xref: /petsc/src/ts/event/tsevent.c (revision e7069c78e74748c563594f592e4924a0e908de35)
1 #include <petsc/private/tsimpl.h> /*I  "petscts.h" I*/
2 
3 #undef __FUNCT__
4 #define __FUNCT__ "TSEventInitialize"
5 /*
6   TSEventInitialize - Initializes TSEvent for TSSolve
7 */
8 PetscErrorCode TSEventInitialize(TSEvent event,TS ts,PetscReal t,Vec U)
9 {
10   PetscErrorCode ierr;
11 
12   PetscFunctionBegin;
13   if (!event) PetscFunctionReturn(0);
14   PetscValidPointer(event,1);
15   PetscValidHeaderSpecific(ts,TS_CLASSID,2);
16   PetscValidHeaderSpecific(U,VEC_CLASSID,4);
17   event->ptime_prev = t;
18   event->iterctr = 0;
19   ierr = (*event->eventhandler)(ts,t,U,event->fvalue_prev,event->ctx);CHKERRQ(ierr);
20   PetscFunctionReturn(0);
21 }
22 
23 #undef __FUNCT__
24 #define __FUNCT__ "TSEventDestroy"
25 PetscErrorCode TSEventDestroy(TSEvent *event)
26 {
27   PetscErrorCode ierr;
28   PetscInt       i;
29 
30   PetscFunctionBegin;
31   PetscValidPointer(event,1);
32   if (!*event) PetscFunctionReturn(0);
33   if (--(*event)->refct > 0) {*event = 0; PetscFunctionReturn(0);}
34 
35   ierr = PetscFree((*event)->fvalue);CHKERRQ(ierr);
36   ierr = PetscFree((*event)->fvalue_prev);CHKERRQ(ierr);
37   ierr = PetscFree((*event)->fvalue_right);CHKERRQ(ierr);
38   ierr = PetscFree((*event)->zerocrossing);CHKERRQ(ierr);
39   ierr = PetscFree((*event)->side);CHKERRQ(ierr);
40   ierr = PetscFree((*event)->direction);CHKERRQ(ierr);
41   ierr = PetscFree((*event)->terminate);CHKERRQ(ierr);
42   ierr = PetscFree((*event)->events_zero);CHKERRQ(ierr);
43   ierr = PetscFree((*event)->vtol);CHKERRQ(ierr);
44 
45   for (i=0; i < (*event)->recsize; i++) {
46     ierr = PetscFree((*event)->recorder.eventidx[i]);CHKERRQ(ierr);
47   }
48   ierr = PetscFree((*event)->recorder.eventidx);CHKERRQ(ierr);
49   ierr = PetscFree((*event)->recorder.nevents);CHKERRQ(ierr);
50   ierr = PetscFree((*event)->recorder.stepnum);CHKERRQ(ierr);
51   ierr = PetscFree((*event)->recorder.time);CHKERRQ(ierr);
52 
53   ierr = PetscViewerDestroy(&(*event)->monitor);CHKERRQ(ierr);
54   ierr = PetscFree(*event);CHKERRQ(ierr);
55   PetscFunctionReturn(0);
56 }
57 
58 #undef __FUNCT__
59 #define __FUNCT__ "TSSetEventTolerances"
