xref: /petsc/src/ts/impls/explicit/rk/rk.c (revision cef76868a9b561b92ddb855d7a42c003b3b23296)
1 /*
2   Code for time stepping with the Runge-Kutta method
3 
4   Notes:
5   The general system is written as
6 
7   Udot = F(t,U)
8 
9 */
10 #include <petsc-private/tsimpl.h>                /*I   "petscts.h"   I*/
11 #include <petscdm.h>
12 
13 static TSRKType  TSRKDefault = TSRK3BS;
14 static PetscBool TSRKRegisterAllCalled;
15 static PetscBool TSRKPackageInitialized;
16 static PetscInt  explicit_stage_time_id;
17 
18 typedef struct _RKTableau *RKTableau;
19 struct _RKTableau {
20   char      *name;
21   PetscInt   order;               /* Classical approximation order of the method i              */
22   PetscInt   s;                   /* Number of stages                                           */
23   PetscBool  FSAL;                /* flag to indicate if tableau is FSAL                        */
24   PetscInt   pinterp;             /* Interpolation order                                        */
25   PetscReal *A,*b,*c;             /* Tableau                                                    */
26   PetscReal *bembed;              /* Embedded formula of order one less (order-1)               */
27   PetscReal *binterp;             /* Dense output formula                                       */
28   PetscReal  ccfl;                /* Placeholder for CFL coefficient relative to forward Euler  */
29 };
30 typedef struct _RKTableauLink *RKTableauLink;
31 struct _RKTableauLink {
32   struct _RKTableau tab;
33   RKTableauLink     next;
34 };
35 static RKTableauLink RKTableauList;
36 
37 typedef struct {
38   RKTableau   tableau;
39   Vec          *Y;               /* States computed during the step */
40   Vec          *YdotRHS;         /* Function evaluations for the non-stiff part */
41   Vec          *VecDeltaLam;     /* Increment of the adjoint sensitivity w.r.t IC at stage*/
42   Vec          *VecDeltaMu;      /* Increment of the adjoint sensitivity w.r.t P at stage*/
43   Vec          *VecSensiTemp;    /* Vector to be timed with Jacobian transpose*/
44   PetscScalar  *work;            /* Scalar work */
45   PetscReal    stage_time;
46   TSStepStatus status;
47 } TS_RK;
48 
49 /*MC
50      TSRK1 - First order forward Euler scheme.
51 
52      This method has one stage.
53 
54      Level: advanced
55 
56 .seealso: TSRK
57 M*/
58 /*MC
59      TSRK2A - Second order RK scheme.
60 
61      This method has two stages.
62 
63      Level: advanced
64 
65 .seealso: TSRK
66 M*/
67 /*MC
68      TSRK3 - Third order RK scheme.
69 
70      This method has three stages.
71 
72      Level: advanced
73 
74 .seealso: TSRK
75 M*/
76 /*MC
77      TSRK3BS - Third order RK scheme of Bogacki-Shampine with 2nd order embedded method.
78 
79      This method has four stages.
80 
81      Level: advanced
82 
83 .seealso: TSRK
84 M*/
85 /*MC
86      TSRK4 - Fourth order RK scheme.
87 
88      This is the classical Runge-Kutta method with four stages.
89 
90      Level: advanced
91 
92 .seealso: TSRK
93 M*/
94 /*MC
95      TSRK5F - Fifth order Fehlberg RK scheme with a 4th order embedded method.
96 
97      This method has six stages.
98 
99      Level: advanced
100 
101 .seealso: TSRK
102 M*/
103 /*MC
104      TSRK5DP - Fifth order Dormand-Prince RK scheme with the 4th order embedded method.
105 
106      This method has seven stages.
107 
108      Level: advanced
109 
110 .seealso: TSRK
111 M*/
112 
113 #undef __FUNCT__
114 #define __FUNCT__ "TSRKRegisterAll"
115 /*@C
116   TSRKRegisterAll - Registers all of the Runge-Kutta explicit methods in TSRK
117 
118   Not Collective, but should be called by all processes which will need the schemes to be registered
119 
120   Level: advanced
121 
122 .keywords: TS, TSRK, register, all
123 
124 .seealso:  TSRKRegisterDestroy()
125 @*/
126 PetscErrorCode TSRKRegisterAll(void)
127 {
128   PetscErrorCode ierr;
129 
130   PetscFunctionBegin;
131   if (TSRKRegisterAllCalled) PetscFunctionReturn(0);
132   TSRKRegisterAllCalled = PETSC_TRUE;
133 
134   {
135     const PetscReal
136       A[1][1] = {{0.0}},
137       b[1]    = {1.0};
138     ierr = TSRKRegister(TSRK1FE,1,1,&A[0][0],b,NULL,NULL,1,b);CHKERRQ(ierr);
139   }
140   {
141     const PetscReal
142       A[2][2]     = {{0.0,0.0},
143                     {1.0,0.0}},
144       b[2]        = {0.5,0.5},
145       bembed[2]   = {1.0,0};
146     ierr = TSRKRegister(TSRK2A,2,2,&A[0][0],b,NULL,bembed,2,b);CHKERRQ(ierr);
147   }
148   {
