GBTRS - 5.2 English - 68552

AOCL API Guide (68552)

Document ID
68552
Release Date
2025-12-29
Version
5.2 English
template<typename T>
void gbtrs(char *trans, integer *n, integer *kl, integer *ku, integer *nrhs, T *ab, integer *ldab, integer *ipiv, T *b, integer *ldb, integer *info)#

GBTRS solves a system of linear equationsA * X = B or A**T * X = B with a general band matrix A using the LU factorization computed by GBTRF

Purpose:

    GBTRS solves a system of linear equations
    A * X = B  or  A**T * X = B
    with a general band matrix A using the LU factorization computed
    by GBTRF.
Parameters:
  • TRANS[in]

    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**T* X = B (Conjugate transpose = Transpose)
  • N[in]

    N is INTEGER

    The order of the matrix A. N >= 0.

  • KL[in]

    KL is INTEGER

    The number of subdiagonals within the band of A. KL >= 0.

  • KU[in]

    KU is INTEGER

    The number of superdiagonals within the band of A. KU >= 0.

  • NRHS[in]

    NRHS is INTEGER

    The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0.

  • AB[in]

    AB is REAL array, dimension (LDAB,N)

    Details of the LU factorization of the band matrix A, as computed by SGBTRF. 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.

  • LDAB[in]

    LDAB is INTEGER

    The leading dimension of the array AB. LDAB >= 2*KL+KU+1.

  • IPIV[in]

    IPIV is INTEGER

    array, dimension (N) The pivot indices; for 1 <= i <= N, row i of the matrix was interchanged with row IPIV(i).

  • B[inout]

    B is REAL array, dimension (LDB,NRHS)

    On entry, the right hand side matrix B. On exit, the solution matrix X.

  • LDB[in]

    LDB is INTEGER

    The leading dimension of the array B. LDB >= fla_max(1,N).

  • INFO[out]

    INFO is INTEGER

    = 0: successful exit

    < 0: if INFO = -i, the i-th argument had an illegal value