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template<typename T>
void ptrfs(integer *n, integer *nrhs, T *d, T *e, T *df, T *ef, T *b, integer *ldb, T *x, integer *ldx, T *ferr, T *berr, T *work, integer *info)# PTRFS improves the computed solution to a system of linear equations.
Purpose:
PTRFS improves the computed solution to a system of linear equations when the coefficient matrix is symmetric positive definite and tridiagonal, and provides error bounds and backward error estimates for the solution.
- Parameters:
N – [in]
N is INTEGER
The order of the matrix A. N >= 0.
NRHS – [in]
NRHS is INTEGER
The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0.
D – [in]
D is REAL array, dimension (N)
The n diagonal elements of the tridiagonal matrix A.
E – [in]
E is REAL array, dimension (N-1)
The (n-1) subdiagonal elements of the tridiagonal matrix A.
DF – [in]
DF is REAL array, dimension (N)
The n diagonal elements of the diagonal matrix D from the factorization computed by SPTTRF.
EF – [in]
EF is REAL array, dimension (N-1)
The (n-1) subdiagonal elements of the unit bidiagonal factor L from the factorization computed by SPTTRF.
B – [in]
B is REAL array, dimension (LDB,NRHS)
The right hand side matrix B.
LDB – [in]
LDB is INTEGER
The leading dimension of the array B. LDB >= fla_max(1,N).
X – [inout]
X is REAL array, dimension (LDX,NRHS)
On entry, the solution matrix X, as computed by SPTTRS. On exit, the improved solution matrix X.
LDX – [in]
LDX is INTEGER
The leading dimension of the array X. LDX >= fla_max(1,N).
FERR – [out]
FERR is REAL array, dimension (NRHS)
The 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).BERR – [out]
BERR is REAL array, dimension (NRHS)
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).
WORK – [out] WORK is COMPLEX array, dimension (N)
RWORK – [out] RWORK is REAL array, dimension (N)
INFO – [out]
INFO is INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value