149     const PetscReal
150       A[3][3] = {{0,0,0},
151                  {2.0/3.0,0,0},
152                  {-1.0/3.0,1.0,0}},
153       b[3]    = {0.25,0.5,0.25};
154     ierr = TSRKRegister(TSRK3,3,3,&A[0][0],b,NULL,NULL,3,b);CHKERRQ(ierr);
155   }
156   {
157     const PetscReal
158       A[4][4] = {{0,0,0,0},
159                  {1.0/2.0,0,0,0},
160                  {0,3.0/4.0,0,0},
161                  {2.0/9.0,1.0/3.0,4.0/9.0,0}},
162       b[4]    = {2.0/9.0,1.0/3.0,4.0/9.0,0},
163       bembed[4] = {7.0/24.0,1.0/4.0,1.0/3.0,1.0/8.0};
164     ierr = TSRKRegister(TSRK3BS,3,4,&A[0][0],b,NULL,bembed,3,b);CHKERRQ(ierr);
165   }
166   {
167     const PetscReal
168       A[4][4] = {{0,0,0,0},
169                  {0.5,0,0,0},
170                  {0,0.5,0,0},
171                  {0,0,1.0,0}},
172       b[4]    = {1.0/6.0,1.0/3.0,1.0/3.0,1.0/6.0};
173     ierr = TSRKRegister(TSRK4,4,4,&A[0][0],b,NULL,NULL,4,b);CHKERRQ(ierr);
174   }
175   {
176     const PetscReal
177       A[6][6]   = {{0,0,0,0,0,0},
178                    {0.25,0,0,0,0,0},
179                    {3.0/32.0,9.0/32.0,0,0,0,0},
180                    {1932.0/2197.0,-7200.0/2197.0,7296.0/2197.0,0,0,0},
181                    {439.0/216.0,-8.0,3680.0/513.0,-845.0/4104.0,0,0},
182                    {-8.0/27.0,2.0,-3544.0/2565.0,1859.0/4104.0,-11.0/40.0,0}},
183       b[6]      = {16.0/135.0,0,6656.0/12825.0,28561.0/56430.0,-9.0/50.0,2.0/55.0},
184       bembed[6] = {25.0/216.0,0,1408.0/2565.0,2197.0/4104.0,-1.0/5.0,0};
185     ierr = TSRKRegister(TSRK5F,5,6,&A[0][0],b,NULL,bembed,5,b);CHKERRQ(ierr);
186   }
187   {
188     const PetscReal
189       A[7][7]   = {{0,0,0,0,0,0,0},
190                    {1.0/5.0,0,0,0,0,0,0},
191                    {3.0/40.0,9.0/40.0,0,0,0,0,0},
192                    {44.0/45.0,-56.0/15.0,32.0/9.0,0,0,0,0},
193                    {19372.0/6561.0,-25360.0/2187.0,64448.0/6561.0,-212.0/729.0,0,0,0},
194                    {9017.0/3168.0,-355.0/33.0,46732.0/5247.0,49.0/176.0,-5103.0/18656.0,0,0},
195                    {35.0/384.0,0,500.0/1113.0,125.0/192.0,-2187.0/6784.0,11.0/84.0,0}},
196       b[7]      = {35.0/384.0,0,500.0/1113.0,125.0/192.0,-2187.0/6784.0,11.0/84.0,0},
197       bembed[7] = {5179.0/57600.0,0,7571.0/16695.0,393.0/640.0,-92097.0/339200.0,187.0/2100.0,1.0/40.0};
198     ierr = TSRKRegister(TSRK5DP,5,7,&A[0][0],b,NULL,bembed,5,b);CHKERRQ(ierr);
199   }
200   PetscFunctionReturn(0);
201 }
202 
203 #undef __FUNCT__
204 #define __FUNCT__ "TSRKRegisterDestroy"
205 /*@C
206    TSRKRegisterDestroy - Frees the list of schemes that were registered by TSRKRegister().
207 
208    Not Collective
209 
210    Level: advanced
211 
212 .keywords: TSRK, register, destroy
213 .seealso: TSRKRegister(), TSRKRegisterAll()
214 @*/
215 PetscErrorCode TSRKRegisterDestroy(void)
216 {
217   PetscErrorCode ierr;
218   RKTableauLink link;
219 
220   PetscFunctionBegin;
221   while ((link = RKTableauList)) {
222     RKTableau t = &link->tab;
223     RKTableauList = link->next;
224     ierr = PetscFree3(t->A,t->b,t->c);  CHKERRQ(ierr);
225     ierr = PetscFree (t->bembed);       CHKERRQ(ierr);
226     ierr = PetscFree (t->binterp);      CHKERRQ(ierr);
227     ierr = PetscFree (t->name);         CHKERRQ(ierr);
228     ierr = PetscFree (link);            CHKERRQ(ierr);
229   }
230   TSRKRegisterAllCalled = PETSC_FALSE;
231   PetscFunctionReturn(0);
232 }
233 
234 #undef __FUNCT__
235 #define __FUNCT__ "TSRKInitializePackage"
236 /*@C
237   TSRKInitializePackage - This function initializes everything in the TSRK package. It is called
238   from PetscDLLibraryRegister() when using dynamic libraries, and on the first call to TSCreate_RK()
239   when using static libraries.
240 
241   Level: developer
242 
243 .keywords: TS, TSRK, initialize, package
244 .seealso: PetscInitialize()
245 @*/
246 PetscErrorCode TSRKInitializePackage(void)
247 {
248   PetscErrorCode ierr;
249 
250   PetscFunctionBegin;
251   if (TSRKPackageInitialized) PetscFunctionReturn(0);
252   TSRKPackageInitialized = PETSC_TRUE;
253   ierr = TSRKRegisterAll();CHKERRQ(ierr);
254   ierr = PetscObjectComposedDataRegister(&explicit_stage_time_id);CHKERRQ(ierr);
255   ierr = PetscRegisterFinalize(TSRKFinalizePackage);CHKERRQ(ierr);
256   PetscFunctionReturn(0);
257 }
258 
259 #undef __FUNCT__
260 #define __FUNCT__ "TSRKFinalizePackage"
261 /*@C
262   TSRKFinalizePackage - This function destroys everything in the TSRK package. It is
263   called from PetscFinalize().
