[Botan-devel] OpenMP = superfast CTR/ECB

Jack Lloyd lloyd at randombit.net
Tue Nov 17 14:10:53 EST 2009


I made the switch for block ciphers to support multi block operations
primarily to support SIMD. However with minimal OpenMP goo it also
helps out pretty dramatically for modes which support parallel
operation:

AES-128/CTR-BE [core] 197.24 (2x faster)
AES-128/ECB [core] 302.06 (2.5x faster)

(This is with ECB and CTR modes set to operate on 256 blocks (= 4Kb)
in parallel; the default is 8 blocks)

Unfortunately it also hurts sequential performance substantially; CBC
goes from ~90 MiB/s to 60 with ICC and 25 with GCC. I'm not sure how
to deal with that yet.



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