Date: 2021-03-03T22:28:03+00:00

Actual source code: ex7.c
petsc-3.14.5 2021-03-03
Report Typos and Errors

      1: static const char help[] = "1D periodic Finite Volume solver by a particular slope limiter with semidiscrete time stepping.\n"
      2:   "  advection   - Constant coefficient scalar advection\n"
      3:   "                u_t       + (a*u)_x               = 0\n"
      4:   "  for this toy problem, we choose different meshsizes for different sub-domains, say\n"
      5:   "                hxs  = (xmax - xmin)/2.0*(hratio+1.0)/Mx, \n"
      6:   "                hxf  = (xmax - xmin)/2.0*(1.0+1.0/hratio)/Mx, \n"
      7:   "  with x belongs to (xmin,xmax), the number of total mesh points is Mx and the ratio between the meshsize of corse\n\n"
      8:   "  grids and fine grids is hratio.\n"
      9:   "  exact       - Exact Riemann solver which usually needs to perform a Newton iteration to connect\n"
     10:   "                the states across shocks and rarefactions\n"
     11:   "  simulation  - use reference solution which is generated by smaller time step size to be true solution,\n"
     12:   "                also the reference solution should be generated by user and stored in a binary file.\n"
     13:   "  characteristic - Limit the characteristic variables, this is usually preferred (default)\n"
     14:   "Several initial conditions can be chosen with -initial N\n\n"
     15:   "The problem size should be set with -da_grid_x M\n\n"
     16:   "This script choose the slope limiter by biased second-order upwind procedure which is proposed by Van Leer in 1994\n"
     17:   "                             u(x_(k+1/2),t) = u(x_k,t) + phi(x_(k+1/2),t)*(u(x_k,t)-u(x_(k-1),t))                 \n"
     18:   "                     limiter phi(x_(k+1/2),t) = max(0,min(r(k+1/2),min(2,gamma(k+1/2)*r(k+1/2)+alpha(k+1/2))))    \n"
     19:   "                             r(k+1/2) = (u(x_(k+1))-u(x_k))/(u(x_k)-u(x_(k-1)))                                   \n"
     20:   "                             alpha(k+1/2) = (h_k*h_(k+1))/(h_(k-1)+h_k)/(h_(k-1)+h_k+h_(k+1))                     \n"
     21:   "                             gamma(k+1/2) = h_k*(h_(k-1)+h_k)/(h_k+h_(k+1))/(h_(k-1)+h_k+h_(k+1))                 \n";

     23: #include <petscts.h>
     24: #include <petscdm.h>
     25: #include <petscdmda.h>
     26: #include <petscdraw.h>
     27: #include <petscmath.h>

     29: PETSC_STATIC_INLINE PetscReal RangeMod(PetscReal a,PetscReal xmin,PetscReal xmax) { PetscReal range = xmax-xmin; return xmin +PetscFmodReal(range+PetscFmodReal(a,range),range); }

     31: /* --------------------------------- Finite Volume data structures ----------------------------------- */

     33: typedef enum {FVBC_PERIODIC, FVBC_OUTFLOW} FVBCType;
     34: static const char *FVBCTypes[] = {"PERIODIC","OUTFLOW","FVBCType","FVBC_",0};

     36: typedef struct {
     37:   PetscErrorCode (*sample)(void*,PetscInt,FVBCType,PetscReal,PetscReal,PetscReal,PetscReal,PetscReal*);
     38:   PetscErrorCode (*flux)(void*,const PetscScalar*,PetscScalar*,PetscReal*);
     39:   PetscErrorCode (*destroy)(void*);
     40:   void           *user;
     41:   PetscInt       dof;
     42:   char           *fieldname[16];
     43: } PhysicsCtx;

     45: typedef struct {
     46:   PhysicsCtx  physics;
     47:   MPI_Comm    comm;
     48:   char        prefix[256];

     50:   /* Local work arrays */
     51:   PetscScalar *flux;            /* Flux across interface                                                      */
     52:   PetscReal   *speeds;          /* Speeds of each wave                                                        */
     53:   PetscScalar *u;               /* value at face                                                              */

     55:   PetscReal   cfl_idt;          /* Max allowable value of 1/Delta t                                           */
     56:   PetscReal   cfl;
     57:   PetscReal   xmin,xmax;
     58:   PetscInt    initial;
     59:   PetscBool   exact;
     60:   PetscBool   simulation;
     61:   FVBCType    bctype;
     62:   PetscInt    hratio;           /* hratio = hslow/hfast */
     63:   IS          isf,iss;
     64:   PetscInt    sf,fs;            /* slow-fast and fast-slow interfaces */
     65: } FVCtx;

     67: /* --------------------------------- Physics ----------------------------------- */
     68: static PetscErrorCode PhysicsDestroy_SimpleFree(void *vctx)
     69: {

     73:   PetscFree(vctx);
     74:   return(0);
     75: }

     77: /* --------------------------------- Advection ----------------------------------- */
     78: typedef struct {
     79:   PetscReal a;                  /* advective velocity */
     80: } AdvectCtx;

     82: static PetscErrorCode PhysicsFlux_Advect(void *vctx,const PetscScalar *u,PetscScalar *flux,PetscReal *maxspeed)
     83: {
     84:   AdvectCtx *ctx = (AdvectCtx*)vctx;
     85:   PetscReal speed;

     88:   speed     = ctx->a;
     89:   flux[0]   = speed*u[0];
     90:   *maxspeed = speed;
     91:   return(0);
     92: }

     94: static PetscErrorCode PhysicsSample_Advect(void *vctx,PetscInt initial,FVBCType bctype,PetscReal xmin,PetscReal xmax,PetscReal t,PetscReal x,PetscReal *u)
     95: {
     96:   AdvectCtx *ctx = (AdvectCtx*)vctx;
     97:   PetscReal a    = ctx->a,x0;

    100:   switch (bctype) {
    101:     case FVBC_OUTFLOW:   x0 = x-a*t; break;
    102:     case FVBC_PERIODIC: x0 = RangeMod(x-a*t,xmin,xmax); break;
    103:     default: SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_UNKNOWN_TYPE,"unknown BCType");
    104:   }
    105:   switch (initial) {
    106:     case 0: u[0] = (x0 < 0) ? 1 : -1; break;
    107:     case 1: u[0] = (x0 < 0) ? -1 : 1; break;
    108:     case 2: u[0] = (0 < x0 && x0 < 1) ? 1 : 0; break;
    109:     case 3: u[0] = PetscSinReal(2*PETSC_PI*x0); break;
    110:     case 4: u[0] = PetscAbs(x0); break;
    111:     case 5: u[0] = (x0 < 0 || x0 > 0.5) ? 0 : PetscSqr(PetscSinReal(2*PETSC_PI*x0)); break;
    112:     case 6: u[0] = (x0 < 0) ? 0 : ((x0 < 1) ? x0 : ((x0 < 2) ? 2-x0 : 0)); break;
    113:     case 7: u[0] = PetscPowReal(PetscSinReal(PETSC_PI*x0),10.0);break;
    114:     default: SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_UNKNOWN_TYPE,"unknown initial condition");
    115:   }
    116:   return(0);
    117: }