264 
265   Level: developer
266 
267 .keywords: Petsc, destroy, package
268 .seealso: PetscFinalize()
269 @*/
270 PetscErrorCode TSRKFinalizePackage(void)
271 {
272   PetscErrorCode ierr;
273 
274   PetscFunctionBegin;
275   TSRKPackageInitialized = PETSC_FALSE;
276   ierr = TSRKRegisterDestroy();CHKERRQ(ierr);
277   PetscFunctionReturn(0);
278 }
279 
280 #undef __FUNCT__
281 #define __FUNCT__ "TSRKRegister"
282 /*@C
283    TSRKRegister - register an RK scheme by providing the entries in the Butcher tableau and optionally embedded approximations and interpolation
284 
285    Not Collective, but the same schemes should be registered on all processes on which they will be used
286 
287    Input Parameters:
288 +  name - identifier for method
289 .  order - approximation order of method
290 .  s - number of stages, this is the dimension of the matrices below
291 .  A - stage coefficients (dimension s*s, row-major)
292 .  b - step completion table (dimension s; NULL to use last row of A)
293 .  c - abscissa (dimension s; NULL to use row sums of A)
294 .  bembed - completion table for embedded method (dimension s; NULL if not available)
295 .  pinterp - Order of the interpolation scheme, equal to the number of columns of binterp
296 -  binterp - Coefficients of the interpolation formula (dimension s*pinterp; NULL to reuse binterpt)
297 
298    Notes:
299    Several RK methods are provided, this function is only needed to create new methods.
300 
301    Level: advanced
302 
303 .keywords: TS, register
304 
305 .seealso: TSRK
306 @*/
307 PetscErrorCode TSRKRegister(TSRKType name,PetscInt order,PetscInt s,
308                                  const PetscReal A[],const PetscReal b[],const PetscReal c[],
309                                  const PetscReal bembed[],
310                                  PetscInt pinterp,const PetscReal binterp[])
311 {
312   PetscErrorCode  ierr;
313   RKTableauLink   link;
314   RKTableau       t;
315   PetscInt        i,j;
316 
317   PetscFunctionBegin;
318   ierr     = PetscMalloc(sizeof(*link),&link);CHKERRQ(ierr);
319   ierr     = PetscMemzero(link,sizeof(*link));CHKERRQ(ierr);
320   t        = &link->tab;
321   ierr     = PetscStrallocpy(name,&t->name);CHKERRQ(ierr);
322   t->order = order;
323   t->s     = s;
324   ierr     = PetscMalloc3(s*s,&t->A,s,&t->b,s,&t->c);CHKERRQ(ierr);
325   ierr     = PetscMemcpy(t->A,A,s*s*sizeof(A[0]));CHKERRQ(ierr);
326   if (b)  { ierr = PetscMemcpy(t->b,b,s*sizeof(b[0]));CHKERRQ(ierr); }
327   else for (i=0; i<s; i++) t->b[i] = A[(s-1)*s+i];
328   if (c)  { ierr = PetscMemcpy(t->c,c,s*sizeof(c[0]));CHKERRQ(ierr); }
329   else for (i=0; i<s; i++) for (j=0,t->c[i]=0; j<s; j++) t->c[i] += A[i*s+j];
330   t->FSAL = PETSC_TRUE;
331   for (i=0; i<s; i++) if (t->A[(s-1)*s+i] != t->b[i]) t->FSAL = PETSC_FALSE;
332   if (bembed) {
333     ierr = PetscMalloc1(s,&t->bembed);CHKERRQ(ierr);
334     ierr = PetscMemcpy(t->bembed,bembed,s*sizeof(bembed[0]));CHKERRQ(ierr);
335   }
336 
337   t->pinterp     = pinterp;
338   ierr           = PetscMalloc1(s*pinterp,&t->binterp);CHKERRQ(ierr);
339   ierr           = PetscMemcpy(t->binterp,binterp,s*pinterp*sizeof(binterp[0]));CHKERRQ(ierr);
340   link->next     = RKTableauList;
341   RKTableauList = link;
342   PetscFunctionReturn(0);
343 }
344 
345 #undef __FUNCT__
346 #define __FUNCT__ "TSEvaluateStep_RK"
347 /*
348  The step completion formula is
349 
350  x1 = x0 + h b^T YdotRHS
351 
352  This function can be called before or after ts->vec_sol has been updated.
353  Suppose we have a completion formula (b) and an embedded formula (be) of different order.
354  We can write
355 
356  x1e = x0 + h be^T YdotRHS
357      = x1 - h b^T YdotRHS + h be^T YdotRHS
358      = x1 + h (be - b)^T YdotRHS
359 
360  so we can evaluate the method with different order even after the step has been optimistically completed.
