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LAPACK
3.7.0
LAPACK: Linear Algebra PACKage
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subroutine zgbt01 | ( | integer | M, |
integer | N, | ||
integer | KL, | ||
integer | KU, | ||
complex*16, dimension( lda, * ) | A, | ||
integer | LDA, | ||
complex*16, dimension( ldafac, * ) | AFAC, | ||
integer | LDAFAC, | ||
integer, dimension( * ) | IPIV, | ||
complex*16, dimension( * ) | WORK, | ||
double precision | RESID | ||
) |
ZGBT01
ZGBT01 reconstructs a band matrix A from its L*U factorization and computes the residual: norm(L*U - A) / ( N * norm(A) * EPS ), where EPS is the machine epsilon. The expression L*U - A is computed one column at a time, so A and AFAC are not modified.
[in] | M | M is INTEGER The number of rows of the matrix A. M >= 0. |
[in] | N | N is INTEGER The number of columns of the matrix A. N >= 0. |
[in] | KL | KL is INTEGER The number of subdiagonals within the band of A. KL >= 0. |
[in] | KU | KU is INTEGER The number of superdiagonals within the band of A. KU >= 0. |
[in,out] | A | A is COMPLEX*16 array, dimension (LDA,N) The original matrix A in band storage, stored in rows 1 to KL+KU+1. |
[in] | LDA | LDA is INTEGER. The leading dimension of the array A. LDA >= max(1,KL+KU+1). |
[in] | AFAC | AFAC is COMPLEX*16 array, dimension (LDAFAC,N) The factored form of the matrix A. AFAC contains the banded factors L and U from the L*U factorization, as computed by ZGBTRF. U is stored as an upper triangular band matrix with KL+KU superdiagonals in rows 1 to KL+KU+1, and the multipliers used during the factorization are stored in rows KL+KU+2 to 2*KL+KU+1. See ZGBTRF for further details. |
[in] | LDAFAC | LDAFAC is INTEGER The leading dimension of the array AFAC. LDAFAC >= max(1,2*KL*KU+1). |
[in] | IPIV | IPIV is INTEGER array, dimension (min(M,N)) The pivot indices from ZGBTRF. |
[out] | WORK | WORK is COMPLEX*16 array, dimension (2*KL+KU+1) |
[out] | RESID | RESID is DOUBLE PRECISION norm(L*U - A) / ( N * norm(A) * EPS ) |
Definition at line 128 of file zgbt01.f.