# opt_einsum.paths.greedy¶

opt_einsum.paths.greedy(inputs, output, size_dict, memory_limit=None, choose_fn=None, cost_fn='memory-removed')[source]

Finds the path by a three stage algorithm:

2. Greedily compute contractions to maximize removed_size

3. Greedily compute outer products.

This algorithm scales quadratically with respect to the maximum number of elements sharing a common dim.

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

• choose_fn (callable, optional) – A function that chooses which contraction to perform from the queu

• cost_fn (callable, optional) – A function that assigns a potential contraction a cost.

Returns

path – The contraction order (a list of tuples of ints).

Return type

list

Examples

>>> isets = [set('abd'), set('ac'), set('bdc')]
>>> oset = set('')
>>> idx_sizes = {'a': 1, 'b':2, 'c':3, 'd':4}
>>> greedy(isets, oset, idx_sizes)
[(0, 2), (0, 1)]