361 */
362 static PetscErrorCode TSEvaluateStep_RK(TS ts,PetscInt order,Vec X,PetscBool *done)
363 {
364   TS_RK         *rk   = (TS_RK*)ts->data;
365   RKTableau      tab  = rk->tableau;
366   PetscScalar   *w    = rk->work;
367   PetscReal      h;
368   PetscInt       s    = tab->s,j;
369   PetscErrorCode ierr;
370 
371   PetscFunctionBegin;
372   switch (rk->status) {
373   case TS_STEP_INCOMPLETE:
374   case TS_STEP_PENDING:
375     h = ts->time_step; break;
376   case TS_STEP_COMPLETE:
377     h = ts->time_step_prev; break;
378   default: SETERRQ(PetscObjectComm((PetscObject)ts),PETSC_ERR_PLIB,"Invalid TSStepStatus");
379   }
380   if (order == tab->order) {
381     if (rk->status == TS_STEP_INCOMPLETE) {
382       ierr = VecCopy(ts->vec_sol,X);CHKERRQ(ierr);
383       for (j=0; j<s; j++) w[j] = h*tab->b[j];
384       ierr = VecMAXPY(X,s,w,rk->YdotRHS);CHKERRQ(ierr);
385     } else {ierr = VecCopy(ts->vec_sol,X);CHKERRQ(ierr);}
386     PetscFunctionReturn(0);
387   } else if (order == tab->order-1) {
388     if (!tab->bembed) goto unavailable;
389     if (rk->status == TS_STEP_INCOMPLETE) { /* Complete with the embedded method (be) */
390       ierr = VecCopy(ts->vec_sol,X);CHKERRQ(ierr);
391       for (j=0; j<s; j++) w[j] = h*tab->bembed[j];
392       ierr = VecMAXPY(X,s,w,rk->YdotRHS);CHKERRQ(ierr);
393     } else {                    /* Rollback and re-complete using (be-b) */
394       ierr = VecCopy(ts->vec_sol,X);CHKERRQ(ierr);
395       for (j=0; j<s; j++) w[j] = h*(tab->bembed[j] - tab->b[j]);
396       ierr = VecMAXPY(X,s,w,rk->YdotRHS);CHKERRQ(ierr);
397     }
398     if (done) *done = PETSC_TRUE;
399     PetscFunctionReturn(0);
400   }
401 unavailable:
402   if (done) *done = PETSC_FALSE;
403   else SETERRQ3(PetscObjectComm((PetscObject)ts),PETSC_ERR_SUP,"RK '%s' of order %D cannot evaluate step at order %D",tab->name,tab->order,order);
404   PetscFunctionReturn(0);
405 }
406 
407 #undef __FUNCT__
408 #define __FUNCT__ "TSStep_RK"
409 static PetscErrorCode TSStep_RK(TS ts)
410 {
411   TS_RK           *rk   = (TS_RK*)ts->data;
412   RKTableau        tab  = rk->tableau;
413   const PetscInt   s    = tab->s;
414   const PetscReal *A = tab->A,*b = tab->b,*c = tab->c;
415   PetscScalar     *w    = rk->work;
416   Vec             *Y    = rk->Y,*YdotRHS = rk->YdotRHS;
417   TSAdapt          adapt;
418   PetscInt         i,j,reject,next_scheme;
419   PetscReal        next_time_step;
420   PetscReal        t;
421   PetscBool        accept;
422   PetscErrorCode   ierr;
423 
424   PetscFunctionBegin;
425 
426   next_time_step = ts->time_step;
427   t              = ts->ptime;
428   accept         = PETSC_TRUE;
429   rk->status     = TS_STEP_INCOMPLETE;
430 
431 
432   for (reject=0; reject<ts->max_reject && !ts->reason; reject++,ts->reject++) {
433     PetscReal h = ts->time_step;
434     ierr = TSPreStep(ts);CHKERRQ(ierr);
435     for (i=0; i<s; i++) {
436       rk->stage_time = t + h*c[i];
437       ierr = TSPreStage(ts,rk->stage_time); CHKERRQ(ierr);
438       ierr = VecCopy(ts->vec_sol,Y[i]);CHKERRQ(ierr);
439       for (j=0; j<i; j++) w[j] = h*A[i*s+j];
440       ierr = VecMAXPY(Y[i],i,w,YdotRHS);CHKERRQ(ierr);
441       ierr = TSPostStage(ts,rk->stage_time,i,Y); CHKERRQ(ierr);
442       ierr = TSGetAdapt(ts,&adapt);CHKERRQ(ierr);
443       ierr = TSAdaptCheckStage(adapt,ts,&accept);CHKERRQ(ierr);
444       if (!accept) goto reject_step;
445       ierr = TSComputeRHSFunction(ts,t+h*c[i],Y[i],YdotRHS[i]);CHKERRQ(ierr);
446     }
447     ierr = TSEvaluateStep(ts,tab->order,ts->vec_sol,NULL);CHKERRQ(ierr);
448     rk->status = TS_STEP_PENDING;
449 
450     /* Register only the current method as a candidate because we're not supporting multiple candidates yet. */
451     ierr = TSGetAdapt(ts,&adapt);CHKERRQ(ierr);
452     ierr = TSAdaptCandidatesClear(adapt);CHKERRQ(ierr);
453     ierr = TSAdaptCandidateAdd(adapt,tab->name,tab->order,1,tab->ccfl,1.*tab->s,PETSC_TRUE);CHKERRQ(ierr);
454     ierr = TSAdaptChoose(adapt,ts,ts->time_step,&next_scheme,&next_time_step,&accept);CHKERRQ(ierr);
455     if (accept) {
456       /* ignore next_scheme for now */
457       ts->ptime    += ts->time_step;
458       ts->time_step = next_time_step;
459       ts->steps++;
460       rk->status = TS_STEP_COMPLETE;
461       ierr = PetscObjectComposedDataSetReal((PetscObject)ts->vec_sol,explicit_stage_time_id,ts->ptime);CHKERRQ(ierr);
