def expm_multiply(A, B, start=None, stop=None, num=None, endpoint=None):
if all(arg is None for arg in (start, stop, num, endpoint)):<EOL><INDENT>X = _expm_multiply_simple(A, B)<EOL><DEDENT>else:<EOL><INDENT>X, status = _expm_multiply_interval(A, B, start, stop, num, endpoint)<EOL><DEDENT>return X<EOL>
Compute the action of the matrix exponential of A on B.

Parameters
----------
A : transposable linear operator
    The operator whose exponential is of interest.
B : ndarray
    The matrix or vector to be multiplied by the matrix exponential of A.
start : scalar, optional
    The starting time point of the sequence.
stop : scalar, optional
    The end time point of the sequence, unless `endpoint` is set to False.
    In that case, the sequence consists of all but the last of ``num + 1``
    evenly spaced time points, so that `stop` is excluded.
    Note that the step size changes when `endpoint` is False.
num : int, optional
    Number of time points to use.
endpoint : bool, optional
    If True, `stop` is the last time point.  Otherwise, it is not included.

Returns
-------
expm_A_B : ndarray
     The result of the action :math:`e^{t_k A} B`.

Notes
-----
The optional arguments defining the sequence of evenly spaced time points
are compatible with the arguments of `numpy.linspace`.

The output ndarray shape is somewhat complicated so I explain it here.
The ndim of the output could be either 1, 2, or 3.
It would be 1 if you are computing the expm action on a single vector
at a single time point.
It would be 2 if you are computing the expm action on a vector
at multiple time points, or if you are computing the expm action
on a matrix at a single time point.
It would be 3 if you want the action on a matrix with multiple
columns at multiple time points.
If multiple time points are requested, expm_A_B[0] will always
be the action of the expm at the first time point,
regardless of whether the action is on a vector or a matrix.

References
----------
.. [1] Awad H. Al-Mohy and Nicholas J. Higham (2011)
       "Computing the Action of the Matrix Exponential,
       with an Application to Exponential Integrators."
       SIAM Journal on Scientific Computing,
       33 (2). pp. 488-511. ISSN 1064-8275
       http://eprints.ma.man.ac.uk/1591/

.. [2] Nicholas J. Higham and Awad H. Al-Mohy (2010)
       "Computing Matrix Functions."
       Acta Numerica,
       19. 159-208. ISSN 0962-4929
       http://eprints.ma.man.ac.uk/1451/