Accelerating the pace of engineering and science

# Documentation Center

• Trial Software
• Product Updates

# mpy

Multiply two objects using fimath object

c = mpy(F,a,b)

## Description

c = mpy(F,a,b) performs elementwise multiplication on a and b using fimath object F. This is helpful in cases when you want to override the fimath objects of a and b, or if the fimath properties associated with a and b are different. The output fi object c has no local fimath.

a and b can both be fi objects with the same dimensions unless one is a scalar. If either a or b is scalar, then c has the dimensions of the nonscalar object. a and b can also be doubles, singles, or integers.

## Examples

In this example, c is the 40-bit product of a and b with fraction length 30.

```a = fi(pi);
b = fi(exp(1));
F = fimath('ProductMode','SpecifyPrecision',...
'ProductWordLength',40,'ProductFractionLength',30);
c = mpy(F, a, b) ```
```c =

8.5397

DataTypeMode: Fixed-point: binary point scaling
Signedness: Signed
WordLength: 40
FractionLength: 30
```

## More About

expand all

### Algorithms

c = mpy(F,a,b) is similar to

```a.fimath = F;
b.fimath = F;
c = a .* b

c =
8.5397

DataTypeMode: Fixed-point: binary point scaling
Signedness: Signed
WordLength: 40
FractionLength: 30

RoundingMethod: nearest
OverflowAction: saturate
ProductMode: SpecifyPrecision
ProductWordLength: 40
ProductFractionLength: 30
SumMode: FullPrecision
```

but not identical. When you use mpy, the fimath properties of a and b are not modified, and the output fi object c has no local fimath. When you use the syntax c = a .* b, where a and b have their own fimath objects, the output fi object c gets assigned the same fimath object as inputs a and b. See fimath Rules for Fixed-Point Arithmetic in the Fixed-Point Designer™ User's Guide for more information.

## See Also

Was this topic helpful?