High-contrast homogenization: Provider.Quenched.SmallContrastSourceGroupNonneg #
Imported from the Apache-2.0 HighContrastHomogenization development at commit
7a13dbcd8d6609264a713373f5c69ceeac870472.
The source group is nonnegative at nonnegative legs #
Two sign facts the entry-slot clause consumes and that no earlier module needed: the sharp summed source constant is nonnegative, and so is the summed source group at nonnegative legs. Both are immediate from the shapes of their own definitions; they are recorded here so the entry-slot clause discharges them rather than carrying them.