fix shared memory bug #185
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sjeaugey
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Mar 4, 2019
The shared memory filename was only based on the destination. While this was OK for rings since only one rank would send data to a given rank, it would crash with trees because they communicate in both directions. Co-authored-by: Rong Ou <rong.ou@gmail.com>
The shared memory filename was only based on the destination. While this was OK for rings since only one rank would send data to a given rank, it would crash with trees because they communicate in both directions. Co-authored-by: Rong Ou <rong.ou@gmail.com>
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When building the tree the connections are bidirectional, the original code was reusing the same shared memory buffer for both directions, causing race conditions. This only happens when
CUDA_VISIBLE_DEVICESare set to single GPUs, thus all connections are through shared memory.For example,
0 <-> 1 <-> 2 <-> 3
both
1and2would use the same buffers for both directions.@sjeaugey