getf2#

sgetf2

Functions

void sgetf2(
    const INT           m,
    const INT           n,
          f32* restrict A,
    const INT           lda,
          INT* restrict ipiv,
          INT*          info
);

void sgetf2(const INT m, const INT n, f32 *restrict A, const INT lda, INT *restrict ipiv, INT *info)#

Computes an LU factorization of a general m-by-n matrix A using partial pivoting with row interchanges (unblocked algorithm).

The factorization has the form

A = P * L * U

where P is a permutation matrix, L is lower triangular with unit diagonal elements, and U is upper triangular.

This is the right-looking Level 2 BLAS version of the algorithm, processing one column at a time. It uses explicit loops for pivot search, row swap, and column scaling to minimize function call overhead for small matrices.

Parameters

in

m

The number of rows of the matrix A. m>=0.

in

n

The number of columns of the matrix A. n>=0.

inout

A

Array of dimension (lda, n). On entry, the m-by-n matrix to be factored. On exit, the factors L and U from the factorization; the unit diagonal elements of L are not stored.

in

lda

The leading dimension of the array A. lda>=max(1,m).

out

ipiv

Array of dimension min(m,n). The pivot indices; row i was interchanged with row ipiv[i].

out

info

info=0: successful exit
info<0: if info=-i, the i-th argument had an illegal value
info>0: if info=i, U(i,i) is exactly zero. The factorization has been completed, but U is exactly singular.

dgetf2

Functions

void dgetf2(
    const INT           m,
    const INT           n,
          f64* restrict A,
    const INT           lda,
          INT* restrict ipiv,
          INT*          info
);

void dgetf2(const INT m, const INT n, f64 *restrict A, const INT lda, INT *restrict ipiv, INT *info)#

Computes an LU factorization of a general m-by-n matrix A using partial pivoting with row interchanges (unblocked algorithm).

The factorization has the form

A = P * L * U

where P is a permutation matrix, L is lower triangular with unit diagonal elements, and U is upper triangular.

This is the right-looking Level 2 BLAS version of the algorithm, processing one column at a time. It uses explicit loops for pivot search, row swap, and column scaling to minimize function call overhead for small matrices.

Parameters

in

m

The number of rows of the matrix A. m>=0.

in

n

The number of columns of the matrix A. n>=0.

inout

A

Array of dimension (lda, n). On entry, the m-by-n matrix to be factored. On exit, the factors L and U from the factorization; the unit diagonal elements of L are not stored.

in

lda

The leading dimension of the array A. lda>=max(1,m).

out

ipiv

Array of dimension min(m,n). The pivot indices; row i was interchanged with row ipiv[i].

out

info

info=0: successful exit
info<0: if info=-i, the i-th argument had an illegal value
info>0: if info=i, U(i,i) is exactly zero. The factorization has been completed, but U is exactly singular.

cgetf2

Functions

void cgetf2(
    const INT           m,
    const INT           n,
          c64* restrict A,
    const INT           lda,
          INT* restrict ipiv,
          INT*          info
);

void cgetf2(const INT m, const INT n, c64 *restrict A, const INT lda, INT *restrict ipiv, INT *info)#

CGETF2 computes an LU factorization of a general m-by-n matrix A using partial pivoting with row interchanges.

The factorization has the form

A = P * L * U

where P is a permutation matrix, L is lower triangular with unit diagonal elements (lower trapezoidal if m>n), and U is upper triangular (upper trapezoidal if m<n).

This is the right-looking Level 2 BLAS version of the algorithm.

Parameters

in

m

The number of rows of the matrix A. m>=0.

in

n

The number of columns of the matrix A. n>=0.

inout

A

Single complex array, dimension (lda, n). On entry, the m-by-n matrix to be factored. On exit, the factors L and U from the factorization A = P*L*U; the unit diagonal elements of L are not stored.

in

lda

The leading dimension of the array A. lda>=max(1,m).

out

ipiv

Integer array, dimension (min(m,n)). The pivot indices; for 0<=i<min(m,n), row i of the matrix was interchanged with row ipiv[i].

out

info

info=0: successful exit
info<0: if info=-i, the i-th argument had an illegal value
info>0: if info=i, U(i,i) is exactly zero. The factorization has been completed, but the factor U is exactly singular, and division by zero will occur if it is used to solve a system of equations.

zgetf2

Functions

void zgetf2(
    const INT            m,
    const INT            n,
          c128* restrict A,
    const INT            lda,
          INT*  restrict ipiv,
          INT*           info
);

void zgetf2(const INT m, const INT n, c128 *restrict A, const INT lda, INT *restrict ipiv, INT *info)#

ZGETF2 computes an LU factorization of a general m-by-n matrix A using partial pivoting with row interchanges.

The factorization has the form

A = P * L * U

where P is a permutation matrix, L is lower triangular with unit diagonal elements (lower trapezoidal if m>n), and U is upper triangular (upper trapezoidal if m<n).

This is the right-looking Level 2 BLAS version of the algorithm.

Parameters

in

m

The number of rows of the matrix A. m>=0.

in

n

The number of columns of the matrix A. n>=0.

inout

A

Double complex array, dimension (lda, n). On entry, the m-by-n matrix to be factored. On exit, the factors L and U from the factorization A = P*L*U; the unit diagonal elements of L are not stored.

in

lda

The leading dimension of the array A. lda>=max(1,m).

out

ipiv

Integer array, dimension (min(m,n)). The pivot indices; for 0<=i<min(m,n), row i of the matrix was interchanged with row ipiv[i].

out

info

info=0: successful exit
info<0: if info=-i, the i-th argument had an illegal value
info>0: if info=i, U(i,i) is exactly zero. The factorization has been completed, but the factor U is exactly singular, and division by zero will occur if it is used to solve a system of equations.