Пример #1
0
int main(int argc,char **argv)
{
  TS             ts;            /* ODE integrator */
  Vec            Y;             /* solution will be stored here */
  Mat            A;             /* Jacobian matrix */
  PetscErrorCode ierr;
  PetscMPIInt    size;
  PetscInt       n = 6;
  PetscScalar    *y;
 
  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     Initialize program
     - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  ierr = PetscInitialize(&argc,&argv,(char*)0,help);CHKERRQ(ierr);
  ierr = MPI_Comm_size(PETSC_COMM_WORLD,&size);CHKERRQ(ierr);
  if (size > 1) SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_SUP,"Only for sequential runs");

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    Create necessary matrix and vectors
    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  ierr = MatCreate(PETSC_COMM_WORLD,&A);CHKERRQ(ierr);
  ierr = MatSetSizes(A,n,n,PETSC_DETERMINE,PETSC_DETERMINE);CHKERRQ(ierr);
  ierr = MatSetFromOptions(A);CHKERRQ(ierr);
  ierr = MatSetUp(A);CHKERRQ(ierr);

  ierr = MatCreateVecs(A,&Y,PETSC_NULL);CHKERRQ(ierr);

  ierr = VecGetArray(Y,&y);CHKERRQ(ierr);
  y[0] = 0.0;
  y[1] = 3.0;
  y[2] = y[1];
  y[3] = 6.0;
  y[4] = 0.0;
  y[5] = 0.0;
  ierr = VecRestoreArray(Y,&y);CHKERRQ(ierr);
  
  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     Create timestepping solver context
     - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  ierr = TSCreate(PETSC_COMM_WORLD,&ts);CHKERRQ(ierr);
  ierr = TSSetProblemType(ts,TS_NONLINEAR);CHKERRQ(ierr);
  ierr = TSSetType(ts,TSARKIMEX);CHKERRQ(ierr);
  ierr = TSSetEquationType(ts,TS_EQ_DAE_IMPLICIT_INDEX1);CHKERRQ(ierr);
  ierr = TSARKIMEXSetFullyImplicit(ts,PETSC_TRUE);CHKERRQ(ierr);
  /*ierr = TSSetType(ts,TSROSW);CHKERRQ(ierr);*/
  ierr = TSSetIFunction(ts,PETSC_NULL,IFunctionImplicit,PETSC_NULL);CHKERRQ(ierr);
  ierr = TSSetIJacobian(ts,A,A,IJacobianImplicit,PETSC_NULL);CHKERRQ(ierr);

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     Set initial conditions
   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  ierr = TSSetSolution(ts,Y);CHKERRQ(ierr);

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     Set solver options
   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  ierr = TSSetDuration(ts,100000,0.15);CHKERRQ(ierr);
  ierr = TSSetInitialTimeStep(ts,0.0,.001);CHKERRQ(ierr);
  ierr = TSSetFromOptions(ts);CHKERRQ(ierr);

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     Do Time stepping
     - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  ierr = TSSolve(ts,Y);CHKERRQ(ierr);
  
  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     Free work space.  All PETSc objects should be destroyed when they are no longer needed.
   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  ierr = MatDestroy(&A);CHKERRQ(ierr);
  ierr = VecDestroy(&Y);CHKERRQ(ierr);
  ierr = TSDestroy(&ts);CHKERRQ(ierr);

  ierr = PetscFinalize();
  return(0);
}
Пример #2
0
int main(int argc,char **argv)
{
  TS                ts;         /* time integrator */
  TSAdapt           adapt;
  Vec               X;          /* solution vector */
  Mat               J;          /* Jacobian matrix */
  PetscInt          steps,maxsteps,ncells,xs,xm,i;
  PetscErrorCode    ierr;
  PetscReal         ftime,dt;
  char              chemfile[PETSC_MAX_PATH_LEN] = "chem.inp",thermofile[PETSC_MAX_PATH_LEN] = "therm.dat";
  struct _User      user;
  TSConvergedReason reason;
  PetscBool         showsolutions = PETSC_FALSE;
  char              **snames,*names;
  Vec               lambda;     /* used with TSAdjoint for sensitivities */

