Annotation of rpl/lapack/lapack/dormr2.f, revision 1.1
1.1 ! bertrand 1: SUBROUTINE DORMR2( SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC,
! 2: $ WORK, INFO )
! 3: *
! 4: * -- LAPACK routine (version 3.2) --
! 5: * -- LAPACK is a software package provided by Univ. of Tennessee, --
! 6: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
! 7: * November 2006
! 8: *
! 9: * .. Scalar Arguments ..
! 10: CHARACTER SIDE, TRANS
! 11: INTEGER INFO, K, LDA, LDC, M, N
! 12: * ..
! 13: * .. Array Arguments ..
! 14: DOUBLE PRECISION A( LDA, * ), C( LDC, * ), TAU( * ), WORK( * )
! 15: * ..
! 16: *
! 17: * Purpose
! 18: * =======
! 19: *
! 20: * DORMR2 overwrites the general real m by n matrix C with
! 21: *
! 22: * Q * C if SIDE = 'L' and TRANS = 'N', or
! 23: *
! 24: * Q'* C if SIDE = 'L' and TRANS = 'T', or
! 25: *
! 26: * C * Q if SIDE = 'R' and TRANS = 'N', or
! 27: *
! 28: * C * Q' if SIDE = 'R' and TRANS = 'T',
! 29: *
! 30: * where Q is a real orthogonal matrix defined as the product of k
! 31: * elementary reflectors
! 32: *
! 33: * Q = H(1) H(2) . . . H(k)
! 34: *
! 35: * as returned by DGERQF. Q is of order m if SIDE = 'L' and of order n
! 36: * if SIDE = 'R'.
! 37: *
! 38: * Arguments
! 39: * =========
! 40: *
! 41: * SIDE (input) CHARACTER*1
! 42: * = 'L': apply Q or Q' from the Left
! 43: * = 'R': apply Q or Q' from the Right
! 44: *
! 45: * TRANS (input) CHARACTER*1
! 46: * = 'N': apply Q (No transpose)
! 47: * = 'T': apply Q' (Transpose)
! 48: *
! 49: * M (input) INTEGER
! 50: * The number of rows of the matrix C. M >= 0.
! 51: *
! 52: * N (input) INTEGER
! 53: * The number of columns of the matrix C. N >= 0.
! 54: *
! 55: * K (input) INTEGER
! 56: * The number of elementary reflectors whose product defines
! 57: * the matrix Q.
! 58: * If SIDE = 'L', M >= K >= 0;
! 59: * if SIDE = 'R', N >= K >= 0.
! 60: *
! 61: * A (input) DOUBLE PRECISION array, dimension
! 62: * (LDA,M) if SIDE = 'L',
! 63: * (LDA,N) if SIDE = 'R'
! 64: * The i-th row must contain the vector which defines the
! 65: * elementary reflector H(i), for i = 1,2,...,k, as returned by
! 66: * DGERQF in the last k rows of its array argument A.
! 67: * A is modified by the routine but restored on exit.
! 68: *
! 69: * LDA (input) INTEGER
! 70: * The leading dimension of the array A. LDA >= max(1,K).
! 71: *
! 72: * TAU (input) DOUBLE PRECISION array, dimension (K)
! 73: * TAU(i) must contain the scalar factor of the elementary
! 74: * reflector H(i), as returned by DGERQF.
! 75: *
! 76: * C (input/output) DOUBLE PRECISION array, dimension (LDC,N)
! 77: * On entry, the m by n matrix C.
! 78: * On exit, C is overwritten by Q*C or Q'*C or C*Q' or C*Q.
! 79: *
! 80: * LDC (input) INTEGER
! 81: * The leading dimension of the array C. LDC >= max(1,M).
! 82: *
! 83: * WORK (workspace) DOUBLE PRECISION array, dimension
! 84: * (N) if SIDE = 'L',
! 85: * (M) if SIDE = 'R'
! 86: *
! 87: * INFO (output) INTEGER
! 88: * = 0: successful exit
! 89: * < 0: if INFO = -i, the i-th argument had an illegal value
! 90: *
! 91: * =====================================================================
! 92: *
! 93: * .. Parameters ..
