opt_einsum.paths.optimal¶
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opt_einsum.paths.
optimal
(inputs, output, size_dict, memory_limit=None)[source]¶ Computes all possible pair contractions in a depth-first recursive manner, sieving results based on
memory_limit
and the best path found so far. Returns the lowest cost path. This algorithm scales factoriallly with respect to the elements in the listinput_sets
.Parameters: - inputs (list) – List of sets that represent the lhs side of the einsum subscript.
- output (set) – Set that represents the rhs side of the overall einsum subscript.
- size_dict (dictionary) – Dictionary of index sizes.
- memory_limit (int) – The maximum number of elements in a temporary array.
Returns: path – The optimal contraction order within the memory limit constraint.
Return type: Examples
>>> isets = [set('abd'), set('ac'), set('bdc')] >>> oset = set('') >>> idx_sizes = {'a': 1, 'b':2, 'c':3, 'd':4} >>> optimal(isets, oset, idx_sizes, 5000) [(0, 2), (0, 1)]