add step length tol to Newton and tol set function

doc/arkode/guide/source/Usage/ARKStep_c_interface/Relaxation.rst

@@ -151,7 +151,7 @@ method.
    :math:`\leq 0.0` will result in the default value being used.
 
    :param arkode_mem: the ARKStep memory structure
-   :param tol: the nonlinear solver residual tolerance to use
+   :param res_tol: the nonlinear solver residual tolerance to use
 
    :retval ARK_SUCCESS: the value was successfully set
    :retval ARK_MEM_NULL: ``arkode_mem`` was ``NULL``
@@ -172,8 +172,8 @@ method.
    will result in the default value being used.
 
    :param arkode_mem: the ARKStep memory structure
-   :param tol: the nonlinear solver relative solution tolerance to use
-   :param tol: the nonlinear solver absolute solution tolerance to use
+   :param rel_tol: the nonlinear solver relative solution tolerance to use
+   :param abs_tol: the nonlinear solver absolute solution tolerance to use
 
    :retval ARK_SUCCESS: the value was successfully set
    :retval ARK_MEM_NULL: ``arkode_mem`` was ``NULL``

doc/arkode/guide/source/Usage/ERKStep_c_interface/Relaxation.rst

@@ -151,7 +151,7 @@ method.
    :math:`\leq 0.0` will result in the default value being used.
 
    :param arkode_mem: the ERKStep memory structure
-   :param tol: the nonlinear solver residual tolerance to use
+   :param res_tol: the nonlinear solver residual tolerance to use
 
    :retval ARK_SUCCESS: the value was successfully set
    :retval ARK_MEM_NULL: ``arkode_mem`` was ``NULL``
@@ -172,8 +172,8 @@ method.
    will result in the default value being used.
 
    :param arkode_mem: the ERKStep memory structure
-   :param tol: the nonlinear solver relative solution tolerance to use
-   :param tol: the nonlinear solver absolute solution tolerance to use
+   :param rel_tol: the nonlinear solver relative solution tolerance to use
+   :param rel_tol: the nonlinear solver absolute solution tolerance to use
 
    :retval ARK_SUCCESS: the value was successfully set
    :retval ARK_MEM_NULL: ``arkode_mem`` was ``NULL``

include/arkode/arkode_arkstep.h

@@ -486,6 +486,8 @@ SUNDIALS_EXPORT int ARKStepSetRelaxSolver(void* arkode_mem,
                                           ARKRelaxSolver solver);
 SUNDIALS_EXPORT int ARKStepSetRelaxResTol(void* arkode_mem,
                                           sunrealtype res_tol);
+SUNDIALS_EXPORT int ARKStepSetRelaxTol(void* arkode_mem, sunrealtype rel_tol,
+                                       sunrealtype abs_tol);
 SUNDIALS_EXPORT int ARKStepSetRelaxUpperBound(void* arkode_mem,
                                               sunrealtype upper);
 SUNDIALS_EXPORT int ARKStepGetNumRelaxFnEvals(void* arkode_mem,

include/arkode/arkode_erkstep.h

@@ -273,6 +273,8 @@ SUNDIALS_EXPORT int ERKStepSetRelaxSolver(void* arkode_mem,
                                           ARKRelaxSolver solver);
 SUNDIALS_EXPORT int ERKStepSetRelaxResTol(void* arkode_mem,
                                           sunrealtype res_tol);
+SUNDIALS_EXPORT int ERKStepSetRelaxTol(void* arkode_mem, sunrealtype rel_tol,
+                                       sunrealtype abs_tol);
 SUNDIALS_EXPORT int ERKStepSetRelaxUpperBound(void* arkode_mem,
                                               sunrealtype upper);
 SUNDIALS_EXPORT int ERKStepGetNumRelaxFnEvals(void* arkode_mem,

src/arkode/arkode_arkstep_io.c

@@ -299,6 +299,12 @@ int ARKStepSetRelaxResTol(void* arkode_mem, sunrealtype res_tol)
   return arkRelaxSetResTol(arkode_mem, res_tol);
 }
 
+int ARKStepSetRelaxTol(void* arkode_mem, sunrealtype rel_tol,
+                       sunrealtype abs_tol)
+{
+  return arkRelaxSetTol(arkode_mem, rel_tol, abs_tol);
+}
+
 int ARKStepSetRelaxUpperBound(void* arkode_mem, sunrealtype upper)
 {
   return arkRelaxSetUpperBound(arkode_mem, upper);

src/arkode/arkode_erkstep_io.c

@@ -190,6 +190,12 @@ int ERKStepSetRelaxResTol(void* arkode_mem, sunrealtype res_tol)
   return arkRelaxSetResTol(arkode_mem, res_tol);
 }
 
