Main Page | See live article | Alphabetical index

Fused Multiply Add

A Fused Multiply Add computes a multiply-accumulate

FMA(A,B,C) = A*B+C

with a single rounding of floating point numbers.

When implemented in a microprocessor this is typically faster than a multiply operation followed by an add. It also allows for getting the bottom half of the multiplication. E.g.,

This is implemented on the PowerPC and Itanium processor families. Because of this instruction there is no need for a hardware divide or square root unit since they can both be implemented using the FMA in software.

The FMA operation will likely be added to IEEE 754 in IEEE 754r.