" href="#mxnet.kvstore.KVStore.push" title="Permalink to this definition"></a></dt>
<dd><p>Pushes a single or a sequence of key-value pairs into the store.</p>
<p>This function returns immediately after adding an operator to the engine.
The actual operation is executed asynchronously after all previous <cite>push</cite>
and <cite>pull</cite> calls for the same input key(s) are finished.
There is no synchronization between workers. One can use <code class="docutils literal"><span class="pre">_barrier()</span></code>
to sync all workers.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name"/>
<col class="field-body"/>
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first last simple">
<li><strong>key</strong> (<em>str or list of str</em>) – Keys.</li>
<li><strong>value</strong> (<em>NDArray or list of NDArray or list of list of NDArray</em>) – Values corresponding to the keys.</li>
<li><strong>priority</strong> (<em>int, optional</em>) – The priority of the push operation.
Higher priority push operations are likely to be executed before
other push actions.</li>
</ul>
</td>
</tr>
</tbody>
</table>
<p class="rubric">Examples</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="c1"># push a single key-value pair</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">push</span><span class="p">(</span><span class="s1">'3'</span><span class="p">,</span> <span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">ones</span><span class="p">(</span><span class="n">shape</span><span class="p">)</span><span class="o">*</span><span class="mi">8</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">pull</span><span class="p">(</span><span class="s1">'3'</span><span class="p">,</span> <span class="n">out</span><span class="o">=</span><span class="n">a</span><span class="p">)</span> <span class="c1"># pull out the value</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">a</span><span class="o">.</span><span class="n">asnumpy</span><span class="p">()</span>
<span class="go">[[ 8. 8. 8.]</span>
<span class="go">[ 8. 8. 8.]]</span>
</pre></div>
</div>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="c1"># aggregate the value and the push</span>
<span class="gp">>>> </span><span class="n">gpus</span> <span class="o">=</span> <span class="p">[</span><span class="n">mx</span><span class="o">.</span><span class="n">gpu</span><span class="p">(</span><span class="n">i</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">4</span><span class="p">)]</span>
<span class="gp">>>> </span><span class="n">b</span> <span class="o">=</span> <span class="p">[</span><span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">ones</span><span class="p">(</span><span class="n">shape</span><span class="p">,</span> <span class="n">gpu</span><span class="p">)</span> <span class="k">for</span> <span class="n">gpu</span> <span class="ow">in</span> <span class="n">gpus</span><span class="p">]</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">push</span><span class="p">(</span><span class="s1">'3'</span><span class="p">,</span> <span class="n">b</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">pull</span><span class="p">(</span><span class="s1">'3'</span><span class="p">,</span> <span class="n">out</span><span class="o">=</span><span class="n">a</span><span class="p">)</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">a</span><span class="o">.</span><span class="n">asnumpy</span><span class="p">()</span>
<span class="go">[[ 4. 4. 4.]</span>
<span class="go">[ 4. 4. 4.]]</span>
</pre></div>
</div>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="c1"># push a list of keys.</span>
<span class="gp">>>> </span><span class="c1"># single device</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">push</span><span class="p">(</span><span class="n">keys</span><span class="p">,</span> <span class="p">[</span><span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">ones</span><span class="p">(</span><span class="n">shape</span><span class="p">)]</span><span class="o">*</span><span class="nb">len</span><span class="p">(</span><span class="n">keys</span><span class="p">))</span>
<span class="gp">>>> </span><span class="n">b</span> <span class="o">=</span> <span class="p">[</span><span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">zeros</span><span class="p">(</span><span class="n">shape</span><span class="p">)]</span><span class="o">*</span><span class="nb">len</span><span class="p">(</span><span class="n">keys</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">pull</span><span class="p">(</span><span class="n">keys</span><span class="p">,</span> <span class="n">out</span><span class="o">=</span><span class="n">b</span><span class="p">)</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">b</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">asnumpy</span><span class="p">()</span>
<span class="go">[[ 1. 1. 1.]</span>
<span class="go">[ 1. 1. 1.]]</span>
</pre></div>
</div>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="c1"># multiple devices:</span>
<span class="gp">>>> </span><span class="n">b</span> <span class="o">=</span> <span class="p">[[</span><span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">ones</span><span class="p">(</span><span class="n">shape</span><span class="p">,</span> <span class="n">gpu</span><span class="p">)</span> <span class="k">for</span> <span class="n">gpu</span> <span class="ow">in</span> <span class="n">gpus</span><span class="p">]]</span> <span class="o">*</span> <span class="nb">len</span><span class="p">(</span><span class="n">keys</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">push</span><span class="p">(</span><span class="n">keys</span><span class="p">,</span> <span class="n">b</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">pull</span><span class="p">(</span><span class="n">keys</span><span class="p">,</span> <span class="n">out</span><span class="o">=</span><span class="n">b</span><span class="p">)</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">b</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="o">.</span><span class="n">asnumpy</span><span class="p">()</span>
<span class="go">[[ 4. 4. 4.]</span>
<span class="go">[ 4. 4. 4.]]</span>
</pre></div>
</div>
</dd></dl>
<dl class="method">
<dt id="mxnet.kvstore.KVStore.pull">
<code class="descname">pull</code><span class="sig-paren">(</span><em>key</em>, <em>out=None</em>, <em>priority=0</em><span class="sig-paren">)</span><a class="headerlink" href="#mxnet.kvstore.KVStore.pull" title="Permalink to this definition"></a></dt>
<dd><p>Pulls a single value or a sequence of values from the store.</p>
<p>This function returns immediately after adding an operator to the engine.
