Annotation of rpl/lapack/lapack/dlauu2.f, revision 1.1
1.1 ! bertrand 1: SUBROUTINE DLAUU2( UPLO, N, A, LDA, INFO )
! 2: *
! 3: * -- LAPACK auxiliary 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 UPLO
! 10: INTEGER INFO, LDA, N
! 11: * ..
! 12: * .. Array Arguments ..
! 13: DOUBLE PRECISION A( LDA, * )
! 14: * ..
! 15: *
! 16: * Purpose
! 17: * =======
! 18: *
! 19: * DLAUU2 computes the product U * U' or L' * L, where the triangular
! 20: * factor U or L is stored in the upper or lower triangular part of
! 21: * the array A.
! 22: *
! 23: * If UPLO = 'U' or 'u' then the upper triangle of the result is stored,
! 24: * overwriting the factor U in A.
! 25: * If UPLO = 'L' or 'l' then the lower triangle of the result is stored,
! 26: * overwriting the factor L in A.
! 27: *
! 28: * This is the unblocked form of the algorithm, calling Level 2 BLAS.
! 29: *
! 30: * Arguments
! 31: * =========
! 32: *
! 33: * UPLO (input) CHARACTER*1
! 34: * Specifies whether the triangular factor stored in the array A
! 35: * is upper or lower triangular:
! 36: * = 'U': Upper triangular
! 37: * = 'L': Lower triangular
! 38: *
! 39: * N (input) INTEGER
! 40: * The order of the triangular factor U or L. N >= 0.
! 41: *
! 42: * A (input/output) DOUBLE PRECISION array, dimension (LDA,N)
! 43: * On entry, the triangular factor U or L.
! 44: * On exit, if UPLO = 'U', the upper triangle of A is
! 45: * overwritten with the upper triangle of the product U * U';
! 46: * if UPLO = 'L', the lower triangle of A is overwritten with
! 47: * the lower triangle of the product L' * L.
! 48: *
! 49: * LDA (input) INTEGER
! 50: * The leading dimension of the array A. LDA >= max(1,N).
! 51: *
! 52: * INFO (output) INTEGER
! 53: * = 0: successful exit
! 54: * < 0: if INFO = -k, the k-th argument had an illegal value
! 55: *
! 56: * =====================================================================
! 57: *
! 58: * .. Parameters ..
! 59: DOUBLE PRECISION ONE
! 60: PARAMETER ( ONE = 1.0D+0 )
! 61: * ..
! 62: * .. Local Scalars ..
! 63: LOGICAL UPPER
! 64: INTEGER I
! 65: DOUBLE PRECISION AII
! 66: * ..
! 67: * .. External Functions ..
! 68: LOGICAL LSAME
! 69: DOUBLE PRECISION DDOT
! 70: EXTERNAL LSAME, DDOT
! 71: * ..
! 72: * .. External Subroutines ..
! 73: EXTERNAL DGEMV, DSCAL, XERBLA
! 74: * ..
! 75: * .. Intrinsic Functions ..
! 76: INTRINSIC MAX
! 77: * ..
! 78: * .. Executable Statements ..
! 79: *
! 80: * Test the input parameters.
! 81: *
! 82: INFO = 0
! 83: UPPER = LSAME( UPLO, 'U' )
! 84: IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
! 85: INFO = -1
! 86: ELSE IF( N.LT.0 ) THEN
! 87: INFO = -2
! 88: ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
! 89: INFO = -4
! 90: END IF
! 91: IF( INFO.NE.0 ) THEN
! 92: CALL XERBLA( 'DLAUU2', -INFO )
! 93: RETURN
! 94: END IF
! 95: *
! 96: * Quick return if possible
! 97: *
! 98: IF( N.EQ.0 )
! 99: $ RETURN
! 100: *
! 101: IF( UPPER ) THEN
! 102: *
! 103: * Compute the product U * U'.
! 104: *
! 105: DO 10 I = 1, N
! 106: AII = A( I, I )
! 107: IF( I.LT.N ) THEN
! 108: A( I, I ) = DDOT( N-I+1, A( I, I ), LDA, A( I, I ), LDA )
! 109: CALL DGEMV( 'No transpose', I-1, N-I, ONE, A( 1, I+1 ),
! 110: $ LDA, A( I, I+1 ), LDA, AII, A( 1, I ), 1 )
! 111: ELSE
! 112: CALL DSCAL( I, AII, A( 1, I ), 1 )
! 113: END IF
! 114: 10 CONTINUE
! 115: *
! 116: ELSE
! 117: *
! 118: * Compute the product L' * L.
! 119: *
! 120: DO 20 I = 1, N
! 121: AII = A( I, I )
! 122: IF( I.LT.N ) THEN
! 123: A( I, I ) = DDOT( N-I+1, A( I, I ), 1, A( I, I ), 1 )
! 124: CALL DGEMV( 'Transpose', N-I, I-1, ONE, A( I+1, 1 ), LDA,
! 125: $ A( I+1, I ), 1, AII, A( I, 1 ), LDA )
! 126: ELSE
! 127: CALL DSCAL( I, AII, A( I, 1 ), LDA )
! 128: END IF
! 129: 20 CONTINUE
! 130: END IF
! 131: *
! 132: RETURN
! 133: *
! 134: * End of DLAUU2
! 135: *
! 136: END
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