Ant-colony optimisation metaheuristic graph colouring function

[professorcode1]

No description provided.

[ntamas]

The reason for the failure is written in the test log if you scroll up a bit in the logs:

==13205==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 8000 byte(s) in 1 object(s) allocated from:
    #0 0x561c260c8048 in __interceptor_calloc (/home/vsts/work/1/s/build/tests/example_igraph_coloring+0xab048) (BuildId: 0c12bb4f24227d1a173a8f2565fe073c9c24f344)
    #1 0x561c2611d036 in igraph_vector_int_init /home/vsts/work/1/s/src/core/vector.pmt:144:21
    #2 0x561c261469f5 in igraph_vertex_coloring_AntColony /home/vsts/work/1/s/src/misc/coloring.c:281:5
    #3 0x561c26104890 in main /home/vsts/work/1/s/examples/simple/igraph_coloring.c:34:5
    #4 0x7f54a1765d8f  (/lib/x86_64-linux-gnu/libc.so.6+0x29d8f) (BuildId: 69389d485a9793dbe873f0ea2c93e02efaa9aa3d)

Direct leak of 272 byte(s) in 1 object(s) allocated from:
    #0 0x561c260c8286 in __interceptor_realloc (/home/vsts/work/1/s/build/tests/example_igraph_coloring+0xab286) (BuildId: 0c12bb4f24227d1a173a8f2565fe073c9c24f344)
    #1 0x561c2611e73a in igraph_vector_int_reserve /home/vsts/work/1/s/src/core/vector.pmt:474:11
    #2 0x561c26107dee in igraph_vector_int_resize /home/vsts/work/1/s/src/core/vector.pmt:1261:5
    #3 0x561c2613dd44 in igraph_i_neighbors /home/vsts/work/1/s/src/graph/type_indexededgelist.c:929:5
    #4 0x561c26146f3a in DSatur /home/vsts/work/1/s/src/misc/coloring.c:205:9
    #5 0x561c26146ba5 in igraph_vertex_coloring_AntColony /home/vsts/work/1/s/src/misc/coloring.c:299:5
    #6 0x561c26104890 in main /home/vsts/work/1/s/examples/simple/igraph_coloring.c:34:5
    #7 0x7f54a1765d8f  (/lib/x86_64-linux-gnu/libc.so.6+0x29d8f) (BuildId: 69389d485a9793dbe873f0ea2c93e02efaa9aa3d)

SUMMARY: AddressSanitizer: 8272 byte(s) leaked in 2 allocation(s).

Basically, you allocate a new vector in saturation_degree but you never free the memory when you are done with it.

The correct usage pattern for allocating and freeing a new int vector would be:

IGRAPH_VECTOR_INIT_INT_FINALLY(&saturation_degree, vc);

[...use the vector the way you want...]

igraph_vector_int_destroy(&saturation_degree);
IGRAPH_FINALLY_CLEAN(1);

IGRAPH_VECTOR_INIT_INT_FINALLY() is a shorthand for this:

IGRAPH_CHECK(igraph_vector_int_init(&saturation_degree, vc));
IGRAPH_FINALLY(igraph_vector_int_destroy, &saturation_degree);

The important bit is the IGRAPH_FINALLY part, which registers the vector to be destroyed should an error happen in any subsequent calls that are wrapped in IGRAPH_CHECK(). When you are done with your vector, you must call igraph_vector_int_destroy() manually, and then remove it from the "finally" stack with IGRAPH_FINALLY_CLEAN(1).

A similar problem exists in DSatur() where you allocate the neighbours vector without proper error handling and cleanup.

If you do not know these macros, check out section 5.4 of the chapter about error handling in the docs.

[professorcode1]

Thank you for the help. I primarily program in C++ with smart pointers so I completely forgot about the manual memory allocation and I didn't know the logs will have debug statements. I will fix it.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 14 days if no further activity occurs. Thank you for your contributions.

[professorcode1]

Commenting to prevent issue from being closed. Can we keep this open for now. I can't continue on it before we settle the situation with the implementation of the sets.

[ntamas]

Removed the stale label so it will remain open until stalebot makes its rounds again :)

[codecov]

Codecov Report

Merging #2250 (3d504fb) into master (e84149a) will increase coverage by 0.00%.
The diff coverage is 87.09%.

@@           Coverage Diff           @@
##           master    #2250   +/-   ##
=======================================
  Coverage   83.46%   83.46%           
=======================================
  Files         376      376           
  Lines       61576    61638   +62     
=======================================
+ Hits        51394    51448   +54     
- Misses      10182    10190    +8     

Impacted Files	Coverage Δ
src/misc/coloring.c	94.76% <87.09%> (-3.69%)	⬇️

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