FLOP measurement

Question

I'm trying to estimate FLOPS for my application using intel vtune Amplifier and I'm using this post here as a guideline : https://software.intel.com/en-us/articles/estimating-flops-using-event-based-sampling-ebs/

The problem is that I can't find the FP_COMP_OPS_EXE event in vtune gui. When I run amplxe-cl with this event config, I get the following error:

amplxe: Error: Invalid Event FP_COMP_OPS_EXE.X87 discarded.

I'm working on CentOS and my processor is intel Xeon

Any help would be appreciated

Answer 1

The available events set can change between processors generations. It is important to know exactly your processor name. The event you mentioned exist for Intel Xeon v2 (Ivybridge based) and you can use following formula to measure the number of floating points operations: FP_COMP_OPS_EXE.SSE_SCALAR_SINGLE + 4 * FP_COMP_OPS_EXE.SSE_PACKED_SINGLE + 8 * SIMD_FP_256.PACKED_SINGLE + FP_COMP_OPS_EXE.SSE_SCALAR_DOUBLE + 2 * FP_COMP_OPS_EXE.SSE_PACKED_DOUBLE + 4 * SIMD_FP_256.PACKED_DOUBLE + FP_COMP_OPS_EXE.X87

For Haswell based processors (Xeon v3) there are no such events and FLOPs calculation is not possible there.

For Broadwell based the formula will be following: FP_ARITH_INST_RETIRED.SCALAR_SINGLE + 4 * FP_ARITH_INST_RETIRED.128B_PACKED_SINGLE + 8 * FP_ARITH_INST_RETIRED.256B_PACKED_SINGLE + FP_ARITH_INST_RETIRED.SCALAR_DOUBLE + 2 * FP_ARITH_INST_RETIRED.128B_PACKED_DOUBLE + 4 * FP_ARITH_INST_RETIRED.256B_PACKED_DOUBLE + INST_RETIRED.X87