  ierr = PetscInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
  ierr = PetscOptionsBegin(PETSC_COMM_WORLD,NULL,"Chemistry solver options","");CHKERRQ(ierr);
  ierr = PetscOptionsString("-chem","CHEMKIN input file","",chemfile,chemfile,sizeof(chemfile),NULL);CHKERRQ(ierr);
  ierr = PetscOptionsString("-thermo","NASA thermo input file","",thermofile,thermofile,sizeof(thermofile),NULL);CHKERRQ(ierr);
  user.pressure = 1.01325e5;    /* Pascal */
  ierr = PetscOptionsReal("-pressure","Pressure of reaction [Pa]","",user.pressure,&user.pressure,NULL);CHKERRQ(ierr);
  user.Tini   = 1550;
  ierr = PetscOptionsReal("-Tini","Initial temperature [K]","",user.Tini,&user.Tini,NULL);CHKERRQ(ierr);
  user.diffus = 100;
  ierr = PetscOptionsReal("-diffus","Diffusion constant","",user.diffus,&user.diffus,NULL);CHKERRQ(ierr);
  ierr = PetscOptionsBool("-draw_solution","Plot the solution for each cell","",showsolutions,&showsolutions,NULL);CHKERRQ(ierr);
  user.diffusion = PETSC_TRUE;
  ierr = PetscOptionsBool("-diffusion","Have diffusion","",user.diffusion,&user.diffusion,NULL);CHKERRQ(ierr);
  user.reactions = PETSC_TRUE;
  ierr = PetscOptionsBool("-reactions","Have reactions","",user.reactions,&user.reactions,NULL);CHKERRQ(ierr);
  ierr = PetscOptionsEnd();CHKERRQ(ierr);

  ierr = TC_initChem(chemfile, thermofile, 0, 1.0);TCCHKERRQ(ierr);
  user.Nspec = TC_getNspec();
  user.Nreac = TC_getNreac();

  ierr    = DMDACreate1d(PETSC_COMM_WORLD,DM_BOUNDARY_PERIODIC,-1,user.Nspec+1,1,NULL,&user.dm);CHKERRQ(ierr);
  ierr    = DMDAGetInfo(user.dm,NULL,&ncells,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL);CHKERRQ(ierr);
  user.dx = 1.0/ncells;  /* Set the coordinates of the cell centers; note final ghost cell is at x coordinate 1.0 */
  ierr    = DMDASetUniformCoordinates(user.dm,0.0,1.0,0.0,1.0,0.0,1.0);CHKERRQ(ierr);

  /* set the names of each field in the DMDA based on the species name */
  ierr = PetscMalloc1((user.Nspec+1)*LENGTHOFSPECNAME,&names);CHKERRQ(ierr);
  ierr = PetscStrcpy(names,"Temp");CHKERRQ(ierr);
  TC_getSnames(user.Nspec,names+LENGTHOFSPECNAME);CHKERRQ(ierr);
  ierr = PetscMalloc1((user.Nspec+2),&snames);CHKERRQ(ierr);
  for (i=0; i<user.Nspec+1; i++) snames[i] = names+i*LENGTHOFSPECNAME;
  snames[user.Nspec+1] = NULL;
  ierr = DMDASetFieldNames(user.dm,(const char * const *)snames);CHKERRQ(ierr);
  ierr = PetscFree(snames);CHKERRQ(ierr);
  ierr = PetscFree(names);CHKERRQ(ierr);


  ierr = DMCreateMatrix(user.dm,&J);CHKERRQ(ierr);
  ierr = DMCreateGlobalVector(user.dm,&X);CHKERRQ(ierr);

  ierr = PetscMalloc3(user.Nspec+1,&user.tchemwork,PetscSqr(user.Nspec+1),&user.Jdense,user.Nspec+1,&user.rows);CHKERRQ(ierr);

