Original Version

1 files changed, 165 insertions, 0 deletions

diff --git a/src/fortran/lapack/dsycon.f b/src/fortran/lapack/dsycon.f
new file mode 100644
index 0000000..711b48c
--- /dev/null
+++ b/src/fortran/lapack/dsycon.f
@@ -0,0 +1,165 @@
+      SUBROUTINE DSYCON( UPLO, N, A, LDA, IPIV, ANORM, RCOND, WORK,
+     $                   IWORK, INFO )
+*
+*  -- LAPACK routine (version 3.1) --
+*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
+*     November 2006
+*
+*     Modified to call DLACN2 in place of DLACON, 5 Feb 03, SJH.
+*
+*     .. Scalar Arguments ..
+      CHARACTER          UPLO
+      INTEGER            INFO, LDA, N
+      DOUBLE PRECISION   ANORM, RCOND
+*     ..
+*     .. Array Arguments ..
+      INTEGER            IPIV( * ), IWORK( * )
+      DOUBLE PRECISION   A( LDA, * ), WORK( * )
+*     ..
+*
+*  Purpose
+*  =======
+*
+*  DSYCON estimates the reciprocal of the condition number (in the
+*  1-norm) of a real symmetric matrix A using the factorization
+*  A = U*D*U**T or A = L*D*L**T computed by DSYTRF.
+*
+*  An estimate is obtained for norm(inv(A)), and the reciprocal of the
+*  condition number is computed as RCOND = 1 / (ANORM * norm(inv(A))).
+*
+*  Arguments
+*  =========
+*
+*  UPLO    (input) CHARACTER*1
+*          Specifies whether the details of the factorization are stored
+*          as an upper or lower triangular matrix.
+*          = 'U':  Upper triangular, form is A = U*D*U**T;
+*          = 'L':  Lower triangular, form is A = L*D*L**T.
+*
+*  N       (input) INTEGER
+*          The order of the matrix A.  N >= 0.
+*
+*  A       (input) DOUBLE PRECISION array, dimension (LDA,N)
+*          The block diagonal matrix D and the multipliers used to
+*          obtain the factor U or L as computed by DSYTRF.
+*
+*  LDA     (input) INTEGER
+*          The leading dimension of the array A.  LDA >= max(1,N).
+*
+*  IPIV    (input) INTEGER array, dimension (N)
+*          Details of the interchanges and the block structure of D
+*          as determined by DSYTRF.
+*
+*  ANORM   (input) DOUBLE PRECISION
+*          The 1-norm of the original matrix A.
+*
+*  RCOND   (output) DOUBLE PRECISION
+*          The reciprocal of the condition number of the matrix A,
+*          computed as RCOND = 1/(ANORM * AINVNM), where AINVNM is an
+*          estimate of the 1-norm of inv(A) computed in this routine.
+*
+*  WORK    (workspace) DOUBLE PRECISION array, dimension (2*N)
+*
+*  IWORK    (workspace) INTEGER array, dimension (N)
+*
+*  INFO    (output) INTEGER
+*          = 0:  successful exit
+*          < 0:  if INFO = -i, the i-th argument had an illegal value
+*
+*  =====================================================================
+*
+*     .. Parameters ..
+      DOUBLE PRECISION   ONE, ZERO
+      PARAMETER          ( ONE = 1.0D+0, ZERO = 0.0D+0 )
+*     ..
+*     .. Local Scalars ..
+      LOGICAL            UPPER
+      INTEGER            I, KASE
+      DOUBLE PRECISION   AINVNM
+*     ..
+*     .. Local Arrays ..
+      INTEGER            ISAVE( 3 )
+*     ..
+*     .. External Functions ..
+      LOGICAL            LSAME
+      EXTERNAL           LSAME
+*     ..
+*     .. External Subroutines ..
+      EXTERNAL           DLACN2, DSYTRS, 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
+      ELSE IF( ANORM.LT.ZERO ) THEN
+         INFO = -6
+      END IF
+      IF( INFO.NE.0 ) THEN
+         CALL XERBLA( 'DSYCON', -INFO )
+         RETURN
+      END IF
+*
+*     Quick return if possible
+*
+      RCOND = ZERO
+      IF( N.EQ.0 ) THEN
+         RCOND = ONE
+         RETURN
+      ELSE IF( ANORM.LE.ZERO ) THEN
+         RETURN
+      END IF
+*
+*     Check that the diagonal matrix D is nonsingular.
+*
+      IF( UPPER ) THEN
+*
+*        Upper triangular storage: examine D from bottom to top
+*
+         DO 10 I = N, 1, -1
+            IF( IPIV( I ).GT.0 .AND. A( I, I ).EQ.ZERO )
+     $         RETURN
+   10    CONTINUE
+      ELSE
+*
+*        Lower triangular storage: examine D from top to bottom.
+*
+         DO 20 I = 1, N
+            IF( IPIV( I ).GT.0 .AND. A( I, I ).EQ.ZERO )
+     $         RETURN
+   20    CONTINUE
+      END IF
+*
+*     Estimate the 1-norm of the inverse.
+*
+      KASE = 0
+   30 CONTINUE
+      CALL DLACN2( N, WORK( N+1 ), WORK, IWORK, AINVNM, KASE, ISAVE )
+      IF( KASE.NE.0 ) THEN
+*
+*        Multiply by inv(L*D*L') or inv(U*D*U').
+*
+         CALL DSYTRS( UPLO, N, 1, A, LDA, IPIV, WORK, N, INFO )
+         GO TO 30
+      END IF
+*
+*     Compute the estimate of the reciprocal condition number.
+*
+      IF( AINVNM.NE.ZERO )
+     $   RCOND = ( ONE / AINVNM ) / ANORM
+*
+      RETURN
+*
+*     End of DSYCON
+*
+      END