Author: Andrew Dados
Date: 09:26:17 07/07/03
Go up one level in this thread
On July 06, 2003 at 23:25:00, Uri Blass wrote:
>In movei I have a number between 0 and 255 and I want to do some functions for
>every 1 that it has in its binary representation(number of functions to
>implement is the same as the number of 1's in the number and there is a
>different function based on the value of the 1)
>
>I do not like to call functions because functions use local varaibles and
>generating a copy of the local varaibles only to forget them may take computer
>time and I also do not use the functions more than once.
>
>I thought to use switch(see the code later in this post) but the problem is that
>switch continue to do everything without break and I want to have switch that
>does not continue to do everything but does not quit and simply forget about the
>fact that I called switch.
>
>Here is the type of the code that I plan to have now.
>I do not like all the if (number&2) or if (number&4) and the question is if I
>can do it faster.
>
>
>i=smallestpower[number];
>switch(i)
>{
> case 0:do list of commands
> if (number==1) break
> else
> {
> number-=1;
> i=smallestpower[number];
> }
> case 1:if (number&2)
> {
> do list of commands
> if (number==2) break;
> else
> {
> number-=2;
> i=smallestpower[number];
> }
> }
> case 2:if (number&4)
> {
> do list of commands
> if (number==4) break;
> else
> {
> number-=4;
> i=smallestpower[number];
> }
> }
> case 3:if (number&8)
> ...
> ...
> case 6:if (number&64)
> ...
> case 7://if you got there you know that number is 128 because you did not get
>out by break so you do not need to check it
>
>
>Uri
boolean checking is way faster then jumps; in your implementation you get about
6 jumps in the code (case is a jump) since you have about 1.2 bit set on
average. I'll try to go down to below 4 jumps average:
if i & (128+64){
if i & 128 {}
if i & 64 {}
if ! i | 63 goto done;
}
if i & (32+16){
if i & 32 {}
if i & 16 {}
if ! i | 15 goto done;
}
if i & (8+4){
if i & 8 {}
if i & 4 {}
}
if i & (2+1){
if i & 2 {}
if i & 1 {}
}
done:
--------------
Since you have small number of average bits set this should be way faster then
case switch.
-Andrew-
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.