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     Create timestepping solver context
     - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  ierr = TSCreate(PETSC_COMM_WORLD,&ts);CHKERRQ(ierr);
  ierr = TSSetDM(ts,user.dm);CHKERRQ(ierr);
  ierr = TSSetType(ts,TSARKIMEX);CHKERRQ(ierr);
  ierr = TSARKIMEXSetFullyImplicit(ts,PETSC_TRUE);CHKERRQ(ierr);
  ierr = TSARKIMEXSetType(ts,TSARKIMEX4);CHKERRQ(ierr);
  ierr = TSSetRHSFunction(ts,NULL,FormRHSFunction,&user);CHKERRQ(ierr);
  ierr = TSSetRHSJacobian(ts,J,J,FormRHSJacobian,&user);CHKERRQ(ierr);

  ftime    = 1.0;
  maxsteps = 10000;
  ierr     = TSSetDuration(ts,maxsteps,ftime);CHKERRQ(ierr);
  ierr     = TSSetExactFinalTime(ts,TS_EXACTFINALTIME_STEPOVER);CHKERRQ(ierr);

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     Set initial conditions
   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  ierr = FormInitialSolution(ts,X,&user);CHKERRQ(ierr);
  ierr = TSSetSolution(ts,X);CHKERRQ(ierr);
  dt   = 1e-10;                 /* Initial time step */
  ierr = TSSetInitialTimeStep(ts,0.0,dt);CHKERRQ(ierr);
  ierr = TSGetAdapt(ts,&adapt);CHKERRQ(ierr);
  ierr = TSAdaptSetStepLimits(adapt,1e-12,1e-4);CHKERRQ(ierr); /* Also available with -ts_adapt_dt_min/-ts_adapt_dt_max */
  ierr = TSSetMaxSNESFailures(ts,-1);CHKERRQ(ierr);            /* Retry step an unlimited number of times */


  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     Pass information to graphical monitoring routine
   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  if (showsolutions) {
    ierr = DMDAGetCorners(user.dm,&xs,NULL,NULL,&xm,NULL,NULL);CHKERRQ(ierr);
    for (i=xs;i<xs+xm;i++) {
      ierr = MonitorCell(ts,&user,i);CHKERRQ(ierr);
    }
  }

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     Set runtime options
   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  ierr = TSSetFromOptions(ts);CHKERRQ(ierr);

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     Set final conditions for sensitivities
   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  ierr = DMCreateGlobalVector(user.dm,&lambda);CHKERRQ(ierr);
  ierr = TSSetCostGradients(ts,1,&lambda,NULL);CHKERRQ(ierr);
  ierr = VecSetValue(lambda,0,1.0,INSERT_VALUES);CHKERRQ(ierr);
  ierr = VecAssemblyBegin(lambda);CHKERRQ(ierr);
  ierr = VecAssemblyEnd(lambda);CHKERRQ(ierr);

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     Solve ODE
     - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  ierr = TSSolve(ts,X);CHKERRQ(ierr);
  ierr = TSGetSolveTime(ts,&ftime);CHKERRQ(ierr);
  ierr = TSGetTimeStepNumber(ts,&steps);CHKERRQ(ierr);
  ierr = TSGetConvergedReason(ts,&reason);CHKERRQ(ierr);
  ierr = PetscPrintf(PETSC_COMM_WORLD,"%s at time %g after %D steps\n",TSConvergedReasons[reason],(double)ftime,steps);CHKERRQ(ierr);

  {
    Vec                max;
    const char * const *names;
    PetscInt           i;
    const PetscReal    *bmax;

    ierr = TSMonitorEnvelopeGetBounds(ts,&max,NULL);CHKERRQ(ierr);
    if (max) {
      ierr = TSMonitorLGGetVariableNames(ts,&names);CHKERRQ(ierr);
      if (names) {
        ierr = VecGetArrayRead(max,&bmax);CHKERRQ(ierr);
        ierr = PetscPrintf(PETSC_COMM_SELF,"Species - maximum mass fraction\n");CHKERRQ(ierr);
        for (i=1; i<user.Nspec; i++) {
          if (bmax[i] > .01) {ierr = PetscPrintf(PETSC_COMM_SELF,"%s %g\n",names[i],bmax[i]);CHKERRQ(ierr);}
        }
        ierr = VecRestoreArrayRead(max,&bmax);CHKERRQ(ierr);
      }
    }
  }

