[PD] Re: [PD-announce] volctl~: an advanced volume control external

[Tim Blechmann]

> you external gets nice click-free vol control at a significant cpu
> cost reduction?  did you do any benchmarking?  definitely adding this
> to my test todo list...

to get some exact results i tested the following:

i did a test with 4096 objects either line~ ->*~ or volctl~

on my machine (p4, 2.5GHz) the line~/*~ combination used about 110% cpu
time ... volctl~ used about 58% ...

so it's about 1.9 times faster ... this was done using blocksizes of 64,
and assembler coded *~ and volctl~ functions using simd instructions ...

i didn't set any envelope values at all ... when changing the volume
line~/*~ will only have the overhead in generating a ramp, volctl~ will
also change the multiplication from vector/scalar to vector/vector
(which hasn't been optimized)...

i'm not sure about the speedup against the msp tree, since it doesn't
use thomas' simd code ... 
single number simd instructions (mulss) will take 1 cycle, parallel
instructions (mulps 4 operands) will take 2 cycles ... also loading data
from the memory to registers will be faster (not shure how much)...

so compared to the msp tree, there should be some further speedup
(that's why i consider it as pretty good idea to add thomas' simd to
pd-0.38)...

cheers ... tim

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