Loop unrolling

[Scary]

At least they taught what loop unrolling / rolling is on his course. Unlike most courses nowadays which consist of "using powerpoint"

On a Computer Science/Software Engineering curriculum? I don't think so.

[VectraMan]

At least they taught what loop unrolling / rolling is on his course. Unlike most courses nowadays which consist of "using powerpoint"

Or worse, Java.



Loop unrolling would work pre Pentium 4 (I think that was the one). That's because the jump would stall the clever look ahead / out of order execution stuff. But with the P4 the clever stuff would guess the most likely outcome of a jump before it got there and assume you'd continue round the loop - no penalty at all for looping, just a small penalty for the exit case. It'd probably be faster not unrolled because there was less code to load.

I went to an Intel course once where they taught this. And what worked on the pre-P4 course (I'm racking my brain trying to remember the names) they told us to forget for the P4.

[AtW]

Loop unrolling these days is executing in parallel on multiple cores.

HTH