Actual source code: tseig.c

petsc-master 2019-09-20
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  2:  #include <petsc/private/tsimpl.h>
  3:  #include <petscdraw.h>

  5: /* ------------------------------------------------------------------------*/
  6: struct _n_TSMonitorSPEigCtx {
  7:   PetscDrawSP drawsp;
  8:   KSP         ksp;
  9:   PetscInt    howoften;  /* when > 0 uses step % howoften, when negative only final solution plotted */
 10:   PetscBool   computeexplicitly;
 11:   MPI_Comm    comm;
 12:   PetscRandom rand;
 13:   PetscReal   xmin,xmax,ymin,ymax;
 14: };


 17: /*@C
 18:    TSMonitorSPEigCtxCreate - Creates a context for use with TS to monitor the eigenvalues of the linearized operator

 20:    Collective on TS

 22:    Input Parameters:
 23: +  host - the X display to open, or null for the local machine
 24: .  label - the title to put in the title bar
 25: .  x, y - the screen coordinates of the upper left coordinate of the window
 26: .  m, n - the screen width and height in pixels
 27: -  howoften - if positive then determines the frequency of the plotting, if -1 then only at the final time

 29:    Output Parameter:
 30: .  ctx - the context

 32:    Options Database Key:
 33: .  -ts_monitor_sp_eig - plot egienvalues of linearized right hand side

 35:    Notes:
 36:    Use TSMonitorSPEigCtxDestroy() to destroy.

 38:    Currently only works if the Jacobian is provided explicitly.

 40:    Currently only works for ODEs u_t - F(t,u) = 0; that is with no mass matrix.

 42:    Level: intermediate

 44: .seealso: TSMonitorSPEigTimeStep(), TSMonitorSet(), TSMonitorLGSolution(), TSMonitorLGError()

 46: @*/
 47: PetscErrorCode  TSMonitorSPEigCtxCreate(MPI_Comm comm,const char host[],const char label[],int x,int y,int m,int n,PetscInt howoften,TSMonitorSPEigCtx *ctx)
 48: {
 49:   PetscDraw      win;
 51:   PC             pc;

 54:   PetscNew(ctx);
 55:   PetscRandomCreate(comm,&(*ctx)->rand);
 56:   PetscRandomSetFromOptions((*ctx)->rand);
 57:   PetscDrawCreate(comm,host,label,x,y,m,n,&win);
 58:   PetscDrawSetFromOptions(win);
 59:   PetscDrawSPCreate(win,1,&(*ctx)->drawsp);
 60:   KSPCreate(comm,&(*ctx)->ksp);
 61:   KSPSetOptionsPrefix((*ctx)->ksp,"ts_monitor_sp_eig_"); /* this is wrong, used use also prefix from the TS */
 62:   KSPSetType((*ctx)->ksp,KSPGMRES);
 63:   KSPGMRESSetRestart((*ctx)->ksp,200);
 64:   KSPSetTolerances((*ctx)->ksp,1.e-10,PETSC_DEFAULT,PETSC_DEFAULT,200);
 65:   KSPSetComputeSingularValues((*ctx)->ksp,PETSC_TRUE);
 66:   KSPSetFromOptions((*ctx)->ksp);
 67:   KSPGetPC((*ctx)->ksp,&pc);
 68:   PCSetType(pc,PCNONE);

 70:   (*ctx)->howoften          = howoften;
 71:   (*ctx)->computeexplicitly = PETSC_FALSE;

 73:   PetscOptionsGetBool(NULL,NULL,"-ts_monitor_sp_eig_explicitly",&(*ctx)->computeexplicitly,NULL);

 75:   (*ctx)->comm = comm;
 76:   (*ctx)->xmin = -2.1;
 77:   (*ctx)->xmax = 1.1;
 78:   (*ctx)->ymin = -1.1;
 79:   (*ctx)->ymax = 1.1;
 80:   return(0);
 81: }

 83: static PetscErrorCode TSLinearStabilityIndicator(TS ts, PetscReal xr,PetscReal xi,PetscBool *flg)
 84: {
 86:   PetscReal      yr,yi;

 89:   TSComputeLinearStability(ts,xr,xi,&yr,&yi);
 90:   if ((yr*yr + yi*yi) <= 1.0) *flg = PETSC_TRUE;
 91:   else *flg = PETSC_FALSE;
 92:   return(0);
 93: }

 95: PetscErrorCode TSMonitorSPEig(TS ts,PetscInt step,PetscReal ptime,Vec v,void *monctx)
 96: {
 97:   TSMonitorSPEigCtx ctx = (TSMonitorSPEigCtx) monctx;
 98:   PetscErrorCode    ierr;
 99:   KSP               ksp = ctx->ksp;
100:   PetscInt          n,N,nits,neig,i,its = 200;
101:   PetscReal         *r,*c,time_step_save;
102:   PetscDrawSP       drawsp = ctx->drawsp;
103:   Mat               A,B;
104:   Vec               xdot;
105:   SNES              snes;

