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scalesim-project / scale-sim-v2

Repository to host and maintain scale-sim-v2 code
MIT License
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Estimated ofmap bandwidth is quite high #107

Open Oliverwang11 opened 2 months ago

Oliverwang11 commented 2 months ago

Hello,

First thanks a lot for your contribution and useful simulator.

I have a question about the estimated ofmap bandwidth, it seems quite high for me. I used the tool to simulate a simple fully connected layer which has 1 1 1 1 256 72 1 hyperparameters. In an output stationary model, I set the output buffer to 4 KB. For a double buffer, 2KB is the active buffer size. And a 2KB buffer is enough for my 72 B output right? So we don't need very high bandwidth to shift the things output.

However, when I run the code, I get an estimated 72 bytes per cycle bandwidth, and I check the code, it seems like in the estimated model, the bandwidth for ofmap is directly assigned to the column length of the PE array, which is quite high.

Did I misunderstand something? Since when I run in estimation model, I get quite a high estimated bandwidth (72) for zero stalls, but when I set the bw to 10, there seems like still no stall for the fc layer which I run.

Best wishes! Thanks in advanced!

ritikraj7 commented 3 weeks ago

Hi @Oliverwang11, I could not understand your hyperparameters. Can you please provide the exact config and topology files? I can try to reproduce the ofmap bandwidths that you are getting.