[Cbc-tickets] [COIN-OR Branch-and-Cut MIP Solver] #158: Segmentation vialation on infeasible problems

[COIN-OR Branch-and-Cut MIP Solver]

#158: Segmentation vialation on infeasible problems
----------------------+------------------------------
Reporter:  dvvarreyn  |      Owner:  tkr
    Type:  defect     |     Status:  new
Priority:  major      |  Component:  Cbc
 Version:  2.8.8      |   Keywords:  memory violation
----------------------+------------------------------
 Hello.

 Running cbc 2.8.12 (could not find in the version list)
 I have encountered memory violation
 {{{
 Cbc0010I After 204000 nodes, 12 on tree, 3.4028235e+38 best solution, best
 possible 8073.3801 (1342.74 seconds)
 Cbc0010I After 205000 nodes, 11 on tree, 3.4028235e+38 best solution, best
 possible 8073.3801 (1348.46 seconds)
 Cbc0010I After 206000 nodes, 8 on tree, 3.4028235e+38 best solution, best
 possible 8298.4579 (1354.24 seconds)
 Cbc0001I Search completed - best objective 3.402823466385289e+38, took
 19355815 iterations and 869001 nodes (1359.25 seconds)
 Cbc0032I Strong branching done 171648 times (2422070 iterations), fathomed
 4617 nodes and fixed 12697 variables
 Cbc0041I Maximum depth 27, 0 variables fixed on reduced cost (662131 nodes
 in complete fathoming taking 6361958 iterations)

 Program received signal SIGSEGV, Segmentation fault.
 [Switching to Thread 0x7fffede6a700 (LWP 26565)]
 0x00007ffff0e66be2 in CbcMain1 (argc=3, argv=0x7fffe8134640, model=...,
 callBack=0x7ffff0e4db85 <dummyCallBack(CbcModel*, int)>,
 parameterData=...) at CbcSolver.cpp:6641
 6641                                                solution2[jColumn] =
 solution[i];
 (gdb) bt
 #0  0x00007ffff0e66be2 in CbcMain1 (argc=3, argv=0x7fffe8134640,
 model=..., callBack=0x7ffff0e4db85 <dummyCallBack(CbcModel*, int)>,
 parameterData=...) at CbcSolver.cpp:6641
 #1  0x00007ffff0e4e1b7 in callCbc1 (input2=0x7ffff1c5124f "-solve",
 model=..., callBack=0x7ffff0e4db85 <dummyCallBack(CbcModel*, int)>,
 parameterData=...) at CbcSolver.cpp:1130
 #2  0x00007ffff0e4de0a in callCbc (input2=0x7ffff1c5124f "-solve",
 babSolver=...) at CbcSolver.cpp:1035
 }}}
 In my case  a problem was infeasible and bestSolution() == solution ==
 nullptr.
 Because there is no checks for that in the code above 6641 an attempt to
 access triggered coredump.

 I believe the code connected with solution2 may be simply removed,  I saw
 no usage for  solution2. I removed locally and it seemed to work.
 (if not take into account some asserts i.e.
 {{{
 Cbc0010I After 206000 nodes, 8 on tree, 3.4028235e+38 best solution, best
 possible 8298.4579 (1356.03 seconds)
 Cbc0001I Search completed - best objective 3.402823466385289e+38, took
 19355815 iterations and 869001 nodes (1361.02 seconds)
 Cbc0032I Strong branching done 171648 times (2422070 iterations), fathomed
 4617 nodes and fixed 12697 variables
 Cbc0041I Maximum depth 27, 0 variables fixed on reduced cost (662131 nodes
 in complete fathoming taking 6361958 iterations)
 Cgl0013I Postprocessed model is infeasible - possible tolerance issue -
 try without preprocessing
 python: CbcSolver.cpp:6769: int CbcMain1(int, const char**, CbcModel&, int
 (*)(CbcModel*, int), CbcSolverUsefulData&): Assertion
 `saveSolver->isProvenOptimal()' failed.

 Program received signal SIGABRT, Aborted.
 [Switching to Thread 0x7fffede6a700 (LWP 29815)]
 0x00007ffff782cbb9 in __GI_raise (sig=sig at entry=6) at
 ../nptl/sysdeps/unix/sysv/linux/raise.c:56
 56      ../nptl/sysdeps/unix/sysv/linux/raise.c: No such file or
 directory.
 (gdb) bt
 #0  0x00007ffff782cbb9 in __GI_raise (sig=sig at entry=6) at
 ../nptl/sysdeps/unix/sysv/linux/raise.c:56
 #1  0x00007ffff782ffc8 in __GI_abort () at abort.c:89
 #2  0x00007ffff7825a76 in __assert_fail_base (fmt=0x7ffff79772b0
 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n",
     assertion=assertion at entry=0x7ffff279805a <error: Cannot access memory
 at address 0x7ffff279805a>, file=file at entry=0x7ffff2796e04 <error: Cannot
 access memory at address 0x7ffff2796e04>,
     line=line at entry=6769,
     function=function at entry=0x7ffff2799400 <CbcMain1(int, char const**,
 CbcModel&, int (*)(CbcModel*, int),
 CbcSolverUsefulData&)::__PRETTY_FUNCTION__> <error: Cannot access memory
 at address 0x7ffff2799400>) at assert.c:92

 }}}
 )


 I hope this information will be helpful. Sorry I can not share exact
 problem to reproduce because it contains confidential data.
 The bug triggers very rare; even slightly modified problems passed
 successfully.

 Thanks.

--
Ticket URL: <https://projects.coin-or.org/Cbc/ticket/158>
COIN-OR Branch-and-Cut MIP Solver <http://projects.coin-or.org/Cbc>
An LP-based branch-and-cut MIP solver.