    119: static PetscErrorCode PhysicsCreate_Advect(FVCtx *ctx)
    120: {
    122:   AdvectCtx      *user;

    125:   PetscNew(&user);
    126:   ctx->physics.sample         = PhysicsSample_Advect;
    127:   ctx->physics.flux           = PhysicsFlux_Advect;
    128:   ctx->physics.destroy        = PhysicsDestroy_SimpleFree;
    129:   ctx->physics.user           = user;
    130:   ctx->physics.dof            = 1;
    131:   PetscStrallocpy("u",&ctx->physics.fieldname[0]);
    132:   user->a = 1;
    133:   PetscOptionsBegin(ctx->comm,ctx->prefix,"Options for advection","");
    134:   {
    135:     PetscOptionsReal("-physics_advect_a","Speed","",user->a,&user->a,NULL);
    136:   }
    137:   PetscOptionsEnd();
    138:   return(0);
    139: }

    141: /* --------------------------------- Finite Volume Solver ----------------------------------- */

    143: static PetscErrorCode FVRHSFunction(TS ts,PetscReal time,Vec X,Vec F,void *vctx)
    144: {
    145:   FVCtx          *ctx = (FVCtx*)vctx;
    147:   PetscInt       i,j,Mx,dof,xs,xm,sf = ctx->sf,fs = ctx->fs;
    148:   PetscReal      hf,hs,cfl_idt = 0;
    149:   PetscScalar    *x,*f,*r,*min,*alpha,*gamma;
    150:   Vec            Xloc;
    151:   DM             da;

    154:   TSGetDM(ts,&da);
    155:   DMGetLocalVector(da,&Xloc);                          /* Xloc contains ghost points                                     */
    156:   DMDAGetInfo(da,0,&Mx,0,0,0,0,0,&dof,0,0,0,0,0);   /* Mx is the number of center points                              */
    157:   hs   = (ctx->xmax-ctx->xmin)/2.0*(ctx->hratio+1.0)/Mx;
    158:   hf   = (ctx->xmax-ctx->xmin)/2.0*(1.0+1.0/ctx->hratio)/Mx;
    159:   DMGlobalToLocalBegin(da,X,INSERT_VALUES,Xloc);       /* X is solution vector which does not contain ghost points       */
    160:   DMGlobalToLocalEnd(da,X,INSERT_VALUES,Xloc);
    161:   VecZeroEntries(F);                                   /* F is the right hand side function corresponds to center points */
    162:   DMDAVecGetArray(da,Xloc,&x);
    163:   DMDAVecGetArray(da,F,&f);
    164:   DMDAGetCorners(da,&xs,0,0,&xm,0,0);
    165:   PetscMalloc4(dof,&r,dof,&min,dof,&alpha,dof,&gamma);

    167:   if (ctx->bctype == FVBC_OUTFLOW) {
    168:     for (i=xs-2; i<0; i++) {
    169:       for (j=0; j<dof; j++) x[i*dof+j] = x[j];
    170:     }
    171:     for (i=Mx; i<xs+xm+2; i++) {
    172:       for (j=0; j<dof; j++) x[i*dof+j] = x[(xs+xm-1)*dof+j];
    173:     }
    174:   }

