[Cbc] Threadsafe usage of Cbc

[Cornelius Riemenschneider]

Hello,

we use CBC via googles or-tools from java in our application.

Compared to scientific problems, our problems are small and solved by Cbc in <1s (which is great!).

As we process requests from users concurrently, we?d also like to call Cbc concurrently.

Currently, this is impossible, because Cbc uses the static parameters array in CbcMain0 and CbcMain1 and thus crashes or reads incorrect parameters.

One backtrace, for example is:

 

#2 0x00007fb3435bf52b in __libc_message (do_abort=<optimized out>, fmt=<optimized out>) at ../sysdeps/unix/sysv/linux/libc_fatal.c:189
#3 0x00007fb3435c8d76 in malloc_printerr (action=3, str=0x7fb3436a1248 "double free or corruption (!prev)", ptr=<optimized out>) at malloc.c:6283
#4 0x00007fb3435cdaac in *__GI___libc_free (mem=<optimized out>) at malloc.c:3738
#5 0x00007fb342733f06 in std::string::assign(std::string const&) () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#6 0x00007fb2d652cb7b in establishParams(int&, CbcOrClpParam*) () from libjnilinearsolver.so
#7 0x00007fb2d64edc3b in CbcMain0(CbcModel&) () from libjnilinearsolver.so
#8 0x00007fb2d6511bec in callCbc(char const*, CbcModel&) () from libjnilinearsolver.so
#9 0x00007fb2d64e3fce in operations_research::CBCInterface::Solve(operations_research::MPSolverParameters const&) () from libjnilinearsolver.so
#10 0x00007fb2d64cfe45 in operations_research::MPSolver::Solve(operations_research::MPSolverParameters const&) () from libjnilinearsolver.so
#11 0x00007fb2d64cff3b in operations_research::MPSolver::Solve() () from libjnilinearsolver.so
#12 0x00007fb2d64c91cf in Java_com_google_ortools_linearsolver_mainJNI_MPSolver_1solve_1_1SWIG_10 () from libjnilinearsolver.so

# from here on it?s just the JVM

 

As I don?t know the code and it?s hard to read, I can?t really fix the problem by myself,

but wouldn?t it be better to move parameters inside CbcModel instead of having a static array laying around?

 

Andi f that?s done (or another solution is found), do you know of any thread-safety issues in cbc?

Keep in mind, we don?t want Cbc to solve our problem in multiple threads, we just want to be able to solve different problems simultaneous.

 

Regards,

Cornelius Riemenschneider

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