<ahref="linear__solver__callback_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">// See go/mpsolver-callbacks for documentation on how to use this file.</span></div>
<divclass="line"><aname="l00030"></a><spanclass="lineno"> 30</span> <spanclass="comment">// The current state of the solver when the callback is invoked.</span></div>
<divclass="line"><aname="l00032"></a><spanclass="lineno"> 32</span> <spanclass="comment">// For Gurobi, similar to the int 'where' in the Gurobi callback API.</span></div>
<divclass="line"><aname="l00033"></a><spanclass="lineno"> 33</span> <spanclass="comment">// See http://www.gurobi.com/documentation/8.0/refman/callback_codes.html</span></div>
<divclass="line"><aname="l00034"></a><spanclass="lineno"> 34</span> <spanclass="comment">// for details.</span></div>
<divclass="line"><aname="l00037"></a><spanclass="lineno"> 37</span> <spanclass="comment">// For regaining control of the main thread in single threaded applications,</span></div>
<divclass="line"><aname="l00038"></a><spanclass="lineno"> 38</span> <spanclass="comment">// not for interacting with the solver.</span></div>
<divclass="line"><aname="l00040"></a><spanclass="lineno"> 40</span> <spanclass="comment">// The solver is currently running presolve.</span></div>
<divclass="line"><aname="l00042"></a><spanclass="lineno"> 42</span> <spanclass="comment">// The solver is currently running the simplex method.</span></div>
<divclass="line"><aname="l00044"></a><spanclass="lineno"> 44</span> <spanclass="comment">// The solver is in the MIP loop (called periodically before starting a new</span></div>
<divclass="line"><aname="l00045"></a><spanclass="lineno"> 45</span> <spanclass="comment">// node). Useful to early termination.</span></div>
<divclass="line"><aname="l00047"></a><spanclass="lineno"> 47</span> <spanclass="comment">// Called every time a new MIP incumbent is found.</span></div>
<divclass="line"><aname="l00049"></a><spanclass="lineno"> 49</span> <spanclass="comment">// Called once per pass of the cut loop inside each MIP node.</span></div>
<divclass="line"><aname="l00051"></a><spanclass="lineno"> 51</span> <spanclass="comment">// Called in each iterate of IPM/barrier method.</span></div>
<divclass="line"><aname="l00053"></a><spanclass="lineno"> 53</span> <spanclass="comment">// The solver is about to log out a message, use this callback to capture it.</span></div>
<divclass="line"><aname="l00055"></a><spanclass="lineno"> 55</span> <spanclass="comment">// The solver is in multi-objective optimization.</span></div>
<divclass="line"><aname="l00061"></a><spanclass="lineno"> 61</span> <spanclass="comment">// When querying solution values or modifying the model during a callback, use</span></div>
<divclass="line"><aname="l00062"></a><spanclass="lineno"> 62</span> <spanclass="comment">// this API, rather than manipulating MPSolver directly. You should only</span></div>
<divclass="line"><aname="l00063"></a><spanclass="lineno"> 63</span> <spanclass="comment">// interact with this object from within MPCallback::RunCallback().</span></div>
<divclass="line"><aname="l00068"></a><spanclass="lineno"> 68</span> <spanclass="comment">// What the solver is currently doing. How you can interact with the solver</span></div>
<divclass="line"><aname="l00069"></a><spanclass="lineno"> 69</span> <spanclass="comment">// from the callback depends on this value.</span></div>
<divclass="line"><aname="l00072"></a><spanclass="lineno"> 72</span> <spanclass="comment">// Always false if event is not kMipSolution or kMipNode, otherwise behavior</span></div>
<divclass="line"><aname="l00073"></a><spanclass="lineno"> 73</span> <spanclass="comment">// may be solver dependent.</span></div>
<divclass="line"><aname="l00075"></a><spanclass="lineno"> 75</span> <spanclass="comment">// For Gurobi, under kMipNode, may be false if the node was not solved to</span></div>
<divclass="line"><aname="l00076"></a><spanclass="lineno"> 76</span> <spanclass="comment">// optimality, see MIPNODE_REL here for details:</span></div>
<divclass="line"><aname="l00080"></a><spanclass="lineno"> 80</span> <spanclass="comment">// Returns the value of variable from the solver's current state.</span></div>
<divclass="line"><aname="l00082"></a><spanclass="lineno"> 82</span> <spanclass="comment">// Call only when CanQueryVariableValues() is true.</span></div>
<divclass="line"><aname="l00084"></a><spanclass="lineno"> 84</span> <spanclass="comment">// At kMipSolution, the solution is integer feasible, while at kMipNode, the</span></div>
<divclass="line"><aname="l00085"></a><spanclass="lineno"> 85</span> <spanclass="comment">// solution solves the current node's LP relaxation (so integer variables may</span></div>
<divclass="line"><aname="l00086"></a><spanclass="lineno"> 86</span> <spanclass="comment">// be fractional).</span></div>
<divclass="line"><aname="l00089"></a><spanclass="lineno"> 89</span> <spanclass="comment">// Adds a constraint to the model that strengths the LP relaxation.</span></div>
<divclass="line"><aname="l00093"></a><spanclass="lineno"> 93</span> <spanclass="comment">// Requires that MPCallback::might_add_cuts() is true.</span></div>
<divclass="line"><aname="l00095"></a><spanclass="lineno"> 95</span> <spanclass="comment">// This constraint must not cut off integer solutions, it should only</span></div>
