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LAPACK
3.7.0
LAPACK: Linear Algebra PACKage
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subroutine cgtrfs | ( | character | TRANS, |
integer | N, | ||
integer | NRHS, | ||
complex, dimension( * ) | DL, | ||
complex, dimension( * ) | D, | ||
complex, dimension( * ) | DU, | ||
complex, dimension( * ) | DLF, | ||
complex, dimension( * ) | DF, | ||
complex, dimension( * ) | DUF, | ||
complex, dimension( * ) | DU2, | ||
integer, dimension( * ) | IPIV, | ||
complex, dimension( ldb, * ) | B, | ||
integer | LDB, | ||
complex, dimension( ldx, * ) | X, | ||
integer | LDX, | ||
real, dimension( * ) | FERR, | ||
real, dimension( * ) | BERR, | ||
complex, dimension( * ) | WORK, | ||
real, dimension( * ) | RWORK, | ||
integer | INFO | ||
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CGTRFS
Download CGTRFS + dependencies [TGZ] [ZIP] [TXT]
CGTRFS improves the computed solution to a system of linear equations when the coefficient matrix is tridiagonal, and provides error bounds and backward error estimates for the solution.
[in] | TRANS | TRANS is CHARACTER*1 Specifies the form of the system of equations: = 'N': A * X = B (No transpose) = 'T': A**T * X = B (Transpose) = 'C': A**H * X = B (Conjugate transpose) |
[in] | N | N is INTEGER The order of the matrix A. N >= 0. |
[in] | NRHS | NRHS is INTEGER The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0. |
[in] | DL | DL is COMPLEX array, dimension (N-1) The (n-1) subdiagonal elements of A. |
[in] | D | D is COMPLEX array, dimension (N) The diagonal elements of A. |
[in] | DU | DU is COMPLEX array, dimension (N-1) The (n-1) superdiagonal elements of A. |
[in] | DLF | DLF is COMPLEX array, dimension (N-1) The (n-1) multipliers that define the matrix L from the LU factorization of A as computed by CGTTRF. |
[in] | DF | DF is COMPLEX array, dimension (N) The n diagonal elements of the upper triangular matrix U from the LU factorization of A. |
[in] | DUF | DUF is COMPLEX array, dimension (N-1) The (n-1) elements of the first superdiagonal of U. |
[in] | DU2 | DU2 is COMPLEX array, dimension (N-2) The (n-2) elements of the second superdiagonal of U. |
[in] | IPIV | IPIV is INTEGER array, dimension (N) The pivot indices; for 1 <= i <= n, row i of the matrix was interchanged with row IPIV(i). IPIV(i) will always be either i or i+1; IPIV(i) = i indicates a row interchange was not required. |
[in] | B | B is COMPLEX array, dimension (LDB,NRHS) The right hand side matrix B. |
[in] | LDB | LDB is INTEGER The leading dimension of the array B. LDB >= max(1,N). |
[in,out] | X | X is COMPLEX array, dimension (LDX,NRHS) On entry, the solution matrix X, as computed by CGTTRS. On exit, the improved solution matrix X. |
[in] | LDX | LDX is INTEGER The leading dimension of the array X. LDX >= max(1,N). |
[out] | FERR | FERR is REAL array, dimension (NRHS) 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. |
[out] | BERR | 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). |
[out] | WORK | WORK is COMPLEX array, dimension (2*N) |
[out] | RWORK | RWORK is REAL array, dimension (N) |
[out] | INFO | INFO is INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value |
ITMAX is the maximum number of steps of iterative refinement.
Definition at line 212 of file cgtrfs.f.