462       break;
463     } else {                    /* Roll back the current step */
464       for (j=0; j<s; j++) w[j] = -h*b[j];
465       ierr = VecMAXPY(ts->vec_sol,s,w,rk->YdotRHS);CHKERRQ(ierr);
466       ts->time_step = next_time_step;
467       rk->status   = TS_STEP_INCOMPLETE;
468     }
469 reject_step: continue;
470   }
471   if (rk->status != TS_STEP_COMPLETE && !ts->reason) ts->reason = TS_DIVERGED_STEP_REJECTED;
472   PetscFunctionReturn(0);
473 }
474 
475 #undef __FUNCT__
476 #define __FUNCT__ "TSAdjointSetUp_RK"
477 static PetscErrorCode TSAdjointSetUp_RK(TS ts)
478 {
479   TS_RK         *rk = (TS_RK*)ts->data;
480   RKTableau      tab;
481   PetscInt       s;
482   PetscErrorCode ierr;
483 
484   PetscFunctionBegin;
485   if (ts->adjointsetupcalled++) PetscFunctionReturn(0);
486   tab  = rk->tableau;
487   s    = tab->s;
488   ierr = VecDuplicateVecs(ts->vecs_sensi[0],s*ts->numberadjs,&rk->VecDeltaLam);CHKERRQ(ierr);
489   if(ts->vecs_sensip) {
490     ierr = VecDuplicateVecs(ts->vecs_sensip[0],s*ts->numberadjs,&rk->VecDeltaMu);CHKERRQ(ierr);
491   }
492   ierr = VecDuplicateVecs(ts->vecs_sensi[0],ts->numberadjs,&rk->VecSensiTemp);CHKERRQ(ierr);
493   PetscFunctionReturn(0);
494 }
495 
496 #undef __FUNCT__
497 #define __FUNCT__ "TSAdjointStep_RK"
498 static PetscErrorCode TSAdjointStep_RK(TS ts)
499 {
500   TS_RK           *rk   = (TS_RK*)ts->data;
501   RKTableau        tab  = rk->tableau;
502   const PetscInt   s    = tab->s;
503   const PetscReal *A = tab->A,*b = tab->b,*c = tab->c;
504   PetscScalar     *w    = rk->work;
505   Vec             *Y    = rk->Y,*VecDeltaLam = rk->VecDeltaLam,*VecDeltaMu = rk->VecDeltaMu,*VecSensiTemp = rk->VecSensiTemp;
506   PetscInt         i,j,nadj;
507   PetscReal        t;
508   PetscErrorCode   ierr;
509   PetscReal        h = ts->time_step;
510   Mat              J,Jp;
511 
512   PetscFunctionBegin;
513   t          = ts->ptime;
514   rk->status = TS_STEP_INCOMPLETE;
515   h = ts->time_step;
516   ierr = TSPreStep(ts);CHKERRQ(ierr);
517   for (i=s-1; i>=0; i--) {
518     rk->stage_time = t + h*(1.0-c[i]);
519     for (nadj=0; nadj<ts->numberadjs; nadj++) {
520       ierr = VecCopy(ts->vecs_sensi[nadj],VecSensiTemp[nadj]);CHKERRQ(ierr);
521       ierr = VecScale(VecSensiTemp[nadj],-h*b[i]);
522       for (j=i+1; j<s; j++) {
523         ierr = VecAXPY(VecSensiTemp[nadj],-h*A[j*s+i],VecDeltaLam[nadj*s+j]);
524       }
525     }
526     /* Stage values of lambda */
527     ierr = TSGetRHSJacobian(ts,&J,&Jp,NULL,NULL);CHKERRQ(ierr);
528     ierr = TSComputeRHSJacobian(ts,rk->stage_time,Y[i],J,Jp);CHKERRQ(ierr);
529     for (nadj=0; nadj<ts->numberadjs; nadj++) {
530       ierr = MatMultTranspose(J,VecSensiTemp[nadj],VecDeltaLam[nadj*s+i]);CHKERRQ(ierr);
531     }
532 
533     /* Stage values of mu */
534     if(ts->vecs_sensip) {
535       ierr = TSAdjointComputeRHSJacobian(ts,rk->stage_time,Y[i],ts->Jacp);CHKERRQ(ierr);
536       for (nadj=0; nadj<ts->numberadjs; nadj++) {
537         ierr = MatMultTranspose(ts->Jacp,VecSensiTemp[nadj],VecDeltaMu[nadj*s+i]);CHKERRQ(ierr);
538       }
539     }
540   }
541 
542   for (j=0; j<s; j++) w[j] = 1.0;
543   for (nadj=0; nadj<ts->numberadjs; nadj++) {
544     ierr = VecMAXPY(ts->vecs_sensi[nadj],s,w,&VecDeltaLam[nadj*s]);CHKERRQ(ierr);
545     if(ts->vecs_sensip) {
546       ierr = VecMAXPY(ts->vecs_sensip[nadj],s,w,&VecDeltaMu[nadj*s]);CHKERRQ(ierr);
547     }
548   }
549   ts->ptime += ts->time_step;
550   ts->steps++;
551   rk->status = TS_STEP_COMPLETE;
552   ierr = PetscObjectComposedDataSetReal((PetscObject)ts->vecs_sensi,explicit_stage_time_id,ts->ptime);CHKERRQ(ierr);
553   if(ts->vecs_sensip) {
554     ierr = PetscObjectComposedDataSetReal((PetscObject)ts->vecs_sensip,explicit_stage_time_id,ts->ptime);CHKERRQ(ierr);
555   }
556   PetscFunctionReturn(0);
557 }
558 
559 #undef __FUNCT__
560 #define __FUNCT__ "TSInterpolate_RK"
561 static PetscErrorCode TSInterpolate_RK(TS ts,PetscReal itime,Vec X)
562 {
563   TS_RK           *rk = (TS_RK*)ts->data;
564   PetscInt         s  = rk->tableau->s,pinterp = rk->tableau->pinterp,i,j;
565   PetscReal        h;
566   PetscReal        tt,t;
567   PetscScalar     *b;
568   const PetscReal *B = rk->tableau->binterp;
569   PetscErrorCode   ierr;
570 
571   PetscFunctionBegin;
