CyberShake migration to Summit

This page is being used to gather information on the effort to migrate CyberShake from Titan to Summit.

Software Status

Initially, we are running each phase on Summit and comparing the output with that on Titan.

• PreCVM: OK
• UCVM:
• Smoothing:
• PreSGT: OK
• PreAWP: OK
• AWP-GPU-SGT:

AWP-GPU-SGT

We arbitrarily selected site s2257 and ran the X-component (the AWP X-component, which is the RWG Y-component) on Summit, to compare to the results on Titan.

Numerical comparison

When comparing all SGT points (test-reference), we get:

Average diff = 1.317764e-12, average percent diff = -3.324251%
Largest diff of 0.000150 at float index 1718660606.
Largest percent diff of 5017404928.000000% at float index 8636382051.

When we only consider points greater than 1e-10 (peak SGT values are usually 1e-4 to 1e-3), we get:

Average diff = 1.317764e-12, average percent diff = 0.133713%, average absolute percent diff = 12.979661%
Largest diff of 0.000150 at float index 1718660606.
Largest percent diff of 7148245.500000% at float index 1626932526.

The average percent diff is much less than before, but we included the absolute percent diff, which reveals that many points differ by considerable amounts and there was some canceling going on when looking at the average percent diff.

As a result of this, we decided to more closely investigate what is causing the differences between the two systems.

Initial plots

We identified point ID 71610 as the point which contains the largest difference between the test and reference SGTs.

Below are plots of this point, comparing the Titan and Summit results and the difference. The zoomed-in version focuses on the 25 seconds with the largest differences.

Full 200-second SGT

125-150 seconds

CUDA versions

The default version of CUDA on Titan is 9.1.85 and on Summit it's 9.2.148. We tried rebuilding the AWP code on Summit with 9.1.85 and GCC and rerunning. It didn't make much difference:

Average diff = 1.272838e-12, average percent diff = 0.133971%, average absolute percent diff = 12.971045%
Largest diff of 0.000150 at float index 1718660606.
Largest percent diff of 7148275.000000% at float index 1626932526

X and Y-only work distribution

We tried distributing the work only across X (PX=120, PY=1, PZ=1)but got similar differences.

X:

Average diff = 1.317764e-12, average percent diff = 0.133713%, average absolute percent diff = 12.979661%
Largest diff of 0.000150 at float index 1718660606.
Largest percent diff of 7148245.500000% at float index 1626932526.

We also tried it across Y (PX=1, PY=210, PZ=1). This resulted in a memory error:

*** Error in `/gpfs/alpine/proj-shared/geo112/CyberShake/software/AWP-GPU-SGT/bin/pmcl3d': free(): invalid size: 
0x0000000040728bc0 ***
======= Backtrace: =========
/lib64/libc.so.6(cfree+0x4a0)[0x2000004f9cd0]
/gpfs/alpine/proj-shared/geo112/CyberShake/software/AWP-GPU-SGT/bin/pmcl3d[0x10008d34]
/gpfs/alpine/proj-shared/geo112/CyberShake/software/AWP-GPU-SGT/bin/pmcl3d[0x10008774]
/lib64/libc.so.6(+0x25100)[0x200000485100]
/lib64/libc.so.6(__libc_start_main+0xc4)[0x2000004852f4]

Smaller SGTs

We tried generating SGTs for the SMALL site, which are about 6% the size of s2257, on both Titan and Summit. We actually saw even larger average differences:

Average diff = 6.027801e-12, average percent diff = -1.673267%, average absolute percent diff = 21.367271%
Largest diff of 0.000067 at float index 175412388.
Largest percent diff of 2091817.000000% at float index 1363132518.