Sparse Tensor

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Python offers an inbuilt library called numpy to manipulate multi-dimensional arrays. The organization and use of this library is a primary requirement for developing the pytensor library.
Sparse Tensor

Sptensor is a class that represents the sparse tensor. A sparse tensor is a dataset in which most of the entries are zero, one such example would be a large diagonal matrix. (which has many zero elements). It does not store the whole values of the tensor object but stores the non-zero values and the corresponding coordinates of them. Sparse tensor storage
formats allow us to only store non-zero values thereby reducing storage requirements and
eliminating unnecessary silent computations involving zero values.

Here are its main attributes:

  • vals (numpy.ndarray)
    A 1-dimensional array of non-zero values of the sparse tensor.
  • subs (numpy.ndarray)
    A 2-dimensional array of coordinates of the values in vals.
  • shape(tuple)

The shape of the sparse tensor.

  • func(binary operator)
    This function is used to construct the sparse tensor as an accumulator.

On top of that, its main functions are:

  • __init__(self, subs, vals,
    shape = None, func=sum.__call__)
    Consturctor for the sptensor class. subs and vals (numpy.ndarray) or (list) are
    coordinates and values of the sptensor.
  • tondarray(self)
    This function returns a numpy. ndarray object that has the same values with the sptensor.
  • permute(self, order)
    By applying this function it will return the sptensor object that is permuted by the given order (list).
  • ipermute(self, order)
    Returns the sptensor object that is permuted by the inverse of the given order (list).
  • copy(self)
    Returns the copied sptensor object of the sptensor.
  • totensor(self)
    Returns the tensor object that has the same values with the sptensor.
  • nnz(self)
    Returns the number of non-zero elements in the sptensor.
  • ndims(self)
    Returns the number of dimensions of the tensor.
  • dimsize(self, ind)
  • Returns the size of the specified dimension. Same as shape[ind].

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