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<divclass="title">subsolver.h</div></div>
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<ahref="subsolver_8h.html">Go to the documentation of this file.</a><divclass="fragment"><divclass="line"><aname="l00001"></a><spanclass="lineno"> 1</span> <spanclass="comment">// Copyright 2010-2018 Google LLC</span></div>
<divclass="line"><aname="l00002"></a><spanclass="lineno"> 2</span> <spanclass="comment">// Licensed under the Apache License, Version 2.0 (the "License");</span></div>
<divclass="line"><aname="l00003"></a><spanclass="lineno"> 3</span> <spanclass="comment">// you may not use this file except in compliance with the License.</span></div>
<divclass="line"><aname="l00004"></a><spanclass="lineno"> 4</span> <spanclass="comment">// You may obtain a copy of the License at</span></div>
<divclass="line"><aname="l00008"></a><spanclass="lineno"> 8</span> <spanclass="comment">// Unless required by applicable law or agreed to in writing, software</span></div>
<divclass="line"><aname="l00009"></a><spanclass="lineno"> 9</span> <spanclass="comment">// distributed under the License is distributed on an "AS IS" BASIS,</span></div>
<divclass="line"><aname="l00010"></a><spanclass="lineno"> 10</span> <spanclass="comment">// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.</span></div>
<divclass="line"><aname="l00011"></a><spanclass="lineno"> 11</span> <spanclass="comment">// See the License for the specific language governing permissions and</span></div>
<divclass="line"><aname="l00012"></a><spanclass="lineno"> 12</span> <spanclass="comment">// limitations under the License.</span></div>
<divclass="line"><aname="l00014"></a><spanclass="lineno"> 14</span> <spanclass="comment">// Simple framework for choosing and distributing a solver "sub-tasks" on a set</span></div>
<divclass="line"><aname="l00015"></a><spanclass="lineno"> 15</span> <spanclass="comment">// of threads.</span></div>
<divclass="line"><aname="l00036"></a><spanclass="lineno"> 36</span> <spanclass="comment">// The API used for distributing work. Each subsolver can generate tasks and</span></div>
<divclass="line"><aname="l00037"></a><spanclass="lineno"> 37</span> <spanclass="comment">// synchronize itself with the rest of the world.</span></div>
<divclass="line"><aname="l00039"></a><spanclass="lineno"> 39</span> <spanclass="comment">// Note that currently only the main thread interact with subsolvers. Only the</span></div>
<divclass="line"><aname="l00040"></a><spanclass="lineno"> 40</span> <spanclass="comment">// tasks generated by GenerateTask() are executed in parallel in a threadpool.</span></div>
<divclass="line"><aname="l00046"></a><spanclass="lineno"> 46</span> <spanclass="comment">// Returns true iff GenerateTask() can be called.</span></div>
<divclass="line"><aname="l00048"></a><spanclass="lineno"> 48</span> <spanclass="comment">// Note(user): In the current design, a SubSolver is never deleted until the</span></div>
<divclass="line"><aname="l00049"></a><spanclass="lineno"> 49</span> <spanclass="comment">// end of the Solve() that created it. But is is okay to always return false</span></div>
<divclass="line"><aname="l00050"></a><spanclass="lineno"> 50</span> <spanclass="comment">// here and release the memory used by the Subsolver internal if there is no</span></div>
<divclass="line"><aname="l00051"></a><spanclass="lineno"> 51</span> <spanclass="comment">// need to call this Subsolver ever again. The overhead of iterating over it</span></div>
<divclass="line"><aname="l00052"></a><spanclass="lineno"> 52</span> <spanclass="comment">// in the main solver loop should be minimal.</span></div>
<divclass="line"><aname="l00055"></a><spanclass="lineno"> 55</span> <spanclass="comment">// Returns a task to run. The task_id is just an ever increasing counter that</span></div>
<divclass="line"><aname="l00056"></a><spanclass="lineno"> 56</span> <spanclass="comment">// correspond to the number of total calls to GenerateTask().</span></div>
<divclass="line"><aname="l00058"></a><spanclass="lineno"> 58</span> <spanclass="comment">// TODO(user): We could use a more complex selection logic and pass in the</span></div>
<divclass="line"><aname="l00059"></a><spanclass="lineno"> 59</span> <spanclass="comment">// deterministic time limit this subtask should run for. Unclear at this</span></div>
<divclass="line"><aname="l00063"></a><spanclass="lineno"> 63</span> <spanclass="comment">// Synchronizes with the external world from this SubSolver point of view.</span></div>
<divclass="line"><aname="l00064"></a><spanclass="lineno"> 64</span> <spanclass="comment">// Also incorporate the results of the latest completed tasks if any.</span></div>
<divclass="line"><aname="l00066"></a><spanclass="lineno"> 66</span> <spanclass="comment">// Note(user): The intended implementation for determinism is that tasks</span></div>
<divclass="line"><aname="l00067"></a><spanclass="lineno"> 67</span> <spanclass="comment">// update asynchronously (and so non-deterministically) global "shared"</span></div>
<divclass="line"><aname="l00068"></a><spanclass="lineno"> 68</span> <spanclass="comment">// classes, but this global state is incorporated by the Subsolver only when</span></div>
<divclass="line"><aname="l00069"></a><spanclass="lineno"> 69</span> <spanclass="comment">// Synchronize() is called.</span></div>
