mars.tensor.prod#

mars.tensor.prod(a, axis=None, dtype=None, out=None, keepdims=None, combine_size=None)[source]#

Return the product of tensor elements over a given axis.

Parameters

  • a (array_like) – Input data.

  • axis (None or int or tuple of ints, optional) –

    Axis or axes along which a product is performed. The default, axis=None, will calculate the product of all the elements in the input tensor. If axis is negative it counts from the last to the first axis.

    If axis is a tuple of ints, a product is performed on all of the axes specified in the tuple instead of a single axis or all the axes as before.

  • dtype (dtype, optional) – The type of the returned tensor, as well as of the accumulator in which the elements are multiplied. The dtype of a is used by default unless a has an integer dtype of less precision than the default platform integer. In that case, if a is signed then the platform integer is used while if a is unsigned then an unsigned integer of the same precision as the platform integer is used.

  • out (Tensor, optional) – Alternative output tensor in which to place the result. It must have the same shape as the expected output, but the type of the output values will be cast if necessary.

  • keepdims (bool, optional) –

    If this is set to True, the axes which are reduced are left in the result as dimensions with size one. With this option, the result will broadcast correctly against the input array.

    If the default value is passed, then keepdims will not be passed through to the prod method of sub-classes of Tensor, however any non-default value will be. If the sub-classes sum method does not implement keepdims any exceptions will be raised.

  • combine_size (int, optional) – The number of chunks to combine.

Returns

product_along_axis – An tensor shaped as a but with the specified axis removed. Returns a reference to out if specified.

Return type

Tensor, see dtype parameter above.

See also

Tensor.prod

equivalent method

Notes

Arithmetic is modular when using integer types, and no error is raised on overflow. That means that, on a 32-bit platform:

>>> import mars.tensor as mt

>>> x = mt.array([536870910, 536870910, 536870910, 536870910])
>>> mt.prod(x).execute()  # random
16

The product of an empty array is the neutral element 1:

>>> mt.prod([]).execute()
1.0

Examples

By default, calculate the product of all elements:

>>> mt.prod([1.,2.]).execute()
2.0

Even when the input array is two-dimensional:

>>> mt.prod([[1.,2.],[3.,4.]]).execute()
24.0

But we can also specify the axis over which to multiply:

>>> mt.prod([[1.,2.],[3.,4.]], axis=1).execute()
array([  2.,  12.])

If the type of x is unsigned, then the output type is the unsigned platform integer:

>>> x = mt.array([1, 2, 3], dtype=mt.uint8)
>>> mt.prod(x).dtype == mt.uint
True

If x is of a signed integer type, then the output type is the default platform integer:

>>> x = mt.array([1, 2, 3], dtype=mt.int8)
>>> mt.prod(x).dtype == int
True