## Game programming

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* or /? Which is faster? Posted by BenGmo on 31 Jan 2000 at 8:06 PM
Which is faster, multiplication or division? Does it matter? Say i had to divide a lot of numbers by 3. Would it be faster to multiply them by 0.333333333? Lets assume that all the numbers are floats.

Re: * or /? Which is faster? Posted by The Watcher^TUHB on 1 Feb 2000 at 3:37 AM
: Which is faster, multiplication or division? Does it matter? Say i had to divide a lot of numbers by 3. Would it be faster to multiply them by 0.333333333? Lets assume that all the numbers are floats.<br>
: <br>
<br>
<br>
Depends, would you call about ten times as fast faster or slower? *grin*. go for the fmul. Always. <br>

Re: Re: * or /? Which is faster? Posted by Zeppo on 1 Feb 2000 at 11:00 AM
A tip!<br>
<br>
If you want to divide, or multiply a number<br>
by a factor that equals n^2 e.g (1, 2, 4, 8, 16..)<br>
use SHL(SHiftLeft) for multiplication, and<br>
SHR(SHiftRight) for division.<br>
<br>
//-------<br>
int x = 12 >> 1; // x is now (12 / 1^2) = 6<br>
int x = 12 << 2; // x is now (12 * 2^2) = 48<br>
//-------<br>
<br>
REMEMBER! it's for int numbers =)<br>
(int)floatVar << x, should work though.<br>
<br>
<br>
SHR, and SHL can speed up programs SO! much..<br>
Trust me.<br>
Always try to get rid of the "*", and "/"<br>
You can use lookuptables with fixed-point math.<br>
//-----------<br>
<br>
float u = x/y * 1024 // x/y << 10<br>
long int z = u;<br>
printf("%f", (float)(u >> 10));<br>
<br>
//-----------<br>
try something like this.<br>
hope this stuff helps.<br>
<br>
<br>

Re: Re: Re: * or /? Which is faster? Posted by BenGmo on 2 Feb 2000 at 9:00 PM
Thanks a lot guys/gals. BTW, any idea why division is ten times slower?

Re: Re: Re: Re: * or /? Which is faster? Posted by Jessie James on 8 Mar 2000 at 5:45 PM
Who gives a rat's ass?<br>
<br>
: Thanks a lot guys/gals. BTW, any idea why division is ten times slower?<br>
: <br>
<br>

Re: Re: Re: * or /? Which is faster? Posted by BenGmo on 2 Feb 2000 at 9:01 PM
Thanks a lot guys/gals. BTW, any idea why division is ten times slower? Seems a little much, you aren't exagerating are you?

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