Have a good baseline! - code::dive / Fastware 2015 - Andrei

• Amdahl’s law
• optimize outside / profile again within the application

• doNotOptimizeAway()

• Baselines - have a good baseline
  • beware of baseline x2 (cache/alloc memory)
  • don’t do sequencing comparison
  • beware of data pattern

• facebook/folly benchmark framework

• Prefer to use:
  • Prefer a[i++] to a[++i] - less data dependency / better hardware usage / better parrallelisation.
  • minimize jump (keep flow)
  • keep pattern access (prefetching)
  • The hotest place on earth is the stack.
  • Globals are bad, because they pessimize everything for the compiler.

followup

• many ALU permit instruction level parallelism
  • to use them have fewer data dependencies
    • eg String to int