    176:   for (i=xs; i<xs+xm+1; i++) {
    177:     PetscReal   maxspeed;
    178:     PetscScalar *u;
    179:     if (i < sf || i > fs+1) {
    180:       u = &ctx->u[0];
    181:       alpha[0] = 1.0/6.0;
    182:       gamma[0] = 1.0/3.0;
    183:       for (j=0; j<dof; j++) {
    184:         r[j] = (x[i*dof+j]-x[(i-1)*dof+j])/(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    185:         min[j] = PetscMin(r[j],2.0);
    186:         u[j] = x[(i-1)*dof+j]+PetscMax(0,PetscMin(min[j],alpha[0]+gamma[0]*r[j]))*(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    187:       }
    188:        (*ctx->physics.flux)(ctx->physics.user,u,ctx->flux,&maxspeed);
    189:       cfl_idt = PetscMax(cfl_idt,PetscAbsScalar(maxspeed/hs));
    190:       if (i > xs) {
    191:         for (j=0; j<dof; j++) f[(i-1)*dof+j] -= ctx->flux[j]/hs;
    192:       }
    193:       if (i < xs+xm) {
    194:         for (j=0; j<dof; j++) f[i*dof+j] += ctx->flux[j]/hs;
    195:       }
    196:     } else if (i == sf) {
    197:       u = &ctx->u[0];
    198:       alpha[0] = hs*hf/(hs+hs)/(hs+hs+hf);
    199:       gamma[0] = hs*(hs+hs)/(hs+hf)/(hs+hs+hf);
    200:       for (j=0; j<dof; j++) {
    201:         r[j] = (x[i*dof+j]-x[(i-1)*dof+j])/(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    202:         min[j] = PetscMin(r[j],2.0);
    203:         u[j] = x[(i-1)*dof+j]+PetscMax(0,PetscMin(min[j],alpha[0]+gamma[0]*r[j]))*(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    204:       }
    205:       (*ctx->physics.flux)(ctx->physics.user,u,ctx->flux,&maxspeed);
    206:       if (i > xs) {
    207:         for (j=0; j<dof; j++) f[(i-1)*dof+j] -= ctx->flux[j]/hs;
    208:       }
    209:       if (i < xs+xm) {
    210:         for (j=0; j<dof; j++) f[i*dof+j] += ctx->flux[j]/hf;
    211:       }
    212:     } else if (i == sf+1) {
    213:       u = &ctx->u[0];
    214:       alpha[0] = hf*hf/(hs+hf)/(hs+hf+hf);
    215:       gamma[0] = hf*(hs+hf)/(hf+hf)/(hs+hf+hf);
    216:       for (j=0; j<dof; j++) {
    217:         r[j] = (x[i*dof+j] - x[(i-1)*dof+j])/(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    218:         min[j] = PetscMin(r[j],2.0);
    219:         u[j] = x[(i-1)*dof+j]+PetscMax(0,PetscMin(min[j],alpha[0]+gamma[0]*r[j]))*(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    220:       }
    221:        (*ctx->physics.flux)(ctx->physics.user,u,ctx->flux,&maxspeed);
    222:       if (i > xs) {
    223:         for (j=0; j<dof; j++) f[(i-1)*dof+j] -= ctx->flux[j]/hf;
    224:       }
    225:       if (i < xs+xm) {
    226:         for (j=0; j<dof; j++) f[i*dof+j] += ctx->flux[j]/hf;
    227:       }
    228:     } else if (i > sf+1 && i < fs) {
    229:       u = &ctx->u[0];
    230:       alpha[0] = 1.0/6.0;
    231:       gamma[0] = 1.0/3.0;
    232:       for (j=0; j<dof; j++) {
    233:         r[j] = (x[i*dof+j] - x[(i-1)*dof+j])/(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    234:         min[j] = PetscMin(r[j],2.0);
    235:         u[j] = x[(i-1)*dof+j]+PetscMax(0,PetscMin(min[j],alpha[0]+gamma[0]*r[j]))*(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    236:       }
    237:       (*ctx->physics.flux)(ctx->physics.user,u,ctx->flux,&maxspeed);
    238:       if (i > xs) {
    239:         for (j=0; j<dof; j++) f[(i-1)*dof+j] -= ctx->flux[j]/hf;
    240:       }
    241:       if (i < xs+xm) {
    242:         for (j=0; j<dof; j++) f[i*dof+j] += ctx->flux[j]/hf;
    243:       }
    244:     } else if (i == fs) {
    245:       u = &ctx->u[0];
    246:       alpha[0] = hf*hs/(hf+hf)/(hf+hf+hs);
    247:       gamma[0] = hf*(hf+hf)/(hf+hs)/(hf+hf+hs);
    248:       for (j=0; j<dof; j++) {
    249:         r[j] = (x[i*dof+j] - x[(i-1)*dof+j])/(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    250:         min[j] = PetscMin(r[j],2.0);
    251:         u[j] = x[(i-1)*dof+j]+PetscMax(0,PetscMin(min[j],alpha[0]+gamma[0]*r[j]))*(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    252:       }
    253:       (*ctx->physics.flux)(ctx->physics.user,u,ctx->flux,&maxspeed);
    254:       if (i > xs) {
    255:         for (j=0; j<dof; j++) f[(i-1)*dof+j] -= ctx->flux[j]/hf;
    256:       }
    257:       if (i < xs+xm) {
    258:         for (j=0; j<dof; j++) f[i*dof+j] += ctx->flux[j]/hs;
    259:       }
    260:     } else if (i == fs+1) {
    261:       u = &ctx->u[0];
    262:       alpha[0] = hs*hs/(hf+hs)/(hf+hs+hs);
    263:       gamma[0] = hs*(hf+hs)/(hs+hs)/(hf+hs+hs);
    264:       for (j=0; j<dof; j++) {
    265:         r[j] = (x[i*dof+j] - x[(i-1)*dof+j])/(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    266:         min[j] = PetscMin(r[j],2.0);
    267:         u[j] = x[(i-1)*dof+j]+PetscMax(0,PetscMin(min[j],alpha[0]+gamma[0]*r[j]))*(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    268:       }
    269:       (*ctx->physics.flux)(ctx->physics.user,u,ctx->flux,&maxspeed);
    270:       if (i > xs) {
    271:         for (j=0; j<dof; j++) f[(i-1)*dof+j] -= ctx->flux[j]/hs;
    272:       }
    273:       if (i < xs+xm) {
    274:         for (j=0; j<dof; j++) f[i*dof+j] += ctx->flux[j]/hs;
    275:       }
    276:     }
    277:   }
    278:   DMDAVecRestoreArray(da,Xloc,&x);
    279:   DMDAVecRestoreArray(da,F,&f);
    280:   DMRestoreLocalVector(da,&Xloc);
    281:   MPI_Allreduce(&cfl_idt,&ctx->cfl_idt,1,MPIU_SCALAR,MPIU_MAX,PetscObjectComm((PetscObject)da));
    282:   if (0) {
    283:     /* We need a way to inform the TS of a CFL constraint, this is a debugging fragment */
    284:     PetscReal dt,tnow;
    285:     TSGetTimeStep(ts,&dt);
    286:     TSGetTime(ts,&tnow);
    287:     if (dt > 0.5/ctx->cfl_idt) {
    288:       if (1) {
    289:         PetscPrintf(ctx->comm,"Stability constraint exceeded at t=%g, dt %g > %g\n",(double)tnow,(double)dt,(double)(0.5/ctx->cfl_idt));
    290:       } else SETERRQ2(PETSC_COMM_SELF,1,"Stability constraint exceeded, %g > %g",(double)dt,(double)(ctx->cfl/ctx->cfl_idt));
    291:     }
    292:   }
    293:   PetscFree4(r,min,alpha,gamma);
    294:   return(0);
    295:  }

    297: static PetscErrorCode FVRHSFunctionslow(TS ts,PetscReal time,Vec X,Vec F,void *vctx)
    298: {
    299:   FVCtx             *ctx = (FVCtx*)vctx;
    300:   PetscErrorCode    ierr;
    301:   PetscInt          i,j,Mx,dof,xs,xm,islow = 0,sf = ctx->sf,fs = ctx->fs;
    302:   PetscReal         hf,hs;
    303:   PetscScalar       *x,*f,*r,*min,*alpha,*gamma;
    304:   Vec               Xloc;
    305:   DM                da;

    308:   TSGetDM(ts,&da);
    309:   DMGetLocalVector(da,&Xloc);                          /* Xloc contains ghost points                                     */
    310:   DMDAGetInfo(da,0,&Mx,0,0,0,0,0,&dof,0,0,0,0,0);   /* Mx is the number of center points                              */
    311:   hs   = (ctx->xmax-ctx->xmin)/2.0*(ctx->hratio+1.0)/Mx;
    312:   hf   = (ctx->xmax-ctx->xmin)/2.0*(1.0+1.0/ctx->hratio)/Mx;
    313:   DMGlobalToLocalBegin(da,X,INSERT_VALUES,Xloc);       /* X is solution vector which does not contain ghost points       */
    314:   DMGlobalToLocalEnd  (da,X,INSERT_VALUES,Xloc);
    315:   VecZeroEntries(F);                                   /* F is the right hand side function corresponds to center points */
    316:   DMDAVecGetArray(da,Xloc,&x);
    317:   VecGetArray(F,&f);
    318:   DMDAGetCorners(da,&xs,0,0,&xm,0,0);
    319:   PetscMalloc4(dof,&r,dof,&min,dof,&alpha,dof,&gamma);

    321:   if (ctx->bctype == FVBC_OUTFLOW) {
    322:     for (i=xs-2; i<0; i++) {
    323:       for (j=0; j<dof; j++) x[i*dof+j] = x[j];
    324:     }
    325:     for (i=Mx; i<xs+xm+2; i++) {
    326:       for (j=0; j<dof; j++) x[i*dof+j] = x[(xs+xm-1)*dof+j];
    327:     }
    328:   }

