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Re: [vox-tech] loop efficiency and testing against zero.
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Re: [vox-tech] loop efficiency and testing against zero.



Peter Jay Salzman wrote:
I've read somewhere that a loop that runs from 0 to some number should be
written to go in reverse order, e.g. instead of:

   for ( int i = 0;  i < 10;  ++i )

we should write:

   for ( int i = 9;  i >= 0;  --i )
I would think this:
	for( int i = MAXINT; i; --i );
is faster than this:
	for( int i = 0; i < MAXINT; ++i );

However, on my machine they both took the
same time -- 3.24 seconds.

I would think the test of 'i'
would be a single instruction and the test
of 'i < MAXINT' would take multiple
instructions. But surprise!

The rationale is that it's faster to test against 0 than some other integer,
but it isn't obvious to me *why* it's faster.

Why is that?

Pete
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