Subsequent attempts to read from the <cite>out</cite> variable will be blocked until the
pull operation completes.</p>
<p><cite>pull</cite> is executed asynchronously after all previous <cite>push</cite> and <cite>pull</cite> calls
for the same input key(s) are finished.</p>
<p>The returned values are gauranteed to be the latest values in the store.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name"/>
<col class="field-body"/>
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first last simple">
<li><strong>key</strong> (<em>int or list of int</em>) – Keys.</li>
<li><strong>out</strong> (<em>NDArray or list of NDArray or list of list of NDArray</em>) – Values corresponding to the keys.</li>
<li><strong>priority</strong> (<em>int, optional</em>) – The priority of the pull operation.
Higher priority pull operations are likely to be executed before
other pull actions.</li>
</ul>
</td>
</tr>
</tbody>
</table>
<p class="rubric">Examples</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="c1"># pull a single key-value pair</span>
<span class="gp">>>> </span><span class="n">a</span> <span class="o">=</span> <span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">zeros</span><span class="p">(</span><span class="n">shape</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">pull</span><span class="p">(</span><span class="s1">'3'</span><span class="p">,</span> <span class="n">out</span><span class="o">=</span><span class="n">a</span><span class="p">)</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">a</span><span class="o">.</span><span class="n">asnumpy</span><span class="p">()</span>
<span class="go">[[ 2. 2. 2.]</span>
<span class="go">[ 2. 2. 2.]]</span>
</pre></div>
</div>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="c1"># pull into multiple devices</span>
<span class="gp">>>> </span><span class="n">b</span> <span class="o">=</span> <span class="p">[</span><span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">ones</span><span class="p">(</span><span class="n">shape</span><span class="p">,</span> <span class="n">gpu</span><span class="p">)</span> <span class="k">for</span> <span class="n">gpu</span> <span class="ow">in</span> <span class="n">gpus</span><span class="p">]</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">pull</span><span class="p">(</span><span class="s1">'3'</span><span class="p">,</span> <span class="n">out</span><span class="o">=</span><span class="n">b</span><span class="p">)</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">b</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">asnumpy</span><span class="p">()</span>
<span class="go">[[ 2. 2. 2.]</span>
<span class="go">[ 2. 2. 2.]]</span>
</pre></div>
</div>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="c1"># pull a list of key-value pairs.</span>
<span class="gp">>>> </span><span class="c1"># On single device</span>
<span class="gp">>>> </span><span class="n">keys</span> <span class="o">=</span> <span class="p">[</span><span class="s1">'5'</span><span class="p">,</span> <span class="s1">'7'</span><span class="p">,</span> <span class="s1">'9'</span><span class="p">]</span>
<span class="gp">>>> </span><span class="n">b</span> <span class="o">=</span> <span class="p">[</span><span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">zeros</span><span class="p">(</span><span class="n">shape</span><span class="p">)]</span><span class="o">*</span><span class="nb">len</span><span class="p">(</span><span class="n">keys</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">pull</span><span class="p">(</span><span class="n">keys</span><span class="p">,</span> <span class="n">out</span><span class="o">=</span><span class="n">b</span><span class="p">)</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">b</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">asnumpy</span><span class="p">()</span>
<span class="go">[[ 2. 2. 2.]</span>
<span class="go">[ 2. 2. 2.]]</span>
<span class="gp">>>> </span><span class="c1"># On multiple devices</span>
<span class="gp">>>> </span><span class="n">b</span> <span class="o">=</span> <span class="p">[[</span><span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">ones</span><span class="p">(</span><span class="n">shape</span><span class="p">,</span> <span class="n">gpu</span><span class="p">)</span> <span class="k">for</span> <span class="n">gpu</span> <span class="ow">in</span> <span class="n">gpus</span><span class="p">]]</span> <span class="o">*</span> <span class="nb">len</span><span class="p">(</span><span class="n">keys</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">pull</span><span class="p">(</span><span class="n">keys</span><span class="p">,</span> <span class="n">out</span><span class="o">=</span><span class="n">b</span><span class="p">)</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">b</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="o">.</span><span class="n">asnumpy</span><span class="p">()</span>
<span class="go">[[ 2. 2. 2.]</span>
<span class="go">[ 2. 2. 2.]]</span>
</pre></div>
</div>
</dd></dl>
<dl class="method">
<dt id="mxnet.kvstore.KVStore.set_optimizer">
<code class="descname">set_optimizer</code><span class="sig-paren">(</span><em>optimizer</em><span class="sig-paren">)</span><a class="headerlink" href="#mxnet.kvstore.KVStore.set_optimizer" title="Permalink to this definition"></a></dt>
<dd><p>Registers an optimizer with the kvstore.</p>
<p>When using a single machine, this function updates the local optimizer.