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     Free work space.
   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  TC_reset();
  ierr = DMDestroy(&user.dm);CHKERRQ(ierr);
  ierr = MatDestroy(&J);CHKERRQ(ierr);
  ierr = VecDestroy(&X);CHKERRQ(ierr);
  ierr = VecDestroy(&lambda);CHKERRQ(ierr);
  ierr = TSDestroy(&ts);CHKERRQ(ierr);
  ierr = PetscFree3(user.tchemwork,user.Jdense,user.rows);CHKERRQ(ierr);
  ierr = PetscFinalize();
  return ierr;
}
Пример #3
0
int main(int argc,char **argv)
{
  TS             ts;
  SNES           snes_alg;
  PetscErrorCode ierr;
  PetscMPIInt    size;
  Userctx        user;
  PetscViewer    Xview,Ybusview;
  Vec            X;
  Mat            J;
  PetscInt       i;

  ierr = PetscInitialize(&argc,&argv,"petscoptions",help);CHKERRQ(ierr);
  ierr = MPI_Comm_size(PETSC_COMM_WORLD,&size);CHKERRQ(ierr);
  if (size > 1) SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_SUP,"Only for sequential runs");

  user.neqs_gen   = 9*ngen; /* # eqs. for generator subsystem */
  user.neqs_net   = 2*nbus; /* # eqs. for network subsystem   */
  user.neqs_pgrid = user.neqs_gen + user.neqs_net;

  /* Create indices for differential and algebraic equations */
  PetscInt *idx2;
  ierr = PetscMalloc1(7*ngen,&idx2);CHKERRQ(ierr);
  for (i=0; i<ngen; i++) {
    idx2[7*i]   = 9*i;   idx2[7*i+1] = 9*i+1; idx2[7*i+2] = 9*i+2; idx2[7*i+3] = 9*i+3;
    idx2[7*i+4] = 9*i+6; idx2[7*i+5] = 9*i+7; idx2[7*i+6] = 9*i+8;
  }
  ierr = ISCreateGeneral(PETSC_COMM_WORLD,7*ngen,idx2,PETSC_COPY_VALUES,&user.is_diff);CHKERRQ(ierr);
  ierr = ISComplement(user.is_diff,0,user.neqs_pgrid,&user.is_alg);CHKERRQ(ierr);
  ierr = PetscFree(idx2);CHKERRQ(ierr);

  /* Read initial voltage vector and Ybus */
  ierr = PetscViewerBinaryOpen(PETSC_COMM_WORLD,"X.bin",FILE_MODE_READ,&Xview);CHKERRQ(ierr);
  ierr = PetscViewerBinaryOpen(PETSC_COMM_WORLD,"Ybus.bin",FILE_MODE_READ,&Ybusview);CHKERRQ(ierr);

  ierr = VecCreate(PETSC_COMM_WORLD,&user.V0);CHKERRQ(ierr);
  ierr = VecSetSizes(user.V0,PETSC_DECIDE,user.neqs_net);CHKERRQ(ierr);
  ierr = VecLoad(user.V0,Xview);CHKERRQ(ierr);

  ierr = MatCreate(PETSC_COMM_WORLD,&user.Ybus);CHKERRQ(ierr);
  ierr = MatSetSizes(user.Ybus,PETSC_DECIDE,PETSC_DECIDE,user.neqs_net,user.neqs_net);CHKERRQ(ierr);
  ierr = MatSetType(user.Ybus,MATBAIJ);CHKERRQ(ierr);
  /*  ierr = MatSetBlockSize(user.Ybus,2);CHKERRQ(ierr); */
  ierr = MatLoad(user.Ybus,Ybusview);CHKERRQ(ierr);

  /* Set run time options */
  ierr = PetscOptionsBegin(PETSC_COMM_WORLD,NULL,"Transient stability fault options","");CHKERRQ(ierr);
  {
    user.tfaulton  = 1.0;
    user.tfaultoff = 1.2;
    user.Rfault    = 0.0001;
    user.faultbus  = 8;
    ierr           = PetscOptionsReal("-tfaulton","","",user.tfaulton,&user.tfaulton,NULL);CHKERRQ(ierr);
    ierr           = PetscOptionsReal("-tfaultoff","","",user.tfaultoff,&user.tfaultoff,NULL);CHKERRQ(ierr);
    ierr           = PetscOptionsInt("-faultbus","","",user.faultbus,&user.faultbus,NULL);CHKERRQ(ierr);
    user.t0        = 0.0;
    user.tmax      = 5.0;
    ierr           = PetscOptionsReal("-t0","","",user.t0,&user.t0,NULL);CHKERRQ(ierr);
    ierr           = PetscOptionsReal("-tmax","","",user.tmax,&user.tmax,NULL);CHKERRQ(ierr);
  }
  ierr = PetscOptionsEnd();CHKERRQ(ierr);

  ierr = PetscViewerDestroy(&Xview);CHKERRQ(ierr);
  ierr = PetscViewerDestroy(&Ybusview);CHKERRQ(ierr);

