What is the definition of MACs ？

[minghongli233]

Hello！
I want to use the code to count the Multi-Adds operations, but I don't know if the Multi-Adds operations and MACs and FLOPs are the same thing.
I'm confused about the definition of MACs and FLOPs, and I'm also not clearly know if the code you provided is to count the MACs or FLOPs .
Could you tell me the definition of them and the difference between them?
Thank you!

[mjjung0925]

This might help! sovrasov/flops-counter.pytorch#16

[minghongli233]

Thanks for your supply! It is really helpful.

[xuxy09]

As far as I can understand, the direct output of the "profile" function is MACs instead of FLOPs. However, the demo code in the readme file uses flops as the name of the output variable. Is this a typo? Thanks.

[haoweiz23]

As far as I can understand, the direct output of the "profile" function is MACs instead of FLOPs. However, the demo code in the readme file uses flops as the name of the output variable. Is this a typo? Thanks.

the demo code in benchmark/readme is wrong. Macs returned by the "profile" function . If you want get the Flops, you should multiply 2.

[ZhangYuef]

I am confused by the FLOPs results in original ResNet paper. Let's take resnet-50 as an example. In ResNet paper the FLOPs value is 3.8G while in this repo we get 4.14G for MACs which means 4.14*2G FLOPs. So can we infer that FLOPs definition is the same here with MACs?

OpCounter
ResNet

[ssgosh]

I am confused by the FLOPs results in original ResNet paper. Let's take resnet-50 as an example. In ResNet paper the FLOPs value is 3.8G while in this repo we get 4.14G for MACs which means 4.14*2G FLOPs. So can we infer that FLOPs definition is the same here with MACs?

OpCounter
ResNet

The original resnet paper reports MACs - see the bottom-right paragraph on page 3: https://arxiv.org/pdf/1512.03385.pdf . Technically a multiply-add is a single floating point operation since 2008 (https://en.wikipedia.org/wiki/IEEE_754-2008_revision), which is probably why they still call it flops. I suppose one could make the distinction as IEEE754-1985 FLOPs vs IEEE754-2008 FLOPs.

[Lyken17]

I made clarification here https://github.com/Lyken17/pytorch-OpCounter/tree/master/benchmark#macs-flops-what-is-the-difference

[YongyuG]

MACs can also defined as "Memory Access Cost" which is strongly relative to inference time, but I think in this repo is Multi-Add Calculation