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    <title>Interface IComputeTask&lt;TArg, TJobRes, TRes&gt;
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            <article class="content wrap" id="_content" data-uid="Apache.Ignite.Core.Compute.IComputeTask`3">
  
  
  <h1 id="Apache_Ignite_Core_Compute_IComputeTask_3" data-uid="Apache.Ignite.Core.Compute.IComputeTask`3" class="text-break">Interface IComputeTask&lt;TArg, TJobRes, TRes&gt;
  </h1>
  <div class="markdown level0 summary"><p>Ignite task interface defines a task that can be executed on the grid. Ignite task
is responsible for splitting business logic into multiple Ignite jobs, receiving
results from individual Ignite jobs executing on remote nodes, and reducing
(aggregating) received jobs&apos; results into final Ignite task result.
<p>
Upon request to execute a task, the system will do the following:
<ul><li>Inject annotated resources into task instance.</li><li>Apply <a class="xref" href="Apache.Ignite.Core.Compute.IComputeTask-3.html#Apache_Ignite_Core_Compute_IComputeTask_3_Map_System_Collections_Generic_IList_Apache_Ignite_Core_Cluster_IClusterNode___0_">Map(IList&lt;IClusterNode&gt;, TArg)</a>.
        This method is responsible for splitting business logic into multiple jobs 
        (units of execution) and mapping them to Ignite nodes.</li><li>System will send mapped Ignite jobs to their respective nodes.</li><li>Once job execution results become available, <a class="xref" href="Apache.Ignite.Core.Compute.IComputeTask-3.html#Apache_Ignite_Core_Compute_IComputeTask_3_OnResult_Apache_Ignite_Core_Compute_IComputeJobResult__1__System_Collections_Generic_IList_Apache_Ignite_Core_Compute_IComputeJobResult__1___">OnResult(IComputeJobResult&lt;TJobRes&gt;, IList&lt;IComputeJobResult&lt;TJobRes&gt;&gt;)</a> method
        will be called for ech received job result. The policy returned by this method will
        determine the way task reacts to every job result.
<p>
If <a class="xref" href="Apache.Ignite.Core.Compute.ComputeJobResultPolicy.html#Apache_Ignite_Core_Compute_ComputeJobResultPolicy_Wait">Wait</a> is returned, task will continue to wait
for other job results. If this result is the last job result, then reduce phase will be
started.
<p>
If <a class="xref" href="Apache.Ignite.Core.Compute.ComputeJobResultPolicy.html#Apache_Ignite_Core_Compute_ComputeJobResultPolicy_Reduce">Reduce</a> is returned, reduce phase will be started
right away without waiting for other jobs completion (all remaining jobs will receive cancel 
request).
<p>
If <a class="xref" href="Apache.Ignite.Core.Compute.ComputeJobResultPolicy.html#Apache_Ignite_Core_Compute_ComputeJobResultPolicy_Failover">Failover</a> is returned, job will be failed over to 
another node for execution. Note that if you use <a class="xref" href="Apache.Ignite.Core.Compute.ComputeTaskAdapter-3.html">ComputeTaskAdapter&lt;TArg, TJobRes, TTaskRes&gt;</a>, it will
automatically fail jobs to another node for 2 well-known failure cases: 1) job has failed to due
to node crash (in this case <a class="xref" href="Apache.Ignite.Core.Compute.IComputeJobResult-1.html#Apache_Ignite_Core_Compute_IComputeJobResult_1_Exception">Exception</a> will return 
<a class="xref" href="Apache.Ignite.Core.Cluster.ClusterTopologyException.html">ClusterTopologyException</a>); 2) job execution was rejected, i.e. remote node 
has cancelled job before it got a chance to execute, while it still was on the waiting list. 
(in this case <a class="xref" href="Apache.Ignite.Core.Compute.IComputeJobResult-1.html#Apache_Ignite_Core_Compute_IComputeJobResult_1_Exception">Exception</a> will return 
<a class="xref" href="Apache.Ignite.Core.Compute.ComputeExecutionRejectedException.html">ComputeExecutionRejectedException</a>).
