Author: Tony Werten
Date: 08:12:58 02/27/03
Go up one level in this thread
On February 27, 2003 at 11:01:20, Tony Werten wrote:
>On February 27, 2003 at 07:44:19, Uri Blass wrote:
>
>>On February 27, 2003 at 05:23:25, Tony Werten wrote:
>>
>>>On February 26, 2003 at 14:04:16, Uri Blass wrote:
>>>
>>>>I had the following code in my program
>>>>
>>>>do
>>>>{
>>>>...
>>>>if (info[target]==EMPTA)
>>>> target+=8;
>>>>else
>>>> target=64;
>>>>}
>>>>while (target<64)
>>>
>>>Less branches:
>>>
>>>do
>>>{
>>>...
>>> tmp:=(info[target]!=EMPTY); // maybe typecast to int ?
>>> target+=(tmp*256)+8;
BTW: target+=(info[target]!=EMPTY)*256+8;
OR: target+=8;
target+=(info[target]!=EMPTY)*256;
will get rid of the tmp variable of course, although it doesn't really get more
readable.
Tony
>>>} while (target<64);
>>>
>>>if (target>256) target=64;
>>>
>>>
>>>But I'm not sure if this works in C. (In pascal compares are garantied to return
>>>0 or 1 )
>>
>>It works in C(except the fact that I need to use a varaible for tmp)
>>
>>I even do not need the last if (target>256) target==64 because target is not
>>used after the loop but I am not sure if it makes me faster.
>>
>>I have many similiar loops and by comparing times by changing one loop
>>I find that it is even slightly slower.
>>
>>I used a global varaible for tmp because if I use a local caraible that I need
>>to define at the beginning of the function then it means that I need to change
>>all the similiar functions in order to practically use it.
>
>Using a global variable will make it slower. IIRC they wil not be loaded in a
>register but stay in main memory. This would mean you get the slowdown of
>loading it in cache.
>
>Using it as a local variable will normally not slow you down, except if the
>function doesn't have any other local variables because now a stack frame will
>need to be set up.
>
>Tony
>
>>
>>Uri
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