If using multiple machines and this operation is invoked from a worker node,
it will serialized the optimizer with pickle and send it to all servers.
The function returns after all servers have been updated.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name"/>
<col class="field-body"/>
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><strong>optimizer</strong> (<a class="reference internal" href="optimization.html#mxnet.optimizer.Optimizer" title="mxnet.optimizer.Optimizer"><em>Optimizer</em></a>) – The new optimizer for the store</td>
</tr>
</tbody>
</table>
<p class="rubric">Examples</p>
<div class="highlight-python"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">kv</span> <span class="o">=</span> <span class="n">mx</span><span class="o">.</span><span class="n">kv</span><span class="o">.</span><span class="n">create</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">shape</span> <span class="o">=</span> <span class="p">(</span><span class="mi">2</span><span class="p">,</span> <span class="mi">2</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">weight</span> <span class="o">=</span> <span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">zeros</span><span class="p">(</span><span class="n">shape</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">init</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="n">weight</span><span class="p">)</span>
<span class="gp">>>> </span><span class="c1"># set the optimizer for kvstore as the default SGD optimizer</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">set_optimizer</span><span class="p">(</span><span class="n">mx</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="gp">>>> </span><span class="n">grad</span> <span class="o">=</span> <span class="n">mx</span><span class="o">.</span><span class="n">nd</span><span class="o">.</span><span class="n">ones</span><span class="p">(</span><span class="n">shape</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">push</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="n">grad</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">kv</span><span class="o">.</span><span class="n">pull</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="n">out</span> <span class="o">=</span> <span class="n">weight</span><span class="p">)</span>
<span class="gp">>>> </span><span class="c1"># weight is updated via gradient descent</span>
<span class="gp">>>> </span><span class="n">weight</span><span class="o">.</span><span class="n">asnumpy</span><span class="p">()</span>
<span class="go">array([[-0.01, -0.01],</span>
<span class="go"> [-0.01, -0.01]], dtype=float32)</span>
</pre></div>
</div>
</dd></dl>
<dl class="attribute">
<dt id="mxnet.kvstore.KVStore.type">
<code class="descname">type</code><a class="headerlink" href="#mxnet.kvstore.KVStore.type" title="Permalink to this definition"></a></dt>
<dd><p>Returns the type of this kvstore.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name"/>
<col class="field-body"/>
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Returns:</th><td class="field-body"><strong>type</strong> –
the string type</td>
</tr>
<tr class="field-even field"><th class="field-name">Return type:</th><td class="field-body">str</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="attribute">
<dt id="mxnet.kvstore.KVStore.rank">
<code class="descname">rank</code><a class="headerlink" href="#mxnet.kvstore.KVStore.rank" title="Permalink to this definition"></a></dt>
<dd><p>Returns the rank of this worker node.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name"/>
<col class="field-body"/>
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Returns:</th><td class="field-body"><strong>rank</strong> –
The rank of this node, which is in range [0, num_workers())</td>
</tr>
<tr class="field-even field"><th class="field-name">Return type:</th><td class="field-body">int</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="attribute">
<dt id="mxnet.kvstore.KVStore.num_workers">
<code class="descname">num_workers</code><a class="headerlink" href="#mxnet.kvstore.KVStore.num_workers" title="Permalink to this definition"></a></dt>
<dd><p>Returns the number of worker nodes.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name"/>
<col class="field-body"/>
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Returns:</th><td class="field-body"><strong>size</strong> –
The number of worker nodes.</td>
</tr>
<tr class="field-even field"><th class="field-name">Return type:</th><td class="field-body">int</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="method">
<dt id="mxnet.kvstore.KVStore.save_optimizer_states">
<code class="descname">save_optimizer_states</code><span class="sig-paren">(</span><em>fname</em><span class="sig-paren">)</span><a class="headerlink" href="#mxnet.kvstore.KVStore.save_optimizer_states" title="Permalink to this definition"></a></dt>
