Actual source code: ex27.c

petsc-3.4.2 2013-07-02
  1: static char help[] = "Test sequential USFFT interface on a uniform DMDA and compares the result to FFTW\n\n";

  3: /*
  4:   Compiling the code:
  5:       This code uses the complex numbers version of PETSc and the FFTW package, so configure
  6:       must be run to enable these.

  8: */

 10: #include <petscmat.h>
 11: #include <petscdmda.h>
 14: PetscInt main(PetscInt argc,char **args)
 15: {
 16:   typedef enum {RANDOM, CONSTANT, TANH, NUM_FUNCS} FuncType;
 17:   const char     *funcNames[NUM_FUNCS] = {"random", "constant", "tanh"};
 18:   Mat            A, AA;
 19:   PetscMPIInt    size;
 20:   PetscInt       N,i, stencil=1,dof=1;
 21:   PetscInt       dim[3] = {10,10,10}, ndim = 3;
 22:   Vec            coords,x,y,z,xx,yy,zz;
 23:   PetscReal      h[3];
 24:   PetscScalar    s;
 25:   PetscRandom    rdm;
 26:   PetscReal      norm, enorm;
 27:   PetscInt       func;
 28:   FuncType       function = TANH;
 29:   DM             da, coordsda;
 30:   PetscBool      view_x = PETSC_FALSE, view_y = PETSC_FALSE, view_z = PETSC_FALSE;

 33:   PetscInitialize(&argc,&args,(char*)0,help);
 34: #if !defined(PETSC_USE_COMPLEX)
 35:   SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_SUP, "This example requires complex numbers");
 36: #endif
 37:   MPI_Comm_size(PETSC_COMM_WORLD, &size);
 38:   if (size != 1) SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_SUP, "This is a uniprocessor example only!");
 39:   PetscOptionsBegin(PETSC_COMM_WORLD, NULL, "USFFT Options", "ex27");
 40:   PetscOptionsEList("-function", "Function type", "ex27", funcNames, NUM_FUNCS, funcNames[function], &func, NULL);
 41:   function = (FuncType) func;
 42:   PetscOptionsEnd();
 43:   PetscOptionsGetBool(NULL,"-view_x",&view_x,NULL);
 44:   PetscOptionsGetBool(NULL,"-view_y",&view_y,NULL);
 45:   PetscOptionsGetBool(NULL,"-view_z",&view_z,NULL);
 46:   PetscOptionsGetIntArray(NULL,"-dim",dim,&ndim,NULL);



 50:   DMDACreate3d(PETSC_COMM_SELF,DMDA_BOUNDARY_NONE,DMDA_BOUNDARY_NONE,DMDA_BOUNDARY_NONE,DMDA_STENCIL_STAR,
 51:                       dim[0], dim[1], dim[2],
 52:                       PETSC_DECIDE, PETSC_DECIDE, PETSC_DECIDE,
 53:                       dof, stencil,
 54:                       NULL, NULL, NULL,
 55:                       &da);
 56:   /* Coordinates */
 57:   DMGetCoordinateDM(da, &coordsda);
 58:   DMGetGlobalVector(coordsda, &coords);
 59:   PetscObjectSetName((PetscObject) coords, "Grid coordinates");
 60:   for (i = 0, N = 1; i < 3; i++) {
 61:     h[i] = 1.0/dim[i];
 62:     PetscScalar *a;
 63:     VecGetArray(coords, &a);
 64:     PetscInt j,k,n = 0;
 65:     for (i = 0; i < 3; ++i) {
 66:       for (j = 0; j < dim[i]; ++j) {
 67:         for (k = 0; k < 3; ++k) {
 68:           a[n] = j*h[i]; /* coordinate along the j-th point in the i-th dimension */
 69:           ++n;
 70:         }
 71:       }
 72:     }
 73:     VecRestoreArray(coords, &a);

 75:   }
 76:   DMSetCoordinates(da, coords);

 78:   /* Work vectors */
 79:   DMGetGlobalVector(da, &x);
 80:   PetscObjectSetName((PetscObject) x, "Real space vector");
 81:   DMGetGlobalVector(da, &xx);
 82:   PetscObjectSetName((PetscObject) xx, "Real space vector");
 83:   DMGetGlobalVector(da, &y);
 84:   PetscObjectSetName((PetscObject) y, "USFFT frequency space vector");
 85:   DMGetGlobalVector(da, &yy);
 86:   PetscObjectSetName((PetscObject) yy, "FFTW frequency space vector");
 87:   DMGetGlobalVector(da, &z);
 88:   PetscObjectSetName((PetscObject) z, "USFFT reconstructed vector");
 89:   DMGetGlobalVector(da, &zz);
 90:   PetscObjectSetName((PetscObject) zz, "FFTW reconstructed vector");

