Previous: zlaset Up: ../lapack-z.html Next: zlassq

NAME ZLASR - perform the transformation A := P*A, when SIDE = 'L' or 'l' ( Left-hand side ) A := A*P', when SIDE = 'R' or 'r' ( Right-hand side ) where A is an m by n complex matrix and P is an orthogonal matrix, SYNOPSIS SUBROUTINE ZLASR( SIDE, PIVOT, DIRECT, M, N, C, S, A, LDA ) CHARACTER DIRECT, PIVOT, SIDE INTEGER LDA, M, N DOUBLE PRECISION C( * ), S( * ) COMPLEX*16 A( LDA, * ) PURPOSE ZLASR performs the transformation consisting of a sequence of plane rotations determined by the parameters PIVOT and DIRECT as follows ( z = m when SIDE = 'L' or 'l' and z = n when SIDE = 'R' or 'r' ): When DIRECT = 'F' or 'f' ( Forward sequence ) then P = P( z - 1 )*...*P( 2 )*P( 1 ), and when DIRECT = 'B' or 'b' ( Backward sequence ) then P = P( 1 )*P( 2 )*...*P( z - 1 ), where P( k ) is a plane rotation matrix for the following planes: when PIVOT = 'V' or 'v' ( Variable pivot ), the plane ( k, k + 1 ) when PIVOT = 'T' or 't' ( Top pivot ), the plane ( 1, k + 1 ) when PIVOT = 'B' or 'b' ( Bottom pivot ), the plane ( k, z ) c( k ) and s( k ) must contain the cosine and sine that define the matrix P( k ). The two by two plane rotation part of the matrix P( k ), R( k ), is assumed to be of the form R( k ) = ( c( k ) s( k ) ). ( -s( k ) c( k ) ) ARGUMENTS SIDE (input) 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' DIRECT (input) CHARACTER*1 Specifies whether P is a forward or backward sequence of plane rotations. = 'F': Forward, P = P( z - 1 )*...*P( 2 )*P( 1 ) = 'B': Backward, P = P( 1 )*P( 2 )*...*P( z - 1 ) PIVOT (input) CHARACTER*1 Specifies the plane for which P(k) is a plane rota- tion matrix. = 'V': Variable pivot, the plane (k,k+1) = 'T': Top pivot, the plane (1,k+1) = 'B': Bottom pivot, the plane (k,z) M (input) INTEGER The number of rows of the matrix A. If m <= 1, an immediate return is effected. N (input) INTEGER The number of columns of the matrix A. If n <= 1, an immediate return is effected. C, S (input) DOUBLE PRECISION arrays, dimension (M-1) if SIDE = 'L' (N-1) if SIDE = 'R' c(k) and s(k) contain the cosine and sine that define the matrix P(k). The two by two plane rotation part of the matrix P(k), R(k), is assumed to be of the form R( k ) = ( c( k ) s( k ) ). ( -s( k ) c( k ) ) A (input/output) COMPLEX*16 array, dimension (LDA,N) The m by n matrix A. On exit, A is overwritten by P*A if SIDE = 'R' or by A*P' if SIDE = 'L'. LDA (input) INTEGER The leading dimension of the array A. LDA >= max(1,M).