scip generates inconsistent solutions with non-default parameters #142
Description
For seed.lp.txt, scip can generate the correct answer (objective = -43484..) with numerics/feastol = 1e-9 (or by default),
BUT, if additionally setting numerics/epsilon = 1e-9 and numerics/sumepsilon = 1e-9 (to follow previous comments), scip returns with an incorrect answer (objective = -43477..).
Is this a new issue?
$> cat options.set
numerics/feastol = 1e-9
numerics/epsilon = 1e-9
numerics/sumepsilon = 1e-9
$>
$>
$> scip -f seed.lp -s options.set
SCIP version 10.0.0 [precision: 8 byte] [memory: block] [mode: debug] [LP solver: SoPlex 8.0.0] [GitHash: 1b1bc790f6]
Copyright (c) 2002-2025 Zuse Institute Berlin (ZIB)
External libraries:
SoPlex 8.0.0 Linear programming solver developed at Zuse Institute Berlin (soplex.zib.de) [GitHash: 85549f2c]
CppAD 20180000.0 Algorithmic Differentiation of C++ algorithms developed by B. Bell (github.com/coin-or/CppAD)
ZLIB 1.2.11 General purpose compression library by J. Gailly and M. Adler (zlib.net)
TinyCThread 1.2 small portable implementation of the C11 threads API (tinycthread.github.io)
GMP 6.2.1 GNU Multiple Precision Arithmetic Library developed by T. Granlund (gmplib.org)
AMPL/MP 4.0.0 AMPL .nl file reader library (github.com/ampl/mp)
Nauty 2.8.8 Computing Graph Automorphism Groups by Brendan D. McKay (users.cecs.anu.edu.au/~bdm/nauty)
sassy 2.0 Symmetry preprocessor by Markus Anders (github.com/markusa4/sassy)
reading user parameter file <options.set>
read problem <seed.lp>
============
original problem has 6 variables (0 bin, 4 int, 2 cont) and 46 constraints
solve problem
=============
presolving:
(round 1, fast) 0 del vars, 0 del conss, 0 add conss, 1 chg bounds, 0 chg sides, 0 chg coeffs, 0 upgd conss, 0 impls, 0 clqs
(0.0s) symmetry computation started: requiring (bin +, int +, cont +), (fixed: bin -, int -, cont -)
(0.0s) no symmetry present (symcode time: 0.00)
presolving (2 rounds: 2 fast, 1 medium, 1 exhaustive):
0 deleted vars, 0 deleted constraints, 0 added constraints, 1 tightened bounds, 0 added holes, 0 changed sides, 0 changed coefficients
0 implications, 0 cliques
presolved problem has 6 variables (0 bin, 4 int, 2 cont) and 46 constraints
presolved problem has 0 implied integral variables (0 bin, 0 int, 0 cont)
46 constraints of type <linear>
Presolving Time: 0.00
time | node | left |LP iter|LP it/n|mem/heur|mdpt |vars |cons |rows |cuts |sepa|confs|strbr| dualbound | primalbound | gap | compl.
0.0s| 1 | 0 | 7 | - | 848k | 0 | 6 | 46 | 46 | 0 | 0 | 0 | 0 |-4.353170e+04 | -- | Inf | unknown
r 0.0s| 1 | 0 | 7 | - |randroun| 0 | 6 | 46 | 46 | 0 | 0 | 0 | 0 |-4.353170e+04 |-4.347703e+04 | 0.13%| unknown
0.0s| 1 | 0 | 8 | - | 905k | 0 | 6 | 46 | 47 | 1 | 1 | 0 | 0 |-4.349725e+04 |-4.347703e+04 | 0.05%| unknown
0.0s| 1 | 0 | 8 | - | 906k | 0 | 6 | 46 | 47 | 1 | 1 | 0 | 0 |-4.349725e+04 |-4.347703e+04 | 0.05%| unknown
0.0s| 1 | 0 | 8 | - | 906k | 0 | 6 | 46 | 46 | 1 | 1 | 0 | 0 |-4.349725e+04 |-4.347703e+04 | 0.05%| unknown
0.0s| 1 | 0 | 9 | - | 906k | 0 | 6 | 46 | 46 | 2 | 2 | 0 | 0 |-4.347703e+04 |-4.347703e+04 | 0.00%| unknown
0.0s| 1 | 0 | 9 | - | 906k | 0 | 6 | 46 | 46 | 2 | 2 | 0 | 0 |-4.347703e+04 |-4.347703e+04 | 0.00%| unknown
SCIP Status : problem is solved [optimal solution found]
Solving Time (sec) : 0.02
Solving Nodes : 1
Primal Bound : -4.34770302451599e+04 (3 solutions)
Dual Bound : -4.34770302451599e+04
Gap : 0.00 %
primal solution (original space):
=================================
objective value: -43477.0302451599
x2 -79 (obj:-35.61)
x3 12 (obj:-67.04)
x4 -48 (obj:94.3)
x5 200 (obj:-60.18)
x1 -200 (obj:99.05)
x0 -190.655653664432 (obj:47.8)