Why GETRF Partial Pivoting and GETRF without Pivoting have a same execution time?

[n_aron]

Hi,

I did some test with GETRF Partial Pivoting version and GETRF Without Pivoting version. I was expected to see Without Pivoting version is faster but they have equal executing time. Do I did some mistake or this is just a normal behavior of GETRF?

[VidyalathaB_Intel]

Hi,

Thanks for reaching out to us.

>>I did some test with GETRF Partial Pivoting version and GETRF Without Pivoting version

Could you please provide us a sample reproducer for both pivot and without pivoting version.

(>>but they have equal executing time

and also how the execution time is being calculated)

And also please provide us your environment details on which you are working

OS & version

MKL version

Regards,

Vidya.

[n_aron]

Thanks Vidya for reply.

Could you please provide us a sample reproducer for both pivot and without pivoting version.

Here is the code for No pivoting version:

https://paste.debian.net/hidden/f47286e6/

And this one for Partial Pivoting version:

https://paste.debian.net/hidden/ba2e5553/

and also how the execution time is being calculated?

        double s_initial = dsecnd();

        dgetrf(&m, &n, A, &lda, ipiv, &info);

        double s_elapsed = (dsecnd() - s_initial);

        printf("Time elapsed PP =%.5f milliseconds\n ", s_elapsed);

I am runing the code like this:

for i in 1 2 4 6 8 10 12 14 16
do

            ./MKL_DGETRF_PP 32000 $i
done

Here the matrix is 32000x32000

And also please provide us your environment details on which you are working

OS & version

Distributor ID: Ubuntu
Description: Ubuntu 18.04.5 LTS
Release: 18.04
Codename: bionic

MKL version

/intel_oneapi/2021_02/

Hardware:

Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
CPU(s): 40
On-line CPU(s) list: 0-39
Thread(s) per core: 2
Core(s) per socket: 10
Socket(s): 2
NUMA node(s): 2
Vendor ID: GenuineIntel
CPU family: 6
Model: 85
Model name: Intel(R) Xeon(R) Silver 4210R CPU @ 2.40GHz
Stepping: 7
CPU MHz: 1000.153
CPU max MHz: 3200.0000
CPU min MHz: 1000.0000
BogoMIPS: 4800.00
Virtualization: VT-x
L1d cache: 32K
L1i cache: 32K
L2 cache: 1024K
L3 cache: 14080K
NUMA node0 CPU(s): 0-9,20-29
NUMA node1 CPU(s): 10-19,30-39
Flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc art arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault epb cat_l3 cdp_l3 invpcid_single intel_ppin ssbd mba ibrs ibpb stibp ibrs_enhanced tpr_shadow vnmi flexpriority ept vpid ept_ad fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid cqm mpx rdt_a avx512f avx512dq rdseed adx smap clflushopt clwb intel_pt avx512cd avx512bw avx512vl xsaveopt xsavec xgetbv1 xsaves cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local dtherm ida arat pln pts hwp hwp_act_window hwp_epp hwp_pkg_req pku ospke avx512_vnni md_clear flush_l1d arch_capabilities

[VidyalathaB_Intel]

Hi,

Thanks for sharing the details.

The issue is reproducible from our end.

We are looking into this issue internally. we will get back to you soon.

Regards,

Vidya.

[n_aron]

Hi,

Any news? Maybe we can share idea, for sure I am not professional like you  

Best regards,

Aron

[Gennady_F_Intel]

which Lapack's function do you check?

I see the links (Here is the code for No pivoting version: https://paste.debian.net/hidden/f47286e6/

And this one for Partial Pivoting version: https://paste.debian.net/hidden/ba2e5553/ )

You provided, point out to the wrong pages.

[Gennady_F_Intel]

The performance benefit will depend on the input matrix.

As we don't see the needed details, The thread is closing and we will no longer respond to this thread. If you require additional assistance from Intel, please start a new thread. Any further interaction in this thread will be considered community only.