# sparse_pwc_sum

Graph.sparse_pwc_sum(terms)

Create the sum of multiple sparse-matrix-valued piecewise-constant functions.

### Parameters

terms (list [SparsePwc ]) – The individual piecewise-constant terms $\{v_j(t)\}$ to sum. All terms must be sparse, have values of the same shape, and have the same total duration but may have different numbers of segments of different durations.

### Returns

The piecewise-constant function of time $\sum_j v_j(t)$. It has the same shape as each of the terms that you provided.

### Return type

SparsePwc

Graph.constant_sparse_pwc_operator : Create constant SparsePwcs.

Graph.pwc_sum : Corresponding operation for Pwcs.

Graph.sparse_pwc_operator : Create SparsePwc operators.

## Examples

Sum two sparse PWC operators.

>>> from scipy.sparse import coo_matrix
>>> sigma_x = np.array([[0, 1], [1, 0]])
>>> sigma_y = np.array([[0, -1j], [1j, 0]])
>>> sp_x = graph.constant_sparse_pwc_operator(duration=0.1, operator=coo_matrix(sigma_x))
>>> sp_y = graph.constant_sparse_pwc_operator(duration=0.1, operator=coo_matrix(sigma_y))
>>> graph.sparse_pwc_sum([sp_x, sp_y])
<SparsePwc: operation_name="sparse_pwc_sum", value_shape=(2, 2)>

See more examples in the How to simulate large open system dynamics user guide.