mat: generalise Outer vector parameters

mat/dense_arithmetic.go

@@ -679,13 +679,22 @@ func (m *Dense) RankOne(a Matrix, alpha float64, x, y *VecDense) {
 	*m = w
 }
 
-// Outer calculates the outer product of x and y, and stores the result
-// in the receiver.
+// Outer calculates the outer product of the column vectors x and y,
+// and stores the result in the receiver.
 //  m = alpha * x * y'
 // In order to update an existing matrix, see RankOne.
-func (m *Dense) Outer(alpha float64, x, y *VecDense) {
-	r := x.Len()
-	c := y.Len()
+func (m *Dense) Outer(alpha float64, x, y Vector) {
+	xr, xc := x.Dims()
+	if xc != 1 {
+		panic(ErrShape)
+	}
+	yr, yc := y.Dims()
+	if yc != 1 {
+		panic(ErrShape)
+	}
+
+	r := xr
+	c := yr
 
 	// Copied from reuseAs with use replaced by useZeroed
 	// and a final zero of the matrix elements if we pass
@@ -707,13 +716,36 @@ func (m *Dense) Outer(alpha float64, x, y *VecDense) {
 		m.capCols = c
 	} else if r != m.mat.Rows || c != m.mat.Cols {
 		panic(ErrShape)
+	}
+
+	var xmat, ymat blas64.Vector
+	fast := true
+	xU, _ := untranspose(x)
+	if rv, ok := xU.(RawVectorer); ok {
+		xmat = rv.RawVector()
+		m.checkOverlap((&VecDense{mat: xmat, n: x.Len()}).asGeneral())
 	} else {
-		m.checkOverlap(x.asGeneral())
-		m.checkOverlap(y.asGeneral())
+		fast = false
+	}
+	yU, _ := untranspose(y)
+	if rv, ok := yU.(RawVectorer); ok {
+		ymat = rv.RawVector()
+		m.checkOverlap((&VecDense{mat: ymat, n: y.Len()}).asGeneral())
+	} else {
+		fast = false
+	}
+
+	if fast {
 		for i := 0; i < r; i++ {
 			zero(m.mat.Data[i*m.mat.Stride : i*m.mat.Stride+c])
 		}
+		blas64.Ger(alpha, xmat, ymat, m.mat)
+		return
 	}
 
-	blas64.Ger(alpha, x.mat, y.mat, m.mat)
+	for i := 0; i < r; i++ {
+		for j := 0; j < c; j++ {
+			m.set(i, j, alpha*x.AtVec(i)*y.AtVec(j))
+		}
+	}
 }