<divclass="line"><aname="l00072"></a><spanclass="lineno"> 72</span> <spanclass="comment">// Returns the score as updated by the completed tasks before the last</span></div>
<divclass="line"><aname="l00073"></a><spanclass="lineno"> 73</span> <spanclass="comment">// Synchronize() call. Everything else being equal, we prefer to run a</span></div>
<divclass="line"><aname="l00074"></a><spanclass="lineno"> 74</span> <spanclass="comment">// SubSolver with the highest score.</span></div>
<divclass="line"><aname="l00079"></a><spanclass="lineno"> 79</span> <spanclass="comment">// Returns the total deterministic time spend by the completed tasks before</span></div>
<divclass="line"><aname="l00080"></a><spanclass="lineno"> 80</span> <spanclass="comment">// the last Synchronize() call.</span></div>
<divclass="line"><aname="l00083"></a><spanclass="lineno"> 83</span> <spanclass="comment">// Returns the name of this SubSolver. Used in logs.</span></div>
<divclass="line"><aname="l00092"></a><spanclass="lineno"> 92</span> <spanclass="comment">// A simple wrapper to add a synchronization point in the list of subsolvers.</span></div>
<divclass="line"><aname="l00105"></a><spanclass="lineno"> 105</span> <spanclass="comment">// Executes the following loop:</span></div>
<divclass="line"><aname="l00106"></a><spanclass="lineno"> 106</span> <spanclass="comment">// 1/ Synchronize all in given order.</span></div>
<divclass="line"><aname="l00107"></a><spanclass="lineno"> 107</span> <spanclass="comment">// 2/ generate and schedule one task from the current "best" subsolver.</span></div>
<divclass="line"><aname="l00108"></a><spanclass="lineno"> 108</span> <spanclass="comment">// 3/ repeat until no extra task can be generated and all tasks are done.</span></div>
<divclass="line"><aname="l00110"></a><spanclass="lineno"> 110</span> <spanclass="comment">// The complexity of each selection is in O(num_subsolvers), but that should</span></div>
<divclass="line"><aname="l00111"></a><spanclass="lineno"> 111</span> <spanclass="comment">// be okay given that we don't expect more than 100 such subsolvers.</span></div>
<divclass="line"><aname="l00113"></a><spanclass="lineno"> 113</span> <spanclass="comment">// Note that it is okay to incorporate "special" subsolver that never produce</span></div>
<divclass="line"><aname="l00114"></a><spanclass="lineno"> 114</span> <spanclass="comment">// any tasks. This can be used to synchronize classes used by many subsolvers</span></div>
<divclass="line"><aname="l00115"></a><spanclass="lineno"> 115</span> <spanclass="comment">// just once for instance.</span></div>
<divclass="line"><aname="l00119"></a><spanclass="lineno"> 119</span> <spanclass="comment">// Similar to NonDeterministicLoop() except this should result in a</span></div>
<divclass="line"><aname="l00120"></a><spanclass="lineno"> 120</span> <spanclass="comment">// deterministic solver provided that all SubSolver respect the Synchronize()</span></div>
<divclass="line"><aname="l00123"></a><spanclass="lineno"> 123</span> <spanclass="comment">// Executes the following loop:</span></div>
<divclass="line"><aname="l00124"></a><spanclass="lineno"> 124</span> <spanclass="comment">// 1/ Synchronize all in given order.</span></div>
<divclass="line"><aname="l00125"></a><spanclass="lineno"> 125</span> <spanclass="comment">// 2/ generate and schedule up to batch_size tasks using an heuristic to select</span></div>
<divclass="line"><aname="l00126"></a><spanclass="lineno"> 126</span> <spanclass="comment">// which one to run.</span></div>
<divclass="line"><aname="l00127"></a><spanclass="lineno"> 127</span> <spanclass="comment">// 3/ wait for all task to finish.</span></div>
<divclass="line"><aname="l00128"></a><spanclass="lineno"> 128</span> <spanclass="comment">// 4/ repeat until no task can be generated in step 2.</span></div>
<divclass="line"><aname="l00133"></a><spanclass="lineno"> 133</span> <spanclass="comment">// Same as above, but specialized implementation for the case num_threads=1.</span></div>
<divclass="line"><aname="l00134"></a><spanclass="lineno"> 134</span> <spanclass="comment">// This avoids using a Threadpool altogether. It should have the same behavior</span></div>
<divclass="line"><aname="l00135"></a><spanclass="lineno"> 135</span> <spanclass="comment">// than the functions above with num_threads=1 and batch_size=1. Note that an</span></div>
<divclass="line"><aname="l00136"></a><spanclass="lineno"> 136</span> <spanclass="comment">// higher batch size will not behave in the same way, even if num_threads=1.</span></div>
<divclass="ttc"id="anamespaceoperations__research_1_1sat_html_a5174cbb2ba52f702d89b3a426b8b2780"><divclass="ttname"><ahref="namespaceoperations__research_1_1sat.html#a5174cbb2ba52f702d89b3a426b8b2780">operations_research::sat::DeterministicLoop</a></div><divclass="ttdeci">void DeterministicLoop(const std::vector< std::unique_ptr< SubSolver >>&subsolvers, int num_threads, int batch_size)</div><divclass="ttdef"><b>Definition:</b><ahref="subsolver_8cc_source.html#l00084">subsolver.cc:84</a></div></div>
<divclass="ttc"id="anamespaceoperations__research_html"><divclass="ttname"><ahref="namespaceoperations__research.html">operations_research</a></div><divclass="ttdoc">The vehicle routing library lets one model and solve generic vehicle routing problems ranging from th...</div><divclass="ttdef"><b>Definition:</b><ahref="dense__doubly__linked__list_8h_source.html#l00021">dense_doubly_linked_list.h:21</a></div></div>
