Editing Branch (computer science) (section)

=== Hardware branch predictors ===
To run any software, hardware [[branch predictor]]s moved the statistics into the electronics. Branch predictors are parts of a processor that guess the outcome of a conditional branch. Then the processor's logic gambles on the guess by beginning to execute the expected instruction flow. An example of a simple hardware branch prediction scheme is to assume that all backward branches (i.e. to a smaller program counter) are taken (because they are part of a loop), and all forward branches (to a larger program counter) are not taken (because they leave a loop). Better branch predictors are developed and validated statistically by running them in simulation on a variety of test programs.  Good predictors usually count the outcomes of previous executions of a branch. Faster, more expensive computers can then run faster by investing in better branch prediction electronics. In a CPU with hardware branch prediction, branch hints let the compiler's presumably superior branch prediction override the hardware's more simplistic branch prediction.