    330:   for (i=xs; i<xs+xm+1; i++) {
    331:     PetscReal   maxspeed;
    332:     PetscScalar *u;
    333:     if (i < sf) {
    334:       u = &ctx->u[0];
    335:       alpha[0] = 1.0/6.0;
    336:       gamma[0] = 1.0/3.0;
    337:       for (j=0; j<dof; j++) {
    338:         r[j] = (x[i*dof+j] - x[(i-1)*dof+j])/(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    339:         min[j] = PetscMin(r[j],2.0);
    340:         u[j] = x[(i-1)*dof+j]+PetscMax(0,PetscMin(min[j],alpha[0]+gamma[0]*r[j]))*(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    341:       }
    342:       (*ctx->physics.flux)(ctx->physics.user,u,ctx->flux,&maxspeed);
    343:       if (i > xs) {
    344:         for (j=0; j<dof; j++) f[(islow-1)*dof+j] -= ctx->flux[j]/hs;
    345:       }
    346:       if (i < xs+xm) {
    347:         for (j=0; j<dof; j++) f[islow*dof+j] += ctx->flux[j]/hs;
    348:         islow++;
    349:       }
    350:     } else if (i == sf) {
    351:       u = &ctx->u[0];
    352:       alpha[0] = hs*hf/(hs+hs)/(hs+hs+hf);
    353:       gamma[0] = hs*(hs+hs)/(hs+hf)/(hs+hs+hf);
    354:       for (j=0; j<dof; j++) {
    355:         r[j] = (x[i*dof+j] - x[(i-1)*dof+j])/(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    356:         min[j] = PetscMin(r[j],2.0);
    357:         u[j] = x[(i-1)*dof+j]+PetscMax(0,PetscMin(min[j],alpha[0]+gamma[0]*r[j]))*(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    358:       }
    359:       (*ctx->physics.flux)(ctx->physics.user,u,ctx->flux,&maxspeed);
    360:       if (i > xs) {
    361:         for (j=0; j<dof; j++) f[(islow-1)*dof+j] -= ctx->flux[j]/hs;
    362:       }
    363:     } else if (i == fs) {
    364:       u = &ctx->u[0];
    365:       alpha[0] = hf*hs/(hf+hf)/(hf+hf+hs);
    366:       gamma[0] = hf*(hf+hf)/(hf+hs)/(hf+hf+hs);
    367:       for (j=0; j<dof; j++) {
    368:         r[j] = (x[i*dof+j] - x[(i-1)*dof+j])/(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    369:         min[j] = PetscMin(r[j],2.0);
    370:         u[j] = x[(i-1)*dof+j]+PetscMax(0,PetscMin(min[j],alpha[0]+gamma[0]*r[j]))*(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    371:       }
    372:       (*ctx->physics.flux)(ctx->physics.user,u,ctx->flux,&maxspeed);
    373:       if (i < xs+xm) {
    374:         for (j=0; j<dof; j++)  f[islow*dof+j] += ctx->flux[j]/hs;
    375:         islow++;
    376:       }
    377:     } else if (i == fs+1) {
    378:       u = &ctx->u[0];
    379:       alpha[0] = hs*hs/(hf+hs)/(hf+hs+hs);
    380:       gamma[0] = hs*(hf+hs)/(hs+hs)/(hf+hs+hs);
    381:       for (j=0; j<dof; j++) {
    382:         r[j] = (x[i*dof+j] - x[(i-1)*dof+j])/(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    383:         min[j] = PetscMin(r[j],2.0);
    384:         u[j] = x[(i-1)*dof+j]+PetscMax(0,PetscMin(min[j],alpha[0]+gamma[0]*r[j]))*(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    385:       }
    386:       (*ctx->physics.flux)(ctx->physics.user,u,ctx->flux,&maxspeed);
    387:       if (i > xs) {
    388:         for (j=0; j<dof; j++) f[(islow-1)*dof+j] -= ctx->flux[j]/hs;
    389:       }
    390:       if (i < xs+xm) {
    391:         for (j=0; j<dof; j++) f[islow*dof+j] += ctx->flux[j]/hs;
    392:         islow++;
    393:       }
    394:     } else if (i > fs+1) {
    395:       u = &ctx->u[0];
    396:       alpha[0] = 1.0/6.0;
    397:       gamma[0] = 1.0/3.0;
    398:       for (j=0; j<dof; j++) {
    399:         r[j] = (x[i*dof+j] - x[(i-1)*dof+j])/(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    400:         min[j] = PetscMin(r[j],2.0);
    401:         u[j] = x[(i-1)*dof+j]+PetscMax(0,PetscMin(min[j],alpha[0]+gamma[0]*r[j]))*(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    402:       }
    403:       (*ctx->physics.flux)(ctx->physics.user,u,ctx->flux,&maxspeed);
    404:       if (i > xs) {
    405:         for (j=0; j<dof; j++) f[(islow-1)*dof+j] -= ctx->flux[j]/hs;
    406:       }
    407:       if (i < xs+xm) {
    408:         for (j=0; j<dof; j++) f[islow*dof+j] += ctx->flux[j]/hs;
    409:         islow++;
    410:       }
    411:     }
    412:   }
    413:   DMDAVecRestoreArray(da,Xloc,&x);
    414:   VecRestoreArray(F,&f);
    415:   DMRestoreLocalVector(da,&Xloc);
    416:   PetscFree4(r,min,alpha,gamma);
    417:   return(0);
    418:  }

    420: static PetscErrorCode FVRHSFunctionfast(TS ts,PetscReal time,Vec X,Vec F,void *vctx)
    421: {
    422:   FVCtx          *ctx = (FVCtx*)vctx;
    424:   PetscInt       i,j,Mx,dof,xs,xm,ifast = 0,sf = ctx->sf,fs = ctx->fs;
    425:   PetscReal      hf,hs;
    426:   PetscScalar    *x,*f,*r,*min,*alpha,*gamma;
    427:   Vec            Xloc;
    428:   DM             da;

    431:   TSGetDM(ts,&da);
    432:   DMGetLocalVector(da,&Xloc);                          /* Xloc contains ghost points                                     */
    433:   DMDAGetInfo(da,0,&Mx,0,0,0,0,0,&dof,0,0,0,0,0);   /* Mx is the number of center points                              */
    434:   hs   = (ctx->xmax-ctx->xmin)/2.0*(ctx->hratio+1.0)/Mx;
    435:   hf   = (ctx->xmax-ctx->xmin)/2.0*(1.0+1.0/ctx->hratio)/Mx;
    436:   DMGlobalToLocalBegin(da,X,INSERT_VALUES,Xloc);       /* X is solution vector which does not contain ghost points       */
    437:   DMGlobalToLocalEnd(da,X,INSERT_VALUES,Xloc);
    438:   VecZeroEntries(F);                                   /* F is the right hand side function corresponds to center points */
    439:   DMDAVecGetArray(da,Xloc,&x);
    440:   VecGetArray(F,&f);
    441:   DMDAGetCorners(da,&xs,0,0,&xm,0,0);
    442:   PetscMalloc4(dof,&r,dof,&min,dof,&alpha,dof,&gamma);