</li><li>Once all results are received or  <a class="xref" href="Apache.Ignite.Core.Compute.IComputeTask-3.html#Apache_Ignite_Core_Compute_IComputeTask_3_OnResult_Apache_Ignite_Core_Compute_IComputeJobResult__1__System_Collections_Generic_IList_Apache_Ignite_Core_Compute_IComputeJobResult__1___">OnResult(IComputeJobResult&lt;TJobRes&gt;, IList&lt;IComputeJobResult&lt;TJobRes&gt;&gt;)</a>
method returned <a class="xref" href="Apache.Ignite.Core.Compute.ComputeJobResultPolicy.html#Apache_Ignite_Core_Compute_ComputeJobResultPolicy_Reduce">Reduce</a> policy, method <a class="xref" href="Apache.Ignite.Core.Compute.IComputeTask-3.html#Apache_Ignite_Core_Compute_IComputeTask_3_Reduce_System_Collections_Generic_IList_Apache_Ignite_Core_Compute_IComputeJobResult__1___">Reduce(IList&lt;IComputeJobResult&lt;TJobRes&gt;&gt;)</a>
is called to aggregate received results into one final result. Once this method is finished the 
execution of the Ignite task is complete. This result will be returned to the user through future.
</li></ul></p>
</div>
  <div class="markdown level0 conceptual"></div>
  <h6><strong>Namespace</strong>: <a class="xref" href="Apache.Ignite.Core.Compute.html">Apache.Ignite.Core.Compute</a></h6>
  <h6><strong>Assembly</strong>: Apache.Ignite.Core.dll</h6>
  <h5 id="Apache_Ignite_Core_Compute_IComputeTask_3_syntax">Syntax</h5>
  <div class="codewrapper">
    <pre><code class="lang-csharp hljs">public interface IComputeTask&lt;in TArg, TJobRes, out TRes&gt;</code></pre>
  </div>
  <h5 class="typeParameters">Type Parameters</h5>
  <table class="table table-bordered table-striped table-condensed">
    <thead>
      <tr>
        <th>Name</th>
        <th>Description</th>
      </tr>
    </thead>
    <tbody>
      <tr>
        <td><span class="parametername">TArg</span></td>
        <td><p>Argument type.</p>
</td>
      </tr>
      <tr>
        <td><span class="parametername">TJobRes</span></td>
        <td><p>Type of job result.</p>
</td>
      </tr>
      <tr>
        <td><span class="parametername">TRes</span></td>
        <td><p>Type of final task result after reduce.</p>
</td>
      </tr>
    </tbody>
  </table>
  <h3 id="methods">Methods
  </h3>
  <a id="Apache_Ignite_Core_Compute_IComputeTask_3_Map_" data-uid="Apache.Ignite.Core.Compute.IComputeTask`3.Map*"></a>
  <h4 id="Apache_Ignite_Core_Compute_IComputeTask_3_Map_System_Collections_Generic_IList_Apache_Ignite_Core_Cluster_IClusterNode___0_" data-uid="Apache.Ignite.Core.Compute.IComputeTask`3.Map(System.Collections.Generic.IList{Apache.Ignite.Core.Cluster.IClusterNode},`0)">Map(IList&lt;IClusterNode&gt;, TArg)</h4>
  <div class="markdown level1 summary"><p>This method is called to map or split Ignite task into multiple Ignite jobs. This is the
first method that gets called when task execution starts.</p>
</div>
  <div class="markdown level1 conceptual"></div>
  <h5 class="decalaration">Declaration</h5>
  <div class="codewrapper">
    <pre><code class="lang-csharp hljs">IDictionary&lt;IComputeJob&lt;TJobRes&gt;, IClusterNode&gt; Map(IList&lt;IClusterNode&gt; subgrid, TArg arg)</code></pre>
  </div>
  <h5 class="parameters">Parameters</h5>
  <table class="table table-bordered table-striped table-condensed">
    <thead>
      <tr>
        <th>Type</th>
        <th>Name</th>
        <th>Description</th>
      </tr>
    </thead>
    <tbody>
      <tr>
