distsq

Distsq Example

SIMD intrinsics are used to compute squared distances between a set of points in R^2. The points are created using:

for i := 0; i < n; i++ {
		x[i] = simd.I32x4{rand.Int31n(maxCoord), rand.Int31n(maxCoord), rand.Int31n(maxCoord), rand.Int31n(maxCoord)}
		y[i] = simd.I32x4{rand.Int31n(maxCoord), rand.Int31n(maxCoord), rand.Int31n(maxCoord), rand.Int31n(maxCoord)}
}

The squared distances are calculated using:

dx := simd.SubI32x4(x[j], x[i])
dy := simd.SubI32x4(y[j], y[i])
sqX := simd.MulI32x4(dx, dx)
sqY := simd.MulI32x4(dy, dy)
sqDist := simd.AddI32x4(sqX, sqY)

Not all distances are computed, e.g. the distance between x[i][0], y[i][0] and x[j][1], y[j][1] is not computed.

Building

The command gensimd and the package github.com/bjwbell/gensimd/simd need to be installed. To do so, execute:

go get github.com/bjwbell/gensimd
go install github.com/bjwbell/gensimd
go get github.com/bjwbell/gensimd/simd

After that, to build and run the example, execute:

go generate
go build
./distsq

This example only uses SIMD instructions on amd64/x86_64, it's untested on other platforms.