    444:   if (ctx->bctype == FVBC_OUTFLOW) {
    445:     for (i=xs-2; i<0; i++) {
    446:       for (j=0; j<dof; j++) x[i*dof+j] = x[j];
    447:     }
    448:     for (i=Mx; i<xs+xm+2; i++) {
    449:       for (j=0; j<dof; j++) x[i*dof+j] = x[(xs+xm-1)*dof+j];
    450:     }
    451:   }

    453:   for (i=xs; i<xs+xm+1; i++) {
    454:     PetscReal   maxspeed;
    455:     PetscScalar *u;
    456:     if (i == sf) {
    457:       u = &ctx->u[0];
    458:       alpha[0] = hs*hf/(hs+hs)/(hs+hs+hf);
    459:       gamma[0] = hs*(hs+hs)/(hs+hf)/(hs+hs+hf);
    460:       for (j=0; j<dof; j++) {
    461:         r[j] = (x[i*dof+j]-x[(i-1)*dof+j])/(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    462:         min[j] = PetscMin(r[j],2.0);
    463:         u[j] = x[(i-1)*dof+j]+PetscMax(0,PetscMin(min[j],alpha[0]+gamma[0]*r[j]))*(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    464:       }
    465:       (*ctx->physics.flux)(ctx->physics.user,u,ctx->flux,&maxspeed);
    466:       if (i < xs+xm) {
    467:         for (j=0; j<dof; j++) f[ifast*dof+j] += ctx->flux[j]/hf;
    468:         ifast++;
    469:       }
    470:     } else if (i == sf+1) {
    471:       u = &ctx->u[0];
    472:       alpha[0] = hf*hf/(hs+hf)/(hs+hf+hf);
    473:       gamma[0] = hf*(hs+hf)/(hf+hf)/(hs+hf+hf);
    474:       for (j=0; j<dof; j++) {
    475:         r[j] = (x[i*dof+j]-x[(i-1)*dof+j])/(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    476:         min[j] = PetscMin(r[j],2.0);
    477:         u[j] = x[(i-1)*dof+j]+PetscMax(0,PetscMin(min[j],alpha[0]+gamma[0]*r[j]))*(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    478:       }
    479:       (*ctx->physics.flux)(ctx->physics.user,u,ctx->flux,&maxspeed);
    480:       if (i > xs) {
    481:         for (j=0; j<dof; j++) f[(ifast-1)*dof+j] -= ctx->flux[j]/hf;
    482:       }
    483:       if (i < xs+xm) {
    484:         for (j=0; j<dof; j++) f[ifast*dof+j] += ctx->flux[j]/hf;
    485:         ifast++;
    486:       }
    487:     } else if (i > sf+1 && i < fs) {
    488:       u = &ctx->u[0];
    489:       alpha[0] = 1.0/6.0;
    490:       gamma[0] = 1.0/3.0;
    491:       for (j=0; j<dof; j++) {
    492:         r[j] = (x[i*dof+j]-x[(i-1)*dof+j])/(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    493:         min[j] = PetscMin(r[j],2.0);
    494:         u[j] = x[(i-1)*dof+j]+PetscMax(0,PetscMin(min[j],alpha[0]+gamma[0]*r[j]))*(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    495:       }
    496:       (*ctx->physics.flux)(ctx->physics.user,u,ctx->flux,&maxspeed);
    497:       if (i > xs) {
    498:         for (j=0; j<dof; j++) f[(ifast-1)*dof+j] -= ctx->flux[j]/hf;
    499:       }
    500:       if (i < xs+xm) {
    501:         for (j=0; j<dof; j++) f[ifast*dof+j] += ctx->flux[j]/hf;
    502:         ifast++;
    503:       }
    504:     } else if (i == fs) {
    505:       u = &ctx->u[0];
    506:       alpha[0] = hf*hs/(hf+hf)/(hf+hf+hs);
    507:       gamma[0] = hf*(hf+hf)/(hf+hs)/(hf+hf+hs);
    508:       for (j=0; j<dof; j++) {
    509:         r[j] = (x[i*dof+j]-x[(i-1)*dof+j])/(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    510:         min[j] = PetscMin(r[j],2.0);
    511:         u[j] = x[(i-1)*dof+j]+PetscMax(0,PetscMin(min[j],alpha[0]+gamma[0]*r[j]))*(x[(i-1)*dof+j]-x[(i-2)*dof+j]);
    512:       }
    513:        (*ctx->physics.flux)(ctx->physics.user,u,ctx->flux,&maxspeed);
    514:       if (i > xs) {
    515:         for (j=0; j<dof; j++) f[(ifast-1)*dof+j] -= ctx->flux[j]/hf;
    516:       }
    517:     }
    518:   }
    519:   DMDAVecRestoreArray(da,Xloc,&x);
    520:   VecRestoreArray(F,&f);
    521:   DMRestoreLocalVector(da,&Xloc);
    522:   PetscFree4(r,min,alpha,gamma);
    523:   return(0);
    524:  }

    526: /* --------------------------------- Finite Volume Solver for slow components ----------------------------------- */

    528: PetscErrorCode FVSample(FVCtx *ctx,DM da,PetscReal time,Vec U)
    529: {
    531:   PetscScalar    *u,*uj,xj,xi;
    532:   PetscInt       i,j,k,dof,xs,xm,Mx,count_slow,count_fast;
    533:   const PetscInt N=200;

