Scippy

SCIP

Solving Constraint Integer Programs

Overview

What is SCIP?

SCIP is a framework to solve constraint integer programs (CIPs) and mixed-integer nonlinear programs. In particular,

  • SCIP incorporates a mixed-integer programming (MIP) solver as well as
  • an LP based mixed-integer nonlinear programming (MINLP) solver, and
  • is a framework for branch-and-cut-and-price.

See the web site of SCIP for more information about licensing and to download SCIP.

Structure of this manual

This manual gives an accessible introduction to the functionality of the SCIP code in the following chapters

Quickstart

Let's consider the following minimal example in LP format. A 4-variable problem with a single, general integer variable and three linear constraints

Maximize
 obj: x1 + 2 x2 + 3 x3 + x4
Subject To
 c1: - x1 + x2 + x3 + 10 x4 <= 20
 c2: x1 - 3 x2 + x3 <= 30
 c3: x2 - 3.5 x4 = 0
Bounds
 0 <= x1 <= 40
 2 <= x4 <= 3
General
 x4
End

Saving this file as "simple.lp" allows to read it into SCIP and solve it.

scip -c "read simple.lp optimize quit"

reads and optimizes this model in no time:

SCIP version 6.0.0 [precision: 8 byte] [memory: block] [mode: optimized] [LP solver: SoPlex 4.0.0] [GitHash: 1af6f3b]
Copyright (C) 2002-2018 Konrad-Zuse-Zentrum fuer Informationstechnik Berlin (ZIB)

External codes: 
  Readline 6.3         GNU library for command line editing (gnu.org/s/readline)
  SoPlex 4.0.0         Linear Programming Solver developed at Zuse Institute Berlin (soplex.zib.de) [GitHash: 82cab95]
  CppAD 20180000.0     Algorithmic Differentiation of C++ algorithms developed by B. Bell (www.coin-or.org/CppAD)
  ZLIB 1.2.8           General purpose compression library by J. Gailly and M. Adler (zlib.net)
  GMP 6.1.0            GNU Multiple Precision Arithmetic Library developed by T. Granlund (gmplib.org)

user parameter file <scip.set> not found - using default parameters


read problem <doc/inc/simpleinstance/simple.lp>
============

original problem has 4 variables (0 bin, 1 int, 0 impl, 3 cont) and 3 constraints

presolving:
(round 1, fast)       2 del vars, 1 del conss, 0 add conss, 4 chg bounds, 0 chg sides, 0 chg coeffs, 0 upgd conss, 0 impls, 0 clqs
(round 2, fast)       2 del vars, 1 del conss, 0 add conss, 6 chg bounds, 0 chg sides, 0 chg coeffs, 0 upgd conss, 0 impls, 0 clqs
(round 3, fast)       2 del vars, 1 del conss, 0 add conss, 7 chg bounds, 0 chg sides, 0 chg coeffs, 0 upgd conss, 0 impls, 0 clqs
   (0.0s) probing cycle finished: starting next cycle
presolving (4 rounds: 4 fast, 1 medium, 1 exhaustive):
 2 deleted vars, 1 deleted constraints, 0 added constraints, 7 tightened bounds, 0 added holes, 0 changed sides, 0 changed coefficients
 2 implications, 0 cliques
presolved problem has 3 variables (1 bin, 0 int, 0 impl, 2 cont) and 2 constraints
      2 constraints of type <linear>
Presolving Time: 0.00

 time | node  | left  |LP iter|LP it/n| mem |mdpt |frac |vars |cons |cols |rows |cuts |confs|strbr|  dualbound   | primalbound  |  gap   
t 0.0s|     1 |     0 |     0 |     - | 563k|   0 |   - |   3 |   2 |   0 |   0 |   0 |   0 |   0 | 1.630000e+02 | 3.400000e+01 | 379.41%
t 0.0s|     1 |     0 |     0 |     - | 563k|   0 |   - |   3 |   2 |   0 |   0 |   0 |   0 |   0 | 1.630000e+02 | 5.300000e+01 | 207.55%
k 0.0s|     1 |     0 |     0 |     - | 566k|   0 |   - |   3 |   2 |   3 |   2 |   0 |   0 |   0 | 1.630000e+02 | 1.225000e+02 |  33.06%
  0.0s|     1 |     0 |     2 |     - | 566k|   0 |   1 |   3 |   2 |   3 |   2 |   0 |   0 |   0 | 1.252083e+02 | 1.225000e+02 |   2.21%
  0.0s|     1 |     0 |     2 |     - | 566k|   0 |   1 |   3 |   2 |   3 |   2 |   0 |   0 |   0 | 1.252083e+02 | 1.225000e+02 |   2.21%
  0.0s|     1 |     0 |     3 |     - | 568k|   0 |   - |   3 |   2 |   3 |   3 |   1 |   0 |   0 | 1.225000e+02 | 1.225000e+02 |   0.00%
  0.0s|     1 |     0 |     3 |     - | 568k|   0 |   - |   3 |   2 |   3 |   3 |   1 |   0 |   0 | 1.225000e+02 | 1.225000e+02 |   0.00%

SCIP Status        : problem is solved [optimal solution found]
Solving Time (sec) : 0.00
Solving Nodes      : 1
Primal Bound       : +1.22500000000000e+02 (3 solutions)
Dual Bound         : +1.22500000000000e+02
Gap                : 0.00 %


Version
6.0.0
scippy.png