perfex and FP_ASSIST

Open discussion of PAPI.

perfex and FP_ASSIST

Postby rschulz » Sat Jul 24, 2010 1:45 am

Hi,

I don't understand how to get the event code for a specific event. In my case I would like to find out what the event code for an FP_ASSIST is. Using the code given by papi_native_avail (0x4000001a), results in the error message "fd/status: Invalid argument". Or is there some other relative simple tool which prints the total count for an event, to test whether an event is working correctly.

Since I always get 0 events with hpctoolkit for FP_ASSIST I am wondering whether this is a problem in hpctoolkit, PAPI, perfctr or the hardware. It is a XEON 5550 and as far as I understand the Intel documentation the underflow in my program should cause a FP_ASSIST. Does someone happen to know whether FP_ASSIST works correctly on Nehalem-EP?

Thanks
Roland
rschulz
 
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Re: perfex and FP_ASSIST

Postby admin » Mon Jul 26, 2010 10:50 am

You can use the papi_command_line utility to see if FP_ASSIST is a properly formed event name and whether or not it counts anything for a predetermined workload (a loop with 1 million flops, I think). Unfortunately, our Nehalem indicates 0 counts for this workload, so I suspect yours will too. Notice that the output of papi_native_avail indicates that FP_ASSIST supports 3 unit masks, or modifiers: ALL, INPUT and OUTPUT. At least one of those modifiers should be specified. I don't know why the utilities aren't showing an error if that isn't the case.
admin
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Re: perfex and FP_ASSIST

Postby rschulz » Mon Jul 26, 2010 1:51 pm

Is it possible to set these modifiers with papi_command_line? I added a few lines to command_line.c causing a denormal and thus would expect to get a count.
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