Understanding performance of masks: test?a^6 vs. ?a^6test vs. ?a^6

[fsdafsadfsdsdaf]

Hey there,

on the same hardware

?a?a?a?a?a?a --- takes ~ 10 Sek at > 70 GH/s
?a?a?a?a?a?atest --- takes ~ 10 Sek at > 70 GH/s
test?a?a?a?a?a?a --- takes about 25 Min at only ~ 500 MH/s

why is it so slow if a prefix is known? It is more common to know a prefix than a suffix, isn't it? - at least that is what I observed.
-S does not improve the performance (it even slows it down quite a lot)

Thanks

[penguinkeeper]

It's a known problem with the way that Hashcat distributes work, it uses the first 4 characters to parallelise, so when the first 4 characters has a large keyspace, it can distribute work across the thousands of GPU cores, but when it's only a single candidate - "test", Hashcat really struggles to fully make use of the whole GPU, causing very low speeds as you're seeing there. It's a known, architectural problem with Hashcat that unfortunately can't (and won't) be solved