Keras
Keras 3 API documentation
Ops API
Linear algebra ops

Linear algebra ops

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cholesky function 

keras.ops.cholesky(x)

Computes the Cholesky decomposition of a positive semi-definite matrix.

Arguments

  • x: Input tensor of shape (..., M, M).

Returns

A tensor of shape (..., M, M) representing the lower triangular Cholesky factor of x.

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det function 

keras.ops.det(x)

Computes the determinant of a square tensor.

Arguments

  • x: Input tensor of shape (..., M, M).

Returns

A tensor of shape (...,) representing the determinant of x.

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eig function 

keras.ops.eig(x)

Computes the eigenvalues and eigenvectors of a square matrix.

Arguments

  • x: Input tensor of shape (..., M, M).

Returns

  • A tuple of two tensors: a tensor of shape (..., M) containing eigenvalues and a tensor of shape (..., M, M) containing eigenvectors.

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eigh function 

keras.ops.eigh(x)

Computes the eigenvalues and eigenvectors of a complex Hermitian.

Arguments

  • x: Input tensor of shape (..., M, M).

Returns

  • A tuple of two tensors: a tensor of shape (..., M) containing eigenvalues and a tensor of shape (..., M, M) containing eigenvectors.

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inv function 

keras.ops.inv(x)

Computes the inverse of a square tensor.

Arguments

  • x: Input tensor of shape (..., M, M).

Returns

A tensor of shape (..., M, M) representing the inverse of x.

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logdet function 

keras.ops.logdet(x)

Computes log of the determinant of a hermitian positive definite matrix.

Arguments

  • x: Input matrix. It must 2D and square.

Returns

The natural log of the determinant of matrix.

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lstsq function 

keras.ops.lstsq(a, b, rcond=None)

Return the least-squares solution to a linear matrix equation.

Computes the vector x that approximately solves the equation a @ x = b. The equation may be under-, well-, or over-determined (i.e., the number of linearly independent rows of a can be less than, equal to, or greater than its number of linearly independent columns). If a is square and of full rank, then x (but for round-off error) is the exact solution of the equation. Else, x minimizes the L2 norm of b - a * x.

If there are multiple minimizing solutions, the one with the smallest L2 norm is returned.

Arguments

  • a: “Coefficient” matrix of shape (M, N).
  • b: Ordinate or “dependent variable” values, of shape (M,) or (M, K). If b is two-dimensional, the least-squares solution is calculated for each of the K columns of b.
  • rcond: Cut-off ratio for small singular values of a. For the purposes of rank determination, singular values are treated as zero if they are smaller than rcond times the largest singular value of a.

Returns

Tensor with shape (N,) or (N, K) containing the least-squares solutions.

NOTE: The output differs from numpy.linalg.lstsq. NumPy returns a tuple with four elements, the first of which being the least-squares solutions and the others being essentially never used. Keras only returns the first value. This is done both to ensure consistency across backends (which cannot be achieved for the other values) and to simplify the API.

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lu_factor function 

keras.ops.lu_factor(x)

Computes the lower-upper decomposition of a square matrix.

Arguments

  • x: A tensor of shape (..., M, M).

Returns

  • A tuple of two tensors: a tensor of shape (..., M, M) containing the lower and upper triangular matrices and a tensor of shape (..., M) containing the pivots.

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norm function 

keras.ops.norm(x, ord=None, axis=None, keepdims=False)

Matrix or vector norm.

This function is able to return one of eight different matrix norms, or one of an infinite number of vector norms (described below), depending on the value of the ord parameter.

Arguments

  • x: Input tensor.
  • ord: Order of the norm (see table under Notes). The default is None.
  • axis: If axis is an integer, it specifies the axis of x along which to compute the vector norms. If axis is a 2-tuple, it specifies the axes that hold 2-D matrices, and the matrix norms of these matrices are computed.
  • keepdims: If this is set to True, the axes which are reduced are left in the result as dimensions with size one.

Note: For values of ord < 1, the result is, strictly speaking, not a mathematical ’norm’, but it may still be useful for various numerical purposes. The following norms can be calculated:

  • For matrices:
  • ord=None: Frobenius norm
  • ord="fro": Frobenius norm
  • ord="nuc": nuclear norm
  • ord=np.inf: max(sum(abs(x), axis=1))
  • ord=-np.inf: min(sum(abs(x), axis=1))
  • ord=0: not supported
  • ord=1: max(sum(abs(x), axis=0))
  • ord=-1: min(sum(abs(x), axis=0))
  • ord=2: 2-norm (largest sing. value)
  • ord=-2: smallest singular value
  • other: not supported
  • For vectors:
  • ord=None: 2-norm
  • ord="fro": not supported
  • ord="nuc": not supported
  • ord=np.inf: max(abs(x))
  • ord=-np.inf: min(abs(x))
  • ord=0: sum(x != 0)
  • ord=1: as below
  • ord=-1: as below
  • ord=2: as below
  • ord=-2: as below
  • other: sum(abs(x)**ord)**(1./ord)

Returns

Norm of the matrix or vector(s).

Example

>>> x = keras.ops.reshape(keras.ops.arange(9, dtype="float32") - 4, (3, 3))
>>> keras.ops.linalg.norm(x)
7.7459664

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qr function 

keras.ops.qr(x, mode="reduced")

Computes the QR decomposition of a tensor.

Arguments

  • x: Input tensor of shape (..., M, N).
  • mode: A string specifying the mode of the QR decomposition.
    • ‘reduced’: Returns the reduced QR decomposition. (default)
    • ‘complete’: Returns the complete QR decomposition.

Returns

A tuple containing two tensors. The first tensor of shape (..., M, K) is the orthogonal matrix q and the second tensor of shape (..., K, N) is the upper triangular matrix r, where K = min(M, N).

Example

>>> x = keras.ops.convert_to_tensor([[1., 2.], [3., 4.], [5., 6.]])
>>> q, r = qr(x)
>>> print(q)
array([[-0.16903079  0.897085]
       [-0.5070925   0.2760267 ]
       [-0.8451542  -0.34503305]], shape=(3, 2), dtype=float32)

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solve function 

keras.ops.solve(a, b)

Solves a linear system of equations given by a x = b.

Arguments

  • a: A tensor of shape (..., M, M) representing the coefficients matrix.
  • b: A tensor of shape (..., M) or (..., M, N) represeting the right-hand side or “dependent variable” matrix.

Returns

A tensor of shape (..., M) or (..., M, N) representing the solution of the linear system. Returned shape is identical to b.

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solve_triangular function 

keras.ops.solve_triangular(a, b, lower=False)

Solves a linear system of equations given by a x = b.

Arguments

  • a: A tensor of shape (..., M, M) representing the coefficients matrix.
  • b: A tensor of shape (..., M) or (..., M, N) represeting the right-hand side or “dependent variable” matrix.

Returns

A tensor of shape (..., M) or (..., M, N) representing the solution of the linear system. Returned shape is identical to b.

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svd function 

keras.ops.svd(x, full_matrices=True, compute_uv=True)

Computes the singular value decomposition of a matrix.

Arguments

  • x: Input tensor of shape (..., M, N).

Returns

  • A tuple of three tensors: a tensor of shape (..., M, M) containing the left singular vectors, a tensor of shape (..., M, N) containing the singular values and a tensor of shape (..., N, N) containing the right singular vectors.