Computes the singular value decomposition of a matrix. More...

Functions

AFAPI void svd (array &u, array &s, array &vt, const array &in)
C++ Interface for SVD decomposition. More...

AFAPI void svdInPlace (array &u, array &s, array &vt, array &in)
C++ Interface for SVD decomposition (in-place) More...

AFAPI af_err af_svd (af_array *u, af_array *s, af_array *vt, const af_array in)
C Interface for SVD decomposition. More...

AFAPI af_err af_svd_inplace (af_array *u, af_array *s, af_array *vt, af_array in)
C Interface for SVD decomposition (in-place) More...

Detailed Description

Computes the singular value decomposition of a matrix.

This function factorizes a matrix $$A$$ into two unitary matrices, $$U$$ and $$V^T$$, and a diagonal matrix $$S$$, such that $$A = USV^T$$. If $$A$$ has $$M$$ rows and $$N$$ columns ( $$M \times N$$), then $$U$$ will be $$M \times M$$, $$V$$ will be $$N \times N$$, and $$S$$ will be $$M \times N$$. However, for $$S$$, this function only returns the non-zero diagonal elements as a sorted (in descending order) 1D array.

To reconstruct the original matrix $$A$$ from the individual factors, the following code snippet can be used:

array U, S, Vt;
af::svd(U, S, Vt, A);
const int MN = std::min(M, N);
array UU = U(span, seq(MN));
array SS = diag(S, 0, false).as(ty);
array VV = Vt(seq(MN), span);
array AA = matmul(UU, SS, VV);

When memory is a concern, and $$A$$ is dispensable, svdInPlace() can be used. However, this in-place version is currently limited to input arrays where $$M \geq N$$.

◆ af_svd()

 AFAPI af_err af_svd ( af_array * u, af_array * s, af_array * vt, const af_array in )

C Interface for SVD decomposition.

Parameters
 [out] u is the output array containing U [out] s is the output array containing the diagonal values of sigma, (singular values of the input matrix)) [out] vt is the output array containing V^H [in] in is the input matrix

◆ af_svd_inplace()

 AFAPI af_err af_svd_inplace ( af_array * u, af_array * s, af_array * vt, af_array in )

C Interface for SVD decomposition (in-place)

Parameters
 [out] u is the output array containing U [out] s is the output array containing the diagonal values of sigma, (singular values of the input matrix)) [out] vt is the output array containing V^H [in,out] in is the input matrix that will contain random data after this operation
Note
Currently, in is limited to arrays where dim0 $$\geq$$ dim1
This is best used when minimizing memory usage and in is dispensable

◆ svd()

 AFAPI void af::svd ( array & u, array & s, array & vt, const array & in )

C++ Interface for SVD decomposition.

Parameters
 [out] u is the output array containing U [out] s is the output array containing the diagonal values of sigma, (singular values of the input matrix)) [out] vt is the output array containing V^H [in] in is the input matrix
Examples:
lin_algebra/svd.cpp.

◆ svdInPlace()

 AFAPI void af::svdInPlace ( array & u, array & s, array & vt, array & in )

C++ Interface for SVD decomposition (in-place)

Parameters
 [out] u is the output array containing U [out] s is the output array containing the diagonal values of sigma, (singular values of the input matrix)) [out] vt is the output array containing V^H [in,out] in is the input matrix and will contain random data after this operation
Note
Currently, in is limited to arrays where dim0 $$\geq$$ dim1
This is best used when minimizing memory usage and in is dispensable