🚀 go-pugleaf

In article 92Aug13120523@vulcan.essex.ac.uk, alien@essex.ac.uk ("Adrian F Clark") writes:
>
>In article <1992Aug10.221247.8016@cfa.harvard.edu> alberto@cfa.harvard.edu (Alberto Accomazzi) writes:
>
>> A far as making the loop tight and fast, if you are only accessing your data
>> in a sequential way, the best thing to do is increment the pointer as in:
>> 
>> function (DATATYPE *data, int xsize, int ysize)
>> {
>>   int x, y;
>>   DATATYPE *dp;
>> 
>>   dp = data;
>>   for (y = 0; y < ysize; y++)
>>     for (x = 0; x < xsize; x++, dp++)
>>       *dp = ...
>> }
>> 
>> Inner loops can be written in a similar fashion.  As far as I know, this
>> will be as fast as you can get.
>
>Actually, you can get just a smidgin faster on most machines:
>
>  dp = data;
>  for (y = 0; y < ysize; y++)
>    for (x = 0; x < xsize; x++)
>      *dp++ = ...
>}
>
>but this is probably even less readable than the other examples
>posted.
>
>

If you compared assembler output, I am pretty sure the code would look
identical for both the above cases. If its speed your after, and who isn't.

dp = data;
xy = ysize*xsize;
while(xy--) *dp++ = ...

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Al Larson                      Internet:   agl@mayo.edu
Biomedical Imaging Resource      
Mayo Foundation                Talk:       (507)-284-4147
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