WavePrefixProduct function

Returns the product of all of the values in the active lanes in this wave with indices less than this lane.

Syntax

<type> WavePrefixProduct(
   <type> value
);

Parameters

value

The value to multiply.

Return value

The product of all the values.

Remarks

The order of operations on this routine cannot be guaranteed. So, effectively, the [precise] flag is ignored within it.

A postfix product can be computed by multiplying the prefix product by the current lane's value.

Note that the active lane with the lowest index will always receive a 1 for its prefix product.

This function is supported from shader model 6.0 in all shader stages.

Examples

uint numToMultiply = 2;
uint prefixProduct = WavePrefixProduct( numToMultiply );

On a machine with a wave size of 8, and all lanes active except lanes 0 and 4, the following values would be returned from WavePrefixProduct.

lane index	status	prefixProduct
0	inactive	n/a
1	active	= 1
2	active	= 1*2
3	active	= 1*2*2
4	inactive	n/a
5	active	= 1*2*2*2
6	active	= 1*2*2*2*2
7	active	= 1*2*2*2*2*2

See also

Overview of Shader Model 6

Shader Model 6