cherfs
cherfs - improve the computed solution to a system of linear equations when the coefficient matrix is Hermitian indefinite, and provides error bounds and backward error estimates for the solution
SUBROUTINE CHERFS( UPLO, N, NRHS, A, LDA, AF, LDAF, IPIVOT, B, LDB,
* X, LDX, FERR, BERR, WORK, WORK2, INFO)
CHARACTER * 1 UPLO
COMPLEX A(LDA,*), AF(LDAF,*), B(LDB,*), X(LDX,*), WORK(*)
INTEGER N, NRHS, LDA, LDAF, LDB, LDX, INFO
INTEGER IPIVOT(*)
REAL FERR(*), BERR(*), WORK2(*)
SUBROUTINE CHERFS_64( UPLO, N, NRHS, A, LDA, AF, LDAF, IPIVOT, B,
* LDB, X, LDX, FERR, BERR, WORK, WORK2, INFO)
CHARACTER * 1 UPLO
COMPLEX A(LDA,*), AF(LDAF,*), B(LDB,*), X(LDX,*), WORK(*)
INTEGER*8 N, NRHS, LDA, LDAF, LDB, LDX, INFO
INTEGER*8 IPIVOT(*)
REAL FERR(*), BERR(*), WORK2(*)
SUBROUTINE HERFS( UPLO, [N], [NRHS], A, [LDA], AF, [LDAF], IPIVOT,
* B, [LDB], X, [LDX], FERR, BERR, [WORK], [WORK2], [INFO])
CHARACTER(LEN=1) :: UPLO
COMPLEX, DIMENSION(:) :: WORK
COMPLEX, DIMENSION(:,:) :: A, AF, B, X
INTEGER :: N, NRHS, LDA, LDAF, LDB, LDX, INFO
INTEGER, DIMENSION(:) :: IPIVOT
REAL, DIMENSION(:) :: FERR, BERR, WORK2
SUBROUTINE HERFS_64( UPLO, [N], [NRHS], A, [LDA], AF, [LDAF],
* IPIVOT, B, [LDB], X, [LDX], FERR, BERR, [WORK], [WORK2], [INFO])
CHARACTER(LEN=1) :: UPLO
COMPLEX, DIMENSION(:) :: WORK
COMPLEX, DIMENSION(:,:) :: A, AF, B, X
INTEGER(8) :: N, NRHS, LDA, LDAF, LDB, LDX, INFO
INTEGER(8), DIMENSION(:) :: IPIVOT
REAL, DIMENSION(:) :: FERR, BERR, WORK2
#include <sunperf.h>
void cherfs(char uplo, int n, int nrhs, complex *a, int lda, complex *af, int ldaf, int *ipivot, complex *b, int ldb, complex *x, int ldx, float *ferr, float *berr, int *info);
void cherfs_64(char uplo, long n, long nrhs, complex *a, long lda, complex *af, long ldaf, long *ipivot, complex *b, long ldb, complex *x, long ldx, float *ferr, float *berr, long *info);
cherfs improves the computed solution to a system of linear
equations when the coefficient matrix is Hermitian indefinite, and
provides error bounds and backward error estimates for the solution.
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* UPLO (input)
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* N (input)
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The order of the matrix A. N >= 0.
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* NRHS (input)
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The number of right hand sides, i.e., the number of columns
of the matrices B and X. NRHS >= 0.
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* A (input)
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The Hermitian 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.
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* LDA (input)
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The leading dimension of the array A. LDA >= max(1,N).
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* AF (input)
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The factored form of the matrix A. AF contains the block
diagonal matrix D and the multipliers used to obtain the
factor U or L from the factorization A = U*D*U**H or
A = L*D*L**H as computed by CHETRF.
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* LDAF (input)
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The leading dimension of the array AF. LDAF >= max(1,N).
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* IPIVOT (input)
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Details of the interchanges and the block structure of D
as determined by CHETRF.
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* B (input)
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The right hand side matrix B.
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* LDB (input)
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The leading dimension of the array B. LDB >= max(1,N).
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* X (input/output)
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On entry, the solution matrix X, as computed by CHETRS.
On exit, the improved solution matrix X.
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* LDX (input)
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The leading dimension of the array X. LDX >= max(1,N).
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* FERR (output)
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The estimated forward error bound for each solution vector
X(j) (the j-th column of the solution matrix X).
If XTRUE is the true solution corresponding to X(j), FERR(j)
is an estimated upper bound for the magnitude of the largest
element in (X(j) - XTRUE) divided by the magnitude of the
largest element in X(j). The estimate is as reliable as
the estimate for RCOND, and is almost always a slight
overestimate of the true error.
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* BERR (output)
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The componentwise relative backward error of each solution
vector X(j) (i.e., the smallest relative change in
any element of A or B that makes X(j) an exact solution).
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* WORK (workspace)
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dimension(2*N)
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* WORK2 (workspace)
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* INFO (output)
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