Documentation

Docs taken from MAGMA documentation at: http://icl.cs.utk.edu/projectsfiles/magma/doxygen/group__magma__getri.html

getri computes the inverse of a matrix using the LU factorization computed by getrf.

This method inverts U and then computes inv(A) by solving the system inv(A)*L = inv(U) for inv(A).

Note that it is generally both faster and more accurate to use gesv, or getrf and getrs, to solve the system AX = B, rather than inverting the matrix and multiplying to form X = inv(A)*B. Only in special instances should an explicit inverse be computed with this routine.

inplace version of getri

Cholesky Decomposition of 2D tensor A. The matrix, A, has to be a positive-definite and either symmetric or complex Hermitian.

The factorization has the form

  A = U**T * U,   if UPLO = U, or
  A = L  * L**T,  if UPLO = L,

where U is an upper triangular matrix and L is lower triangular.

infix version of potrf.

Returns the inverse of 2D tensor A given its Cholesky decomposition chol.

Square matrix chol should be triangular.

Triangle specifies matrix chol as either upper or lower triangular.

inplace version of potri.

Returns the solution to linear system AX = B using the Cholesky decomposition chol of 2D tensor A.

Square matrix chol should be triangular; and, righthand side matrix B should be of full rank.

Triangle specifies matrix chol as either upper or lower triangular.

Inplace version of potri. Mutating tensor B in place.

Compute a QR decomposition of the matrix x: matrices q and r such that x = q * r, with q orthogonal and r upper triangular. This returns the thin (reduced) QR factorization.

Note that precision may be lost if the magnitudes of the elements of x are large.

Note also that, while it should always give you a valid decomposition, it may not give you the same one across platforms - it will depend on your LAPACK implementation.

Note: Irrespective of the original strides, the returned matrix q will be transposed, i.e. with strides 1, m instead of m, 1.

Inplace version of qr

This is a low-level function for calling LAPACK directly. You'll generally want to use qr instead.

Computes a QR decomposition of a, but without constructing Q and R as explicit separate matrices. Rather, this directly calls the underlying LAPACK function ?geqrf which produces a sequence of "elementary reflectors". See LAPACK documentation from MKL for further details and <http://icl.cs.utk.edu/projectsfiles/magma/doxygen/group__magma__geqrf.html for MAGMA documentation>.

Note that, because this is low-level code, hasktorch just calls Torch directly.

(e, V) <- geev A returns eigenvalues and eigenvectors of a general real square matrix A.

A and V are m × m matrices and e is an m-dimensional vector.

This function calculates all right eigenvalues (and vectors) of A such that A = V diag(e) V.

The EigenReturn argument defines computation of eigenvectors or eigenvalues only. It determines if only eigenvalues are computed or if both eigenvalues and eigenvectors are computed.

The eigenvalues returned follow LAPACK convention and are returned as complex (real/imaginary) pairs of numbers (2 * m dimensional tensor).

Also called the "eig" fuction in torch.

In-place version of geev.

Note: Irrespective of the original strides, the returned matrix V will be transposed, i.e. with strides 1, m instead of m, 1.

alias to geev to match Torch naming conventions.

alias to geev_ to match Torch naming conventions.

(e, V) <- syev A returns eigenvalues and eigenvectors of a symmetric real matrix A.

A and V are m × m matrices and e is a m-dimensional vector.

This function calculates all eigenvalues (and vectors) of A such that A = V diag(e) V.

The EigenReturn argument defines computation of eigenvectors or eigenvalues only.

Since the input matrix A is supposed to be symmetric, only one triangular portion is used. The Triangle argument indicates if this should be the upper or lower triangle.

Inplace version of syev

Note: Irrespective of the original strides, the returned matrix V will be transposed, i.e. with strides 1, m instead of m, 1.

alias to syev to match Torch naming conventions.

alias to syev to match Torch naming conventions.

(X, LU) <- gesv B A returns the solution of AX = B and LU contains L and U factors for LU factorization of A.

A has to be a square and non-singular matrix (a 2D tensor). A and LU are m × m, X is m × k and B is m × k.

Inplace version of gesv.

In this case x and lu will be used for temporary storage and returning the result.

• x will contain the solution X.
• lu will contain L and U factors for LU factorization of A.

Note: Irrespective of the original strides, the returned matrices x and lu will be transposed, i.e. with strides 1, m instead of m, 1.

Solution of least squares and least norm problems for a full rank m × n matrix A.

• If n ≤ m, then solve ||AX-B||_F.
• If n > m, then solve min ||X||_F such that AX = B.

On return, first n rows of x matrix contains the solution and the rest contains residual information. Square root of sum squares of elements of each column of x starting at row n + 1 is the residual for corresponding column.

Inplace version of gels.

Note: Irrespective of the original strides, the returned matrices resb and resa will be transposed, i.e. with strides 1, m instead of m, 1.

(U, S, V) <- svd A returns the singular value decomposition of a real matrix A of size n × m such that A = USV'*.

U is n × n, S is n × m and V is m × m.

The ComputeSingularValues argument represents the number of singular values to be computed. SomeSVs stands for "some" (FIXME: figure out what that means) and AllSVs stands for all.

Inplace version of gesvd.

Note: Irrespective of the original strides, the returned matrix U will be transposed, i.e. with strides 1, n instead of n, 1.

gesvd, computing A = U*Σ*transpose(V).

NOTE: "gesvd, computing A = U*Σ*transpose(V)." is only inferred documentation. This documentation was made by stites, inferring from the description of the gesvd docs at <https://software.intel.com/en-us/mkl-developer-reference-c-gesvd the intel mkl documentation>.

Inplace version of gesvd2_.

Argument to specify whether the upper or lower triangular decomposition should be used in potrf and potrf_.

Argument to be passed to geev, syev, and their inplace variants. Determines if the a function should only compute eigenvalues or both eigenvalues and eigenvectors.

Represents the number of singular values to be computed in gesvd and gesvd2. While fairly opaque about how many values are computed, Torch says we either compute "some" or all of the values.