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<article id="content">
<header>
<h1 class="title">Module <code>miplearn.components.relaxation</code></h1>
</header>
<section id="section-intro">
<details class="source">
<summary>
<span>Expand source code</span>
</summary>
<pre><code class="python"># MIPLearn: Extensible Framework for Learning-Enhanced Mixed-Integer Optimization
# Copyright (C) 2020, UChicago Argonne, LLC. All rights reserved.
# Released under the modified BSD license. See COPYING.md for more details.
import logging
from miplearn.classifiers.counting import CountingClassifier
from miplearn.components.component import Component
from miplearn.components.composite import CompositeComponent
from miplearn.components.steps.convert_tight import ConvertTightIneqsIntoEqsStep
from miplearn.components.steps.drop_redundant import DropRedundantInequalitiesStep
from miplearn.components.steps.relax_integrality import RelaxIntegralityStep
logger = logging.getLogger(__name__)
class RelaxationComponent(Component):
&#34;&#34;&#34;
A Component that tries to build a relaxation that is simultaneously strong and easy
to solve. Currently, this component is composed by three steps:
- RelaxIntegralityStep
- DropRedundantInequalitiesStep
- ConvertTightIneqsIntoEqsStep
Parameters
----------
redundant_classifier : Classifier, optional
Classifier used to predict if a constraint is likely redundant. One deep
copy of this classifier is made for each constraint category.
redundant_threshold : float, optional
If the probability that a constraint is redundant exceeds this threshold, the
constraint is dropped from the linear relaxation.
tight_classifier : Classifier, optional
Classifier used to predict if a constraint is likely to be tight. One deep
copy of this classifier is made for each constraint category.
tight_threshold : float, optional
If the probability that a constraint is tight exceeds this threshold, the
constraint is converted into an equality constraint.
slack_tolerance : float, optional
If a constraint has slack greater than this threshold, then the constraint is
considered loose. By default, this threshold equals a small positive number to
compensate for numerical issues.
check_feasibility : bool, optional
If true, after the problem is solved, the component verifies that all dropped
constraints are still satisfied, re-adds the violated ones and resolves the
problem. This loop continues until either no violations are found, or a maximum
number of iterations is reached.
violation_tolerance : float, optional
If `check_dropped` is true, a constraint is considered satisfied during the
check if its violation is smaller than this tolerance.
max_check_iterations : int
If `check_dropped` is true, set the maximum number of iterations in the lazy
constraint loop.
&#34;&#34;&#34;
def __init__(
self,
redundant_classifier=CountingClassifier(),
redundant_threshold=0.95,
tight_classifier=CountingClassifier(),
tight_threshold=0.95,
slack_tolerance=1e-5,
check_feasibility=False,
violation_tolerance=1e-5,
max_check_iterations=3,
):
self.steps = [
RelaxIntegralityStep(),
DropRedundantInequalitiesStep(
classifier=redundant_classifier,
threshold=redundant_threshold,
slack_tolerance=slack_tolerance,
violation_tolerance=violation_tolerance,
max_iterations=max_check_iterations,
check_feasibility=check_feasibility,
),
ConvertTightIneqsIntoEqsStep(
classifier=tight_classifier,
threshold=tight_threshold,
slack_tolerance=slack_tolerance,
),
]
self.composite = CompositeComponent(self.steps)
def before_solve(self, solver, instance, model):
self.composite.before_solve(solver, instance, model)
def after_solve(self, solver, instance, model, stats, training_data):
self.composite.after_solve(solver, instance, model, stats, training_data)
def fit(self, training_instances):
self.composite.fit(training_instances)
def iteration_cb(self, solver, instance, model):
return self.composite.iteration_cb(solver, instance, model)</code></pre>
</details>
</section>
<section>
</section>
<section>
</section>
<section>
</section>
<section>
<h2 class="section-title" id="header-classes">Classes</h2>
<dl>
<dt id="miplearn.components.relaxation.RelaxationComponent"><code class="flex name class">
<span>class <span class="ident">RelaxationComponent</span></span>
<span>(</span><span>redundant_classifier=CountingClassifier(mean=None), redundant_threshold=0.95, tight_classifier=CountingClassifier(mean=None), tight_threshold=0.95, slack_tolerance=1e-05, check_feasibility=False, violation_tolerance=1e-05, max_check_iterations=3)</span>
