Actual source code: ex47cu.cu

petsc-3.5.2 2014-09-08
Report Typos and Errors
  1: static char help[] = "Solves -Laplacian u - exp(u) = 0,  0 < x < 1 using GPU\n\n";
  2: /*
  3:    Same as ex47.c except it also uses the GPU to evaluate the function
  4: */

  6: #include <petscdm.h>
  7: #include <petscdmda.h>
  8: #include <petscsnes.h>
  9: #include <petsccusp.h>

 11: #include <thrust/for_each.h>
 12: #include <thrust/tuple.h>
 13: #include <thrust/iterator/constant_iterator.h>
 14: #include <thrust/iterator/counting_iterator.h>
 15: #include <thrust/iterator/zip_iterator.h>

 17: extern PetscErrorCode ComputeFunction(SNES,Vec,Vec,void*), ComputeJacobian(SNES,Vec,Mat,Mat,void*);
 18: PetscBool useCUSP = PETSC_FALSE;

 20: int main(int argc,char **argv)
 21: {
 22:   SNES           snes;
 23:   Vec            x,f;
 24:   Mat            J;
 25:   DM             da;
 27:   char           *tmp,typeName[256];
 28:   PetscBool      flg;

 30:   PetscInitialize(&argc,&argv,(char*)0,help);
 31:   PetscOptionsGetString(NULL,"-dm_vec_type",typeName,256,&flg);
 32:   if (flg) {
 33:     PetscStrstr(typeName,"cusp",&tmp);
 34:     if (tmp) useCUSP = PETSC_TRUE;
 35:   }

 37:   DMDACreate1d(PETSC_COMM_WORLD,DM_BOUNDARY_NONE,-8,1,1,NULL,&da);
 38:   DMCreateGlobalVector(da,&x); VecDuplicate(x,&f);
 39:   DMSetMatType(da,MATAIJ);
 40:   DMCreateMatrix(da,&J);

 42:   SNESCreate(PETSC_COMM_WORLD,&snes);
 43:   SNESSetFunction(snes,f,ComputeFunction,da);
 44:   SNESSetJacobian(snes,J,J,ComputeJacobian,da);
 45:   SNESSetFromOptions(snes);
 46:   SNESSolve(snes,NULL,x);

 48:   MatDestroy(&J);
 49:   VecDestroy(&x);
 50:   VecDestroy(&f);
 51:   SNESDestroy(&snes);
 52:   DMDestroy(&da);

 54:   PetscFinalize();
 55:   return 0;
 56: }

 58: struct ApplyStencil
 59: {
 60:   template <typename Tuple>
 61:   __host__ __device__
 62:   void operator()(Tuple t)
 63:   {
 64:     /* f = (2*x_i - x_(i+1) - x_(i-1))/h - h*exp(x_i) */
 65:     thrust::get<0>(t) = 1;
 66:     if ((thrust::get<4>(t) > 0) && (thrust::get<4>(t) < thrust::get<5>(t)-1)) {
 67:       thrust::get<0>(t) = (2.0*thrust::get<1>(t) - thrust::get<2>(t) - thrust::get<3>(t)) / (thrust::get<6>(t)) - (thrust::get<6>(t))*exp(thrust::get<1>(t));
 68:     } else if (thrust::get<4>(t) == 0) {
 69:       thrust::get<0>(t) = thrust::get<1>(t) / (thrust::get<6>(t));
 70:     } else if (thrust::get<4>(t) == thrust::get<5>(t)-1) {
 71:       thrust::get<0>(t) = thrust::get<1>(t) / (thrust::get<6>(t));
 72:     }
 73:   }
 74: };

 76: PetscErrorCode ComputeFunction(SNES snes,Vec x,Vec f,void *ctx)
 77: {
 78:   PetscInt       i,Mx,xs,xm,xstartshift,xendshift,fstart,lsize;
 79:   PetscScalar    *xx,*ff,hx;
 80:   DM             da = (DM) ctx;
 81:   Vec            xlocal;
 83:   PetscMPIInt    rank,size;
 84:   MPI_Comm       comm;
 85:   cusp::array1d<PetscScalar,cusp::device_memory> *xarray,*farray;

 87:   DMDAGetInfo(da,PETSC_IGNORE,&Mx,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE);
 88:   hx   = 1.0/(PetscReal)(Mx-1);
 89:   DMGetLocalVector(da,&xlocal);
 90:   DMGlobalToLocalBegin(da,x,INSERT_VALUES,xlocal);
 91:   DMGlobalToLocalEnd(da,x,INSERT_VALUES,xlocal);

 93:   if (useCUSP) {
 94:     VecCUSPGetArrayRead(xlocal,&xarray);
 95:     VecCUSPGetArrayWrite(f,&farray);
 96:     PetscObjectGetComm((PetscObject)da,&comm);
 97:     MPI_Comm_size(comm,&size);
 98:     MPI_Comm_rank(comm,&rank);
 99:     if (rank) xstartshift = 1;
100:     else xstartshift = 0;
101:     if (rank != size-1) xendshift = 1;
102:     else xendshift = 0;
103:     VecGetOwnershipRange(f,&fstart,NULL);
104:     VecGetLocalSize(x,&lsize);
105:     try {
106:       thrust::for_each(
107:         thrust::make_zip_iterator(
108:           thrust::make_tuple(
109:             farray->begin(),
110:             xarray->begin()+xstartshift,
111:             xarray->begin()+xstartshift + 1,
112:             xarray->begin()+xstartshift - 1,
113:             thrust::counting_iterator<int>(fstart),
114:             thrust::constant_iterator<int>(Mx),
115:             thrust::constant_iterator<PetscScalar>(hx))),
116:         thrust::make_zip_iterator(
117:           thrust::make_tuple(
118:             farray->end(),
119:             xarray->end()-xendshift,
120:             xarray->end()-xendshift + 1,
121:             xarray->end()-xendshift - 1,
122:             thrust::counting_iterator<int>(fstart) + lsize,
123:             thrust::constant_iterator<int>(Mx),
124:             thrust::constant_iterator<PetscScalar>(hx))),
125:         ApplyStencil());
126:     }
127:     catch (char *all) {
128:       PetscPrintf(PETSC_COMM_WORLD, "Thrust is not working\n");
129:     }
130:     VecCUSPRestoreArrayRead(xlocal,&xarray);
131:     VecCUSPRestoreArrayWrite(f,&farray);
132:   } else {
133:     DMDAVecGetArray(da,xlocal,&xx);
134:     DMDAVecGetArray(da,f,&ff);
135:     DMDAGetCorners(da,&xs,NULL,NULL,&xm,NULL,NULL);

137:     for (i=xs; i<xs+xm; i++) {
138:       if (i == 0 || i == Mx-1) ff[i] = xx[i]/hx;
139:       else ff[i] =  (2.0*xx[i] - xx[i-1] - xx[i+1])/hx - hx*PetscExpScalar(xx[i]);
140:     }
141:     DMDAVecRestoreArray(da,xlocal,&xx);
142:     DMDAVecRestoreArray(da,f,&ff);
143:   }
144:   DMRestoreLocalVector(da,&xlocal);
145:   //  VecView(x,0);printf("f\n");
146:   //  VecView(f,0);
147:   return 0;

149: }
150: PetscErrorCode ComputeJacobian(SNES snes,Vec x,Mat J,Mat B,void *ctx)
151: {
152:   DM             da = (DM) ctx;
153:   PetscInt       i,Mx,xm,xs;
154:   PetscScalar    hx,*xx;
155:   Vec            xlocal;

158:   DMDAGetInfo(da,PETSC_IGNORE,&Mx,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE,PETSC_IGNORE);
159:   hx   = 1.0/(PetscReal)(Mx-1);
160:   DMGetLocalVector(da,&xlocal);DMGlobalToLocalBegin(da,x,INSERT_VALUES,xlocal);
161:   DMGlobalToLocalEnd(da,x,INSERT_VALUES,xlocal);
162:   DMDAVecGetArray(da,xlocal,&xx);
163:   DMDAGetCorners(da,&xs,NULL,NULL,&xm,NULL,NULL);

165:   for (i=xs; i<xs+xm; i++) {
166:     if (i == 0 || i == Mx-1) {
167:       MatSetValue(J,i,i,1.0/hx,INSERT_VALUES);
168:     } else {
169:       MatSetValue(J,i,i-1,-1.0/hx,INSERT_VALUES);
170:       MatSetValue(J,i,i,2.0/hx - hx*PetscExpScalar(xx[i]),INSERT_VALUES);
171:       MatSetValue(J,i,i+1,-1.0/hx,INSERT_VALUES);
172:     }
173:   }
174:   MatAssemblyBegin(J,MAT_FINAL_ASSEMBLY);
175:   MatAssemblyEnd(J,MAT_FINAL_ASSEMBLY);
176:   DMDAVecRestoreArray(da,xlocal,&xx);
177:   DMRestoreLocalVector(da,&xlocal);
178:   return 0;
179: }