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LAPACK
3.7.0
LAPACK: Linear Algebra PACKage
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subroutine strt05 | ( | character | UPLO, |
character | TRANS, | ||
character | DIAG, | ||
integer | N, | ||
integer | NRHS, | ||
real, dimension( lda, * ) | A, | ||
integer | LDA, | ||
real, dimension( ldb, * ) | B, | ||
integer | LDB, | ||
real, dimension( ldx, * ) | X, | ||
integer | LDX, | ||
real, dimension( ldxact, * ) | XACT, | ||
integer | LDXACT, | ||
real, dimension( * ) | FERR, | ||
real, dimension( * ) | BERR, | ||
real, dimension( * ) | RESLTS | ||
) |
STRT05
STRT05 tests the error bounds from iterative refinement for the computed solution to a system of equations A*X = B, where A is a triangular n by n matrix. RESLTS(1) = test of the error bound = norm(X - XACT) / ( norm(X) * FERR ) A large value is returned if this ratio is not less than one. RESLTS(2) = residual from the iterative refinement routine = the maximum of BERR / ( (n+1)*EPS + (*) ), where (*) = (n+1)*UNFL / (min_i (abs(A)*abs(X) +abs(b))_i )
[in] | UPLO | UPLO is CHARACTER*1 Specifies whether the matrix A is upper or lower triangular. = 'U': Upper triangular = 'L': Lower triangular |
[in] | TRANS | TRANS is CHARACTER*1 Specifies the form of the system of equations. = 'N': A * X = B (No transpose) = 'T': A'* X = B (Transpose) = 'C': A'* X = B (Conjugate transpose = Transpose) |
[in] | DIAG | DIAG is CHARACTER*1 Specifies whether or not the matrix A is unit triangular. = 'N': Non-unit triangular = 'U': Unit triangular |
[in] | N | N is INTEGER The number of rows of the matrices X, B, and XACT, and the order of the matrix A. N >= 0. |
[in] | NRHS | NRHS is INTEGER The number of columns of the matrices X, B, and XACT. NRHS >= 0. |
[in] | A | A is REAL array, dimension (LDA,N) The triangular matrix A. If UPLO = 'U', the leading n by n upper triangular part of the array A contains the upper triangular matrix, and the strictly lower triangular part of A is not referenced. If UPLO = 'L', the leading n by n lower triangular part of the array A contains the lower triangular matrix, and the strictly upper triangular part of A is not referenced. If DIAG = 'U', the diagonal elements of A are also not referenced and are assumed to be 1. |
[in] | LDA | LDA is INTEGER The leading dimension of the array A. LDA >= max(1,N). |
[in] | B | B is REAL array, dimension (LDB,NRHS) The right hand side vectors for the system of linear equations. |
[in] | LDB | LDB is INTEGER The leading dimension of the array B. LDB >= max(1,N). |
[in] | X | X is REAL array, dimension (LDX,NRHS) The computed solution vectors. Each vector is stored as a column of the matrix X. |
[in] | LDX | LDX is INTEGER The leading dimension of the array X. LDX >= max(1,N). |
[in] | XACT | XACT is REAL array, dimension (LDX,NRHS) The exact solution vectors. Each vector is stored as a column of the matrix XACT. |
[in] | LDXACT | LDXACT is INTEGER The leading dimension of the array XACT. LDXACT >= max(1,N). |
[in] | FERR | FERR is REAL array, dimension (NRHS) The estimated forward error bounds for each solution vector X. If XTRUE is the true solution, FERR bounds the magnitude of the largest entry in (X - XTRUE) divided by the magnitude of the largest entry in X. |
[in] | BERR | BERR is REAL array, dimension (NRHS) The componentwise relative backward error of each solution vector (i.e., the smallest relative change in any entry of A or B that makes X an exact solution). |
[out] | RESLTS | RESLTS is REAL array, dimension (2) The maximum over the NRHS solution vectors of the ratios: RESLTS(1) = norm(X - XACT) / ( norm(X) * FERR ) RESLTS(2) = BERR / ( (n+1)*EPS + (*) ) |
Definition at line 183 of file strt05.f.