IV31593: PERFORMANCE PROBLEM WITH XLSMPOPTS BINDING OPTION

Fixes are available

APAR status

Closed as program error.

Error description

A runtime performance degradation is seen when using the
XLSMPOPTS binding option as follows:

=====Compile Line:
xlf_r -O -q64 -qsmp=omp matmul.f -o matmul.exe

=====Testcase:
$ cat matmul.f
     program matmul1
      implicit none
      real*8, allocatable, dimension(:,:,:) :: a,b,c
      integer, parameter :: n = 4000
      integer i

      allocate(a(n,n,0:1),b(n,n,0:1),c(n,n,0:1))
      a = 1.d0
      b = 1.d0
!$OMP parallel do private(i)
      do i = 0,1
       c(:,:,i) = matmul(a(:,:,i),b(:,:,i))
      enddo
      deallocate(a,b,c)
      end
$

====Runtime output:
#!/bin/ksh
set -x
export XLFRTEOPTS=intrinthds=1
export XLSMPOPTS=parthds=2
time ./matmul.exe
export XLSMPOPTS=parthds=2:bindlist=proc=0,2
time ./matmul.exe

The following are from a Power7 booted in SMT-2 mode (3.56GHz)

$ ./run
+ export XLFRTEOPTS=intrinthds=1
+ export XLSMPOPTS=parthds=2
+ ./matmul.exe

real    0m27.04s
user    0m45.03s
sys     0m0.00s
+ export XLSMPOPTS=parthds=2:bindlist=proc=0,2
+ ./matmul.exe



real    1m6.88s
user    0m57.23s
sys     0m0.00s

Local fix

```
N/A
```

Problem summary

USERS AFFECTED:
Users using the bind and bindlist options of XLSMPOPTS are
potentially affected by this issue.

PROBLEM DESCRIPTION:
When using the bind or bindlist options of XLSMPOPTS, the
compiler does not respect it and binds all threads to one CPU
causing a performance degradation during runtime.

Problem conclusion

The issue was in the binding code within the compiler that binds
threads to different CPUs. This has been fixed.

Temporary fix

Comments

APAR Information

APAR number
IV31593
Reported component name
XL SMP AIX
Reported component ID
5725C7401
Reported release
310
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt
Submitted date
2012-11-07
Closed date
2012-11-28
Last modified date
2012-11-28

APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:

Fix information

Fixed component name
XL SMP AIX
Fixed component ID
5725C7401

Applicable component levels

R310 PSY
UP

[{"Line of Business":{"code":"LOB57","label":"Power"},"Business Unit":{"code":"BU058","label":"IBM Infrastructure w\/TPS"},"Product":{"code":"SSGH4D","label":"XL Fortran for AIX"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"14.1"}]

Document Information

Modified date:
01 October 2021

Tips

IV31593: PERFORMANCE PROBLEM WITH XLSMPOPTS BINDING OPTION

Fixes are available

Subscribe

APAR status

Closed as program error.

Error description

Local fix

Problem summary

Problem conclusion

Temporary fix

Comments

APAR Information

APAR number

Reported component name

Reported component ID

Reported release

Status

PE

HIPER

Special Attention

Submitted date

Closed date

Last modified date

APAR is sysrouted FROM one or more of the following:

APAR is sysrouted TO one or more of the following:

Fix information

Fixed component name

Fixed component ID

Applicable component levels

R310 PSY

Document Information

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