<dd><p>Saves the optimizer (updater) state to a file. This is often used when checkpointing
the model during training.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name"/>
<col class="field-body"/>
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><strong>fname</strong> (<em>str</em>) – Path to the output states file.</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="method">
<dt id="mxnet.kvstore.KVStore.load_optimizer_states">
<code class="descname">load_optimizer_states</code><span class="sig-paren">(</span><em>fname</em><span class="sig-paren">)</span><a class="headerlink" href="#mxnet.kvstore.KVStore.load_optimizer_states" title="Permalink to this definition"></a></dt>
<dd><p>Loads the optimizer (updater) state from the file.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name"/>
<col class="field-body"/>
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><strong>fname</strong> (<em>str</em>) – Path to input states file.</td>
</tr>
</tbody>
</table>
</dd></dl>
</dd></dl>
<dl class="function">
<dt id="mxnet.kvstore.create">
<code class="descclassname">mxnet.kvstore.</code><code class="descname">create</code><span class="sig-paren">(</span><em>name='local'</em><span class="sig-paren">)</span><a class="headerlink" href="#mxnet.kvstore.create" title="Permalink to this definition"></a></dt>
<dd><p>Creates a new KVStore.</p>
<p>For single machine training, there are two commonly used types:</p>
<p><code class="docutils literal"><span class="pre">local</span></code>: Copies all gradients to CPU memory and updates weights there.</p>
<p><code class="docutils literal"><span class="pre">device</span></code>: Aggregates gradients and updates weights on GPUs. With this setting,
the KVStore also attempts to use GPU peer-to-peer communication,
potentially accelerating the communication.</p>
<p>For distributed training, KVStore also supports a number of types:</p>
<p><code class="docutils literal"><span class="pre">dist_sync</span></code>: Behaves similarly to <code class="docutils literal"><span class="pre">local</span></code> but with one major difference.
With <code class="docutils literal"><span class="pre">dist_sync</span></code>, batch-size now means the batch size used on each machine.
So if there are <code class="docutils literal"><span class="pre">n</span></code> machines and we use batch size <code class="docutils literal"><span class="pre">b</span></code>,
then <code class="docutils literal"><span class="pre">dist_sync</span></code> behaves like <code class="docutils literal"><span class="pre">local</span></code> with batch size <code class="docutils literal"><span class="pre">n</span> <span class="pre">*</span> <span class="pre">b</span></code>.</p>
<p><code class="docutils literal"><span class="pre">dist_device_sync</span></code>: Identical to <code class="docutils literal"><span class="pre">dist_sync</span></code> with the difference similar
to <code class="docutils literal"><span class="pre">device</span></code> vs <code class="docutils literal"><span class="pre">local</span></code>.</p>
<p><code class="docutils literal"><span class="pre">dist_async</span></code>: Performs asynchronous updates.
The weights are updated whenever gradients are received from any machine.
No two updates happen on the same weight at the same time. However, the order is not
guaranteed.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name"/>
<col class="field-body"/>
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><strong>name</strong> (<em>{'local', 'device', 'dist_sync', 'dist_device_sync', 'dist_async'}</em>) – The type of KVStore.</td>
</tr>
<tr class="field-even field"><th class="field-name">Returns:</th><td class="field-body"><strong>kv</strong> –
The created KVStore.</td>
</tr>
<tr class="field-odd field"><th class="field-name">Return type:</th><td class="field-body"><a class="reference internal" href="#mxnet.kvstore.KVStore" title="mxnet.kvstore.KVStore">KVStore</a></td>
</tr>
</tbody>
</table>
</dd></dl>
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<h3><a href="../../index.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">KVStore API</a><ul>
<li><a class="reference internal" href="#basic-push-and-pull">Basic Push and Pull</a><ul>
<li><a class="reference internal" href="#initialization">Initialization</a></li>
<li><a class="reference internal" href="#push-aggregation-and-updater">Push, Aggregation, and Updater</a></li>
<li><a class="reference internal" href="#pull">Pull</a></li>
</ul>
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<li><a class="reference internal" href="#list-key-value-pairs">List Key-Value Pairs</a></li>
<li><a class="reference internal" href="#api-reference">API Reference</a></li>
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