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# PuLP : Python LP Modeler
# Version 1.4.2
# Copyright (c) 2002-2005, Jean-Sebastien Roy (js@jeannot.org)
# Modifications Copyright (c) 2007- Stuart Anthony Mitchell (s.mitchell@auckland.ac.nz)
# $Id:solvers.py 1791 2008-04-23 22:54:34Z smit023 $
# Permission is hereby granted, free of charge, to any person obtaining a
# copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
# The above copyright notice and this permission notice shall be included
# in all copies or substantial portions of the Software.
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
# OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
# IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
# CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
# TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE."""
from .core import LpSolver_CMD, subprocess, PulpSolverError
from .. import constants
import warnings
class XPRESS(LpSolver_CMD):
"""The XPRESS LP solver"""
name = "XPRESS"
def __init__(
self,
mip=True,
msg=True,
timeLimit=None,
gapRel=None,
options=None,
keepFiles=False,
path=None,
maxSeconds=None,
targetGap=None,
heurFreq=None,
heurStra=None,
coverCuts=None,
preSolve=None,
):
"""
Initializes the Xpress solver.
:param bool mip: if False, assume LP even if integer variables
:param bool msg: if False, no log is shown
:param float timeLimit: maximum time for solver (in seconds)
:param float gapRel: relative gap tolerance for the solver to stop (in fraction)
:param maxSeconds: deprecated for timeLimit
:param targetGap: deprecated for gapRel
:param heurFreq: the frequency at which heuristics are used in the tree search
:param heurStra: heuristic strategy
:param coverCuts: the number of rounds of lifted cover inequalities at the top node
:param preSolve: whether presolving should be performed before the main algorithm
:param options: Adding more options, e.g. options = ["NODESELECTION=1", "HEURDEPTH=5"]
More about Xpress options and control parameters please see
http://tomopt.com/docs/xpress/tomlab_xpress008.php
"""
if maxSeconds:
warnings.warn("Parameter maxSeconds is being depreciated for timeLimit")
if timeLimit is not None:
warnings.warn(
"Parameter timeLimit and maxSeconds passed, using timeLimit"
)
else:
timeLimit = maxSeconds
if targetGap is not None:
warnings.warn("Parameter targetGap is being depreciated for gapRel")
if gapRel is not None:
warnings.warn("Parameter gapRel and epgap passed, using gapRel")
else:
gapRel = targetGap
LpSolver_CMD.__init__(
self,
gapRel=gapRel,
mip=mip,
msg=msg,
timeLimit=timeLimit,
options=options,
path=path,
keepFiles=keepFiles,
heurFreq=heurFreq,
heurStra=heurStra,
coverCuts=coverCuts,
preSolve=preSolve,
)
def defaultPath(self):
return self.executableExtension("optimizer")
def available(self):
"""True if the solver is available"""
return self.executable(self.path)
def actualSolve(self, lp):
"""Solve a well formulated lp problem"""
if not self.executable(self.path):
raise PulpSolverError("PuLP: cannot execute " + self.path)
tmpLp, tmpSol = self.create_tmp_files(lp.name, "lp", "prt")
lp.writeLP(tmpLp, writeSOS=1, mip=self.mip)
xpress = subprocess.Popen(
[self.path, lp.name],
shell=True,
stdin=subprocess.PIPE,
universal_newlines=True,
)
if not self.msg:
xpress.stdin.write("OUTPUTLOG=0\n")
xpress.stdin.write("READPROB " + tmpLp + "\n")
if self.timeLimit:
xpress.stdin.write("MAXTIME=%d\n" % self.timeLimit)
targetGap = self.optionsDict.get("gapRel")
if targetGap:
xpress.stdin.write("MIPRELSTOP=%f\n" % targetGap)
heurFreq = self.optionsDict.get("heurFreq")
if heurFreq:
xpress.stdin.write("HEURFREQ=%d\n" % heurFreq)
heurStra = self.optionsDict.get("heurStra")
if heurStra:
xpress.stdin.write("HEURSTRATEGY=%d\n" % heurStra)
coverCuts = self.optionsDict.get("coverCuts")
if coverCuts:
xpress.stdin.write("COVERCUTS=%d\n" % coverCuts)
preSolve = self.optionsDict.get("preSolve")
if preSolve:
xpress.stdin.write("PRESOLVE=%d\n" % preSolve)
for option in self.options:
xpress.stdin.write(option + "\n")
if lp.sense == constants.LpMaximize:
xpress.stdin.write("MAXIM\n")
else:
xpress.stdin.write("MINIM\n")
if lp.isMIP() and self.mip:
xpress.stdin.write("GLOBAL\n")
xpress.stdin.write("WRITEPRTSOL " + tmpSol + "\n")
xpress.stdin.write("QUIT\n")
if xpress.wait() != 0:
raise PulpSolverError("PuLP: Error while executing " + self.path)
status, values = self.readsol(tmpSol)
self.delete_tmp_files(tmpLp, tmpSol)
lp.assignVarsVals(values)
if abs(lp.infeasibilityGap(self.mip)) > 1e-5: # Arbitrary
status = constants.LpStatusInfeasible
lp.assignStatus(status)
return status
@staticmethod
def readsol(filename):
"""Read an XPRESS solution file"""
with open(filename) as f:
for i in range(6):
f.readline()
_line = f.readline().split()
rows = int(_line[2])
cols = int(_line[5])
for i in range(3):
f.readline()
statusString = f.readline().split()[0]
# TODO: check status for Integer Feasible
xpressStatus = {
"Optimal": constants.LpStatusOptimal,
}
if statusString not in xpressStatus:
raise PulpSolverError(
"Unknown status returned by XPRESS: " + statusString
)
status = xpressStatus[statusString]
values = {}
while 1:
_line = f.readline()
if _line == "":
break
line = _line.split()
if len(line) and line[0] == "C":
name = line[2]
value = float(line[4])
values[name] = value
return status, values
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