    536:   if (!ctx->physics.sample) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"Physics has not provided a sampling function");
    537:   DMDAGetInfo(da,0,&Mx,0,0,0,0,0,&dof,0,0,0,0,0);
    538:   DMDAGetCorners(da,&xs,0,0,&xm,0,0);
    539:   DMDAVecGetArray(da,U,&u);
    540:   PetscMalloc1(dof,&uj);
    541:   const PetscReal hs = (ctx->xmax-ctx->xmin)/2.0*(ctx->hratio+1.0)/Mx;
    542:   const PetscReal hf = (ctx->xmax-ctx->xmin)/2.0*(1.0+1.0/ctx->hratio)/Mx;
    543:   count_slow = Mx/(1+ctx->hratio);
    544:   count_fast = Mx-count_slow;
    545:   for (i=xs; i<xs+xm; i++) {
    546:     if (i*hs+0.5*hs<(ctx->xmax-ctx->xmin)*0.25) {
    547:       xi = ctx->xmin+0.5*hs+i*hs;
    548:       /* Integrate over cell i using trapezoid rule with N points. */
    549:       for (k=0; k<dof; k++) u[i*dof+k] = 0;
    550:       for (j=0; j<N+1; j++) {
    551:         xj = xi+hs*(j-N/2)/(PetscReal)N;
    552:         (*ctx->physics.sample)(ctx->physics.user,ctx->initial,ctx->bctype,ctx->xmin,ctx->xmax,time,xj,uj);
    553:         for (k=0; k<dof; k++) u[i*dof+k] += ((j==0 || j==N) ? 0.5 : 1.0)*uj[k]/N;
    554:       }
    555:     } else if ((ctx->xmax-ctx->xmin)*0.25+(i-count_slow/2)*hf+0.5*hf<(ctx->xmax-ctx->xmin)*0.75) {
    556:       xi = ctx->xmin+(ctx->xmax-ctx->xmin)*0.25+0.5*hf+(i-count_slow/2)*hf;
    557:       /* Integrate over cell i using trapezoid rule with N points. */
    558:       for (k=0; k<dof; k++) u[i*dof+k] = 0;
    559:       for (j=0; j<N+1; j++) {
    560:         xj = xi+hf*(j-N/2)/(PetscReal)N;
    561:         (*ctx->physics.sample)(ctx->physics.user,ctx->initial,ctx->bctype,ctx->xmin,ctx->xmax,time,xj,uj);
    562:         for (k=0; k<dof; k++) u[i*dof+k] += ((j==0 || j==N) ? 0.5 : 1.0)*uj[k]/N;
    563:       }
    564:     } else {
    565:       xi = ctx->xmin+(ctx->xmax-ctx->xmin)*0.75+0.5*hs+(i-count_slow/2-count_fast)*hs;
    566:       /* Integrate over cell i using trapezoid rule with N points. */
    567:       for (k=0; k<dof; k++) u[i*dof+k] = 0;
    568:       for (j=0; j<N+1; j++) {
    569:         xj = xi+hs*(j-N/2)/(PetscReal)N;
    570:         (*ctx->physics.sample)(ctx->physics.user,ctx->initial,ctx->bctype,ctx->xmin,ctx->xmax,time,xj,uj);
    571:         for (k=0; k<dof; k++) u[i*dof+k] += ((j==0 || j==N) ? 0.5 : 1.0)*uj[k]/N;
    572:       }
    573:     }
    574:   }
    575:   DMDAVecRestoreArray(da,U,&u);
    576:   PetscFree(uj);
    577:   return(0);
    578: }

    580: static PetscErrorCode SolutionStatsView(DM da,Vec X,PetscViewer viewer)
    581: {
    582:   PetscErrorCode    ierr;
    583:   PetscReal         xmin,xmax;
    584:   PetscScalar       sum,tvsum,tvgsum;
    585:   const PetscScalar *x;
    586:   PetscInt          imin,imax,Mx,i,j,xs,xm,dof;
    587:   Vec               Xloc;
    588:   PetscBool         iascii;

    591:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);
    592:   if (iascii) {
    593:     /* PETSc lacks a function to compute total variation norm (difficult in multiple dimensions), we do it here */
    594:     DMGetLocalVector(da,&Xloc);
    595:     DMGlobalToLocalBegin(da,X,INSERT_VALUES,Xloc);
    596:     DMGlobalToLocalEnd(da,X,INSERT_VALUES,Xloc);
    597:     DMDAVecGetArrayRead(da,Xloc,(void*)&x);
    598:     DMDAGetCorners(da,&xs,0,0,&xm,0,0);
    599:     DMDAGetInfo(da,0,&Mx,0,0,0,0,0,&dof,0,0,0,0,0);
    600:     tvsum = 0;
    601:     for (i=xs; i<xs+xm; i++) {
    602:       for (j=0; j<dof; j++) tvsum += PetscAbsScalar(x[i*dof+j]-x[(i-1)*dof+j]);
    603:     }
    604:     MPI_Allreduce(&tvsum,&tvgsum,1,MPIU_SCALAR,MPIU_SUM,PetscObjectComm((PetscObject)da));
    605:     DMDAVecRestoreArrayRead(da,Xloc,(void*)&x);
    606:     DMRestoreLocalVector(da,&Xloc);

    608:     VecMin(X,&imin,&xmin);
    609:     VecMax(X,&imax,&xmax);
    610:     VecSum(X,&sum);
    611:     PetscViewerASCIIPrintf(viewer,"Solution range [%g,%g] with minimum at %D, mean %g, ||x||_TV %g\n",(double)xmin,(double)xmax,imin,(double)(sum/Mx),(double)(tvgsum/Mx));
    612:   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"Viewer type not supported");
    613:   return(0);
    614: }

    616: static PetscErrorCode SolutionErrorNorms(FVCtx *ctx,DM da,PetscReal t,Vec X,PetscReal *nrm1)
    617: {
    618:   PetscErrorCode    ierr;
    619:   Vec               Y;
    620:   PetscInt          i,Mx,count_slow=0,count_fast=0;
    621:   const PetscScalar *ptr_X,*ptr_Y;

    624:   VecGetSize(X,&Mx);
    625:   VecDuplicate(X,&Y);
    626:   FVSample(ctx,da,t,Y);
    627:   const PetscReal hs = (ctx->xmax-ctx->xmin)/2.0*(ctx->hratio+1.0)/Mx;
    628:   const PetscReal hf = (ctx->xmax-ctx->xmin)/2.0*(1.0+1.0/ctx->hratio)/Mx;
    629:   count_slow = (PetscReal)Mx/(1.0+ctx->hratio);
    630:   count_fast = Mx-count_slow;
    631:   VecGetArrayRead(X,&ptr_X);
    632:   VecGetArrayRead(Y,&ptr_Y);
    633:   for (i=0; i<Mx; i++) {
    634:     if (i < count_slow/2 || i > count_slow/2+count_fast-1) *nrm1 +=  hs*PetscAbs(ptr_X[i]-ptr_Y[i]);
    635:     else *nrm1 += hf*PetscAbs(ptr_X[i]-ptr_Y[i]);
    636:   }
    637:   VecRestoreArrayRead(X,&ptr_X);
    638:   VecRestoreArrayRead(Y,&ptr_Y);
    639:   VecDestroy(&Y);
    640:   return(0);
    641: }

    643: int main(int argc,char *argv[])
    644: {
    645:   char              physname[256] = "advect",final_fname[256] = "solution.m";
    646:   PetscFunctionList physics = 0;
    647:   MPI_Comm          comm;
    648:   TS                ts;
    649:   DM                da;
    650:   Vec               X,X0,R;
    651:   FVCtx             ctx;
    652:   PetscInt          i,k,dof,xs,xm,Mx,draw = 0,count_slow,count_fast,islow = 0,ifast = 0,*index_slow,*index_fast;
    653:   PetscBool         view_final = PETSC_FALSE;
    654:   PetscReal         ptime;
    655:   PetscErrorCode    ierr;

    657:   PetscInitialize(&argc,&argv,0,help);if (ierr) return ierr;
    658:   comm = PETSC_COMM_WORLD;
    659:   PetscMemzero(&ctx,sizeof(ctx));

    661:   /* Register physical models to be available on the command line */
    662:   PetscFunctionListAdd(&physics,"advect",PhysicsCreate_Advect);

