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Completely wrong results of sgemm & dgemm with ACML 6.0.6 on Intel CPUs?

Question asked by bugchucker on Oct 31, 2014
Latest reply on Mar 11, 2015 by tangjinchuan

Hello everybody,

 

while trying to check the performance of my computer's GPU (Pitcairn)

I noticed that even when submitting the calculation to host cpu as default

results in completely wrong results of sgemm & dgemm.

 

The system consists of an Intel Xeon E5-2670 CPU and an AMD/ATI FirePro W7000 card,

running an Ubuntu 14.04.

 

The test-setup consists of two 1500 x 1500 matrices, initialized element-wise to a random value between 0 and 1.

The destination matrix was once calculated 'by-hand, and once by a dgemm call.

 

The maximum absolute element-wise difference between 'by-hand' and dgemm was

Difference: 4158414.672035371885

using acml-6.0.6.13/gfortran64. The result is clearly wrong.

 

Just to see that the acml6 did send it to the host cpu (ACML_LOG_FILTER=1):

GemmThreshold: transa( N ), transb( N ), m( 1500 ), n( 1500 ), k( 1500 ), alpha.real( 1 ), alpha.imag( 0 ), lda( 1500 ), ldb( 1500 ), beta.real( 0 ), beta.imag( 0 ), ldc( 1500 ), prec( d ), usegpu( 0 )

 

 

Whereas linking the same binary with acml-5.3.1/gfortran64 you get the

roughly expected difference of

Difference:   0.000000020023

 

 

For checking and reference, the small test program is attached.

Here the test-case is only in double-precision, but the same

happens with single precision.

 

Has anybody noticed this before?

 

 

Regards,

 

bugchucker

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