60 /*@
61    TSSetEventTolerances - Set tolerances for event zero crossings when using event handler
62 
63    Logically Collective
64 
65    Input Arguments:
66 +  ts - time integration context
67 .  tol - scalar tolerance, PETSC_DECIDE to leave current value
68 -  vtol - array of tolerances or NULL, used in preference to tol if present
69 
70    Options Database Keys:
71 .  -ts_event_tol <tol> tolerance for event zero crossing
72 
73    Notes:
74    Must call TSSetEventHandler() before setting the tolerances.
75 
76    The size of vtol is equal to the number of events.
77 
78    Level: beginner
79 
80 .seealso: TS, TSEvent, TSSetEventHandler()
81 @*/
82 PetscErrorCode TSSetEventTolerances(TS ts,PetscReal tol,PetscReal vtol[])
83 {
84   TSEvent        event;
85   PetscInt       i;
86 
87   PetscFunctionBegin;
88   PetscValidHeaderSpecific(ts,TS_CLASSID,1);
89   if (vtol) PetscValidRealPointer(vtol,3);
90   if (!ts->event) SETERRQ(PetscObjectComm((PetscObject)ts),PETSC_ERR_USER,"Must set the events first by calling TSSetEventHandler()");
91 
92   event = ts->event;
93   if (vtol) {
94     for (i=0; i < event->nevents; i++) event->vtol[i] = vtol[i];
95   } else {
96     if (tol != PETSC_DECIDE || tol != PETSC_DEFAULT) {
97       for (i=0; i < event->nevents; i++) event->vtol[i] = tol;
98     }
99   }
100   PetscFunctionReturn(0);
101 }
102 
103 #undef __FUNCT__
104 #define __FUNCT__ "TSSetEventHandler"
105 /*@C
106    TSSetEventHandler - Sets a monitoring function used for detecting events
107 
108    Logically Collective on TS
109 
110    Input Parameters:
111 +  ts - the TS context obtained from TSCreate()
112 .  nevents - number of local events
113 .  direction - direction of zero crossing to be detected. -1 => Zero crossing in negative direction,
114                +1 => Zero crossing in positive direction, 0 => both ways (one for each event)
115 .  terminate - flag to indicate whether time stepping should be terminated after
116                event is detected (one for each event)
117 .  eventhandler - event monitoring routine
118 .  postevent - [optional] post-event function
119 -  ctx       - [optional] user-defined context for private data for the
120                event monitor and post event routine (use NULL if no
121                context is desired)
122 
123    Calling sequence of eventhandler:
124    PetscErrorCode PetscEventHandler(TS ts,PetscReal t,Vec U,PetscScalar fvalue[],void* ctx)
125 
126    Input Parameters:
127 +  ts  - the TS context
128 .  t   - current time
129 .  U   - current iterate
130 -  ctx - [optional] context passed with eventhandler
131 
132    Output parameters:
133 .  fvalue    - function value of events at time t
134 
135    Calling sequence of postevent:
136    PetscErrorCode PostEvent(TS ts,PetscInt nevents_zero,PetscInt events_zero[],PetscReal t,Vec U,PetscBool forwardsolve,void* ctx)
137 
138    Input Parameters:
139 +  ts - the TS context
140 .  nevents_zero - number of local events whose event function is zero
141 .  events_zero  - indices of local events which have reached zero
142 .  t            - current time
143 .  U            - current solution
144 .  forwardsolve - Flag to indicate whether TS is doing a forward solve (1) or adjoint solve (0)
145 -  ctx          - the context passed with eventhandler
146 
147    Level: intermediate
148 
149 .keywords: TS, event, set
150 
151 .seealso: TSCreate(), TSSetTimeStep(), TSSetConvergedReason()
152 @*/
153 PetscErrorCode TSSetEventHandler(TS ts,PetscInt nevents,PetscInt direction[],PetscBool terminate[],PetscErrorCode (*eventhandler)(TS,PetscReal,Vec,PetscScalar[],void*),PetscErrorCode (*postevent)(TS,PetscInt,PetscInt[],PetscReal,Vec,PetscBool,void*),void *ctx)
154 {
155   PetscErrorCode ierr;
156   TSEvent        event;
157   PetscInt       i;
158   PetscBool      flg;
159 #if defined PETSC_USE_REAL_SINGLE
160   PetscReal      tol=1e-4;
161 #else
162   PetscReal      tol=1e-6;
163 #endif
164 
165   PetscFunctionBegin;
166   PetscValidHeaderSpecific(ts,TS_CLASSID,1);
167   PetscValidIntPointer(direction,2);
168   PetscValidIntPointer(terminate,3);
169 
170   ierr = PetscNewLog(ts,&event);CHKERRQ(ierr);
171   ierr = PetscMalloc1(nevents,&event->fvalue);CHKERRQ(ierr);
172   ierr = PetscMalloc1(nevents,&event->fvalue_prev);CHKERRQ(ierr);
173   ierr = PetscMalloc1(nevents,&event->fvalue_right);CHKERRQ(ierr);
174   ierr = PetscMalloc1(nevents,&event->zerocrossing);CHKERRQ(ierr);
175   ierr = PetscMalloc1(nevents,&event->side);CHKERRQ(ierr);
176   ierr = PetscMalloc1(nevents,&event->direction);CHKERRQ(ierr);
177   ierr = PetscMalloc1(nevents,&event->terminate);CHKERRQ(ierr);
178   ierr = PetscMalloc1(nevents,&event->vtol);CHKERRQ(ierr);
179   for (i=0; i < nevents; i++) {
180     event->direction[i] = direction[i];
181     event->terminate[i] = terminate[i];
182     event->zerocrossing[i] = PETSC_FALSE;
183     event->side[i] = 0;
184   }
185   ierr = PetscMalloc1(nevents,&event->events_zero);CHKERRQ(ierr);
186   event->nevents = nevents;
187   event->eventhandler = eventhandler;
188   event->postevent = postevent;
189   event->ctx = ctx;
190 
191   event->recsize = 8;  /* Initial size of the recorder */
192   ierr = PetscOptionsBegin(((PetscObject)ts)->comm,"","TS Event options","");CHKERRQ(ierr);
193   {
194     ierr = PetscOptionsReal("-ts_event_tol","Scalar event tolerance for zero crossing check","TSSetEventTolerances",tol,&tol,NULL);CHKERRQ(ierr);
195     ierr = PetscOptionsName("-ts_event_monitor","Print choices made by event handler","",&flg);CHKERRQ(ierr);
196     ierr = PetscOptionsInt("-ts_event_recorder_initial_size","Initial size of event recorder","",event->recsize,&event->recsize,NULL);CHKERRQ(ierr);
197   }
198   PetscOptionsEnd();
199 
200   ierr = PetscMalloc1(event->recsize,&event->recorder.time);CHKERRQ(ierr);
201   ierr = PetscMalloc1(event->recsize,&event->recorder.stepnum);CHKERRQ(ierr);
202   ierr = PetscMalloc1(event->recsize,&event->recorder.nevents);CHKERRQ(ierr);
203   ierr = PetscMalloc1(event->recsize,&event->recorder.eventidx);CHKERRQ(ierr);
204   for (i=0; i < event->recsize; i++) {
205     ierr = PetscMalloc1(event->nevents,&event->recorder.eventidx[i]);CHKERRQ(ierr);
206   }
207   /* Initialize the event recorder */
208   event->recorder.ctr = 0;
209 
210   for (i=0; i < event->nevents; i++) event->vtol[i] = tol;
211   if (flg) {ierr = PetscViewerASCIIOpen(PETSC_COMM_SELF,"stdout",&event->monitor);CHKERRQ(ierr);}
212 
213   ierr = TSEventDestroy(&ts->event);CHKERRQ(ierr);
214   ts->event = event;
215   ts->event->refct = 1;
216   PetscFunctionReturn(0);
217 }
218 
219 #undef __FUNCT__
220 #define __FUNCT__ "TSEventRecorderResize"
221 /*
222   TSEventRecorderResize - Resizes (2X) the event recorder arrays whenever the recording limit (event->recsize)
223                           is reached.