<divclass="line"><aname="l00096"></a><spanclass="lineno"> 96</span> <spanclass="comment">// strengthen the LP (behavior is undefined otherwise). Use</span></div>
<divclass="line"><aname="l00097"></a><spanclass="lineno"> 97</span> <spanclass="comment">// MPCallbackContext::AddLazyConstriant() if you are cutting off integer</span></div>
<divclass="line"><aname="l00101"></a><spanclass="lineno"> 101</span> <spanclass="comment">// Adds a constraint to the model that cuts off an undesired integer solution.</span></div>
<divclass="line"><aname="l00103"></a><spanclass="lineno"> 103</span> <spanclass="comment">// Call only when the event is kMipSolution or kMipNode.</span></div>
<divclass="line"><aname="l00105"></a><spanclass="lineno"> 105</span> <spanclass="comment">// Requires that MPCallback::might_add_lazy_constraints() is true.</span></div>
<divclass="line"><aname="l00107"></a><spanclass="lineno"> 107</span> <spanclass="comment">// Use this to avoid adding a large number of constraints to the model where</span></div>
<divclass="line"><aname="l00108"></a><spanclass="lineno"> 108</span> <spanclass="comment">// most are expected to not be needed.</span></div>
<divclass="line"><aname="l00110"></a><spanclass="lineno"> 110</span> <spanclass="comment">// Given an integral solution, AddLazyConstraint() MUST be able to detect if</span></div>
<divclass="line"><aname="l00111"></a><spanclass="lineno"> 111</span> <spanclass="comment">// there is a violated constraint, and it is guaranteed that every integer</span></div>
<divclass="line"><aname="l00112"></a><spanclass="lineno"> 112</span> <spanclass="comment">// solution will be checked by AddLazyConstraint().</span></div>
<divclass="line"><aname="l00114"></a><spanclass="lineno"> 114</span> <spanclass="comment">// Warning(rander): in some solvers, e.g. Gurobi, an integer solution may not</span></div>
<divclass="line"><aname="l00115"></a><spanclass="lineno"> 115</span> <spanclass="comment">// respect a previously added lazy constraint, so you may need to add a</span></div>
<divclass="line"><aname="l00116"></a><spanclass="lineno"> 116</span> <spanclass="comment">// constraint more than once (e.g. due to threading issues).</span></div>
<divclass="line"><aname="l00119"></a><spanclass="lineno"> 119</span> <spanclass="comment">// Suggests a (potentially partial) variable assignment to the solver, to be</span></div>
<divclass="line"><aname="l00120"></a><spanclass="lineno"> 120</span> <spanclass="comment">// used as a feasible solution (or part of one). If the assignment is partial,</span></div>
<divclass="line"><aname="l00121"></a><spanclass="lineno"> 121</span> <spanclass="comment">// certain solvers (e.g. Gurobi) will try to compute a feasible solution from</span></div>
<divclass="line"><aname="l00122"></a><spanclass="lineno"> 122</span> <spanclass="comment">// the partial assignment. Returns the objective value of the solution if the</span></div>
<divclass="line"><aname="l00129"></a><spanclass="lineno"> 129</span> <spanclass="comment">// Returns the number of nodes explored so far in the branch and bound tree,</span></div>
<divclass="line"><aname="l00130"></a><spanclass="lineno"> 130</span> <spanclass="comment">// which 0 at the root node and > 0 otherwise.</span></div>
<divclass="line"><aname="l00132"></a><spanclass="lineno"> 132</span> <spanclass="comment">// Call only when the event is kMipSolution or kMipNode.</span></div>
<divclass="line"><aname="l00136"></a><spanclass="lineno"> 136</span> <spanclass="comment">// Extend this class with model specific logic, and register through</span></div>
<divclass="line"><aname="l00137"></a><spanclass="lineno"> 137</span> <spanclass="comment">// MPSolver::SetCallback, passing a pointer to this object.</span></div>
<divclass="line"><aname="l00139"></a><spanclass="lineno"> 139</span> <spanclass="comment">// See go/mpsolver-callbacks for additional documentation.</span></div>
<divclass="line"><aname="l00142"></a><spanclass="lineno"> 142</span> <spanclass="comment">// If you intend to call call MPCallbackContext::AddCut(), you must set</span></div>
<divclass="line"><aname="l00143"></a><spanclass="lineno"> 143</span> <spanclass="comment">// might_add_cuts below to be true. Likewise for</span></div>
<divclass="line"><aname="l00144"></a><spanclass="lineno"> 144</span> <spanclass="comment">// MPCallbackContext::AddLazyConstraint() and might_add_lazy_constraints.</span></div>
<divclass="line"><aname="l00150"></a><spanclass="lineno"> 150</span> <spanclass="comment">// Threading behavior may be solver dependent:</span></div>
<divclass="line"><aname="l00151"></a><spanclass="lineno"> 151</span> <spanclass="comment">// * Gurobi: RunCallback always runs on the same thread that you called</span></div>
<divclass="line"><aname="l00152"></a><spanclass="lineno"> 152</span> <spanclass="comment">// MPSolver::Solve() on, even when Gurobi uses multiple threads.</span></div>
<divclass="line"><aname="l00165"></a><spanclass="lineno"> 165</span> <spanclass="comment">// Single callback that runs the list of callbacks given at construction, in</span></div>
<divclass="line"><aname="l00171"></a><spanclass="lineno"> 171</span> <spanclass="comment">// Runs all callbacks from the list given at construction, in sequence.</span></div>
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