  /* Create DMs for generator and network subsystems */
  ierr = DMDACreate1d(PETSC_COMM_WORLD,DM_BOUNDARY_NONE,user.neqs_gen,1,1,NULL,&user.dmgen);CHKERRQ(ierr);
  ierr = DMSetOptionsPrefix(user.dmgen,"dmgen_");CHKERRQ(ierr);
  ierr = DMDACreate1d(PETSC_COMM_WORLD,DM_BOUNDARY_NONE,user.neqs_net,1,1,NULL,&user.dmnet);CHKERRQ(ierr);
  ierr = DMSetOptionsPrefix(user.dmnet,"dmnet_");CHKERRQ(ierr);
  /* Create a composite DM packer and add the two DMs */
  ierr = DMCompositeCreate(PETSC_COMM_WORLD,&user.dmpgrid);CHKERRQ(ierr);
  ierr = DMSetOptionsPrefix(user.dmpgrid,"pgrid_");CHKERRQ(ierr);
  ierr = DMCompositeAddDM(user.dmpgrid,user.dmgen);CHKERRQ(ierr);
  ierr = DMCompositeAddDM(user.dmpgrid,user.dmnet);CHKERRQ(ierr);

  ierr = DMCreateGlobalVector(user.dmpgrid,&X);CHKERRQ(ierr);

  ierr = MatCreate(PETSC_COMM_WORLD,&J);CHKERRQ(ierr);
  ierr = MatSetSizes(J,PETSC_DECIDE,PETSC_DECIDE,user.neqs_pgrid,user.neqs_pgrid);CHKERRQ(ierr);
  ierr = MatSetFromOptions(J);CHKERRQ(ierr);
  ierr = PreallocateJacobian(J,&user);CHKERRQ(ierr);

  /* Create matrix to save solutions at each time step */
  user.stepnum = 0;

  ierr = MatCreateSeqDense(PETSC_COMM_SELF,user.neqs_pgrid+1,1002,NULL,&user.Sol);CHKERRQ(ierr);
  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     Create timestepping solver context
     - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  ierr = TSCreate(PETSC_COMM_WORLD,&ts);CHKERRQ(ierr);
  ierr = TSSetProblemType(ts,TS_NONLINEAR);CHKERRQ(ierr);
  ierr = TSSetEquationType(ts,TS_EQ_DAE_IMPLICIT_INDEX1);CHKERRQ(ierr);
  ierr = TSARKIMEXSetFullyImplicit(ts,PETSC_TRUE);CHKERRQ(ierr);
  ierr = TSSetIFunction(ts,NULL,(TSIFunction) IFunction,&user);CHKERRQ(ierr);
  ierr = TSSetIJacobian(ts,J,J,(TSIJacobian)IJacobian,&user);CHKERRQ(ierr);
  ierr = TSSetApplicationContext(ts,&user);CHKERRQ(ierr);

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     Set initial conditions
   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  ierr = SetInitialGuess(X,&user);CHKERRQ(ierr);
  /* Just to set up the Jacobian structure */
  Vec          Xdot;
  MatStructure flg;
  ierr = VecDuplicate(X,&Xdot);CHKERRQ(ierr);
  ierr = IJacobian(ts,0.0,X,Xdot,0.0,J,J,&flg,&user);CHKERRQ(ierr);
  ierr = VecDestroy(&Xdot);CHKERRQ(ierr);

