Question

Which of the following can reduce the loop overhead and thus increase the speed?

(a) loop unrolling

(b) loop tiling

(c) loop permutation

(d) loop fusion

This question was addressed to me during an interview for a job.

This interesting question is from High Level Optimization in portion Implementing Embedded System: Hardware/Software Codesign of Embedded Systems

Answer 1

Correct option is (a) loop unrolling

Explanation: The loop unrolling can reduce the loop overhead, that is the fewer branches per execution of the loop body, which in turn increases the speed but is only restricted to loops with a constant number of iteration. The unrolling can increase the code size.