RHS Jacobian filter includes intermediate reactions

Jacobian sparsity filter in networks/rhs.H does not exclude intermediate reactions as intended

Summary

RHS::is_jacobian_term_used() attempts to exclude intermediate reactions (those with any __extra__ species index > NumSpec) when deciding if a Jacobian entry is needed. The implementation uses || across <= NumSpec tests, which is almost always true, so intermediate reactions are not filtered out.

Severity

Medium (primarily correctness-of-pruning/performance; can increase unnecessary Jacobian work and obscure intended sparsity behavior)

Affected Code

• networks/rhs.H
  • around lines 235-240 and 256-260

Why This Is a Bug

The comments state that reactions with extra species should be excluded. That requires all participating species IDs to be within NumSpec (&& logic). The current || logic admits any reaction with at least one in-network species, including intermediate reactions.

Proposed Patch

--- a/networks/rhs.H
+++ b/networks/rhs.H
@@
-            if (data.species_A <= NumSpec ||
-                data.species_B <= NumSpec ||
-                data.species_C <= NumSpec ||
-                data.species_D <= NumSpec ||
-                data.species_E <= NumSpec ||
-                data.species_F <= NumSpec) {
+            if (data.species_A <= NumSpec &&
+                data.species_B <= NumSpec &&
+                data.species_C <= NumSpec &&
+                data.species_D <= NumSpec &&
+                data.species_E <= NumSpec &&
+                data.species_F <= NumSpec) {
                 is_spec_1_used = 1;
             }
@@
-            if (data.species_A <= NumSpec ||
-                data.species_B <= NumSpec ||
-                data.species_C <= NumSpec ||
-                data.species_D <= NumSpec ||
-                data.species_E <= NumSpec ||
-                data.species_F <= NumSpec) {
+            if (data.species_A <= NumSpec &&
+                data.species_B <= NumSpec &&
+                data.species_C <= NumSpec &&
+                data.species_D <= NumSpec &&
+                data.species_E <= NumSpec &&
+                data.species_F <= NumSpec) {
                 is_spec_2_used = 1;
             }

Validation

• Compare Jacobian nonzero pattern before/after for a network with intermediate reactions.
• Confirm species evolution and energy RHS/Jacobian numerics are unchanged (only pruning logic should change).

Start in networks/rhs.H at RHS::is_jacobian_term_used(), focusing on the two species-use checks around lines 235-240 and 256-260. Review the existing comments and compare the Jacobian nonzero pattern before and after on a network with intermediate reactions; done means intermediate reactions are excluded while species evolution, energy RHS, and Jacobian numerics remain unchanged.