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import numpy as np
from ... import opcodes as OperandDef
from ..utils import infer_dtype
from .core import TensorUnaryOp
from .utils import arithmetic_operand
@arithmetic_operand(sparse_mode="unary")
class TensorExp(TensorUnaryOp):
_op_type_ = OperandDef.EXP
_func_name = "exp"
[docs]@infer_dtype(np.exp)
def exp(x, out=None, where=None, **kwargs):
r"""
Calculate the exponential of all elements in the input tensor.
Parameters
----------
x : array_like
Input values.
out : Tensor, None, or tuple of Tensor and None, optional
A location into which the result is stored. If provided, it must have
a shape that the inputs broadcast to. If not provided or `None`,
a freshly-allocated tensor is returned. A tuple (possible only as a
keyword argument) must have length equal to the number of outputs.
where : array_like, optional
Values of True indicate to calculate the ufunc at that position, values
of False indicate to leave the value in the output alone.
**kwargs
For other keyword-only arguments, see the
:ref:`ufunc docs <ufuncs.kwargs>`.
Returns
-------
out : Tensor
Output tensor, element-wise exponential of `x`.
See Also
--------
expm1 : Calculate ``exp(x) - 1`` for all elements in the array.
exp2 : Calculate ``2**x`` for all elements in the array.
Notes
-----
The irrational number ``e`` is also known as Euler's number. It is
approximately 2.718281, and is the base of the natural logarithm,
``ln`` (this means that, if :math:`x = \ln y = \log_e y`,
then :math:`e^x = y`. For real input, ``exp(x)`` is always positive.
For complex arguments, ``x = a + ib``, we can write
:math:`e^x = e^a e^{ib}`. The first term, :math:`e^a`, is already
known (it is the real argument, described above). The second term,
:math:`e^{ib}`, is :math:`\cos b + i \sin b`, a function with
magnitude 1 and a periodic phase.
References
----------
.. [1] Wikipedia, "Exponential function",
http://en.wikipedia.org/wiki/Exponential_function
.. [2] M. Abramovitz and I. A. Stegun, "Handbook of Mathematical Functions
with Formulas, Graphs, and Mathematical Tables," Dover, 1964, p. 69,
http://www.math.sfu.ca/~cbm/aands/page_69.htm
Examples
--------
Plot the magnitude and phase of ``exp(x)`` in the complex plane:
>>> import mars.tensor as mt
>>> import matplotlib.pyplot as plt
>>> x = mt.linspace(-2*mt.pi, 2*mt.pi, 100)
>>> xx = x + 1j * x[:, mt.newaxis] # a + ib over complex plane
>>> out = mt.exp(xx)
>>> plt.subplot(121)
>>> plt.imshow(mt.abs(out).execute(),
... extent=[-2*mt.pi, 2*mt.pi, -2*mt.pi, 2*mt.pi], cmap='gray')
>>> plt.title('Magnitude of exp(x)')
>>> plt.subplot(122)
>>> plt.imshow(mt.angle(out).execute(),
... extent=[-2*mt.pi, 2*mt.pi, -2*mt.pi, 2*mt.pi], cmap='hsv')
>>> plt.title('Phase (angle) of exp(x)')
>>> plt.show()
"""
op = TensorExp(**kwargs)
return op(x, out=out, where=where)