        <td><span class="xref">System.Collections.Generic.IList</span>&lt;<a class="xref" href="Apache.Ignite.Core.Cluster.IClusterNode.html">IClusterNode</a>&gt;</td>
        <td><span class="parametername">subgrid</span></td>
        <td><p>Nodes available for this task execution. Note that order of nodes is
guaranteed to be randomized by container. This ensures that every time you simply iterate 
through Ignite nodes, the order of nodes will be random which over time should result into 
all nodes being used equally.</p>
</td>
      </tr>
      <tr>
        <td><span class="xref">TArg</span></td>
        <td><span class="parametername">arg</span></td>
        <td><p>Task execution argument. Can be <code>null</code>. This is the same argument
as the one passed into <code>ICompute.Execute()</code> methods.</p>
</td>
      </tr>
    </tbody>
  </table>
  <h5 class="returns">Returns</h5>
  <table class="table table-bordered table-striped table-condensed">
    <thead>
      <tr>
        <th>Type</th>
        <th>Description</th>
      </tr>
    </thead>
    <tbody>
      <tr>
        <td><span class="xref">System.Collections.Generic.IDictionary</span>&lt;<a class="xref" href="Apache.Ignite.Core.Compute.IComputeJob-1.html">IComputeJob</a>&lt;TJobRes&gt;, <a class="xref" href="Apache.Ignite.Core.Cluster.IClusterNode.html">IClusterNode</a>&gt;</td>
        <td><p>Map of Ignite jobs assigned to subgrid node. If <code>null</code> or empty map is returned,
exception will be thrown.</p>
</td>
      </tr>
    </tbody>
  </table>
  <a id="Apache_Ignite_Core_Compute_IComputeTask_3_OnResult_" data-uid="Apache.Ignite.Core.Compute.IComputeTask`3.OnResult*"></a>
  <h4 id="Apache_Ignite_Core_Compute_IComputeTask_3_OnResult_Apache_Ignite_Core_Compute_IComputeJobResult__1__System_Collections_Generic_IList_Apache_Ignite_Core_Compute_IComputeJobResult__1___" data-uid="Apache.Ignite.Core.Compute.IComputeTask`3.OnResult(Apache.Ignite.Core.Compute.IComputeJobResult{`1},System.Collections.Generic.IList{Apache.Ignite.Core.Compute.IComputeJobResult{`1}})">OnResult(IComputeJobResult&lt;TJobRes&gt;, IList&lt;IComputeJobResult&lt;TJobRes&gt;&gt;)</h4>
  <div class="markdown level1 summary"><p>Asynchronous callback invoked every time a result from remote execution is
received. It is ultimately upto this method to return a policy based
on which the system will either wait for more results, reduce results
received so far, or failover this job to another node. See 
<a class="xref" href="Apache.Ignite.Core.Compute.ComputeJobResultPolicy.html">ComputeJobResultPolicy</a> for more information.</p>
</div>
  <div class="markdown level1 conceptual"></div>
  <h5 class="decalaration">Declaration</h5>
  <div class="codewrapper">
    <pre><code class="lang-csharp hljs">ComputeJobResultPolicy OnResult(IComputeJobResult&lt;TJobRes&gt; res, IList&lt;IComputeJobResult&lt;TJobRes&gt;&gt; rcvd)</code></pre>
  </div>
  <h5 class="parameters">Parameters</h5>
  <table class="table table-bordered table-striped table-condensed">
    <thead>
      <tr>
        <th>Type</th>
        <th>Name</th>
        <th>Description</th>
      </tr>
    </thead>
    <tbody>
      <tr>
        <td><a class="xref" href="Apache.Ignite.Core.Compute.IComputeJobResult-1.html">IComputeJobResult</a>&lt;TJobRes&gt;</td>
        <td><span class="parametername">res</span></td>
        <td><p>Received remote Ignite executable result.</p>