    664:   ctx.comm = comm;
    665:   ctx.cfl  = 0.9;
    666:   ctx.bctype = FVBC_PERIODIC;
    667:   ctx.xmin = -1.0;
    668:   ctx.xmax = 1.0;
    669:   PetscOptionsBegin(comm,NULL,"Finite Volume solver options","");
    670:   PetscOptionsReal("-xmin","X min","",ctx.xmin,&ctx.xmin,NULL);
    671:   PetscOptionsReal("-xmax","X max","",ctx.xmax,&ctx.xmax,NULL);
    672:   PetscOptionsInt("-draw","Draw solution vector, bitwise OR of (1=initial,2=final,4=final error)","",draw,&draw,NULL);
    673:   PetscOptionsString("-view_final","Write final solution in ASCII MATLAB format to given file name","",final_fname,final_fname,sizeof(final_fname),&view_final);
    674:   PetscOptionsInt("-initial","Initial condition (depends on the physics)","",ctx.initial,&ctx.initial,NULL);
    675:   PetscOptionsBool("-exact","Compare errors with exact solution","",ctx.exact,&ctx.exact,NULL);
    676:   PetscOptionsBool("-simulation","Compare errors with reference solution","",ctx.simulation,&ctx.simulation,NULL);
    677:   PetscOptionsReal("-cfl","CFL number to time step at","",ctx.cfl,&ctx.cfl,NULL);
    678:   PetscOptionsEnum("-bc_type","Boundary condition","",FVBCTypes,(PetscEnum)ctx.bctype,(PetscEnum*)&ctx.bctype,NULL);
    679:   PetscOptionsInt("-hratio","Spacing ratio","",ctx.hratio,&ctx.hratio,NULL);
    680:   PetscOptionsEnd();

    682:   /* Choose the physics from the list of registered models */
    683:   {
    684:     PetscErrorCode (*r)(FVCtx*);
    685:     PetscFunctionListFind(physics,physname,&r);
    686:     if (!r) SETERRQ1(PETSC_COMM_SELF,1,"Physics '%s' not found",physname);
    687:     /* Create the physics, will set the number of fields and their names */
    688:     (*r)(&ctx);
    689:   }

    691:   /* Create a DMDA to manage the parallel grid */
    692:   DMDACreate1d(comm,DM_BOUNDARY_PERIODIC,50,ctx.physics.dof,2,NULL,&da);
    693:   DMSetFromOptions(da);
    694:   DMSetUp(da);
    695:   /* Inform the DMDA of the field names provided by the physics. */
    696:   /* The names will be shown in the title bars when run with -ts_monitor_draw_solution */
    697:   for (i=0; i<ctx.physics.dof; i++) {
    698:     DMDASetFieldName(da,i,ctx.physics.fieldname[i]);
    699:   }
    700:   DMDAGetInfo(da,0,&Mx,0,0,0,0,0,&dof,0,0,0,0,0);
    701:   DMDAGetCorners(da,&xs,0,0,&xm,0,0);

    703:   /* Set coordinates of cell centers */
    704:   DMDASetUniformCoordinates(da,ctx.xmin+0.5*(ctx.xmax-ctx.xmin)/Mx,ctx.xmax+0.5*(ctx.xmax-ctx.xmin)/Mx,0,0,0,0);

    706:   /* Allocate work space for the Finite Volume solver (so it doesn't have to be reallocated on each function evaluation) */
    707:   PetscMalloc3(dof,&ctx.u,dof,&ctx.flux,dof,&ctx.speeds);

    709:   /* Create a vector to store the solution and to save the initial state */
    710:   DMCreateGlobalVector(da,&X);
    711:   VecDuplicate(X,&X0);
    712:   VecDuplicate(X,&R);

    714:   /* create index for slow parts and fast parts*/
    715:   count_slow = Mx/(1+ctx.hratio);
    716:   if (count_slow%2) SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_USER,"Please adjust grid size Mx (-da_grid_x) and hratio (-hratio) so that Mx/(1+hartio) is even");
    717:   count_fast = Mx-count_slow;
    718:   ctx.sf = count_slow/2;
    719:   ctx.fs = ctx.sf + count_fast;
    720:   PetscMalloc1(xm*dof,&index_slow);
    721:   PetscMalloc1(xm*dof,&index_fast);
    722:   for (i=xs; i<xs+xm; i++) {
    723:     if (i < count_slow/2 || i > count_slow/2+count_fast-1)
    724:       for (k=0; k<dof; k++) index_slow[islow++] = i*dof+k;
    725:     else
    726:       for (k=0; k<dof; k++) index_fast[ifast++] = i*dof+k;
    727:   }
    728:   ISCreateGeneral(PETSC_COMM_WORLD,islow,index_slow,PETSC_COPY_VALUES,&ctx.iss);
    729:   ISCreateGeneral(PETSC_COMM_WORLD,ifast,index_fast,PETSC_COPY_VALUES,&ctx.isf);

    731:   /* Create a time-stepping object */
    732:   TSCreate(comm,&ts);
    733:   TSSetDM(ts,da);
    734:   TSSetRHSFunction(ts,R,FVRHSFunction,&ctx);
    735:   TSRHSSplitSetIS(ts,"slow",ctx.iss);
    736:   TSRHSSplitSetIS(ts,"fast",ctx.isf);
    737:   TSRHSSplitSetRHSFunction(ts,"slow",NULL,FVRHSFunctionslow,&ctx);
    738:   TSRHSSplitSetRHSFunction(ts,"fast",NULL,FVRHSFunctionfast,&ctx);

    740:   TSSetType(ts,TSMPRK);
    741:   TSSetMaxTime(ts,10);
    742:   TSSetExactFinalTime(ts,TS_EXACTFINALTIME_STEPOVER);

    744:   /* Compute initial conditions and starting time step */
    745:   FVSample(&ctx,da,0,X0);
    746:   FVRHSFunction(ts,0,X0,X,(void*)&ctx); /* Initial function evaluation, only used to determine max speed */
    747:   VecCopy(X0,X);                        /* The function value was not used so we set X=X0 again */
    748:   TSSetTimeStep(ts,ctx.cfl/ctx.cfl_idt);
    749:   TSSetFromOptions(ts); /* Take runtime options */
    750:   SolutionStatsView(da,X,PETSC_VIEWER_STDOUT_WORLD);
    751:   {
    752:     PetscInt          steps;
    753:     PetscScalar       mass_initial,mass_final,mass_difference,mass_differenceg;
    754:     const PetscScalar *ptr_X,*ptr_X0;
    755:     const PetscReal   hs  = (ctx.xmax-ctx.xmin)/2.0/count_slow;
    756:     const PetscReal   hf  = (ctx.xmax-ctx.xmin)/2.0/count_fast;
    757:     TSSolve(ts,X);
    758:     TSGetSolveTime(ts,&ptime);
    759:     TSGetStepNumber(ts,&steps);
    760:     /* calculate the total mass at initial time and final time */
    761:     mass_initial = 0.0;
    762:     mass_final   = 0.0;
    763:     DMDAVecGetArrayRead(da,X0,(void*)&ptr_X0);
    764:     DMDAVecGetArrayRead(da,X,(void*)&ptr_X);
    765:     for (i=xs; i<xs+xm; i++) {
    766:       if (i < ctx.sf || i > ctx.fs-1) {
    767:         for (k=0; k<dof; k++) {
    768:           mass_initial = mass_initial+hs*ptr_X0[i*dof+k];
    769:           mass_final = mass_final+hs*ptr_X[i*dof+k];
    770:         }
    771:       } else {
    772:         for (k=0; k<dof; k++) {
    773:           mass_initial = mass_initial+hf*ptr_X0[i*dof+k];
    774:           mass_final = mass_final+hf*ptr_X[i*dof+k];
    775:         }
    776:       }
    777:     }
    778:     DMDAVecRestoreArrayRead(da,X0,(void*)&ptr_X0);
    779:     DMDAVecRestoreArrayRead(da,X,(void*)&ptr_X);
    780:     mass_difference = mass_final-mass_initial;
    781:     MPI_Allreduce(&mass_difference,&mass_differenceg,1,MPIU_SCALAR,MPIU_SUM,comm);
    782:     PetscPrintf(comm,"Mass difference %g\n",(double)mass_differenceg);
    783:     PetscPrintf(comm,"Final time %g, steps %D\n",(double)ptime,steps);
    784:     if (ctx.exact) {
    785:       PetscReal nrm1 = 0;
    786:       SolutionErrorNorms(&ctx,da,ptime,X,&nrm1);
    787:       PetscPrintf(comm,"Error ||x-x_e||_1 %g\n",(double)nrm1);
    788:     }
    789:     if (ctx.simulation) {
    790:       PetscReal         nrm1 = 0;
    791:       PetscViewer       fd;
    792:       char              filename[PETSC_MAX_PATH_LEN] = "binaryoutput";
    793:       Vec               XR;
    794:       PetscBool         flg;
    795:       const PetscScalar *ptr_XR;
    796:       PetscOptionsGetString(NULL,NULL,"-f",filename,sizeof(filename),&flg);
    797:       if (!flg) SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_USER,"Must indicate binary file with the -f option");
    798:       PetscViewerBinaryOpen(PETSC_COMM_WORLD,filename,FILE_MODE_READ,&fd);
    799:       VecDuplicate(X0,&XR);
    800:       VecLoad(XR,fd);
    801:       PetscViewerDestroy(&fd);
    802:       VecGetArrayRead(X,&ptr_X);
    803:       VecGetArrayRead(XR,&ptr_XR);
    804:       for (i=0; i<Mx; i++) {
    805:         if (i < count_slow/2 || i > count_slow/2+count_fast-1) nrm1 = nrm1 + hs*PetscAbs(ptr_X[i]-ptr_XR[i]);
    806:         else nrm1 = nrm1 + hf*PetscAbs(ptr_X[i]-ptr_XR[i]);
    807:       }
    808:       VecRestoreArrayRead(X,&ptr_X);
    809:       VecRestoreArrayRead(XR,&ptr_XR);
    810:       PetscPrintf(comm,"Error ||x-x_e||_1 %g\n",(double)nrm1);
    811:       VecDestroy(&XR);
    812:     }
    813:   }

    815:   SolutionStatsView(da,X,PETSC_VIEWER_STDOUT_WORLD);
    816:   if (draw & 0x1) { VecView(X0,PETSC_VIEWER_DRAW_WORLD); }
    817:   if (draw & 0x2) { VecView(X,PETSC_VIEWER_DRAW_WORLD); }
    818:   if (draw & 0x4) {
    819:     Vec Y;
    820:     VecDuplicate(X,&Y);
    821:     FVSample(&ctx,da,ptime,Y);
    822:     VecAYPX(Y,-1,X);
    823:     VecView(Y,PETSC_VIEWER_DRAW_WORLD);
    824:     VecDestroy(&Y);
    825:   }

    827:   if (view_final) {
    828:     PetscViewer viewer;
    829:     PetscViewerASCIIOpen(PETSC_COMM_WORLD,final_fname,&viewer);
    830:     PetscViewerPushFormat(viewer,PETSC_VIEWER_ASCII_MATLAB);
    831:     VecView(X,viewer);
    832:     PetscViewerPopFormat(viewer);
    833:     PetscViewerDestroy(&viewer);
    834:   }

    836:   /* Clean up */
    837:   (*ctx.physics.destroy)(ctx.physics.user);
    838:   for (i=0; i<ctx.physics.dof; i++) {PetscFree(ctx.physics.fieldname[i]);}
    839:   PetscFree3(ctx.u,ctx.flux,ctx.speeds);
    840:   ISDestroy(&ctx.iss);
    841:   ISDestroy(&ctx.isf);
    842:   VecDestroy(&X);
    843:   VecDestroy(&X0);
    844:   VecDestroy(&R);
    845:   DMDestroy(&da);
    846:   TSDestroy(&ts);
    847:   PetscFree(index_slow);
    848:   PetscFree(index_fast);
    849:   PetscFunctionListDestroy(&physics);
    850:   PetscFinalize();
    851:   return ierr;
    852: }

    854: /*TEST

    856:     build:
    857:       requires: !complex

    859:     test:
    860:       args: -da_grid_x 60 -initial 7 -xmin -1 -xmax 1 -hratio 2 -ts_dt 0.025 -ts_max_steps 24 -ts_type rk -ts_rk_type 2a -ts_rk_dtratio 2 -ts_rk_multirate -ts_use_splitrhsfunction 0

    862:     test:
    863:       suffix: 2
    864:       args: -da_grid_x 60 -initial 7 -xmin -1 -xmax 1 -hratio 2 -ts_dt 0.025 -ts_max_steps 24 -ts_type rk -ts_rk_type 2a -ts_rk_dtratio 2 -ts_rk_multirate -ts_use_splitrhsfunction 1
    865:       output_file: output/ex7_1.out

    867:     test:
    868:       suffix: 3
    869:       args: -da_grid_x 60 -initial 7 -xmin -1 -xmax 1 -hratio 2 -ts_dt 0.025 -ts_max_steps 24 -ts_type mprk -ts_mprk_type 2a22 -ts_use_splitrhsfunction 0

    871:     test:
    872:       suffix: 4
    873:       args: -da_grid_x 60 -initial 7 -xmin -1 -xmax 1 -hratio 2 -ts_dt 0.025 -ts_max_steps 24 -ts_type mprk -ts_mprk_type 2a22 -ts_use_splitrhsfunction 1
    874:       output_file: output/ex7_3.out

    876:     test:
    877:       suffix: 5
    878:       nsize: 2
    879:       args: -da_grid_x 60 -initial 7 -xmin -1 -xmax 1 -hratio 2 -ts_dt 0.025 -ts_max_steps 24 -ts_type mprk -ts_mprk_type 2a22 -ts_use_splitrhsfunction 1
    880:       output_file: output/ex7_3.out
    881: TEST*/