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DLAHR2Run Method

Purpose ======= DLAHR2 reduces the first NB columns of A real general n-BY-(n-k+1) matrix A so that elements below the k-th subdiagonal are zero. The reduction is performed by an orthogonal similarity transformation Q' * A * Q. The routine returns the matrices V and T which determine Q as a block reflector I - V*T*V', and also the matrix Y = A * V * T. This is an auxiliary routine called by DGEHRD.

Namespace: DotNumerics.LinearAlgebra.CSLapack
Assembly: DWSIM.MathOps.DotNumerics (in DWSIM.MathOps.DotNumerics.dll) Version: 1.0.0.0 (1.0.0.0)
Syntax
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public void Run(
	int N,
	int K,
	int NB,
	ref double[] A,
	int offset_a,
	int LDA,
	ref double[] TAU,
	int offset_tau,
	ref double[] T,
	int offset_t,
	int LDT,
	ref double[] Y,
	int offset_y,
	int LDY
)
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Parameters

N  Int32
(input) INTEGER The order of the matrix A.
K  Int32
(input) INTEGER The offset for the reduction. Elements below the k-th subdiagonal in the first NB columns are reduced to zero. K .LT. N.
NB  Int32
(input) INTEGER The number of columns to be reduced.
A  Double
(input/output) DOUBLE PRECISION array, dimension (LDA,N-K+1) On entry, the n-by-(n-k+1) general matrix A. On exit, the elements on and above the k-th subdiagonal in the first NB columns are overwritten with the corresponding elements of the reduced matrix; the elements below the k-th subdiagonal, with the array TAU, represent the matrix Q as a product of elementary reflectors. The other columns of A are unchanged. See Further Details.
offset_a  Int32
 
LDA  Int32
(input) INTEGER The leading dimension of the array A. LDA .GE. max(1,N).
TAU  Double
(output) DOUBLE PRECISION array, dimension (NB) The scalar factors of the elementary reflectors. See Further Details.
offset_tau  Int32
 
T  Double
(output) DOUBLE PRECISION array, dimension (LDT,NB) The upper triangular matrix T.
offset_t  Int32
 
LDT  Int32
(input) INTEGER The leading dimension of the array T. LDT .GE. NB.
Y  Double
(output) DOUBLE PRECISION array, dimension (LDY,NB) The n-by-nb matrix Y.
offset_y  Int32
 
LDY  Int32
(input) INTEGER The leading dimension of the array Y. LDY .GE. N.
See Also