+int ERKStepSetRelaxTol(void* arkode_mem, sunrealtype rel_tol,
+                       sunrealtype abs_tol)
+{
+  return arkRelaxSetTol(arkode_mem, rel_tol, abs_tol);
+}
+
 int ERKStepSetRelaxUpperBound(void* arkode_mem, sunrealtype upper)
 {
   return arkRelaxSetUpperBound(arkode_mem, upper);

src/arkode/arkode_relaxation.c

@@ -112,6 +112,7 @@ static int arkRelaxResidualJacobian(sunrealtype relax_param,
 static int arkRelaxNewtonSolve(ARKodeMem ark_mem)
 {
   int i, retval;
+  sunrealtype tol, delta;
   ARKodeRelaxMem relax_mem = ark_mem->relax_mem;
 
   for (i = 0; i < ark_mem->relax_mem->max_iters; i++)
@@ -122,17 +123,25 @@ static int arkRelaxNewtonSolve(ARKodeMem ark_mem)
     if (retval) return retval;
 
     /* Check for convergence */
-    if (SUNRabs(relax_mem->res) < relax_mem->res_tol) return ARK_SUCCESS;
+    if (SUNRabs(relax_mem->res) < relax_mem->res_tol) { return ARK_SUCCESS; }
 
-    /* Compute Jacobian and update */
+    /* Compute Jacobian */
     retval = arkRelaxResidualJacobian(relax_mem->relax_param, &(relax_mem->jac),
                                       ark_mem);
     if (retval) return retval;
 
-    relax_mem->relax_param -= relax_mem->res / relax_mem->jac;
+    /* Update step length tolerance and solution */
+    tol = (relax_mem->rel_tol * SUNRabs(relax_mem->relax_param)
+           + relax_mem->abs_tol);
+
+    delta = relax_mem->res / relax_mem->jac;
+    relax_mem->relax_param -= delta;
 
     /* Update cumulative iteration count */
     relax_mem->nls_iters++;
+
+    /* Check for small update */
+    if (SUNRabs(delta) < tol) { return ARK_SUCCESS; }
   }
 
   return ARK_RELAX_SOLVE_RECV;
@@ -333,7 +342,7 @@ static int arkRelaxFixedPointSolve(ARKodeMem ark_mem)
     if (retval) return retval;
 
     /* Check for convergence */
-    if (SUNRabs(relax_mem->res) < relax_mem->res_tol) return ARK_SUCCESS;
+    if (SUNRabs(relax_mem->res) < relax_mem->res_tol) { return ARK_SUCCESS; }
 
     relax_mem->relax_param -= relax_mem->res;
 
@@ -503,7 +512,8 @@ int arkRelaxSetResTol(void* arkode_mem, sunrealtype res_tol)
   ARKodeMem ark_mem;
   ARKodeRelaxMem relax_mem;
 
-  retval = arkRelaxAccessMem(arkode_mem, "arkRelaxSetResTol", &ark_mem, &relax_mem);
+  retval = arkRelaxAccessMem(arkode_mem, "arkRelaxSetResTol", &ark_mem,
+                             &relax_mem);
   if (retval) return retval;
 
   if (res_tol > SUN_RCONST(0.0)) relax_mem->res_tol = res_tol;
@@ -512,6 +522,25 @@ int arkRelaxSetResTol(void* arkode_mem, sunrealtype res_tol)
   return ARK_SUCCESS;
 }
 
+int arkRelaxSetTol(void* arkode_mem, sunrealtype rel_tol, sunrealtype abs_tol)
+{
+  int retval;
+  ARKodeMem ark_mem;
+  ARKodeRelaxMem relax_mem;
+
+  retval = arkRelaxAccessMem(arkode_mem, "arkRelaxSetTol", &ark_mem,
+                             &relax_mem);
+  if (retval) return retval;
+
+  if (rel_tol > SUN_RCONST(0.0)) relax_mem->rel_tol = rel_tol;
+  else relax_mem->rel_tol = ARK_RELAX_DEFAULT_REL_TOL;
+
+  if (abs_tol > SUN_RCONST(0.0)) relax_mem->abs_tol = abs_tol;
+  else relax_mem->abs_tol = ARK_RELAX_DEFAULT_ABS_TOL;
+
+  return ARK_SUCCESS;
+}
+
 int arkRelaxSetUpperBound(void* arkode_mem, sunrealtype upper)
 {
   int retval;

src/arkode/arkode_relaxation_impl.h

@@ -118,6 +118,7 @@ int arkRelaxSetMaxFails(void* arkode_mem, int max_fails);
 int arkRelaxSetMaxIters(void* arkode_mem, int max_iters);
 int arkRelaxSetSolver(void* arkode_mem, ARKRelaxSolver solver);
 int arkRelaxSetResTol(void* arkode_mem, sunrealtype res_tol);
+int arkRelaxSetTol(void* arkode_mem, sunrealtype rel_tol, sunrealtype abs_tol);
 int arkRelaxSetUpperBound(void* arkode_mem, sunrealtype upper);
 
 int arkRelaxGetNumRelaxFnEvals(void* arkode_mem, long int* r_evals);