Single Vector Summation using Einsum with Sparse Partials

This is an example of how to properly use the einsum function to compute the summation of a single vector while using sparse partial derivative.

from openmdao.api import Problem
import numpy as np
from omtools.api import Group
import omtools.api as ot


class ExampleVectorSummationSparse(Group):
    def setup(self):
        a = np.arange(4)
        vec = self.declare_input('a', val=a)

        self.register_output(
            'einsum_summ1_sparse_derivs',
            ot.einsum(vec, subscripts='i->', partial_format='sparse'))


prob = Problem()
prob.model = ExampleVectorSummationSparse()
prob.setup(force_alloc_complex=True)
prob.run_model()

print('a', prob['a'].shape)
print(prob['a'])
print('einsum_summ1_sparse_derivs', prob['einsum_summ1_sparse_derivs'].shape)
print(prob['einsum_summ1_sparse_derivs'])

a (4,)
[0. 1. 2. 3.]
einsum_summ1_sparse_derivs (1,)
[6.]