Tools for Tuning 1

• Instrument and simulate on PC (gprof, Quantify, hand-crafted)

• Read your compiler manual: understand the switches available to you and what is reliable

• Analyse assembly output: learn to love your compiler

• Consider assembly code for critical components

• Understand your hardware, eg ROM/RAM speeds

• Examine locking granularity, thread priorities, data layout, interrupt load, major algorithms, inner loops

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EXAMPLE: Tweaking C to optimise assembler output for Mandelbrot curve program on Sun 3/60 beat the published top speed of the FPU and the code remained portable!

CHECKLIST:

• Do you know what you are tuning for?

• If more than one, rank, weight and measure.

• Do you have the right tool or tools?

• Have you looked at your compiler output, bus activity, etc?

• Do you know what your tools cannot see? (Eg many tools can’t see cache misses and pipeline empties.)

• Do you understand the relative speeds (etc) of RAM vs ROM storage of code and data?

• Do you know how to tune instructions for different processor versions (eg blends on VC and SPARCompiler) or different cache styles (SPARCompiler)?