getf2#

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

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

The pivot indices; row i was interchanged with row ipiv[i]. Array of dimension min(m,n), 0-based.

out
info

Exit status.

  • = 0: successful exit

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

  • > 0: if info = i, U(i-1,i-1) is exactly zero. The factorization has been completed, but U is exactly singular.

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

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

The pivot indices; row i was interchanged with row ipiv[i]. Array of dimension min(m,n), 0-based.

out
info

Exit status.

  • = 0: successful exit

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

  • > 0: if info = i, U(i-1,i-1) is exactly zero. The factorization has been completed, but U is exactly singular.

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]. 0-based.

out
info

= 0: successful exit < 0: if info = -i, the i-th argument had an illegal value > 0: if info = i, U(i-1,i-1) 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.

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]. 0-based.

out
info

= 0: successful exit < 0: if info = -i, the i-th argument had an illegal value > 0: if info = i, U(i-1,i-1) 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.

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