Initializing help system before first use

Loading a problem


Type: Programming
Rating: 2 (easy-medium)
Description: Shows how directly load a problem and solve it in Python
File(s): example_loadlp.py, example_loadqp.py, example_loadqcqp.py, example_loadmiqcqp.py, example_loadmiqcqp_sos.py


example_loadlp.py
#!/bin/env python

import xpress as xp

p = xp.problem()

# fill in a problem with three variables and four constraints

p.loadproblem("",  # probname
              ['G', 'G', 'E', 'L'],  # qrtypes
              [-2.4, -3, 4, 5],  # rhs
              None,  # range
              [3, 4, 5],  # obj
              [0, 2, 4, 8],  # mstart
              None,  # mnel
              [0, 1, 2, 3, 0, 1, 2, 3],  # mrwind
              [1, 1, 1, 1, 1, 1, 1, 1],  # dmatval
              [-1, -1, -1],  # lb
              [3, 5, 8],  # ub
              colnames=['x1', 'x2', 'x3'],  # column names
              rownames=['row1', 'row2', 'row3', 'constr_04'])  # row    names

p.write("loadlp", "lp")
p.solve()

# Create another variable and add it, then modify the objective
# function. Note that the objective function is replaced by, not
# amended with, the new objective

x = xp.var()
p.addVariable(x)
p.setObjective(x**2 + 2*x + 444)
p.solve()
p.write("updated", "lp")

example_loadqp.py
#!/bin/env python

# example of loadproblem() that adds a quadratic objective

import xpress as xp

p = xp.problem()

# fill in a problem with three variables and four constraints

p.loadproblem("",  # probname
              ['G', 'G', 'E', 'L'],  # qrtypes
              [-2.4, -3, 4, 5],  # rhs
              None,  # range
              [3, 4, 5],  # obj
              [0, 2, 4, 8],  # mstart
              None,  # mnel
              [0, 1, 2, 3, 0, 1, 2, 3],  # mrwind
              [1, 1, 1, 1, 1, 1, 1, 1],  # dmatval
              [-1, -1, -1],  # lb
              [3, 5, 8],  # ub
              [0, 0, 0, 1, 1, 2],  # mqobj1
              [0, 1, 2, 1, 2, 2],  # mqobj1
              [2, 1, 1, 2, 1, 2])        # dqe

p.write("loadedq", "lp")
p.solve()

example_loadqcqp.py
#!/bin/env python

# example using loadproblem to create a quadratically constrained
# quadratic problem.

import xpress as xp

p = xp.problem()

# fill in a problem with three variables and four constraints

p.loadproblem("",  # probname
              ['G', 'G', 'L', 'L'],  # qrtypes
              [-2.4, -3, 4, 5],  # rhs
              None,  # range
              [3, 4, 5],  # obj
              [0, 2, 4, 8],  # mstart
              None,  # mnel
              [0, 1, 2, 3, 0, 1, 2, 3],  # mrwind
              [1, 1, 1, 1, 1, 1, 1, 1],  # dmatval
              [-1, -1, -1],  # lb
              [3, 5, 8],  # ub
              [0, 0, 0, 1, 1, 2],  # mqobj1
              [0, 1, 2, 1, 2, 2],  # mqobj1
              [2, 1, 1, 2, 1, 2],  # dqe
              [2, 3],  # qcrows
              [2, 3],  # qcnquads
              [1, 2, 0, 0, 2],  # qcmqcol1
              [1, 2, 0, 2, 2],  # qcmqcol2
              [3, 4, 1, 1, 1])           # qcdqval

p.write("loadedqc", "lp")
p.solve()

example_loadmiqcqp.py
#!/bin/env python

# Example: create a MIQCQP using the loadproblem() function

import xpress as xp

p = xp.problem()

# fill in a problem with three variables and four constraints

p.loadproblem("",  # probname
              ['G', 'G', 'L', 'L'],  # qrtypes
              [-2.4, -3, 4, 5],  # rhs
              None,  # range
              [3, 4, 5],  # obj
              [0, 2, 4, 8],  # mstart
              None,  # mnel
              [0, 1, 2, 3, 0, 1, 2, 3],  # mrwind
              [1, 1, 1, 1, 1, 1, 1, 1],  # dmatval
              [-1, -1, -1],  # lb
              [3, 5, 8],  # ub
              [0, 0, 0, 1, 1, 2],  # mqobj1
              [0, 1, 2, 1, 2, 2],  # mqobj1
              [2, 1, 1, 2, 1, 2],  # dqe
              [2, 3],  # qcrows
              [2, 3],  # qcnquads
              [1, 2, 0, 0, 2],  # qcmqcol1
              [1, 2, 0, 2, 2],  # qcmqcol2
              [3, 4, 1, 1, 1],  # qcdqval
              ['I', 'B'],  # qgtype
              [0, 1],  # mgcols
              [0, 2],  # dlim
              colnames=['y01', 'y02', 'y03'],  # column names
              rownames=['row01', 'row02', 'row03', 'row04'])  # row    names

p.write("loadedqcg", "lp")
p.solve()
print(p.getSolution())

example_loadmiqcqp_sos.py
#!/bin/env python

# Example that uses loadproblem() to create a Mixed Integer
# Quadratically Constrained Quadratic Programming problem with two
# Special Ordered Sets

import xpress as xp

p = xp.problem()

p.loadproblem("",  # probname
              ['G', 'G', 'L', 'L'],  # qrtypes
              [-2.4, -3, 4, 5],  # rhs
              None,  # range
              [3, 4, 5],  # obj
              [0, 2, 4, 8],  # mstart
              None,  # mnel
              [0, 1, 2, 3, 0, 1, 2, 3],  # mrwind
              [1, 1, 1, 1, 1, 1, 1, 1],  # dmatval
              [-1, -1, -1],  # lb
              [3, 5, 8],  # ub
              [0, 0, 0, 1, 1, 2],  # mqobj1
              [0, 1, 2, 1, 2, 2],  # mqobj1
              [2, 1, 1, 2, 1, 2],  # dqe
              [2, 3],  # qcrows
              [2, 3],  # qcnquads
              [1, 2, 0, 0, 2],  # qcmqcol1
              [1, 2, 0, 2, 2],  # qcmqcol2
              [3, 4, 1, 1, 1],  # qcdqval
              ['I', 'S'],  # qgtype
              [0, 1],  # mgcols
              [0, 2],  # dlim
              ['1', '1'],  # qstype
              [0, 2, 4],  # msstart
              [0, 1, 0, 2],  # mscols
              [1.1, 1.2, 1.3, 1.4])      # dref

p.write("loadedqcgs", "lp")
p.solve()

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