 92:   PetscPrintf(PETSC_COMM_SELF, "%3-D: USFFT on vector of ");
 93:   for (i = 0, N = 1; i < 3; i++) {
 94:     PetscPrintf(PETSC_COMM_SELF, "dim[%d] = %d ",i,dim[i]);
 95:     N   *= dim[i];
 96:   }
 97:   PetscPrintf(PETSC_COMM_SELF, "; total size %d \n",N);


100:   if (function == RANDOM) {
101:     PetscRandomCreate(PETSC_COMM_SELF, &rdm);
102:     PetscRandomSetFromOptions(rdm);
103:     VecSetRandom(x, rdm);
104:     PetscRandomDestroy(&rdm);
105:   } else if (function == CONSTANT) {
106:     VecSet(x, 1.0);
107:   } else if (function == TANH) {
108:     PetscScalar *a;
109:     VecGetArray(x, &a);
110:     PetscInt j,k = 0;
111:     for (i = 0; i < 3; ++i) {
112:       for (j = 0; j < dim[i]; ++j) {
113:         a[k] = tanh((j - dim[i]/2.0)*(10.0/dim[i]));
114:         ++k;
115:       }
116:     }
117:     VecRestoreArray(x, &a);
118:   }
119:   if (view_x) {
120:     VecView(x, PETSC_VIEWER_STDOUT_WORLD);
121:   }
122:   VecCopy(x,xx);

124:   VecNorm(x,NORM_2,&norm);
125:   PetscPrintf(PETSC_COMM_SELF, "|x|_2 = %g\n",norm);

127:   /* create USFFT object */
128:   MatCreateSeqUSFFT(coords,da,&A);
129:   /* create FFTW object */
130:   MatCreateSeqFFTW(PETSC_COMM_SELF,3,dim,&AA);

132:   /* apply USFFT and FFTW FORWARD "preemptively", so the fftw_plans can be reused on different vectors */
133:   MatMult(A,x,z);
134:   MatMult(AA,xx,zz);
135:   /* Now apply USFFT and FFTW forward several (3) times */
136:   for (i=0; i<3; ++i) {
137:     MatMult(A,x,y);
138:     MatMult(AA,xx,yy);
139:     MatMultTranspose(A,y,z);
140:     MatMultTranspose(AA,yy,zz);
141:   }

143:   if (view_y) {
144:     PetscPrintf(PETSC_COMM_WORLD, "y = \n");
145:     VecView(y, PETSC_VIEWER_STDOUT_WORLD);
146:     PetscPrintf(PETSC_COMM_WORLD, "yy = \n");
147:     VecView(yy, PETSC_VIEWER_STDOUT_WORLD);
148:   }

150:   if (view_z) {
151:     PetscPrintf(PETSC_COMM_WORLD, "z = \n");
152:     VecView(z, PETSC_VIEWER_STDOUT_WORLD);
153:     PetscPrintf(PETSC_COMM_WORLD, "zz = \n");
154:     VecView(zz, PETSC_VIEWER_STDOUT_WORLD);
155:   }

157:   /* compare x and z. USFFT computes an unnormalized DFT, thus z = N*x */
158:   s    = 1.0/(PetscReal)N;
159:   VecScale(z,s);
160:   VecAXPY(x,-1.0,z);
161:   VecNorm(x,NORM_1,&enorm);
162:   PetscPrintf(PETSC_COMM_SELF, "|x-z| = %g\n",enorm);

164:   /* compare xx and zz. FFTW computes an unnormalized DFT, thus zz = N*x */
165:   s    = 1.0/(PetscReal)N;
166:   VecScale(zz,s);
167:   VecAXPY(xx,-1.0,zz);
168:   VecNorm(xx,NORM_1,&enorm);
169:   PetscPrintf(PETSC_COMM_SELF, "|xx-zz| = %g\n",enorm);

171:   /* compare y and yy: USFFT and FFTW results*/
172:   VecNorm(y,NORM_2,&norm);
173:   VecAXPY(y,-1.0,yy);
174:   VecNorm(y,NORM_1,&enorm);
175:   PetscPrintf(PETSC_COMM_SELF, "|y|_2 = %g\n",norm);
176:   PetscPrintf(PETSC_COMM_SELF, "|y-yy| = %g\n",enorm);

178:   /* compare z and zz: USFFT and FFTW results*/
179:   VecNorm(z,NORM_2,&norm);
180:   VecAXPY(z,-1.0,zz);
181:   VecNorm(z,NORM_1,&enorm);
182:   PetscPrintf(PETSC_COMM_SELF, "|z|_2 = %g\n",norm);
183:   PetscPrintf(PETSC_COMM_SELF, "|z-zz| = %g\n",enorm);


186:   /* free spaces */
187:   DMRestoreGlobalVector(da,&x);
188:   DMRestoreGlobalVector(da,&xx);
189:   DMRestoreGlobalVector(da,&y);
190:   DMRestoreGlobalVector(da,&yy);
191:   DMRestoreGlobalVector(da,&z);
192:   DMRestoreGlobalVector(da,&zz);
193:   VecDestroy(&coords);
194:   DMDestroy(&da);
195:   PetscFinalize();
196:   return 0;
197: }