Re: Optimizing basic operations
- Posted by Spock Jul 22, 2013
- 6495 views
Please inform if any of you have a trick to optimize the simple comparison and assignment operators. I'm especially interested in optimizing this logic: If X is greater than Y then assign the value of X to Y. Is it possible to use something like pointers at a low machine level to speed up the assignment? All of X and all of Y will be integers. Thanks in advance.
James, If I were working on a project like yours and needed ultimate speed I would use assembly code, eg, the following (untested and needing modification) snippet will do this operation without branching:
if eax > ebx then ebx += eax end if
"xor edx, edx" "cmp eax, ebx" "setle dl" "dec edx" "and edx, eax" "add ebx, edx"
Simply converting this snippet to machine code, poking it somewhere, and calling it with X and Y parameters will not help speed-wise as the overhead of actually calling the machine code routine will completely offset the very real speed gains that you would get from it.
Now, there are some (I'm talking about people on other programming forums..) who don't worry much about code speed, probably because they don't get to code much beyond some lame business app, but the plain truth is that the faster you can go the more you can do.
If it were possible to access X and Y in a linear fashion (in the algorithm) it would probably be not too difficult to construct a small assembly code framework to do all the processing. However, if you needed to do some fancy memory allocation or something tricky (eg, recursion) as part of the algorithm, well, things might get too complex to contemplate using asm.
Exactly what is your algorithm? It might be possible to realize it using asm, or maybe not.
Spock
