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Module « scipy.sparse.linalg »
Signature de la fonction minres
def minres(A, b, x0=None, *, rtol=1e-05, shift=0.0, maxiter=None, M=None, callback=None, show=False, check=False)
Description
help(scipy.sparse.linalg.minres)
Use MINimum RESidual iteration to solve Ax=b
MINRES minimizes norm(Ax - b) for a real symmetric matrix A. Unlike
the Conjugate Gradient method, A can be indefinite or singular.
If shift != 0 then the method solves (A - shift*I)x = b
Parameters
----------
A : {sparse array, ndarray, LinearOperator}
The real symmetric N-by-N matrix of the linear system
Alternatively, ``A`` can be a linear operator which can
produce ``Ax`` using, e.g.,
``scipy.sparse.linalg.LinearOperator``.
b : ndarray
Right hand side of the linear system. Has shape (N,) or (N,1).
Returns
-------
x : ndarray
The converged solution.
info : integer
Provides convergence information:
0 : successful exit
>0 : convergence to tolerance not achieved, number of iterations
<0 : illegal input or breakdown
Other Parameters
----------------
x0 : ndarray
Starting guess for the solution.
shift : float
Value to apply to the system ``(A - shift * I)x = b``. Default is 0.
rtol : float
Tolerance to achieve. The algorithm terminates when the relative
residual is below ``rtol``.
maxiter : integer
Maximum number of iterations. Iteration will stop after maxiter
steps even if the specified tolerance has not been achieved.
M : {sparse array, ndarray, LinearOperator}
Preconditioner for A. The preconditioner should approximate the
inverse of A. Effective preconditioning dramatically improves the
rate of convergence, which implies that fewer iterations are needed
to reach a given error tolerance.
callback : function
User-supplied function to call after each iteration. It is called
as callback(xk), where xk is the current solution vector.
show : bool
If ``True``, print out a summary and metrics related to the solution
during iterations. Default is ``False``.
check : bool
If ``True``, run additional input validation to check that `A` and
`M` (if specified) are symmetric. Default is ``False``.
Examples
--------
>>> import numpy as np
>>> from scipy.sparse import csc_array
>>> from scipy.sparse.linalg import minres
>>> A = csc_array([[3, 2, 0], [1, -1, 0], [0, 5, 1]], dtype=float)
>>> A = A + A.T
>>> b = np.array([2, 4, -1], dtype=float)
>>> x, exitCode = minres(A, b)
>>> print(exitCode) # 0 indicates successful convergence
0
>>> np.allclose(A.dot(x), b)
True
References
----------
Solution of sparse indefinite systems of linear equations,
C. C. Paige and M. A. Saunders (1975),
SIAM J. Numer. Anal. 12(4), pp. 617-629.
https://web.stanford.edu/group/SOL/software/minres/
This file is a translation of the following MATLAB implementation:
https://web.stanford.edu/group/SOL/software/minres/minres-matlab.zip
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