Tuning Comments

• First priority with any program is correctness, it does not matter how fast a program is if it wrong

• Algorithms:

  • Algorithms can make an immense difference, e.g. O(n^2) vs. O(n log n) sorting
  • Most local optimizations only provide constant factor improvement
  • The fastest code is the code that never executes

• Make use of the compiler optimizer:

  • -O3 in gcc
  • -fprofile-arcs and -fbranch-probabilities to improve code

• GCC generates the same code regardless of -g, keep the -g so OProfile can do a better job mapping profiling information back to code

Notes: