Issue #3682 Only enforce Sundials stop time if possible

The event handling can cause the stopping time to decrease to a smaller value than the
internal time reached by Sundials variable step size solver.
When this happens, simply do not enforce the stopping time

casadi/core/integrator.cpp

@@ -420,8 +420,8 @@ int Integrator::eval(const double** arg, double** res,
         if (next_event(m)) return 1;
       }
       // Advance solution
-      if (verbose_) casadi_message("Integrating forward to output time " + str(m->k) + ": t_next = "
-        + str(m->t_next) + ", t_stop = " + str(m->t_stop));
+      if (verbose_) casadi_message("Interval " + str(m->k) + ": Integrating forward from "
+        + str(m->t) + " to " + str(m->t_next) + ", t_stop = " + str(m->t_stop));
       advance(m);
       // Update current time
       m->t = m->t_next;

casadi/interfaces/sundials/cvodes_interface.cpp

@@ -238,7 +238,6 @@ void CvodesInterface::reset(IntegratorMemory* mem, bool first_call) const {
   // Only reinitialize solver at first call or if event handling is required
   // May want to always enable this after more testing
   if (first_call || ne_ > 0) {
-    casadi_message("reinitializing cvodes")
     // Re-initialize forward integration
     THROWING(CVodeReInit, m->mem, m->t, m->v_xz);
 
@@ -261,7 +260,11 @@ void CvodesInterface::advance(IntegratorMemory* mem) const {
   auto m = to_mem(mem);
 
   // Do not integrate past change in input signals or past the end
-  THROWING(CVodeSetStopTime, m->mem, m->t_stop);
+  // The event handling may cause the stop time to become smaller than internal time reached,
+  // in which case the stop time cannot be enforced
+  if (m->t_stop >= m->tcur) {
+    THROWING(CVodeSetStopTime, m->mem, m->t_stop);
+  }
 
   // Integrate, unless already at desired time
   const double ttol = 1e-9;

casadi/interfaces/sundials/idas_interface.cpp

@@ -393,8 +393,13 @@ void IdasInterface::reset(IntegratorMemory* mem, bool first_call) const {
 void IdasInterface::advance(IntegratorMemory* mem) const {
   auto m = to_mem(mem);
 
+
   // Do not integrate past change in input signals or past the end
-  THROWING(IDASetStopTime, m->mem, m->t_stop);
+  // The event handling may cause the stop time to become smaller than internal time reached,
+  // in which case the stop time cannot be enforced
+  if (m->t_stop >= m->tcur) {
+    THROWING(IDASetStopTime, m->mem, m->t_stop);
+  }
 
   // Integrate, unless already at desired time
   double ttol = 1e-9;   // tolerance

casadi/interfaces/sundials/sundials_interface.cpp

@@ -347,7 +347,8 @@ void SundialsInterface::reset_stats(SundialsMemory* m) const {
   // Reset stats, forward problem
   m->nsteps = m->nfevals = m->nlinsetups = m->netfails = 0;
   m->qlast = m->qcur = -1;
-  m->hinused = m->hlast = m->hcur = m->tcur = casadi::nan;
+  m->tcur = t0_;
+  m->hinused = m->hlast = m->hcur = casadi::nan;
   m->nniters = m->nncfails = 0;
 
   // Reset stats, backward problem