// Outer calculates the outer product of x and y, and stores the result
// in the receiver. In order to update to an existing matrix, see RankOne.
// m = x * y'
func (m *Dense) Outer(x, y *Vector) {
r := x.Len()
c := y.Len()
// Copied from reuseAs with use replaced by useZeroed
// and a final zero of the matrix elements if we pass
// the shape checks.
// TODO(kortschak): Factor out into reuseZeroedAs if
// we find another case that needs it.
if m.mat.Rows > m.capRows || m.mat.Cols > m.capCols {
// Panic as a string, not a mat64.Error.
panic("mat64: caps not correctly set")
}
if m.isZero() {
m.mat = blas64.General{
Rows: r,
Cols: c,
Stride: c,
Data: useZeroed(m.mat.Data, r*c),
}
m.capRows = r
m.capCols = c
} else if r != m.mat.Rows || c != m.mat.Cols {
panic(ErrShape)
} else {
for i := 0; i < r; i++ {
zero(m.mat.Data[i*m.mat.Stride : i*m.mat.Stride+c])
}
}
blas64.Ger(1, x.mat, y.mat, m.mat)
}
// RankOne performs a rank-one update to the matrix a and stores the result
// in the receiver. If a is zero, see Outer.
// m = a + alpha * x * y'
func (m *Dense) RankOne(a Matrix, alpha float64, x, y *Vector) {
ar, ac := a.Dims()
if x.Len() != ar {
panic(ErrShape)
}
if y.Len() != ac {
panic(ErrShape)
}
var w Dense
if m == a {
w = *m
}
w.reuseAs(ar, ac)
// Copy over to the new memory if necessary
if m != a {
w.Copy(a)
}
blas64.Ger(alpha, x.mat, y.mat, w.mat)
*m = w
}