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Diffstat (limited to 'SRC/dlauu2.f')
| -rw-r--r-- | SRC/dlauu2.f | 135 |
1 files changed, 135 insertions, 0 deletions
diff --git a/SRC/dlauu2.f b/SRC/dlauu2.f new file mode 100644 index 00000000..092bdda1 --- /dev/null +++ b/SRC/dlauu2.f @@ -0,0 +1,135 @@ + SUBROUTINE DLAUU2( UPLO, N, A, LDA, INFO ) +* +* -- LAPACK auxiliary routine (version 3.1) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + CHARACTER UPLO + INTEGER INFO, LDA, N +* .. +* .. Array Arguments .. + DOUBLE PRECISION A( LDA, * ) +* .. +* +* Purpose +* ======= +* +* DLAUU2 computes the product U * U' or L' * L, where the triangular +* factor U or L is stored in the upper or lower triangular part of +* the array A. +* +* If UPLO = 'U' or 'u' then the upper triangle of the result is stored, +* overwriting the factor U in A. +* If UPLO = 'L' or 'l' then the lower triangle of the result is stored, +* overwriting the factor L in A. +* +* This is the unblocked form of the algorithm, calling Level 2 BLAS. +* +* Arguments +* ========= +* +* UPLO (input) CHARACTER*1 +* Specifies whether the triangular factor stored in the array A +* is upper or lower triangular: +* = 'U': Upper triangular +* = 'L': Lower triangular +* +* N (input) INTEGER +* The order of the triangular factor U or L. N >= 0. +* +* A (input/output) DOUBLE PRECISION array, dimension (LDA,N) +* On entry, the triangular factor U or L. +* On exit, if UPLO = 'U', the upper triangle of A is +* overwritten with the upper triangle of the product U * U'; +* if UPLO = 'L', the lower triangle of A is overwritten with +* the lower triangle of the product L' * L. +* +* LDA (input) INTEGER +* The leading dimension of the array A. LDA >= max(1,N). +* +* INFO (output) INTEGER +* = 0: successful exit +* < 0: if INFO = -k, the k-th argument had an illegal value +* +* ===================================================================== +* +* .. Parameters .. + DOUBLE PRECISION ONE + PARAMETER ( ONE = 1.0D+0 ) +* .. +* .. Local Scalars .. + LOGICAL UPPER + INTEGER I + DOUBLE PRECISION AII +* .. +* .. External Functions .. + LOGICAL LSAME + DOUBLE PRECISION DDOT + EXTERNAL LSAME, DDOT +* .. +* .. External Subroutines .. + EXTERNAL DGEMV, DSCAL, XERBLA +* .. +* .. Intrinsic Functions .. + INTRINSIC MAX +* .. +* .. Executable Statements .. +* +* Test the input parameters. +* + INFO = 0 + UPPER = LSAME( UPLO, 'U' ) + IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN + INFO = -1 + ELSE IF( N.LT.0 ) THEN + INFO = -2 + ELSE IF( LDA.LT.MAX( 1, N ) ) THEN + INFO = -4 + END IF + IF( INFO.NE.0 ) THEN + CALL XERBLA( 'DLAUU2', -INFO ) + RETURN + END IF +* +* Quick return if possible +* + IF( N.EQ.0 ) + $ RETURN +* + IF( UPPER ) THEN +* +* Compute the product U * U'. +* + DO 10 I = 1, N + AII = A( I, I ) + IF( I.LT.N ) THEN + A( I, I ) = DDOT( N-I+1, A( I, I ), LDA, A( I, I ), LDA ) + CALL DGEMV( 'No transpose', I-1, N-I, ONE, A( 1, I+1 ), + $ LDA, A( I, I+1 ), LDA, AII, A( 1, I ), 1 ) + ELSE + CALL DSCAL( I, AII, A( 1, I ), 1 ) + END IF + 10 CONTINUE +* + ELSE +* +* Compute the product L' * L. +* + DO 20 I = 1, N + AII = A( I, I ) + IF( I.LT.N ) THEN + A( I, I ) = DDOT( N-I+1, A( I, I ), 1, A( I, I ), 1 ) + CALL DGEMV( 'Transpose', N-I, I-1, ONE, A( I+1, 1 ), LDA, + $ A( I+1, I ), 1, AII, A( I, 1 ), LDA ) + ELSE + CALL DSCAL( I, AII, A( I, 1 ), LDA ) + END IF + 20 CONTINUE + END IF +* + RETURN +* +* End of DLAUU2 +* + END |