  /* Save initial solution */
  PetscScalar *x,*mat;
  PetscInt idx=user.stepnum*(user.neqs_pgrid+1);
  ierr = MatDenseGetArray(user.Sol,&mat);CHKERRQ(ierr);
  ierr = VecGetArray(X,&x);CHKERRQ(ierr);

  mat[idx] = 0.0;

  ierr = PetscMemcpy(mat+idx+1,x,user.neqs_pgrid*sizeof(PetscScalar));CHKERRQ(ierr);
  ierr = MatDenseRestoreArray(user.Sol,&mat);CHKERRQ(ierr);
  ierr = VecRestoreArray(X,&x);CHKERRQ(ierr);
  user.stepnum++;

  ierr = TSSetDuration(ts,1000,user.tfaulton);CHKERRQ(ierr);
  ierr = TSSetInitialTimeStep(ts,0.0,0.01);CHKERRQ(ierr);
  ierr = TSSetFromOptions(ts);CHKERRQ(ierr);
  ierr = TSSetPostStep(ts,SaveSolution);CHKERRQ(ierr);

  user.alg_flg = PETSC_FALSE;
  /* Prefault period */
  ierr = TSSolve(ts,X);CHKERRQ(ierr);

  /* Create the nonlinear solver for solving the algebraic system */
  /* Note that although the algebraic system needs to be solved only for
     Idq and V, we reuse the entire system including xgen. The xgen
     variables are held constant by setting their residuals to 0 and
     putting a 1 on the Jacobian diagonal for xgen rows
  */
  Vec F_alg;
  ierr = VecDuplicate(X,&F_alg);CHKERRQ(ierr);
  ierr = SNESCreate(PETSC_COMM_WORLD,&snes_alg);CHKERRQ(ierr);
  ierr = SNESSetFunction(snes_alg,F_alg,AlgFunction,&user);CHKERRQ(ierr);
  ierr = MatZeroEntries(J);CHKERRQ(ierr);
  ierr = SNESSetJacobian(snes_alg,J,J,AlgJacobian,&user);CHKERRQ(ierr);
  ierr = SNESSetOptionsPrefix(snes_alg,"alg_");CHKERRQ(ierr);
  ierr = SNESSetFromOptions(snes_alg);CHKERRQ(ierr);

  /* Apply disturbance - resistive fault at user.faultbus */
  /* This is done by adding shunt conductance to the diagonal location
     in the Ybus matrix */
  PetscInt    row_loc,col_loc;
  PetscScalar val;
  row_loc = 2*user.faultbus; col_loc = 2*user.faultbus+1; /* Location for G */
  val     = 1/user.Rfault;
  ierr    = MatSetValues(user.Ybus,1,&row_loc,1,&col_loc,&val,ADD_VALUES);CHKERRQ(ierr);
  row_loc = 2*user.faultbus+1; col_loc = 2*user.faultbus; /* Location for G */
  val     = 1/user.Rfault;
  ierr    = MatSetValues(user.Ybus,1,&row_loc,1,&col_loc,&val,ADD_VALUES);CHKERRQ(ierr);

  ierr = MatAssemblyBegin(user.Ybus,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatAssemblyEnd(user.Ybus,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);

  user.alg_flg = PETSC_TRUE;
  /* Solve the algebraic equations */
  ierr = SNESSolve(snes_alg,NULL,X);CHKERRQ(ierr);

  /* Save fault-on solution */
  idx      = user.stepnum*(user.neqs_pgrid+1);
  ierr     = MatDenseGetArray(user.Sol,&mat);CHKERRQ(ierr);
  ierr     = VecGetArray(X,&x);CHKERRQ(ierr);
  mat[idx] = user.tfaulton;
  ierr     = PetscMemcpy(mat+idx+1,x,user.neqs_pgrid*sizeof(PetscScalar));CHKERRQ(ierr);
  ierr     = MatDenseRestoreArray(user.Sol,&mat);CHKERRQ(ierr);
  ierr     = VecRestoreArray(X,&x);CHKERRQ(ierr);
  user.stepnum++;

  /* Disturbance period */
  ierr = TSSetDuration(ts,1000,user.tfaultoff);CHKERRQ(ierr);
  ierr = TSSetInitialTimeStep(ts,user.tfaulton,.01);CHKERRQ(ierr);

  user.alg_flg = PETSC_FALSE;

  ierr = TSSolve(ts,X);CHKERRQ(ierr);