108:   if (step < 0) return(0); /* -1 indicates interpolated solution */
109:   if (!step) return(0);
110:   if (((ctx->howoften > 0) && (!(step % ctx->howoften))) || ((ctx->howoften == -1) && ts->reason)) {
111:     VecDuplicate(v,&xdot);
112:     TSGetSNES(ts,&snes);
113:     SNESGetJacobian(snes,&A,&B,NULL,NULL);
114:     MatDuplicate(A,MAT_DO_NOT_COPY_VALUES,&B);
115:     /*
116:        This doesn't work because methods keep and use internal information about the shift so it
117:        seems we would need code for each method to trick the correct Jacobian in being computed.
118:      */
119:     time_step_save = ts->time_step;
120:     ts->time_step  = PETSC_MAX_REAL;

122:     SNESComputeJacobian(snes,v,A,B);

124:     ts->time_step  = time_step_save;

126:     KSPSetOperators(ksp,B,B);
127:     VecGetSize(v,&n);
128:     if (n < 200) its = n;
129:     KSPSetTolerances(ksp,1.e-10,PETSC_DEFAULT,PETSC_DEFAULT,its);
130:     VecSetRandom(xdot,ctx->rand);
131:     KSPSolve(ksp,xdot,xdot);
132:     VecDestroy(&xdot);
133:     KSPGetIterationNumber(ksp,&nits);
134:     N    = nits+2;

136:     if (nits) {
137:       PetscDraw     draw;
138:       PetscReal     pause;
139:       PetscDrawAxis axis;
140:       PetscReal     xmin,xmax,ymin,ymax;

142:       PetscDrawSPReset(drawsp);
143:       PetscDrawSPSetLimits(drawsp,ctx->xmin,ctx->xmax,ctx->ymin,ctx->ymax);
144:       PetscMalloc2(PetscMax(n,N),&r,PetscMax(n,N),&c);
145:       if (ctx->computeexplicitly) {
146:         KSPComputeEigenvaluesExplicitly(ksp,n,r,c);
147:         neig = n;
148:       } else {
149:         KSPComputeEigenvalues(ksp,N,r,c,&neig);
150:       }
151:       /* We used the positive operator to be able to reuse KSPs that require positive definiteness, now flip the spectrum as is conventional for ODEs */
152:       for (i=0; i<neig; i++) r[i] = -r[i];
153:       for (i=0; i<neig; i++) {
154:         if (ts->ops->linearstability) {
155:           PetscReal fr,fi;
156:           TSComputeLinearStability(ts,r[i],c[i],&fr,&fi);
157:           if ((fr*fr + fi*fi) > 1.0) {
158:             PetscPrintf(ctx->comm,"Linearized Eigenvalue %g + %g i linear stability function %g norm indicates unstable scheme \n",(double)r[i],(double)c[i],(double)(fr*fr + fi*fi));
159:           }
160:         }
161:         PetscDrawSPAddPoint(drawsp,r+i,c+i);
162:       }
163:       PetscFree2(r,c);
164:       PetscDrawSPGetDraw(drawsp,&draw);
165:       PetscDrawGetPause(draw,&pause);
166:       PetscDrawSetPause(draw,0.0);
167:       PetscDrawSPDraw(drawsp,PETSC_TRUE);
168:       PetscDrawSetPause(draw,pause);
169:       if (ts->ops->linearstability) {
170:         PetscDrawSPGetAxis(drawsp,&axis);
171:         PetscDrawAxisGetLimits(axis,&xmin,&xmax,&ymin,&ymax);
172:         PetscDrawIndicatorFunction(draw,xmin,xmax,ymin,ymax,PETSC_DRAW_CYAN,(PetscErrorCode (*)(void*,PetscReal,PetscReal,PetscBool*))TSLinearStabilityIndicator,ts);
173:         PetscDrawSPDraw(drawsp,PETSC_FALSE);
174:       }
175:       PetscDrawSPSave(drawsp);
176:     }
177:     MatDestroy(&B);
178:   }
179:   return(0);
180: }

182: /*@C
183:    TSMonitorSPEigCtxDestroy - Destroys a scatter plot context that was created with TSMonitorSPEigCtxCreate().

185:    Collective on TSMonitorSPEigCtx

187:    Input Parameter:
188: .  ctx - the monitor context

190:    Level: intermediate

192: .seealso: TSMonitorSPEigCtxCreate(),  TSMonitorSet(), TSMonitorSPEig();
193: @*/
194: PetscErrorCode  TSMonitorSPEigCtxDestroy(TSMonitorSPEigCtx *ctx)
195: {
196:   PetscDraw      draw;

200:   PetscDrawSPGetDraw((*ctx)->drawsp,&draw);
201:   PetscDrawDestroy(&draw);
202:   PetscDrawSPDestroy(&(*ctx)->drawsp);
203:   KSPDestroy(&(*ctx)->ksp);
204:   PetscRandomDestroy(&(*ctx)->rand);
205:   PetscFree(*ctx);
206:   return(0);
207: }