</td>
      </tr>
      <tr>
        <td><span class="xref">System.Collections.Generic.IList</span>&lt;<a class="xref" href="Apache.Ignite.Core.Compute.IComputeJobResult-1.html">IComputeJobResult</a>&lt;TJobRes&gt;&gt;</td>
        <td><span class="parametername">rcvd</span></td>
        <td><p>All previously received results. Note that if task class has
<a class="xref" href="Apache.Ignite.Core.Compute.ComputeTaskNoResultCacheAttribute.html">ComputeTaskNoResultCacheAttribute</a> attribute, then this list will be empty.</p>
</td>
      </tr>
    </tbody>
  </table>
  <h5 class="returns">Returns</h5>
  <table class="table table-bordered table-striped table-condensed">
    <thead>
      <tr>
        <th>Type</th>
        <th>Description</th>
      </tr>
    </thead>
    <tbody>
      <tr>
        <td><a class="xref" href="Apache.Ignite.Core.Compute.ComputeJobResultPolicy.html">ComputeJobResultPolicy</a></td>
        <td><p>Result policy that dictates how to process further upcoming job results.</p>
</td>
      </tr>
    </tbody>
  </table>
  <a id="Apache_Ignite_Core_Compute_IComputeTask_3_Reduce_" data-uid="Apache.Ignite.Core.Compute.IComputeTask`3.Reduce*"></a>
  <h4 id="Apache_Ignite_Core_Compute_IComputeTask_3_Reduce_System_Collections_Generic_IList_Apache_Ignite_Core_Compute_IComputeJobResult__1___" data-uid="Apache.Ignite.Core.Compute.IComputeTask`3.Reduce(System.Collections.Generic.IList{Apache.Ignite.Core.Compute.IComputeJobResult{`1}})">Reduce(IList&lt;IComputeJobResult&lt;TJobRes&gt;&gt;)</h4>
  <div class="markdown level1 summary"><p>Reduces (or aggregates) results received so far into one compound result to be returned to 
caller via future.
<p>
Note, that if some jobs did not succeed and could not be failed over then the list of
results passed into this method will include the failed results. Otherwise, failed
results will not be in the list.</p>
</div>
  <div class="markdown level1 conceptual"></div>
  <h5 class="decalaration">Declaration</h5>
  <div class="codewrapper">
    <pre><code class="lang-csharp hljs">TRes Reduce(IList&lt;IComputeJobResult&lt;TJobRes&gt;&gt; results)</code></pre>
  </div>
  <h5 class="parameters">Parameters</h5>
  <table class="table table-bordered table-striped table-condensed">
    <thead>
      <tr>
        <th>Type</th>
        <th>Name</th>
        <th>Description</th>
      </tr>
    </thead>
    <tbody>
      <tr>
        <td><span class="xref">System.Collections.Generic.IList</span>&lt;<a class="xref" href="Apache.Ignite.Core.Compute.IComputeJobResult-1.html">IComputeJobResult</a>&lt;TJobRes&gt;&gt;</td>
        <td><span class="parametername">results</span></td>
        <td><p>Received job results. Note that if task class has 
<a class="xref" href="Apache.Ignite.Core.Compute.ComputeTaskNoResultCacheAttribute.html">ComputeTaskNoResultCacheAttribute</a> attribute, then this list will be empty.</p>
</td>
      </tr>
    </tbody>
  </table>
  <h5 class="returns">Returns</h5>
  <table class="table table-bordered table-striped table-condensed">
    <thead>
      <tr>
        <th>Type</th>
        <th>Description</th>
      </tr>
    </thead>
    <tbody>
      <tr>
        <td><span class="xref">TRes</span></td>
        <td><p>Task result constructed from results of remote executions.</p>
</td>
      </tr>
    </tbody>
  </table>
</article>
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