Fix indeterministic behavior in Scoreboard::checkCollision function

accel-sim / accel-sim-framework

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Fix indeterministic behavior in Scoreboard::checkCollision function #220

Closed LAhmos closed 1 year ago

LAhmos commented 1 year ago

Fix indeterministic behavior in Scoreboard::checkCollision (reporting false RAW/WAW) function caused by uninitialized 'pred' variable when parsing the trace.

cesar-avalos3 commented 1 year ago

So https://github.com/accel-sim/gpgpu-sim_distribution/blob/e033c1f2dd7019ffe2733e24c096ad0dbc0d2299/src/gpgpu-sim/scoreboard.cc#LL138C1-L138C52 was causing the issue? Great catch

LAhmos commented 1 year ago

Yes, in some cases, the pred register was receiving values that caused collisions, resulting in false RAW/WAW reports. I see consistent results now

tgrogers commented 1 year ago

Nice work! This is precisely the reason we need to fix the warnings ;)

nothingface0 commented 1 year ago

I can verify that, after re-running some of the problematic rodinia 3.1 benchmarks with the proposed fix and building for release with -O3, the results are consistent and deterministic.

The benchmarks I ran (8 times each) were the following:

hotspot: 512_2_2___data_temp_512___data_power_512_output_out
hotspot: 1024_2_2___data_temp_1024___data_power_1024_output_out
dwt2d: __data_rgb_bmp__d_1024x1024__f__5__l_3

Great work @LAhmos :)