</code></dt>
<dd>
<section class="desc"><p>A Component that tries to build a relaxation that is simultaneously strong and easy
to solve. Currently, this component is composed by three steps:</p>
<ul>
<li>RelaxIntegralityStep</li>
<li>DropRedundantInequalitiesStep</li>
<li>ConvertTightIneqsIntoEqsStep</li>
</ul>
<h2 id="parameters">Parameters</h2>
<dl>
<dt><strong><code>redundant_classifier</code></strong> :&ensp;<code>Classifier</code>, optional</dt>
<dd>Classifier used to predict if a constraint is likely redundant. One deep
copy of this classifier is made for each constraint category.</dd>
<dt><strong><code>redundant_threshold</code></strong> :&ensp;<code>float</code>, optional</dt>
<dd>If the probability that a constraint is redundant exceeds this threshold, the
constraint is dropped from the linear relaxation.</dd>
<dt><strong><code>tight_classifier</code></strong> :&ensp;<code>Classifier</code>, optional</dt>
<dd>Classifier used to predict if a constraint is likely to be tight. One deep
copy of this classifier is made for each constraint category.</dd>
<dt><strong><code>tight_threshold</code></strong> :&ensp;<code>float</code>, optional</dt>
<dd>If the probability that a constraint is tight exceeds this threshold, the
constraint is converted into an equality constraint.</dd>
<dt><strong><code>slack_tolerance</code></strong> :&ensp;<code>float</code>, optional</dt>
<dd>If a constraint has slack greater than this threshold, then the constraint is
considered loose. By default, this threshold equals a small positive number to
compensate for numerical issues.</dd>
<dt><strong><code>check_feasibility</code></strong> :&ensp;<code>bool</code>, optional</dt>
<dd>If true, after the problem is solved, the component verifies that all dropped
constraints are still satisfied, re-adds the violated ones and resolves the
problem. This loop continues until either no violations are found, or a maximum
number of iterations is reached.</dd>
<dt><strong><code>violation_tolerance</code></strong> :&ensp;<code>float</code>, optional</dt>
<dd>If <code>check_dropped</code> is true, a constraint is considered satisfied during the
check if its violation is smaller than this tolerance.</dd>
<dt><strong><code>max_check_iterations</code></strong> :&ensp;<code>int</code></dt>
<dd>If <code>check_dropped</code> is true, set the maximum number of iterations in the lazy
constraint loop.</dd>
</dl></section>
<details class="source">
<summary>
<span>Expand source code</span>
</summary>
<pre><code class="python">class RelaxationComponent(Component):
&#34;&#34;&#34;
A Component that tries to build a relaxation that is simultaneously strong and easy
to solve. Currently, this component is composed by three steps:
- RelaxIntegralityStep
- DropRedundantInequalitiesStep
- ConvertTightIneqsIntoEqsStep
Parameters
----------
redundant_classifier : Classifier, optional
Classifier used to predict if a constraint is likely redundant. One deep
copy of this classifier is made for each constraint category.
redundant_threshold : float, optional
If the probability that a constraint is redundant exceeds this threshold, the
constraint is dropped from the linear relaxation.
tight_classifier : Classifier, optional
Classifier used to predict if a constraint is likely to be tight. One deep
copy of this classifier is made for each constraint category.
tight_threshold : float, optional
If the probability that a constraint is tight exceeds this threshold, the
constraint is converted into an equality constraint.
slack_tolerance : float, optional
If a constraint has slack greater than this threshold, then the constraint is
considered loose. By default, this threshold equals a small positive number to
compensate for numerical issues.
check_feasibility : bool, optional
If true, after the problem is solved, the component verifies that all dropped
constraints are still satisfied, re-adds the violated ones and resolves the
problem. This loop continues until either no violations are found, or a maximum
number of iterations is reached.
violation_tolerance : float, optional
If `check_dropped` is true, a constraint is considered satisfied during the
check if its violation is smaller than this tolerance.
max_check_iterations : int
If `check_dropped` is true, set the maximum number of iterations in the lazy
constraint loop.
