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Diffstat (limited to '2.3-1/src/fortran/lapack/dpotrf.f')
| -rw-r--r-- | 2.3-1/src/fortran/lapack/dpotrf.f | 183 |
1 files changed, 183 insertions, 0 deletions
diff --git a/2.3-1/src/fortran/lapack/dpotrf.f b/2.3-1/src/fortran/lapack/dpotrf.f new file mode 100644 index 00000000..8449df6d --- /dev/null +++ b/2.3-1/src/fortran/lapack/dpotrf.f @@ -0,0 +1,183 @@ + SUBROUTINE DPOTRF( UPLO, N, A, LDA, INFO ) +* +* -- LAPACK 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 +* ======= +* +* DPOTRF computes the Cholesky factorization of a real symmetric +* positive definite matrix A. +* +* The factorization has the form +* A = U**T * U, if UPLO = 'U', or +* A = L * L**T, if UPLO = 'L', +* where U is an upper triangular matrix and L is lower triangular. +* +* This is the block version of the algorithm, calling Level 3 BLAS. +* +* Arguments +* ========= +* +* UPLO (input) CHARACTER*1 +* = 'U': Upper triangle of A is stored; +* = 'L': Lower triangle of A is stored. +* +* N (input) INTEGER +* The order of the matrix A. N >= 0. +* +* A (input/output) DOUBLE PRECISION array, dimension (LDA,N) +* On entry, the symmetric matrix A. If UPLO = 'U', the leading +* N-by-N upper triangular part of A contains the upper +* triangular part of the matrix A, and the strictly lower +* triangular part of A is not referenced. If UPLO = 'L', the +* leading N-by-N lower triangular part of A contains the lower +* triangular part of the matrix A, and the strictly upper +* triangular part of A is not referenced. +* +* On exit, if INFO = 0, the factor U or L from the Cholesky +* factorization A = U**T*U or A = L*L**T. +* +* LDA (input) INTEGER +* The leading dimension of the array A. LDA >= max(1,N). +* +* INFO (output) INTEGER +* = 0: successful exit +* < 0: if INFO = -i, the i-th argument had an illegal value +* > 0: if INFO = i, the leading minor of order i is not +* positive definite, and the factorization could not be +* completed. +* +* ===================================================================== +* +* .. Parameters .. + DOUBLE PRECISION ONE + PARAMETER ( ONE = 1.0D+0 ) +* .. +* .. Local Scalars .. + LOGICAL UPPER + INTEGER J, JB, NB +* .. +* .. External Functions .. + LOGICAL LSAME + INTEGER ILAENV + EXTERNAL LSAME, ILAENV +* .. +* .. External Subroutines .. + EXTERNAL DGEMM, DPOTF2, DSYRK, DTRSM, XERBLA +* .. +* .. Intrinsic Functions .. + INTRINSIC MAX, MIN +* .. +* .. 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( 'DPOTRF', -INFO ) + RETURN + END IF +* +* Quick return if possible +* + IF( N.EQ.0 ) + $ RETURN +* +* Determine the block size for this environment. +* + NB = ILAENV( 1, 'DPOTRF', UPLO, N, -1, -1, -1 ) + IF( NB.LE.1 .OR. NB.GE.N ) THEN +* +* Use unblocked code. +* + CALL DPOTF2( UPLO, N, A, LDA, INFO ) + ELSE +* +* Use blocked code. +* + IF( UPPER ) THEN +* +* Compute the Cholesky factorization A = U'*U. +* + DO 10 J = 1, N, NB +* +* Update and factorize the current diagonal block and test +* for non-positive-definiteness. +* + JB = MIN( NB, N-J+1 ) + CALL DSYRK( 'Upper', 'Transpose', JB, J-1, -ONE, + $ A( 1, J ), LDA, ONE, A( J, J ), LDA ) + CALL DPOTF2( 'Upper', JB, A( J, J ), LDA, INFO ) + IF( INFO.NE.0 ) + $ GO TO 30 + IF( J+JB.LE.N ) THEN +* +* Compute the current block row. +* + CALL DGEMM( 'Transpose', 'No transpose', JB, N-J-JB+1, + $ J-1, -ONE, A( 1, J ), LDA, A( 1, J+JB ), + $ LDA, ONE, A( J, J+JB ), LDA ) + CALL DTRSM( 'Left', 'Upper', 'Transpose', 'Non-unit', + $ JB, N-J-JB+1, ONE, A( J, J ), LDA, + $ A( J, J+JB ), LDA ) + END IF + 10 CONTINUE +* + ELSE +* +* Compute the Cholesky factorization A = L*L'. +* + DO 20 J = 1, N, NB +* +* Update and factorize the current diagonal block and test +* for non-positive-definiteness. +* + JB = MIN( NB, N-J+1 ) + CALL DSYRK( 'Lower', 'No transpose', JB, J-1, -ONE, + $ A( J, 1 ), LDA, ONE, A( J, J ), LDA ) + CALL DPOTF2( 'Lower', JB, A( J, J ), LDA, INFO ) + IF( INFO.NE.0 ) + $ GO TO 30 + IF( J+JB.LE.N ) THEN +* +* Compute the current block column. +* + CALL DGEMM( 'No transpose', 'Transpose', N-J-JB+1, JB, + $ J-1, -ONE, A( J+JB, 1 ), LDA, A( J, 1 ), + $ LDA, ONE, A( J+JB, J ), LDA ) + CALL DTRSM( 'Right', 'Lower', 'Transpose', 'Non-unit', + $ N-J-JB+1, JB, ONE, A( J, J ), LDA, + $ A( J+JB, J ), LDA ) + END IF + 20 CONTINUE + END IF + END IF + GO TO 40 +* + 30 CONTINUE + INFO = INFO + J - 1 +* + 40 CONTINUE + RETURN +* +* End of DPOTRF +* + END |