Apply minor suggestions from code review

Co-authored-by: David Gardner <[email protected]>

CHANGELOG.md

@@ -81,6 +81,10 @@ Fixed loading the default IMEX-MRI method if `ARKodeSetOrder` is used to specify
 a third or fourth order method. Previously, the default second order method
 was loaded in both cases.
 
+Fixed a bug in MRIStep where the data supplied to the Hermite interpolation module did
+not include contributions from the fast right-hand side function. With this fix, users
+will see one additional fast right-hand side function evaluation per slow step with the
+Hermite interpolation option.
 Fixed a CMake configuration issue related to aliasing an `ALIAS` target when
 using `ENABLE_KLU=ON` in combination with a static-only build of SuiteSparse.
 

doc/shared/RecentChanges.rst

@@ -85,6 +85,10 @@ Fixed loading the default IMEX-MRI method if :c:func:`ARKodeSetOrder` is used to
 specify a third or fourth order method. Previously, the default second order method
 was loaded in both cases.
 
+Fixed a bug in MRIStep where the data supplied to the Hermite interpolation module did
+not include contributions from the fast right-hand side function. With this fix, users
+will see one additional fast right-hand side function evaluation per slow step with the
+Hermite interpolation option.
 Fixed a CMake configuration issue related to aliasing an ``ALIAS`` target when
 using ``ENABLE_KLU=ON`` in combination with a static-only build of SuiteSparse.
 

src/arkode/arkode_mristep.c

@@ -2601,13 +2601,12 @@ int mriStep_TakeStepMRISR(ARKodeMem ark_mem, sunrealtype* dsmPtr, int* nflagPtr)
 #endif
       }
 
-      /* combine both RHS into Fse for ImEx problems, and zero Fsi[0] since
+      /* combine both RHS into Fse for ImEx problems since
          fast forcing function only depends on Omega coefficients */
       if (step_mem->implicit_rhs && step_mem->explicit_rhs)
       {
         N_VLinearSum(ONE, step_mem->Fse[stage], ONE, step_mem->Fsi[stage],
                      step_mem->Fse[stage]);
-        /*N_VConst(ZERO, step_mem->Fsi[stage]);*/
       }
     }