Vector instruction set in HPC Perf. Characterization

[Smith__John]

Hi,

I am currently profiling a program by using VTune.

The attached image shows that there are more than 2 vector instructions.

I am wondering if there are more than 2 vector instruction set in the "HPC Performance Characterization", this means that a certain function uses all of the instructions? or they are the possible candidate vector instructions that are used by the function?

It would be appreciated if anyone could let me know.

Thanks.

[Dmitry_P_Intel1]

Hello,t

VTune does static analysis of a function body and lists all vector instruction sets that were recognized.

Could you please specify in more details what you meant under "candidate vector instructions" to give you more precise answer?

Thank you, Regards, Dmitry

[Smith__John]

Hello, Dmitry

I meant I was wondering whether or not some of those instructions are executed in practice.

For example,

If there were three instructions such as AVX, AVX2, SSE in the vector instruction set slot, but only AVX instruction was executed actually.

Is this case possible?

or 

All three instructions above are executed during its execution time?

Thank you

[AthiraM_Intel · Accepted solution]

Hi,

Usage of instruction set does not depend on which analysis you run – i.e. HPC Performance Characterization or Hotspot analysis. Instruction sets are generated by the compiler and which are analyzed by these profiling tools.

Intel VTune is a profiling tool that analyzes your application, it lists instruction set(s) used  in your application. The vector instruction sets listed by Intel VTune are the ones used by your application and not suitable candidates. Tools like Intel Advisor can list the possible candidates and the performance improvement that can be achieved by using a different instruction set.

Hope this clarifies your query.

[AthiraM_Intel]

Hi,

Could you please confirm whether the solution provided was helpful.

[AthiraM_Intel]

Hi,

We hope your query is answered. We are closing this thread.

Please feel free to open a new thread if you have any further queries.

Thanks