25 Oct 2000
(updated 25 Oct 2000 at 23:39 UTC) »
Been, amoungst other stuff, optimising my DES
implemenation today. The key setup time has tripled at the
moment (though I have an idea how to get that down), but the
number of cycles taken to process a 64 bit block is down to
12% of the original. This was achived by a mixture of static
preprocessing, preprocessing the key setup, removing most
uint64_t values and using two uint32_t values where possible
(my target plaform is the ARM, so 32 bit operations are a
Good Thing(tm)), and applying some human optimisation to the
bit permutations. So far this has been just using C - I've
not needed to use any asm - I've managed to express
everything I want so far in C.
Next a little more optimisation of the C version,
I try and apply hardware to some parts of the algorithm
(mainly the bit swizling). I have two hardware versions in
mind - one a plain partial hardware/software implementation,
and one which uses partial evalution to put the key into the
Managed to half the key setup time. I've completely
removed 64 bit values except as the inputs to the algorithm.
By a BOE calculation, it can now process about 0.8Mbytes/sec
on a 1GHz XScale/StrongARM, but that's not including
cache-misses. Not particularly impressive.
Had to reboot a keyboard today. I think the
microcontroller inside had got confused, and the PC it was
attached to refused to acknowledge it until I powered off
the machine (rebooting it didn't help).
Installed GNAT (the gnu Ada compiler) today - scary.
got flashbacks to when I was being taught Real Time Systems
Learned how to use a diablo.
Oh, and I forgot to say congrats to
adamd who submitted his PhD
last week. He now seems to have a perpetual smile on his