// Dot computes the inner product of
// two vectors d = xi*yi + xj*yj + xz*yz+...
func Dot(n int, x, y []float64) (d float64) {
if n == 3 {
d = x[0]*y[0] + x[1]*y[1] + x[2]*y[2]
} else if n == 4 {
d = x[0]*y[0] + x[1]*y[1] + x[2]*y[2] + x[3]*y[3]
} else if n == 6 {
d = x[0]*y[0] + x[1]*y[1] + x[2]*y[2] + x[3]*y[3] + x[4]*y[4] + x[5]*y[5]
} else {
d = blas.Ddot(n, x, 1, y, 1)
}
return
}
// MVMul multiplies a matrix with a vector
// y = alpha*A*x + y
func MVMul(N, m, n int, alpha float64, A, x, y []float64) {
if N != n {
panic("vec: Dimensions invalid. A.Cols() != Vec.Len()")
}
if alpha == 0 {
return
}
if alpha == 1 {
goto alg
}
blas.Dscal(N, alpha, A, 1)
goto alg
alg:
{
if N < 8 {
idx, ptr := 0, 0
extra := n - n%4
ub := ((n / 4) * 4) - 1
for i := 0; i < m; i++ {
idx = i * n
for j := 0; j < ub; j += 4 {
ptr = idx + j
y[i] += A[ptr]*x[j] + A[ptr+1]*x[j+1] + A[ptr+2]*x[j+2] + A[ptr+3]*x[j+3]
}
for j := extra; j < n; j++ {
y[i] += A[idx+j] * x[j]
}
}
return
}
for i := 0; i < m; i++ {
y[i] += blas.Ddot(N, A[n*i:n*i+n], 1, x, 1)
}
}
}
func dot64(X, Y []float64) float64 {
return blas.Ddot(len(X), X, 1, Y, 1)
}