Source code for torch_geometric.utils.softmax

from torch_scatter import scatter_max, scatter_add

from .num_nodes import maybe_num_nodes

[docs]def softmax(src, index, num_nodes=None): r"""Computes a sparsely evaluated softmax. Given a value tensor :attr:`src`, this function first groups the values along the first dimension based on the indices specified in :attr:`index`, and then proceeds to compute the softmax individually for each group. Args: src (Tensor): The source tensor. index (LongTensor): The indices of elements for applying the softmax. num_nodes (int, optional): The number of nodes, *i.e.* :obj:`max_val + 1` of :attr:`index`. (default: :obj:`None`) :rtype: :class:`Tensor` """ num_nodes = maybe_num_nodes(index, num_nodes) out = src - scatter_max(src, index, dim=0, dim_size=num_nodes)[0][index] out = out.exp() out = out / ( scatter_add(out, index, dim=0, dim_size=num_nodes)[index] + 1e-16) return out