224 */
225 static PetscErrorCode TSEventRecorderResize(TSEvent event)
226 {
227   PetscErrorCode ierr;
228   PetscReal      *time;
229   PetscInt       *stepnum;
230   PetscInt       *nevents;
231   PetscInt       **eventidx;
232   PetscInt       i,fact=2;
233 
234   PetscFunctionBegin;
235 
236   /* Create large arrays */
237   ierr = PetscMalloc1(fact*event->recsize,&time);CHKERRQ(ierr);
238   ierr = PetscMalloc1(fact*event->recsize,&stepnum);CHKERRQ(ierr);
239   ierr = PetscMalloc1(fact*event->recsize,&nevents);CHKERRQ(ierr);
240   ierr = PetscMalloc1(fact*event->recsize,&eventidx);CHKERRQ(ierr);
241   for (i=0; i < fact*event->recsize; i++) {
242     ierr = PetscMalloc1(event->nevents,&eventidx[i]);CHKERRQ(ierr);
243   }
244 
245   /* Copy over data */
246   ierr = PetscMemcpy(time,event->recorder.time,event->recsize*sizeof(PetscReal));CHKERRQ(ierr);
247   ierr = PetscMemcpy(stepnum,event->recorder.stepnum,event->recsize*sizeof(PetscInt));CHKERRQ(ierr);
248   ierr = PetscMemcpy(nevents,event->recorder.nevents,event->recsize*sizeof(PetscInt));CHKERRQ(ierr);
249   for (i=0; i < event->recsize; i++) {
250     ierr = PetscMemcpy(eventidx[i],event->recorder.eventidx[i],event->recorder.nevents[i]*sizeof(PetscInt));CHKERRQ(ierr);
251   }
252 
253   /* Destroy old arrays */
254   for (i=0; i < event->recsize; i++) {
255     ierr = PetscFree(event->recorder.eventidx[i]);CHKERRQ(ierr);
256   }
257   ierr = PetscFree(event->recorder.eventidx);CHKERRQ(ierr);
258   ierr = PetscFree(event->recorder.nevents);CHKERRQ(ierr);
259   ierr = PetscFree(event->recorder.stepnum);CHKERRQ(ierr);
260   ierr = PetscFree(event->recorder.time);CHKERRQ(ierr);
261 
262   /* Set pointers */
263   event->recorder.time = time;
264   event->recorder.stepnum = stepnum;
265   event->recorder.nevents = nevents;
266   event->recorder.eventidx = eventidx;
267 
268   /* Double size */
269   event->recsize *= fact;
270 
271   PetscFunctionReturn(0);
272 }
273 
274 /*
275    Helper rutine to handle user postenvents and recording
276 */
277 #undef __FUNCT__
278 #define __FUNCT__ "TSPostEvent"
279 static PetscErrorCode TSPostEvent(TS ts,PetscReal t,Vec U)
280 {
281   PetscErrorCode ierr;
282   TSEvent        event = ts->event;
283   PetscBool      terminate = PETSC_FALSE;
284   PetscBool      restart = PETSC_FALSE;
285   PetscInt       i,ctr,stepnum;
286   PetscBool      ts_terminate,ts_restart;
287   PetscBool      forwardsolve = PETSC_TRUE; /* Flag indicating that TS is doing a forward solve */
288 
289   PetscFunctionBegin;
290   if (event->postevent) {
291     PetscObjectState state_prev,state_post;
292     ierr = PetscObjectStateGet((PetscObject)U,&state_prev);CHKERRQ(ierr);
293     ierr = (*event->postevent)(ts,event->nevents_zero,event->events_zero,t,U,forwardsolve,event->ctx);CHKERRQ(ierr);
294     ierr = PetscObjectStateGet((PetscObject)U,&state_post);CHKERRQ(ierr);
295     if (state_prev != state_post) restart = PETSC_TRUE;
296   }
297 
298   /* Handle termination events and step restart */
299   for (i=0; i<event->nevents_zero; i++) if (event->terminate[event->events_zero[i]]) terminate = PETSC_TRUE;
300   ierr = MPIU_Allreduce(&terminate,&ts_terminate,1,MPIU_BOOL,MPI_LOR,((PetscObject)ts)->comm);CHKERRQ(ierr);
301   if (ts_terminate) {ierr = TSSetConvergedReason(ts,TS_CONVERGED_EVENT);CHKERRQ(ierr);}
302   event->status = ts_terminate ? TSEVENT_NONE : TSEVENT_RESET_NEXTSTEP;
303   ierr = MPIU_Allreduce(&restart,&ts_restart,1,MPIU_BOOL,MPI_LOR,((PetscObject)ts)->comm);CHKERRQ(ierr);
304   if (ts_restart) ts->steprestart = PETSC_TRUE;
305 
306   event->ptime_prev = t;
307   /* Reset event residual functions as states might get changed by the postevent callback */
308   if (event->postevent) {ierr = (*event->eventhandler)(ts,t,U,event->fvalue,event->ctx);CHKERRQ(ierr);}
309   /* Cache current event residual functions */
310   for (i=0; i < event->nevents; i++) event->fvalue_prev[i] = event->fvalue[i];
311 
312   /* Record the event in the event recorder */
313   ierr = TSGetTimeStepNumber(ts,&stepnum);CHKERRQ(ierr);
314   ctr = event->recorder.ctr;
315   if (ctr == event->recsize) {
316     ierr = TSEventRecorderResize(event);CHKERRQ(ierr);
317   }
318   event->recorder.time[ctr] = t;
319   event->recorder.stepnum[ctr] = stepnum;
320   event->recorder.nevents[ctr] = event->nevents_zero;
321   for (i=0; i<event->nevents_zero; i++) event->recorder.eventidx[ctr][i] = event->events_zero[i];
322   event->recorder.ctr++;
323   PetscFunctionReturn(0);
324 }
325 
326 /* Uses Anderson-Bjorck variant of regula falsi method */
327 PETSC_STATIC_INLINE PetscReal TSEventComputeStepSize(PetscReal tleft,PetscReal t,PetscReal tright,PetscScalar fleft,PetscScalar f,PetscScalar fright,PetscInt side,PetscReal dt)
328 {
329   PetscReal new_dt, scal = 1.0;
330   if (PetscRealPart(fleft)*PetscRealPart(f) < 0) {
331     if (side == 1) {
332       scal = (PetscRealPart(fright) - PetscRealPart(f))/PetscRealPart(fright);
333       if (scal < PETSC_SMALL) scal = 0.5;
334     }
335     new_dt = (scal*PetscRealPart(fleft)*t - PetscRealPart(f)*tleft)/(scal*PetscRealPart(fleft) - PetscRealPart(f)) - tleft;
336   } else {
337     if (side == -1) {
338       scal = (PetscRealPart(fleft) - PetscRealPart(f))/PetscRealPart(fleft);
339       if (scal < PETSC_SMALL) scal = 0.5;
340     }
341     new_dt = (PetscRealPart(f)*tright - scal*PetscRealPart(fright)*t)/(PetscRealPart(f) - scal*PetscRealPart(fright)) - t;
342   }
343   return PetscMin(dt,new_dt);
344 }
345 
346 
347 #undef __FUNCT__
348 #define __FUNCT__ "TSEventHandler"
349 PetscErrorCode TSEventHandler(TS ts)
350 {
351   PetscErrorCode ierr;
352   TSEvent        event;
353   PetscReal      t;
354   Vec            U;
355   PetscInt       i;
356   PetscReal      dt,dt_min;
357   PetscInt       rollback=0,in[2],out[2];
358   PetscInt       fvalue_sign,fvalueprev_sign;
359 
360   PetscFunctionBegin;
361   PetscValidHeaderSpecific(ts,TS_CLASSID,1);
362   if (!ts->event) PetscFunctionReturn(0);
363   event = ts->event;
364 
365   ierr = TSGetTime(ts,&t);CHKERRQ(ierr);
366   ierr = TSGetTimeStep(ts,&dt);CHKERRQ(ierr);
367   ierr = TSGetSolution(ts,&U);CHKERRQ(ierr);
368 
369   if (event->status == TSEVENT_NONE) {
370     if (ts->steps == 1) /* After first successful step */
371       event->timestep_orig = ts->ptime - ts->ptime_prev;
372     event->timestep_prev = dt;
373   }
374 
375   if (event->status == TSEVENT_RESET_NEXTSTEP) {
376     /* Restore time step */
377     dt = PetscMin(event->timestep_orig,event->timestep_prev);
378     ierr = TSSetTimeStep(ts,dt);CHKERRQ(ierr);
379     event->status = TSEVENT_NONE;
380   }
381 
