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Subject: question about optimizing loops

Author: Uri Blass

Date: 13:02:56 08/22/03


I have  many cases when I want to do something for all the 1's of a number that
is
0-255

I do something like this if I am sure that the number is not 0(I start with
while if the number can be 0)

do
{
  j=smallest_power[i];
/*for example smallest_power[34]=1 because 34=2^1+2^5 and 1 is the smallest
power in this representation*/
  f(j);
  i&=i-1;
}
while (i>0);

I believe that it is not optimal because I calculate information that I do not
need and it is better to have something like

for (k=0;k<weight[i];k++)
f(power[i][k]);

I already have the relevant array weight[i] that gives me the number of 1's but
before generating the array power[i][k] that gives the value of the k power of i
I prefer to ask here maybe someone has a better idea.

Note that I am even not sure if the second idea is faster because I am afraid
that calling array of 2 dimensions may be slower.

Uri



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