/*
* Applies a real elementary reflector H to a real m by n matrix A,
* from either the left or the right. H is represented in the form
*
* H = I - tau * ( 1 ) * ( 1 v.T )
* ( v )
*
* where tau is a real scalar and v is a real vector.
*
* If tau = 0, then H is taken to be the unit matrix.
*
* A is /a1\ a1 := a1 - w1
* \A2/ A2 := A2 - v*w1
* w1 := tau*(a1 + A2.T*v) if side == LEFT
* := tau*(a1 + A2*v) if side == RIGHT
*
* Intermediate work space w1 required as parameter, no allocation.
*/
func applyHHTo2x1(tau, v, a1, A2, w1 *matrix.FloatMatrix, flags Flags) {
tval := tau.GetAt(0, 0)
if tval == 0.0 {
return
}
// maybe with Scale(0.0), Axpy(w1, a1, 1.0)
a1.CopyTo(w1)
if flags&LEFT != 0 {
// w1 = a1 + A2.T*v
MVMult(w1, A2, v, 1.0, 1.0, TRANSA)
} else {
// w1 = a1 + A2*v
MVMult(w1, A2, v, 1.0, 1.0, NOTRANS)
}
// w1 = tau*w1
Scale(w1, tval)
// a1 = a1 - w1
a1.Minus(w1)
// A2 = A2 - v*w1
if flags&LEFT != 0 {
MVRankUpdate(A2, v, w1, -1.0)
} else {
MVRankUpdate(A2, w1, v, -1.0)
}
}
/* From LAPACK/dlarf.f
*
* Applies a real elementary reflector H to a real m by n matrix A,
* from either the left or the right. H is represented in the form
*
* H = I - tau * ( 1 ) * ( 1 v.T )
* ( v )
*
* where tau is a real scalar and v is a real vector.
*
* If tau = 0, then H is taken to be the unit matrix.
*
* A is /a1\ a1 := a1 - w1
* \A2/ A2 := A2 - v*w1
* w1 := tau*(a1 + A2.T*v) if side == LEFT
* := tau*(a1 + A2*v) if side == RIGHT
*
* Allocates/frees intermediate work space matrix w1.
*/
func applyHouseholder(tau, v, a1, A2 *matrix.FloatMatrix, flags Flags) {
tval := tau.GetAt(0, 0)
if tval == 0.0 {
return
}
w1 := a1.Copy()
if flags&LEFT != 0 {
// w1 = a1 + A2.T*v
MVMult(w1, A2, v, 1.0, 1.0, TRANSA)
} else {
// w1 = a1 + A2*v
MVMult(w1, A2, v, 1.0, 1.0, NOTRANS)
}
// w1 = tau*w1
Scale(w1, tval)
// a1 = a1 - w1
a1.Minus(w1)
// A2 = A2 - v*w1
MVRankUpdate(A2, v, w1, -1.0)
}
func nrmError(ref, val *matrix.FloatMatrix) (nrm float64, diff *matrix.FloatMatrix) {
diff = ref.Minus(val)
nrm = blas.Nrm2(diff).Float()
return
}