c++ - Calculating GFlops -

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i'm wondering how calculate gflops program of mine like, let's say, cuda application.

do need measure execution time , number of floating point operations in code? if had operation "logf", count 1 flop?

the number of actual floating point operations depend on how code written (compilers can optimize in both directions - is, merging common operatoions c = (a * 4.0 + b * 4.0); can becomes c = (a + b) * 4.0, 1 less wrote. compiler can convert more operations:

 c = / b;

may turn into:

 temp = 1 / b;  c = temp * a;

(this because 1/x "simpler" y/x, , multiplication faster division).

as mentioned in comments, floating point operations (log, sin, cos, etc) take more one, more ten, operations result.

another factor take account "loads" , "stores". these can quite hard predict, highly dependant on compilers code generation, number of registers available compiler @ given point, etc, etc. whether loads , stores count or not depends on how @ things, count towards total execution time. if there lot of data work through, each step simple (e.g. c = + b a, b , c vectors), time fetch data memory longer execution time of add. on other hand, c = log(a) + log(b); "hide" time load , store results, because log takes lot longer load or store operations.


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