572   if (!B) SETERRQ1(PetscObjectComm((PetscObject)ts),PETSC_ERR_SUP,"TSRK %s does not have an interpolation formula",rk->tableau->name);
573   switch (rk->status) {
574   case TS_STEP_INCOMPLETE:
575   case TS_STEP_PENDING:
576     h = ts->time_step;
577     t = (itime - ts->ptime)/h;
578     break;
579   case TS_STEP_COMPLETE:
580     h = ts->time_step_prev;
581     t = (itime - ts->ptime)/h + 1; /* In the interval [0,1] */
582     break;
583   default: SETERRQ(PetscObjectComm((PetscObject)ts),PETSC_ERR_PLIB,"Invalid TSStepStatus");
584   }
585   ierr = PetscMalloc1(s,&b);CHKERRQ(ierr);
586   for (i=0; i<s; i++) b[i] = 0;
587   for (j=0,tt=t; j<pinterp; j++,tt*=t) {
588     for (i=0; i<s; i++) {
589       b[i]  += h * B[i*pinterp+j] * tt;
590     }
591   }
592   ierr = VecCopy(rk->Y[0],X);CHKERRQ(ierr);
593   ierr = VecMAXPY(X,s,b,rk->YdotRHS);CHKERRQ(ierr);
594   ierr = PetscFree(b);CHKERRQ(ierr);
595   PetscFunctionReturn(0);
596 }
597 
598 /*------------------------------------------------------------*/
599 #undef __FUNCT__
600 #define __FUNCT__ "TSReset_RK"
601 static PetscErrorCode TSReset_RK(TS ts)
602 {
603   TS_RK         *rk = (TS_RK*)ts->data;
604   PetscInt       s;
605   PetscErrorCode ierr;
606 
607   PetscFunctionBegin;
608   if (!rk->tableau) PetscFunctionReturn(0);
609   s    = rk->tableau->s;
610   ierr = VecDestroyVecs(s,&rk->Y);CHKERRQ(ierr);
611   ierr = VecDestroyVecs(s,&rk->YdotRHS);CHKERRQ(ierr);
612   ierr = VecDestroyVecs(s*ts->numberadjs,&rk->VecDeltaLam);CHKERRQ(ierr);
613   ierr = VecDestroyVecs(s*ts->numberadjs,&rk->VecDeltaMu);CHKERRQ(ierr);
614   ierr = VecDestroyVecs(ts->numberadjs,&rk->VecSensiTemp);CHKERRQ(ierr);
615   ierr = PetscFree(rk->work);CHKERRQ(ierr);
616   PetscFunctionReturn(0);
617 }
618 
619 #undef __FUNCT__
620 #define __FUNCT__ "TSDestroy_RK"
621 static PetscErrorCode TSDestroy_RK(TS ts)
622 {
623   PetscErrorCode ierr;
624 
625   PetscFunctionBegin;
626   ierr = TSReset_RK(ts);CHKERRQ(ierr);
627   ierr = PetscFree(ts->data);CHKERRQ(ierr);
628   ierr = PetscObjectComposeFunction((PetscObject)ts,"TSRKGetType_C",NULL);CHKERRQ(ierr);
629   ierr = PetscObjectComposeFunction((PetscObject)ts,"TSRKSetType_C",NULL);CHKERRQ(ierr);
630   PetscFunctionReturn(0);
631 }
632 
633 
634 #undef __FUNCT__
635 #define __FUNCT__ "DMCoarsenHook_TSRK"
636 static PetscErrorCode DMCoarsenHook_TSRK(DM fine,DM coarse,void *ctx)
637 {
638   PetscFunctionBegin;
639   PetscFunctionReturn(0);
640 }
641 
642 #undef __FUNCT__
643 #define __FUNCT__ "DMRestrictHook_TSRK"
644 static PetscErrorCode DMRestrictHook_TSRK(DM fine,Mat restrct,Vec rscale,Mat inject,DM coarse,void *ctx)
645 {
646   PetscFunctionBegin;
647   PetscFunctionReturn(0);
648 }
649 
650 
651 #undef __FUNCT__
652 #define __FUNCT__ "DMSubDomainHook_TSRK"
653 static PetscErrorCode DMSubDomainHook_TSRK(DM dm,DM subdm,void *ctx)
654 {
655   PetscFunctionBegin;
656   PetscFunctionReturn(0);
657 }
658 
659 #undef __FUNCT__
660 #define __FUNCT__ "DMSubDomainRestrictHook_TSRK"
661 static PetscErrorCode DMSubDomainRestrictHook_TSRK(DM dm,VecScatter gscat,VecScatter lscat,DM subdm,void *ctx)
662 {
663 
664   PetscFunctionBegin;
665   PetscFunctionReturn(0);
666 }
667 /*
668 #undef __FUNCT__
669 #define __FUNCT__ "RKSetAdjCoe"
670 static PetscErrorCode RKSetAdjCoe(RKTableau tab)
671 {
672   PetscReal *A,*b;
673   PetscInt        s,i,j;
674   PetscErrorCode  ierr;
675 
676   PetscFunctionBegin;
677   s    = tab->s;
678   ierr = PetscMalloc2(s*s,&A,s,&b);CHKERRQ(ierr);
679 
680   for (i=0; i<s; i++)
681     for (j=0; j<s; j++) {
682       A[i*s+j] = (tab->b[s-1-i]==0) ? 0: -tab->A[s-1-i+(s-1-j)*s] * tab->b[s-1-j] / tab->b[s-1-i];
683       ierr = PetscPrintf(PETSC_COMM_WORLD,"Coefficients: A[%D][%D]=%.6f\n",i,j,A[i*s+j]);CHKERRQ(ierr);
684     }
685 
686   for (i=0; i<s; i++) b[i] = (tab->b[s-1-i]==0)? 0: -tab->b[s-1-i];
687 
688   ierr  = PetscMemcpy(tab->A,A,s*s*sizeof(A[0]));CHKERRQ(ierr);
689   ierr  = PetscMemcpy(tab->b,b,s*sizeof(b[0]));CHKERRQ(ierr);
690   ierr  = PetscFree2(A,b);CHKERRQ(ierr);
691   PetscFunctionReturn(0);
692 }
693 */
694 #undef __FUNCT__
695 #define __FUNCT__ "TSSetUp_RK"
696 static PetscErrorCode TSSetUp_RK(TS ts)
697 {
698   TS_RK         *rk = (TS_RK*)ts->data;
699   RKTableau      tab;
700   PetscInt       s;
701   PetscErrorCode ierr;
702   DM             dm;