&#34;&#34;&#34;
def __init__(
self,
redundant_classifier=CountingClassifier(),
redundant_threshold=0.95,
tight_classifier=CountingClassifier(),
tight_threshold=0.95,
slack_tolerance=1e-5,
check_feasibility=False,
violation_tolerance=1e-5,
max_check_iterations=3,
):
self.steps = [
RelaxIntegralityStep(),
DropRedundantInequalitiesStep(
classifier=redundant_classifier,
threshold=redundant_threshold,
slack_tolerance=slack_tolerance,
violation_tolerance=violation_tolerance,
max_iterations=max_check_iterations,
check_feasibility=check_feasibility,
),
ConvertTightIneqsIntoEqsStep(
classifier=tight_classifier,
threshold=tight_threshold,
slack_tolerance=slack_tolerance,
),
]
self.composite = CompositeComponent(self.steps)
def before_solve(self, solver, instance, model):
self.composite.before_solve(solver, instance, model)
def after_solve(self, solver, instance, model, stats, training_data):
self.composite.after_solve(solver, instance, model, stats, training_data)
def fit(self, training_instances):
self.composite.fit(training_instances)
def iteration_cb(self, solver, instance, model):
return self.composite.iteration_cb(solver, instance, model)</code></pre>
</details>
<h3>Ancestors</h3>
<ul class="hlist">
<li><a title="miplearn.components.component.Component" href="component.html#miplearn.components.component.Component">Component</a></li>
<li>abc.ABC</li>
</ul>
<h3>Methods</h3>
<dl>
<dt id="miplearn.components.relaxation.RelaxationComponent.fit"><code class="name flex">
<span>def <span class="ident">fit</span></span>(<span>self, training_instances)</span>
</code></dt>
<dd>
<section class="desc"></section>
<details class="source">
<summary>
<span>Expand source code</span>
</summary>
<pre><code class="python">def fit(self, training_instances):
self.composite.fit(training_instances)</code></pre>
</details>
</dd>
</dl>
<h3>Inherited members</h3>
<ul class="hlist">
<li><code><b><a title="miplearn.components.component.Component" href="component.html#miplearn.components.component.Component">Component</a></b></code>:
<ul class="hlist">
<li><code><a title="miplearn.components.component.Component.after_solve" href="component.html#miplearn.components.component.Component.after_solve">after_solve</a></code></li>
<li><code><a title="miplearn.components.component.Component.before_solve" href="component.html#miplearn.components.component.Component.before_solve">before_solve</a></code></li>
<li><code><a title="miplearn.components.component.Component.iteration_cb" href="component.html#miplearn.components.component.Component.iteration_cb">iteration_cb</a></code></li>
</ul>
</li>
</ul>
</dd>
</dl>
</section>
</article>
<nav id="sidebar">
<h1>Index</h1>
<div class="toc">
<ul></ul>
</div>
<ul id="index">
<li><h3>Super-module</h3>
<ul>
<li><code><a title="miplearn.components" href="index.html">miplearn.components</a></code></li>
</ul>
</li>
<li><h3><a href="#header-classes">Classes</a></h3>
<ul>
<li>
<h4><code><a title="miplearn.components.relaxation.RelaxationComponent" href="#miplearn.components.relaxation.RelaxationComponent">RelaxationComponent</a></code></h4>
<ul class="">
<li><code><a title="miplearn.components.relaxation.RelaxationComponent.fit" href="#miplearn.components.relaxation.RelaxationComponent.fit">fit</a></code></li>
</ul>
</li>
</ul>
</li>
</ul>
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