382   if (event->status == TSEVENT_NONE) {
383     event->ptime_end = t;
384   }
385 
386   ierr = (*event->eventhandler)(ts,t,U,event->fvalue,event->ctx);CHKERRQ(ierr);
387 
388   for (i=0; i < event->nevents; i++) {
389     if (PetscAbsScalar(event->fvalue[i]) < event->vtol[i]) {
390       event->status = TSEVENT_ZERO;
391       event->fvalue_right[i] = event->fvalue[i];
392       continue;
393     }
394     fvalue_sign = PetscSign(PetscRealPart(event->fvalue[i]));
395     fvalueprev_sign = PetscSign(PetscRealPart(event->fvalue_prev[i]));
396     if (fvalueprev_sign != 0 && (fvalue_sign != fvalueprev_sign) && (PetscAbsScalar(event->fvalue_prev[i]) > event->vtol[i])) {
397       switch (event->direction[i]) {
398       case -1:
399         if (fvalue_sign < 0) {
400           rollback = 1;
401 
402           /* Compute new time step */
403           dt = TSEventComputeStepSize(event->ptime_prev,t,event->ptime_right,event->fvalue_prev[i],event->fvalue[i],event->fvalue_right[i],event->side[i],dt);
404 
405           if (event->monitor) {
406             ierr = PetscViewerASCIIPrintf(event->monitor,"TSEvent: iter %D - Event %D interval detected [%g - %g]\n",event->iterctr,i,(double)event->ptime_prev,(double)t);CHKERRQ(ierr);
407           }
408           event->fvalue_right[i] = event->fvalue[i];
409           event->side[i] = 1;
410 
411           if (!event->iterctr) event->zerocrossing[i] = PETSC_TRUE;
412           event->status = TSEVENT_LOCATED_INTERVAL;
413         }
414         break;
415       case 1:
416         if (fvalue_sign > 0) {
417           rollback = 1;
418 
419           /* Compute new time step */
420           dt = TSEventComputeStepSize(event->ptime_prev,t,event->ptime_right,event->fvalue_prev[i],event->fvalue[i],event->fvalue_right[i],event->side[i],dt);
421 
422           if (event->monitor) {
423             ierr = PetscViewerASCIIPrintf(event->monitor,"TSEvent: iter %D - Event %D interval detected [%g - %g]\n",event->iterctr,i,(double)event->ptime_prev,(double)t);CHKERRQ(ierr);
424           }
425           event->fvalue_right[i] = event->fvalue[i];
426           event->side[i] = 1;
427 
428           if (!event->iterctr) event->zerocrossing[i] = PETSC_TRUE;
429           event->status = TSEVENT_LOCATED_INTERVAL;
430         }
431         break;
432       case 0:
433         rollback = 1;
434 
435         /* Compute new time step */
436         dt = TSEventComputeStepSize(event->ptime_prev,t,event->ptime_right,event->fvalue_prev[i],event->fvalue[i],event->fvalue_right[i],event->side[i],dt);
437 
438         if (event->monitor) {
439           ierr = PetscViewerASCIIPrintf(event->monitor,"TSEvent: iter %D - Event %D interval detected [%g - %g]\n",event->iterctr,i,(double)event->ptime_prev,(double)t);CHKERRQ(ierr);
440         }
441         event->fvalue_right[i] = event->fvalue[i];
442         event->side[i] = 1;
443 
444         if (!event->iterctr) event->zerocrossing[i] = PETSC_TRUE;
445         event->status = TSEVENT_LOCATED_INTERVAL;
446 
447         break;
448       }
449     }
450   }
451 
452   in[0] = event->status; in[1] = rollback;
453   ierr = MPIU_Allreduce(in,out,2,MPIU_INT,MPI_MAX,PetscObjectComm((PetscObject)ts));CHKERRQ(ierr);
454   event->status = (TSEventStatus)out[0]; rollback = out[1];
455   if (rollback) event->status = TSEVENT_LOCATED_INTERVAL;
