Calculating FLOPS (Floating-point Operations per Seconds)

Question

How can I calculate FLOPS of my application? If I have the total number of executed instructions, I can divide it by the execution time. But, how to count the number of executed instructions?

My question is general and answer for any language is highly appreciated. But I am looking to find a solution for my application which is developed by C/C++ and CUDA.

I do not know whether the tags are proper, please correct me if I am wrong.

Answer 1

What I do if the number of floating point operations is not easily modeled is to produce two executables: One that is the production version and gives me the execution time, and an instrumented one that counts all floating point operations while performing them (surely that will be slow, but that doesn't matter for our purpose). Then I can compute the FLOP/s value by dividing the number of floating point ops from the second executable by the time from the first one.

This could probably even be automated, but I haven't had a need for this so far.

Answer 2

You should mathematically model what's done with your data. Isolate one loop iteration. Then count all simple floating-point additions, multiplications, divisions, etc. For example, y = x * 2 * (y + z*w) is 4 floating-point operations. Multiply the resulting number by the number of iterations. The result will be the number of instructions you're searching for.