  /* Remove the fault */
  row_loc = 2*user.faultbus; col_loc = 2*user.faultbus+1;
  val     = -1/user.Rfault;
  ierr    = MatSetValues(user.Ybus,1,&row_loc,1,&col_loc,&val,ADD_VALUES);CHKERRQ(ierr);
  row_loc = 2*user.faultbus+1; col_loc = 2*user.faultbus;
  val     = -1/user.Rfault;
  ierr    = MatSetValues(user.Ybus,1,&row_loc,1,&col_loc,&val,ADD_VALUES);CHKERRQ(ierr);

  ierr = MatAssemblyBegin(user.Ybus,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatAssemblyEnd(user.Ybus,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);

  ierr = MatZeroEntries(J);CHKERRQ(ierr);

  user.alg_flg = PETSC_TRUE;

  /* Solve the algebraic equations */
  ierr = SNESSolve(snes_alg,NULL,X);CHKERRQ(ierr);

  /* Save tfault off solution */
  idx      = user.stepnum*(user.neqs_pgrid+1);
  ierr     = MatDenseGetArray(user.Sol,&mat);CHKERRQ(ierr);
  ierr     = VecGetArray(X,&x);CHKERRQ(ierr);
  mat[idx] = user.tfaultoff;
  ierr     = PetscMemcpy(mat+idx+1,x,user.neqs_pgrid*sizeof(PetscScalar));CHKERRQ(ierr);
  ierr     = MatDenseRestoreArray(user.Sol,&mat);CHKERRQ(ierr);
  ierr     = VecRestoreArray(X,&x);CHKERRQ(ierr);
  user.stepnum++;

  /* Post-disturbance period */
  ierr = TSSetDuration(ts,1000,user.tmax);CHKERRQ(ierr);
  ierr = TSSetInitialTimeStep(ts,user.tfaultoff,.01);CHKERRQ(ierr);

  user.alg_flg = PETSC_TRUE;

  ierr = TSSolve(ts,X);CHKERRQ(ierr);

  ierr = MatAssemblyBegin(user.Sol,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatAssemblyEnd(user.Sol,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);

  Mat         A;
  PetscScalar *amat;
  ierr = MatCreateSeqDense(PETSC_COMM_SELF,user.neqs_pgrid+1,user.stepnum,NULL,&A);CHKERRQ(ierr);
  ierr = MatDenseGetArray(user.Sol,&mat);CHKERRQ(ierr);
  ierr = MatDenseGetArray(A,&amat);CHKERRQ(ierr);
  ierr = PetscMemcpy(amat,mat,(user.stepnum*(user.neqs_pgrid+1))*sizeof(PetscScalar));CHKERRQ(ierr);
  ierr = MatDenseRestoreArray(A,&amat);CHKERRQ(ierr);
  ierr = MatDenseRestoreArray(user.Sol,&mat);CHKERRQ(ierr);
  PetscViewer viewer;
  ierr = PetscViewerBinaryOpen(PETSC_COMM_SELF,"out.bin",FILE_MODE_WRITE,&viewer);CHKERRQ(ierr);
  ierr = MatView(A,viewer);CHKERRQ(ierr);
  ierr = PetscViewerDestroy(&viewer);CHKERRQ(ierr);
  ierr = MatDestroy(&A);CHKERRQ(ierr);
  ierr = SNESDestroy(&snes_alg);CHKERRQ(ierr);
  ierr = VecDestroy(&F_alg);CHKERRQ(ierr);
  ierr = MatDestroy(&J);CHKERRQ(ierr);
  ierr = MatDestroy(&user.Ybus);CHKERRQ(ierr);
  ierr = MatDestroy(&user.Sol);CHKERRQ(ierr);
  ierr = VecDestroy(&X);CHKERRQ(ierr);
  ierr = VecDestroy(&user.V0);CHKERRQ(ierr);
  ierr = DMDestroy(&user.dmgen);CHKERRQ(ierr);
  ierr = DMDestroy(&user.dmnet);CHKERRQ(ierr);
  ierr = DMDestroy(&user.dmpgrid);CHKERRQ(ierr);
  ierr = ISDestroy(&user.is_diff);CHKERRQ(ierr);
  ierr = ISDestroy(&user.is_alg);CHKERRQ(ierr);
  ierr = TSDestroy(&ts);CHKERRQ(ierr);
  ierr = PetscFinalize();
  return(0);
}