Validation of random graph construction #7
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After the graph has been constructed, dumps all the edges to a list and compares with the list of randomly generated edges.
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Parallel random graph construction in GraphBIG is not implemented correctly.
To illustrate the problem, I added validation code to the end of the parallel random graph construction benchmark. It dumps the graph back to an edge list after construction, and then compares with the randomly generated list the graph was constructed from. When I run with more than 1 thread, the validation usually fails, although it occasionally passes.
C++ standard library containers like
vector,list, andunordered_mapare not thread-safe. Callingpush_backconcurrently on the same data structure without synchronization is leading to data corruption in this benchmark. Locking each vertex before adding an edge should solve the problem, but this will have a significant impact on performance.