703 
704   PetscFunctionBegin;
705   if (!rk->tableau) {
706     ierr = TSRKSetType(ts,TSRKDefault);CHKERRQ(ierr);
707   }
708   tab  = rk->tableau;
709   s    = tab->s;
710   ierr = VecDuplicateVecs(ts->vec_sol,s,&rk->Y);CHKERRQ(ierr);
711   ierr = VecDuplicateVecs(ts->vec_sol,s,&rk->YdotRHS);CHKERRQ(ierr);
712   ierr = PetscMalloc1(s,&rk->work);CHKERRQ(ierr);
713   ierr = TSGetDM(ts,&dm);CHKERRQ(ierr);
714   if (dm) {
715     ierr = DMCoarsenHookAdd(dm,DMCoarsenHook_TSRK,DMRestrictHook_TSRK,ts);CHKERRQ(ierr);
716     ierr = DMSubDomainHookAdd(dm,DMSubDomainHook_TSRK,DMSubDomainRestrictHook_TSRK,ts);CHKERRQ(ierr);
717   }
718   PetscFunctionReturn(0);
719 }
720 
721 
722 /*------------------------------------------------------------*/
723 
724 #undef __FUNCT__
725 #define __FUNCT__ "TSSetFromOptions_RK"
726 static PetscErrorCode TSSetFromOptions_RK(PetscOptions *PetscOptionsObject,TS ts)
727 {
728   PetscErrorCode ierr;
729   char           rktype[256];
730 
731   PetscFunctionBegin;
732   ierr = PetscOptionsHead(PetscOptionsObject,"RK ODE solver options");CHKERRQ(ierr);
733   {
734     RKTableauLink  link;
735     PetscInt       count,choice;
736     PetscBool      flg;
737     const char   **namelist;
738     ierr = PetscStrncpy(rktype,TSRKDefault,sizeof(rktype));CHKERRQ(ierr);
739     for (link=RKTableauList,count=0; link; link=link->next,count++) ;
740     ierr = PetscMalloc1(count,&namelist);CHKERRQ(ierr);
741     for (link=RKTableauList,count=0; link; link=link->next,count++) namelist[count] = link->tab.name;
742     ierr      = PetscOptionsEList("-ts_rk_type","Family of RK method","TSRKSetType",(const char*const*)namelist,count,rktype,&choice,&flg);CHKERRQ(ierr);
743     ierr      = TSRKSetType(ts,flg ? namelist[choice] : rktype);CHKERRQ(ierr);
744     ierr      = PetscFree(namelist);CHKERRQ(ierr);
745   }
746   ierr = PetscOptionsTail();CHKERRQ(ierr);
747   PetscFunctionReturn(0);
748 }
749 
750 #undef __FUNCT__
751 #define __FUNCT__ "PetscFormatRealArray"
752 static PetscErrorCode PetscFormatRealArray(char buf[],size_t len,const char *fmt,PetscInt n,const PetscReal x[])
753 {
754   PetscErrorCode ierr;
755   PetscInt       i;
756   size_t         left,count;
757   char           *p;
758 
759   PetscFunctionBegin;
760   for (i=0,p=buf,left=len; i<n; i++) {
761     ierr = PetscSNPrintfCount(p,left,fmt,&count,x[i]);CHKERRQ(ierr);
762     if (count >= left) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Insufficient space in buffer");
763     left -= count;
764     p    += count;
765     *p++  = ' ';
766   }
767   p[i ? 0 : -1] = 0;
768   PetscFunctionReturn(0);
769 }
770 
771 #undef __FUNCT__
772 #define __FUNCT__ "TSView_RK"
773 static PetscErrorCode TSView_RK(TS ts,PetscViewer viewer)
774 {
775   TS_RK         *rk   = (TS_RK*)ts->data;
776   RKTableau      tab  = rk->tableau;
777   PetscBool      iascii;
778   PetscErrorCode ierr;
779   TSAdapt        adapt;
780 
781   PetscFunctionBegin;
782   ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);CHKERRQ(ierr);
783   if (iascii) {
784     TSRKType rktype;
785     char     buf[512];
786     ierr = TSRKGetType(ts,&rktype);CHKERRQ(ierr);
787     ierr = PetscViewerASCIIPrintf(viewer,"  RK %s\n",rktype);CHKERRQ(ierr);
788     ierr = PetscFormatRealArray(buf,sizeof(buf),"% 8.6f",tab->s,tab->c);CHKERRQ(ierr);
789     ierr = PetscViewerASCIIPrintf(viewer,"  Abscissa     c = %s\n",buf);CHKERRQ(ierr);
790     ierr = PetscViewerASCIIPrintf(viewer,"FSAL: %s\n",tab->FSAL ? "yes" : "no");CHKERRQ(ierr);
791   }
792   ierr = TSGetAdapt(ts,&adapt);CHKERRQ(ierr);
793   ierr = TSAdaptView(adapt,viewer);CHKERRQ(ierr);
794   PetscFunctionReturn(0);
795 }
796 
797 #undef __FUNCT__
798 #define __FUNCT__ "TSLoad_RK"
799 static PetscErrorCode TSLoad_RK(TS ts,PetscViewer viewer)
800 {
801   PetscErrorCode ierr;
802   TSAdapt        tsadapt;
803 
804   PetscFunctionBegin;
805   ierr = TSGetAdapt(ts,&tsadapt);CHKERRQ(ierr);
806   ierr = TSAdaptLoad(tsadapt,viewer);CHKERRQ(ierr);
807   PetscFunctionReturn(0);
808 }
809 
810 #undef __FUNCT__
811 #define __FUNCT__ "TSRKSetType"
812 /*@C
813   TSRKSetType - Set the type of RK scheme
814 
815   Logically collective
816 
817   Input Parameter:
818 +  ts - timestepping context
819 -  rktype - type of RK-scheme
820 
821   Level: intermediate
822 