! 94: DOUBLE PRECISION ONE
! 95: PARAMETER ( ONE = 1.0D+0 )
! 96: * ..
! 97: * .. Local Scalars ..
! 98: LOGICAL LEFT, NOTRAN
! 99: INTEGER I, I1, I2, I3, MI, NI, NQ
! 100: DOUBLE PRECISION AII
! 101: * ..
! 102: * .. External Functions ..
! 103: LOGICAL LSAME
! 104: EXTERNAL LSAME
! 105: * ..
! 106: * .. External Subroutines ..
! 107: EXTERNAL DLARF, XERBLA
! 108: * ..
! 109: * .. Intrinsic Functions ..
! 110: INTRINSIC MAX
! 111: * ..
! 112: * .. Executable Statements ..
! 113: *
! 114: * Test the input arguments
! 115: *
! 116: INFO = 0
! 117: LEFT = LSAME( SIDE, 'L' )
! 118: NOTRAN = LSAME( TRANS, 'N' )
! 119: *
! 120: * NQ is the order of Q
! 121: *
! 122: IF( LEFT ) THEN
! 123: NQ = M
! 124: ELSE
! 125: NQ = N
! 126: END IF
! 127: IF( .NOT.LEFT .AND. .NOT.LSAME( SIDE, 'R' ) ) THEN
! 128: INFO = -1
! 129: ELSE IF( .NOT.NOTRAN .AND. .NOT.LSAME( TRANS, 'T' ) ) THEN
! 130: INFO = -2
! 131: ELSE IF( M.LT.0 ) THEN
! 132: INFO = -3
! 133: ELSE IF( N.LT.0 ) THEN
! 134: INFO = -4
! 135: ELSE IF( K.LT.0 .OR. K.GT.NQ ) THEN
! 136: INFO = -5
! 137: ELSE IF( LDA.LT.MAX( 1, K ) ) THEN
! 138: INFO = -7
! 139: ELSE IF( LDC.LT.MAX( 1, M ) ) THEN
! 140: INFO = -10
! 141: END IF
! 142: IF( INFO.NE.0 ) THEN
! 143: CALL XERBLA( 'DORMR2', -INFO )
! 144: RETURN
! 145: END IF
! 146: *
! 147: * Quick return if possible
! 148: *
! 149: IF( M.EQ.0 .OR. N.EQ.0 .OR. K.EQ.0 )
! 150: $ RETURN
! 151: *
! 152: IF( ( LEFT .AND. .NOT.NOTRAN ) .OR. ( .NOT.LEFT .AND. NOTRAN ) )
! 153: $ THEN
! 154: I1 = 1
! 155: I2 = K
! 156: I3 = 1
! 157: ELSE
! 158: I1 = K
! 159: I2 = 1
! 160: I3 = -1
! 161: END IF
! 162: *
! 163: IF( LEFT ) THEN
! 164: NI = N
! 165: ELSE
! 166: MI = M
! 167: END IF
! 168: *
! 169: DO 10 I = I1, I2, I3
! 170: IF( LEFT ) THEN
! 171: *
! 172: * H(i) is applied to C(1:m-k+i,1:n)
! 173: *
! 174: MI = M - K + I
! 175: ELSE
! 176: *
! 177: * H(i) is applied to C(1:m,1:n-k+i)
! 178: *
! 179: NI = N - K + I
! 180: END IF
! 181: *
! 182: * Apply H(i)
! 183: *
! 184: AII = A( I, NQ-K+I )
! 185: A( I, NQ-K+I ) = ONE
! 186: CALL DLARF( SIDE, MI, NI, A( I, 1 ), LDA, TAU( I ), C, LDC,
! 187: $ WORK )
! 188: A( I, NQ-K+I ) = AII
! 189: 10 CONTINUE
! 190: RETURN
! 191: *
! 192: * End of DORMR2
! 193: *
! 194: END
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