def expm(ctx, A, method='taylor'):
        r"""
        Computes the matrix exponential of a square matrix `A`, which is defined
        by the power series

        .. math ::

            \exp(A) = I + A + \frac{A^2}{2!} + \frac{A^3}{3!} + \ldots

        With method='taylor', the matrix exponential is computed
        using the Taylor series. With method='pade', Pade approximants
        are used instead.

        **Examples**

        Basic examples::

            >>> from mpmath import *
            >>> mp.dps = 15; mp.pretty = True
            >>> expm(zeros(3))
            [1.0  0.0  0.0]
            [0.0  1.0  0.0]
            [0.0  0.0  1.0]
            >>> expm(eye(3))
            [2.71828182845905               0.0               0.0]
            [             0.0  2.71828182845905               0.0]
            [             0.0               0.0  2.71828182845905]
            >>> expm([[1,1,0],[1,0,1],[0,1,0]])
            [ 3.86814500615414  2.26812870852145  0.841130841230196]
            [ 2.26812870852145  2.44114713886289   1.42699786729125]
            [0.841130841230196  1.42699786729125    1.6000162976327]
            >>> expm([[1,1,0],[1,0,1],[0,1,0]], method='pade')
            [ 3.86814500615414  2.26812870852145  0.841130841230196]
            [ 2.26812870852145  2.44114713886289   1.42699786729125]
            [0.841130841230196  1.42699786729125    1.6000162976327]
            >>> expm([[1+j, 0], [1+j,1]])
            [(1.46869393991589 + 2.28735528717884j)                        0.0]
            [  (1.03776739863568 + 3.536943175722j)  (2.71828182845905 + 0.0j)]

        Matrices with large entries are allowed::

            >>> expm(matrix([[1,2],[2,3]])**25)
            [5.65024064048415e+2050488462815550  9.14228140091932e+2050488462815550]
            [9.14228140091932e+2050488462815550  1.47925220414035e+2050488462815551]

        The identity `\exp(A+B) = \exp(A) \exp(B)` does not hold for
        noncommuting matrices::

            >>> A = hilbert(3)
            >>> B = A + eye(3)
            >>> chop(mnorm(A*B - B*A))
            0.0
            >>> chop(mnorm(expm(A+B) - expm(A)*expm(B)))
            0.0
            >>> B = A + ones(3)
            >>> mnorm(A*B - B*A)
            1.8
            >>> mnorm(expm(A+B) - expm(A)*expm(B))
            42.0927851137247

        """
        if method == 'pade':
            prec = ctx.prec
            try:
                A = ctx.matrix(A)
                ctx.prec += 2*A.rows
                res = ctx._exp_pade(A)
            finally:
                ctx.prec = prec
            return res
        A = ctx.matrix(A)
        prec = ctx.prec
        j = int(max(1, ctx.mag(ctx.mnorm(A,'inf'))))
        j += int(0.5*prec**0.5)
        try:
            ctx.prec += 10 + 2*j
            tol = +ctx.eps
            A = A/2**j
            T = A
            Y = A**0 + A
            k = 2
            while 1:
                T *= A * (1/ctx.mpf(k))
                if tol < ctx.mnorm(T, 'inf'):
                    break
                Y += T
                k += 1
            for k in xrange(j):
                Y = Y*Y
        finally:
            ctx.prec = prec
        Y *= 1
        return Y
dataset/ETHPy150Open fredrik-johansson/mpmath/mpmath/matrices/calculus.py/MatrixCalculusMethods.expm/swapped operands of `<`