'which one loop is faster and why?' Thread RSS Feed

which one loop is faster and why?

Fri, 21 Jan 2011 10:51:32 -0700

which one is faster

1. for(i=0;i<num;i++)
2. for(i=num;i>0;i--)
assume that no code optimization and microprocessor has flags

Re: which one loop is faster and why?

Sat, 22 Jan 2011 06:20:20 -0700

Technically speaking these for loops will NOT do the same work, because index has different values (i will never be EQUAL to num in loop #1, but in loop $2 it WILL). The performance in FOR() part should be the same.

Re: which one loop is faster and why?

Sun, 23 Jan 2011 00:07:47 -0700

but answer is given that 2nd loop is fast..i don't why there is some condition given regarding flags..

Re: which one loop is faster and why?

Thu, 12 May 2011 14:25:28 -0700

As per the dis-assembly in the 1st for loop, an additional instruction is required to set the flag if index has reached the 'num' value. Where as in the 2nd for loop, the index can be directly checked if it's greater than zero.