Annotation of rpl/lapack/lapack/dlatzm.f, revision 1.1
1.1 ! bertrand 1: SUBROUTINE DLATZM( SIDE, M, N, V, INCV, TAU, C1, C2, LDC, WORK )
! 2: *
! 3: * -- LAPACK routine (version 3.2) --
! 4: * -- LAPACK is a software package provided by Univ. of Tennessee, --
! 5: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
! 6: * November 2006
! 7: *
! 8: * .. Scalar Arguments ..
! 9: CHARACTER SIDE
! 10: INTEGER INCV, LDC, M, N
! 11: DOUBLE PRECISION TAU
! 12: * ..
! 13: * .. Array Arguments ..
! 14: DOUBLE PRECISION C1( LDC, * ), C2( LDC, * ), V( * ), WORK( * )
! 15: * ..
! 16: *
! 17: * Purpose
! 18: * =======
! 19: *
! 20: * This routine is deprecated and has been replaced by routine DORMRZ.
! 21: *
! 22: * DLATZM applies a Householder matrix generated by DTZRQF to a matrix.
! 23: *
! 24: * Let P = I - tau*u*u', u = ( 1 ),
! 25: * ( v )
! 26: * where v is an (m-1) vector if SIDE = 'L', or a (n-1) vector if
! 27: * SIDE = 'R'.
! 28: *
! 29: * If SIDE equals 'L', let
! 30: * C = [ C1 ] 1
! 31: * [ C2 ] m-1
! 32: * n
! 33: * Then C is overwritten by P*C.
! 34: *
! 35: * If SIDE equals 'R', let
! 36: * C = [ C1, C2 ] m
! 37: * 1 n-1
! 38: * Then C is overwritten by C*P.
! 39: *
! 40: * Arguments
! 41: * =========
! 42: *
! 43: * SIDE (input) CHARACTER*1
! 44: * = 'L': form P * C
! 45: * = 'R': form C * P
! 46: *
! 47: * M (input) INTEGER
! 48: * The number of rows of the matrix C.
! 49: *
! 50: * N (input) INTEGER
! 51: * The number of columns of the matrix C.
! 52: *
! 53: * V (input) DOUBLE PRECISION array, dimension
! 54: * (1 + (M-1)*abs(INCV)) if SIDE = 'L'
! 55: * (1 + (N-1)*abs(INCV)) if SIDE = 'R'
! 56: * The vector v in the representation of P. V is not used
! 57: * if TAU = 0.
! 58: *
! 59: * INCV (input) INTEGER
! 60: * The increment between elements of v. INCV <> 0
! 61: *
! 62: * TAU (input) DOUBLE PRECISION
! 63: * The value tau in the representation of P.
! 64: *
! 65: * C1 (input/output) DOUBLE PRECISION array, dimension
! 66: * (LDC,N) if SIDE = 'L'
! 67: * (M,1) if SIDE = 'R'
! 68: * On entry, the n-vector C1 if SIDE = 'L', or the m-vector C1
! 69: * if SIDE = 'R'.
! 70: *
! 71: * On exit, the first row of P*C if SIDE = 'L', or the first
! 72: * column of C*P if SIDE = 'R'.
! 73: *
! 74: * C2 (input/output) DOUBLE PRECISION array, dimension
! 75: * (LDC, N) if SIDE = 'L'
! 76: * (LDC, N-1) if SIDE = 'R'
! 77: * On entry, the (m - 1) x n matrix C2 if SIDE = 'L', or the
! 78: * m x (n - 1) matrix C2 if SIDE = 'R'.
! 79: *
! 80: * On exit, rows 2:m of P*C if SIDE = 'L', or columns 2:m of C*P
! 81: * if SIDE = 'R'.
! 82: *
! 83: * LDC (input) INTEGER
! 84: * The leading dimension of the arrays C1 and C2. LDC >= (1,M).
! 85: *
! 86: * WORK (workspace) DOUBLE PRECISION array, dimension
! 87: * (N) if SIDE = 'L'
! 88: * (M) if SIDE = 'R'
! 89: *
! 90: * =====================================================================
! 91: *
! 92: * .. Parameters ..
! 93: DOUBLE PRECISION ONE, ZERO
! 94: PARAMETER ( ONE = 1.0D+0, ZERO = 0.0D+0 )
! 95: * ..
! 96: * .. External Subroutines ..
! 97: EXTERNAL DAXPY, DCOPY, DGEMV, DGER
! 98: * ..
! 99: * .. External Functions ..
! 100: LOGICAL LSAME
! 101: EXTERNAL LSAME
! 102: * ..
! 103: * .. Intrinsic Functions ..
! 104: INTRINSIC MIN
! 105: * ..
! 106: * .. Executable Statements ..
! 107: *
! 108: IF( ( MIN( M, N ).EQ.0 ) .OR. ( TAU.EQ.ZERO ) )
! 109: $ RETURN
! 110: *
! 111: IF( LSAME( SIDE, 'L' ) ) THEN
! 112: *
! 113: * w := C1 + v' * C2
! 114: *
! 115: CALL DCOPY( N, C1, LDC, WORK, 1 )
! 116: CALL DGEMV( 'Transpose', M-1, N, ONE, C2, LDC, V, INCV, ONE,
! 117: $ WORK, 1 )
! 118: *
! 119: * [ C1 ] := [ C1 ] - tau* [ 1 ] * w'
! 120: * [ C2 ] [ C2 ] [ v ]
! 121: *
! 122: CALL DAXPY( N, -TAU, WORK, 1, C1, LDC )
! 123: CALL DGER( M-1, N, -TAU, V, INCV, WORK, 1, C2, LDC )
! 124: *
! 125: ELSE IF( LSAME( SIDE, 'R' ) ) THEN
! 126: *
! 127: * w := C1 + C2 * v
! 128: *
! 129: CALL DCOPY( M, C1, 1, WORK, 1 )
! 130: CALL DGEMV( 'No transpose', M, N-1, ONE, C2, LDC, V, INCV, ONE,
! 131: $ WORK, 1 )
! 132: *
! 133: * [ C1, C2 ] := [ C1, C2 ] - tau* w * [ 1 , v']
! 134: *
! 135: CALL DAXPY( M, -TAU, WORK, 1, C1, 1 )
! 136: CALL DGER( M, N-1, -TAU, WORK, 1, V, INCV, C2, LDC )
! 137: END IF
! 138: *
! 139: RETURN
! 140: *
! 141: * End of DLATZM
! 142: *
! 143: END
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