dlasr.f (3)  Linux Man Pages
NAME
dlasr.f 
SYNOPSIS
Functions/Subroutines
subroutine dlasr (SIDE, PIVOT, DIRECT, M, N, C, S, A, LDA)
DLASR applies a sequence of plane rotations to a general rectangular matrix.
Function/Subroutine Documentation
subroutine dlasr (characterSIDE, characterPIVOT, characterDIRECT, integerM, integerN, double precision, dimension( * )C, double precision, dimension( * )S, double precision, dimension( lda, * )A, integerLDA)
DLASR applies a sequence of plane rotations to a general rectangular matrix.
Purpose:

DLASR applies a sequence of plane rotations to a real matrix A, from either the left or the right. When SIDE = 'L', the transformation takes the form A := P*A and when SIDE = 'R', the transformation takes the form A := A*P**T where P is an orthogonal matrix consisting of a sequence of z plane rotations, with z = M when SIDE = 'L' and z = N when SIDE = 'R', and P**T is the transpose of P. When DIRECT = 'F' (Forward sequence), then P = P(z1) * ... * P(2) * P(1) and when DIRECT = 'B' (Backward sequence), then P = P(1) * P(2) * ... * P(z1) where P(k) is a plane rotation matrix defined by the 2by2 rotation R(k) = ( c(k) s(k) ) = ( s(k) c(k) ). When PIVOT = 'V' (Variable pivot), the rotation is performed for the plane (k,k+1), i.e., P(k) has the form P(k) = ( 1 ) ( ... ) ( 1 ) ( c(k) s(k) ) ( s(k) c(k) ) ( 1 ) ( ... ) ( 1 ) where R(k) appears as a rank2 modification to the identity matrix in rows and columns k and k+1. When PIVOT = 'T' (Top pivot), the rotation is performed for the plane (1,k+1), so P(k) has the form P(k) = ( c(k) s(k) ) ( 1 ) ( ... ) ( 1 ) ( s(k) c(k) ) ( 1 ) ( ... ) ( 1 ) where R(k) appears in rows and columns 1 and k+1. Similarly, when PIVOT = 'B' (Bottom pivot), the rotation is performed for the plane (k,z), giving P(k) the form P(k) = ( 1 ) ( ... ) ( 1 ) ( c(k) s(k) ) ( 1 ) ( ... ) ( 1 ) ( s(k) c(k) ) where R(k) appears in rows and columns k and z. The rotations are performed without ever forming P(k) explicitly.
Parameters:

SIDE
SIDE is CHARACTER*1 Specifies whether the plane rotation matrix P is applied to A on the left or the right. = 'L': Left, compute A := P*A = 'R': Right, compute A:= A*P**T
PIVOTPIVOT is CHARACTER*1 Specifies the plane for which P(k) is a plane rotation matrix. = 'V': Variable pivot, the plane (k,k+1) = 'T': Top pivot, the plane (1,k+1) = 'B': Bottom pivot, the plane (k,z)
DIRECTDIRECT is CHARACTER*1 Specifies whether P is a forward or backward sequence of plane rotations. = 'F': Forward, P = P(z1)*...*P(2)*P(1) = 'B': Backward, P = P(1)*P(2)*...*P(z1)
MM is INTEGER The number of rows of the matrix A. If m <= 1, an immediate return is effected.
NN is INTEGER The number of columns of the matrix A. If n <= 1, an immediate return is effected.
CC is DOUBLE PRECISION array, dimension (M1) if SIDE = 'L' (N1) if SIDE = 'R' The cosines c(k) of the plane rotations.
SS is DOUBLE PRECISION array, dimension (M1) if SIDE = 'L' (N1) if SIDE = 'R' The sines s(k) of the plane rotations. The 2by2 plane rotation part of the matrix P(k), R(k), has the form R(k) = ( c(k) s(k) ) ( s(k) c(k) ).
AA is DOUBLE PRECISION array, dimension (LDA,N) The MbyN matrix A. On exit, A is overwritten by P*A if SIDE = 'R' or by A*P**T if SIDE = 'L'.
LDALDA is INTEGER The leading dimension of the array A. LDA >= max(1,M).
Author:

Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
 September 2012
Definition at line 200 of file dlasr.f.
Author
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