How to calculate MIPS for an algorithm for ARM processor

Question

I have been asked recently to produced the MIPS (million of instructions per second) for an algorithm we have developed. The algorithm is exposed by a set of C-style functions.

Answer 1

Some notes:

1. MIPS is often used as a general "capacity" measure for processors, especially in the soft real-time/embedded field where you do want to ensure that you do not overload a processor with work. Note that this IS instructions per second, as the time is very important!

2. MIPS used in this fashion is quite unscientific.

3. MIPS used in this fashion is still often the best approximation there is for sizing a system and determining the speed of the processor. It might well be off by 25%, but never mind...

4. Counting MIPS requires a processor that is close to what you are using. The right instruction set is obviously crucial, to capture the actual instruction stream from the actual compiler in use.

You cannot in any way approximate this on a PC. You need to bring out one of a few tools to do this right:

1. Use an instruction-set simulator for the target archicture such as Qemu, ARM's own tools, Synopsys, CoWare, Virtutech, or VaST. These are fast but can count instructions pretty well, and will support the right instruction set. Barring extensive use of expensive instructions like integer divide (and please no floating point), these numbers tend to be usefully close.

2. Find a clock-cycle accurate simulator for your target processor (or something close), which will give pretty good estimate of pipeline effects etc. Once again, get it from ARM or from Carbon SoCDesigner.

3. Get a development board for the processor family you are targeting, or an ARM close to it design, and profile the application there. You don't use an ARM9 to profile for an ARM11, but an ARM11 might be a good approximation for an ARM Cortex-A8/A9 for example.