john
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openwall
md5crypt-opencl often autotuning poorly (on nvidia 2080ti)
As mentioned in #5006, I noticed md5crypt-opencl would often autotune to too low values resulting in significantly lower speed.
In 10 runs on a 2080ti:
| ws | speed (many salts) | num times |
|---|---|---|
| 256, 34816 | 12916K c/s | 6 |
| 256, 4456448 | 23014K c/s | 2 |
| 256, 2228224 | 22825K c/s | 1 |
| 256, 139264 | 21547K c/s | 1 |
I haven't seen this behavior with any other format but it would sure be nice to avoid that lowest setting.
At autotune-time, the speed is obviously detected as on par with the higher ws figures, such as 22524K c/s
Often, the 34816 come from back-tracking in autotune, but not always:
Of 10 runs (not same runs as above), 8 ended up with 34816 from back-tracking, 1 ended up with 34816 from not back-tracking and a single run ended up with 139264.
On 10 runs with real cracking for 10 seconds at that low GWS of 34816, the speed were 12564K-14360K c/s.
On 10 runs with real cracking for 10 seconds at the second lowest GWS (from above) of 139264, the speed were 20542K-21202K c/s.
So this is not a benchmark issue but definitely an autotune issue with IRL impact.
I think this is so bad I added a bug label, even if it's not (I guess) technically a bug.