LAPACK
3.6.1
LAPACK: Linear Algebra PACKage
|
subroutine dtpt02 | ( | character | UPLO, |
character | TRANS, | ||
character | DIAG, | ||
integer | N, | ||
integer | NRHS, | ||
double precision, dimension( * ) | AP, | ||
double precision, dimension( ldx, * ) | X, | ||
integer | LDX, | ||
double precision, dimension( ldb, * ) | B, | ||
integer | LDB, | ||
double precision, dimension( * ) | WORK, | ||
double precision | RESID | ||
) |
DTPT02
DTPT02 computes the residual for the computed solution to a triangular system of linear equations A*x = b or A'*x = b when the triangular matrix A is stored in packed format. Here A' is the transpose of A and x and b are N by NRHS matrices. The test ratio is the maximum over the number of right hand sides of norm(b - op(A)*x) / ( norm(op(A)) * norm(x) * EPS ), where op(A) denotes A or A' and EPS is the machine epsilon.
[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 operation applied to A. = '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 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 matrices X and B. NRHS >= 0. |
[in] | AP | AP is DOUBLE PRECISION array, dimension (N*(N+1)/2) The upper or lower triangular matrix A, packed columnwise in a linear array. The j-th column of A is stored in the array AP as follows: if UPLO = 'U', AP((j-1)*j/2 + i) = A(i,j) for 1<=i<=j; if UPLO = 'L', AP((j-1)*(n-j) + j*(j+1)/2 + i-j) = A(i,j) for j<=i<=n. |
[in] | X | X is DOUBLE PRECISION array, dimension (LDX,NRHS) The computed solution vectors for the system of linear equations. |
[in] | LDX | LDX is INTEGER The leading dimension of the array X. LDX >= max(1,N). |
[in] | B | B is DOUBLE PRECISION 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). |
[out] | WORK | WORK is DOUBLE PRECISION array, dimension (N) |
[out] | RESID | RESID is DOUBLE PRECISION The maximum over the number of right hand sides of norm(op(A)*x - b) / ( norm(op(A)) * norm(x) * EPS ). |
Definition at line 143 of file dtpt02.f.