Can this be converted to sse

[zemtex]

Can this be optimized using SSE? Can anyone do it for me, it calculates multipliers of 3 and 5, if the modulus is 0, the number should be added to the result.

[dedndave]

not sure about SSE
but you could certainly speed it up a lot by using multiply-to-divide
a while back, qWord made an excellent tool for getting the "magic" numbers
http://www.masm32.com/board/index.php?topic=9937.msg72815#msg72815

another way to go would be to do something like a Sieve of Eratosthenes
http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes

[qWord]

Can this be optimized using SSE?

maybe, when using doubles for division. This would require to examine the fraction bits after division.

[zemtex]

I converted it to FPU instructions using various mixes of these instructions

Code Select Expand


            ;FTST ; Compares st0 with zero and sets FPU flags
;FCMOVNE ST(0), ST(i) ; move if not equal
;FINIT ; clear all
;FLDZ ; st(0) = 0 (everything else is pushed further down)
;FLD1 ; st(0) = 1 (everything else is pushed further down)
;FINCSTP ; rotates stackregisters upwards,   st(0) becomes st(7) and st(1) becomes st(0) etc.
;FDECSTP ; rotates stackregisters downwards, st(7) becomes st(0) and st(7) becomes st(0) etc.
;FPREM1 ; st(0) / st(1) og kalkulerer remainder og lagrer i st(0)
;FCOMI st(0), st(1) ; cmp st0 with st1, eflags will be set. carry flag is set if st0 less than st1

These are not actual code, it is just a reference that I use when coding, the order of these instructions matters not. After I picked a selection of a few of these, the code ended up being slower than the code you see in the first post.

[dedndave]

even though you have to go through 2 loops, the addition method is probably fastest
make a loop for multiples of 3 and another for multiples of 5

[zemtex]

Can you show me a sample of that?

[dedndave]

well - you just add the "divisor" to an accumulated total in each loop
the result is always a multiple of the divisor, so you always add it
the loop is reasonably fast, because all passes are valid and because you are adding instead of dividing

i will review your code - and see what i can come up with for some test code

[dedndave]

ok - give this a try...

[dedndave]

you could probably speed that up some more by using another register
in the 5's loop....
use one register to hold 5 and another to hold 10
swap the 2 registers on each pass

[jj2007]

you could probably speed that up

Hey, Dave, make a serious effort please. Your code is only a factor 70 faster - add a proc that's called Fast, not just Faster :green

[dedndave]

 :P

proof that the code design phase is more important than instruction optimization

[qWord]

is it intended, that the result overflows?

[dedndave]

ummm - no - lol

let me look at it

i figured he was happy with the answer his code generated - and mine generated the same answer

[dedndave]

wow - it overflows by a lot, too   :P

i get a total of 2333333416666668 - 16 decimal digits

is this for Project Euler ?
it looks like problem #1, which only goes up to 1000

[zemtex]

dedndave, it doesn't really matter, it works for testing the speed.  :U

It's amazing what kind of terror a div instruction can do. Can it be further optimized?