456 
457   event->nevents_zero = 0;
458   if (event->status == TSEVENT_ZERO) {
459     for (i=0; i < event->nevents; i++) {
460       if (PetscAbsScalar(event->fvalue[i]) < event->vtol[i]) {
461         event->events_zero[event->nevents_zero++] = i;
462         if (event->monitor) {
463           ierr = PetscViewerASCIIPrintf(event->monitor,"TSEvent: Event %D zero crossing at time %g located in %D iterations\n",i,(double)t,event->iterctr);CHKERRQ(ierr);
464         }
465         event->zerocrossing[i] = PETSC_FALSE;
466       }
467       event->side[i] = 0;
468     }
469     ierr = TSPostEvent(ts,t,U);CHKERRQ(ierr);
470 
471     dt = event->ptime_end - t;
472     if (PetscAbsReal(dt) < PETSC_SMALL) dt += PetscMin(event->timestep_orig,event->timestep_prev); /* XXX Should be done better */
473     ierr = TSSetTimeStep(ts,dt);CHKERRQ(ierr);
474     event->iterctr = 0;
475     PetscFunctionReturn(0);
476   }
477 
478   if (event->status == TSEVENT_LOCATED_INTERVAL) {
479     ierr = TSRollBack(ts);CHKERRQ(ierr);
480     ierr = TSSetConvergedReason(ts,TS_CONVERGED_ITERATING);CHKERRQ(ierr);
481     event->status = TSEVENT_PROCESSING;
482     event->ptime_right = t;
483   } else {
484     for (i=0; i < event->nevents; i++) {
485       if (event->status == TSEVENT_PROCESSING && event->zerocrossing[i]) {
486         /* Compute new time step */
487         dt = TSEventComputeStepSize(event->ptime_prev,t,event->ptime_right,event->fvalue_prev[i],event->fvalue[i],event->fvalue_right[i],event->side[i],dt);
488         event->side[i] = -1;
489       }
490       event->fvalue_prev[i] = event->fvalue[i];
491     }
492     if (event->monitor && event->status == TSEVENT_PROCESSING) {
493       ierr = PetscViewerASCIIPrintf(event->monitor,"TSEvent: iter %D - Stepping forward as no event detected in interval [%g - %g]\n",event->iterctr,(double)event->ptime_prev,(double)t);CHKERRQ(ierr);
494     }
495     event->ptime_prev = t;
496   }
497 
498   if (event->status == TSEVENT_PROCESSING) event->iterctr++;
499 
500   ierr = MPIU_Allreduce(&dt,&dt_min,1,MPIU_REAL,MPIU_MIN,PetscObjectComm((PetscObject)ts));CHKERRQ(ierr);
501   ierr = TSSetTimeStep(ts,dt_min);CHKERRQ(ierr);
502   PetscFunctionReturn(0);
503 }
504 
505 #undef __FUNCT__
506 #define __FUNCT__ "TSAdjointEventHandler"
507 PetscErrorCode TSAdjointEventHandler(TS ts)
508 {
509   PetscErrorCode ierr;
510   TSEvent        event;
511   PetscReal      t;
512   Vec            U;
513   PetscInt       ctr;
514   PetscBool      forwardsolve=PETSC_FALSE; /* Flag indicating that TS is doing an adjoint solve */
515 
516   PetscFunctionBegin;
517   PetscValidHeaderSpecific(ts,TS_CLASSID,1);
518   if (!ts->event) PetscFunctionReturn(0);
519   event = ts->event;
520 
521   ierr = TSGetTime(ts,&t);CHKERRQ(ierr);
522   ierr = TSGetSolution(ts,&U);CHKERRQ(ierr);
523 
524   ctr = event->recorder.ctr-1;
525   if (ctr >= 0 && PetscAbsReal(t - event->recorder.time[ctr]) < PETSC_SMALL) {
526     /* Call the user postevent function */
527     if (event->postevent) {
528       ierr = (*event->postevent)(ts,event->recorder.nevents[ctr],event->recorder.eventidx[ctr],t,U,forwardsolve,event->ctx);CHKERRQ(ierr);
529       event->recorder.ctr--;
530     }
531   }
532 
533   PetscBarrier((PetscObject)ts);
534   PetscFunctionReturn(0);
535 }
536