823 .seealso: TSRKGetType(), TSRK, TSRK2, TSRK3, TSRKPRSSP2, TSRK4, TSRK5
824 @*/
825 PetscErrorCode TSRKSetType(TS ts,TSRKType rktype)
826 {
827   PetscErrorCode ierr;
828 
829   PetscFunctionBegin;
830   PetscValidHeaderSpecific(ts,TS_CLASSID,1);
831   ierr = PetscTryMethod(ts,"TSRKSetType_C",(TS,TSRKType),(ts,rktype));CHKERRQ(ierr);
832   PetscFunctionReturn(0);
833 }
834 
835 #undef __FUNCT__
836 #define __FUNCT__ "TSRKGetType"
837 /*@C
838   TSRKGetType - Get the type of RK scheme
839 
840   Logically collective
841 
842   Input Parameter:
843 .  ts - timestepping context
844 
845   Output Parameter:
846 .  rktype - type of RK-scheme
847 
848   Level: intermediate
849 
850 .seealso: TSRKGetType()
851 @*/
852 PetscErrorCode TSRKGetType(TS ts,TSRKType *rktype)
853 {
854   PetscErrorCode ierr;
855 
856   PetscFunctionBegin;
857   PetscValidHeaderSpecific(ts,TS_CLASSID,1);
858   ierr = PetscUseMethod(ts,"TSRKGetType_C",(TS,TSRKType*),(ts,rktype));CHKERRQ(ierr);
859   PetscFunctionReturn(0);
860 }
861 
862 #undef __FUNCT__
863 #define __FUNCT__ "TSRKGetType_RK"
864 PetscErrorCode  TSRKGetType_RK(TS ts,TSRKType *rktype)
865 {
866   TS_RK     *rk = (TS_RK*)ts->data;
867   PetscErrorCode ierr;
868 
869   PetscFunctionBegin;
870   if (!rk->tableau) {
871     ierr = TSRKSetType(ts,TSRKDefault);CHKERRQ(ierr);
872   }
873   *rktype = rk->tableau->name;
874   PetscFunctionReturn(0);
875 }
876 #undef __FUNCT__
877 #define __FUNCT__ "TSRKSetType_RK"
878 PetscErrorCode  TSRKSetType_RK(TS ts,TSRKType rktype)
879 {
880   TS_RK     *rk = (TS_RK*)ts->data;
881   PetscErrorCode ierr;
882   PetscBool      match;
883   RKTableauLink link;
884 
885   PetscFunctionBegin;
886   if (rk->tableau) {
887     ierr = PetscStrcmp(rk->tableau->name,rktype,&match);CHKERRQ(ierr);
888     if (match) PetscFunctionReturn(0);
889   }
890   for (link = RKTableauList; link; link=link->next) {
891     ierr = PetscStrcmp(link->tab.name,rktype,&match);CHKERRQ(ierr);
892     if (match) {
893       ierr = TSReset_RK(ts);CHKERRQ(ierr);
894       rk->tableau = &link->tab;
895       PetscFunctionReturn(0);
896     }
897   }
898   SETERRQ1(PetscObjectComm((PetscObject)ts),PETSC_ERR_ARG_UNKNOWN_TYPE,"Could not find '%s'",rktype);
899   PetscFunctionReturn(0);
900 }
901 
902 #undef __FUNCT__
903 #define __FUNCT__ "TSGetStages_RK"
904 static PetscErrorCode  TSGetStages_RK(TS ts,PetscInt *ns,Vec **Y)
905 {
906   TS_RK          *rk = (TS_RK*)ts->data;
907 
908   PetscFunctionBegin;
909   *ns = rk->tableau->s;
910   if(Y) *Y  = rk->Y;
911   PetscFunctionReturn(0);
912 }
913 
914 
915 /* ------------------------------------------------------------ */
916 /*MC
917       TSRK - ODE and DAE solver using Runge-Kutta schemes
918 
919   The user should provide the right hand side of the equation
920   using TSSetRHSFunction().
921 
922   Notes:
923   The default is TSRK3, it can be changed with TSRKSetType() or -ts_rk_type
924 
925   Level: beginner
926 
927 .seealso:  TSCreate(), TS, TSSetType(), TSRKSetType(), TSRKGetType(), TSRKSetFullyImplicit(), TSRK2D, TTSRK2E, TSRK3,
928            TSRK4, TSRK5, TSRKPRSSP2, TSRKBPR3, TSRKType, TSRKRegister()
929 
930 M*/
931 #undef __FUNCT__
932 #define __FUNCT__ "TSCreate_RK"
933 PETSC_EXTERN PetscErrorCode TSCreate_RK(TS ts)
934 {
935   TS_RK     *th;
936   PetscErrorCode ierr;
937 
938   PetscFunctionBegin;
939 #if !defined(PETSC_USE_DYNAMIC_LIBRARIES)
940   ierr = TSRKInitializePackage();CHKERRQ(ierr);
941 #endif
942 
943   ts->ops->reset          = TSReset_RK;
944   ts->ops->destroy        = TSDestroy_RK;
945   ts->ops->view           = TSView_RK;
946   ts->ops->load           = TSLoad_RK;
947   ts->ops->setup          = TSSetUp_RK;
948   ts->ops->adjointsetup   = TSAdjointSetUp_RK;
949   ts->ops->step           = TSStep_RK;
950   ts->ops->interpolate    = TSInterpolate_RK;
951   ts->ops->evaluatestep   = TSEvaluateStep_RK;
952   ts->ops->setfromoptions = TSSetFromOptions_RK;
953   ts->ops->getstages      = TSGetStages_RK;
954   ts->ops->adjointstep    = TSAdjointStep_RK;
955 
956   ierr = PetscNewLog(ts,&th);CHKERRQ(ierr);
957   ts->data = (void*)th;
958 
959   ierr = PetscObjectComposeFunction((PetscObject)ts,"TSRKGetType_C",TSRKGetType_RK);CHKERRQ(ierr);
960   ierr = PetscObjectComposeFunction((PetscObject)ts,"TSRKSetType_C",TSRKSetType_RK);CHKERRQ(ierr);
961   PetscFunctionReturn(0);
962 }
963