Control expression contraction; fast fma()

#pragma OPENCL FP_CONTRACT on-off-switch

on-off-switch is one of:
     ON, OFF or DEFAULT.
     The DEFAULT value is ON.

FP_FAST_FMAF
FP_FAST_FMA
FP_FAST_FMA_HALF

FP_CONTRACT

The FP_CONTRACT pragma takes the form:

#pragma OPENCL FP_CONTRACT on-off-switch

FP_CONTRACT can be used to allow (if the state is on) or disallow (if the state is off) the implementation to contract expressions. Each pragma can occur either outside external declarations or preceding all explicit declarations and statements inside a compound statement.

The parameter on-off-switch is one of ON, OFF or DEFAULT. The DEFAULT value is ON.

When outside external declarations, the pragma takes effect from its occurrence until another FP_CONTRACT pragma is encountered, or until the end of the translation unit. When inside a compound statement, the pragma takes effect from its occurrence until another FP_CONTRACT pragma is encountered (including within a nested compound statement), or until the end of the compound statement; at the end of a compound statement the state for the pragma is restored to its condition just before the compound statement. If this pragma is used in any other context, the behavior is undefined.

FP_FAST_FMAF, FP_FAST_FMA, and FP_FAST_FMA_HALF

The FP_FAST_FMAF macro indicates whether the fma function is fast compared with direct code for single precision floating-point. If defined, the FP_FAST_FMAF macro shall indicate that the fma() function generally executes about as fast as, or faster than, a multiply and an add of float operands.

The FP_FAST_FMA macro indicates whether the fma family of functions are fast compared with direct code for double precision floating-point. If defined, the FP_FAST_FMA macro shall indicate that the fma() function generally executes about as fast as, or faster than, a multiply and an add of double operands.

The FP_FAST_FMA_HALF macro indicates whether the fma() family of functions are fast compared with direct code for half precision floating-point. If defined, the FP_FAST_FMA_HALF macro shall indicate that the fma() function generally executes about as fast as, or faster than, a multiply and an add of half operands

Also see

Specification