Annotation of rpl/lapack/lapack/dlauum.f, revision 1.1
1.1 ! bertrand 1: SUBROUTINE DLAUUM( 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: * DLAUUM 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 blocked form of the algorithm, calling Level 3 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, IB, NB
! 65: * ..
! 66: * .. External Functions ..
! 67: LOGICAL LSAME
! 68: INTEGER ILAENV
! 69: EXTERNAL LSAME, ILAENV
! 70: * ..
! 71: * .. External Subroutines ..
! 72: EXTERNAL DGEMM, DLAUU2, DSYRK, DTRMM, XERBLA
! 73: * ..
! 74: * .. Intrinsic Functions ..
! 75: INTRINSIC MAX, MIN
! 76: * ..
! 77: * .. Executable Statements ..
! 78: *
! 79: * Test the input parameters.
! 80: *
! 81: INFO = 0
! 82: UPPER = LSAME( UPLO, 'U' )
! 83: IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
! 84: INFO = -1
! 85: ELSE IF( N.LT.0 ) THEN
! 86: INFO = -2
! 87: ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
! 88: INFO = -4
! 89: END IF
! 90: IF( INFO.NE.0 ) THEN
! 91: CALL XERBLA( 'DLAUUM', -INFO )
! 92: RETURN
! 93: END IF
! 94: *
! 95: * Quick return if possible
! 96: *
! 97: IF( N.EQ.0 )
! 98: $ RETURN
! 99: *
! 100: * Determine the block size for this environment.
! 101: *
! 102: NB = ILAENV( 1, 'DLAUUM', UPLO, N, -1, -1, -1 )
! 103: *
! 104: IF( NB.LE.1 .OR. NB.GE.N ) THEN
! 105: *
! 106: * Use unblocked code
! 107: *
! 108: CALL DLAUU2( UPLO, N, A, LDA, INFO )
! 109: ELSE
! 110: *
! 111: * Use blocked code
! 112: *
! 113: IF( UPPER ) THEN
! 114: *
! 115: * Compute the product U * U'.
! 116: *
! 117: DO 10 I = 1, N, NB
! 118: IB = MIN( NB, N-I+1 )
! 119: CALL DTRMM( 'Right', 'Upper', 'Transpose', 'Non-unit',
! 120: $ I-1, IB, ONE, A( I, I ), LDA, A( 1, I ),
! 121: $ LDA )
! 122: CALL DLAUU2( 'Upper', IB, A( I, I ), LDA, INFO )
! 123: IF( I+IB.LE.N ) THEN
! 124: CALL DGEMM( 'No transpose', 'Transpose', I-1, IB,
! 125: $ N-I-IB+1, ONE, A( 1, I+IB ), LDA,
! 126: $ A( I, I+IB ), LDA, ONE, A( 1, I ), LDA )
! 127: CALL DSYRK( 'Upper', 'No transpose', IB, N-I-IB+1,
! 128: $ ONE, A( I, I+IB ), LDA, ONE, A( I, I ),
! 129: $ LDA )
! 130: END IF
! 131: 10 CONTINUE
! 132: ELSE
! 133: *
! 134: * Compute the product L' * L.
! 135: *
! 136: DO 20 I = 1, N, NB
! 137: IB = MIN( NB, N-I+1 )
! 138: CALL DTRMM( 'Left', 'Lower', 'Transpose', 'Non-unit', IB,
! 139: $ I-1, ONE, A( I, I ), LDA, A( I, 1 ), LDA )
! 140: CALL DLAUU2( 'Lower', IB, A( I, I ), LDA, INFO )
! 141: IF( I+IB.LE.N ) THEN
! 142: CALL DGEMM( 'Transpose', 'No transpose', IB, I-1,
! 143: $ N-I-IB+1, ONE, A( I+IB, I ), LDA,
! 144: $ A( I+IB, 1 ), LDA, ONE, A( I, 1 ), LDA )
! 145: CALL DSYRK( 'Lower', 'Transpose', IB, N-I-IB+1, ONE,
! 146: $ A( I+IB, I ), LDA, ONE, A( I, I ), LDA )
! 147: END IF
! 148: 20 CONTINUE
! 149: END IF
! 150: END IF
! 151: *
! 152: RETURN
! 153: *
! 154: * End of DLAUUM
! 155: *
! 156: END
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