Actual source code: ex1.c
petsc-3.5.4 2015-05-23
2: static char help[] = "Basic vector routines.\n\n";
4: /*T
5: Concepts: vectors^basic routines;
6: Processors: n
7: T*/
9: /*
10: Include "petscvec.h" so that we can use vectors. Note that this file
11: automatically includes:
12: petscsys.h - base PETSc routines petscis.h - index sets
13: petscviewer.h - viewers
14: */
16: #include <petscvec.h>
20: int main(int argc,char **argv)
21: {
22: Vec x,y,w; /* vectors */
23: Vec *z; /* array of vectors */
24: PetscReal norm,v,v1,v2,maxval;
25: PetscInt n = 20,maxind;
27: PetscScalar one = 1.0,two = 2.0,three = 3.0,dots[3],dot;
29: PetscInitialize(&argc,&argv,(char*)0,help);
30: PetscOptionsGetInt(NULL,"-n",&n,NULL);
32: /*
33: Create a vector, specifying only its global dimension.
34: When using VecCreate(), VecSetSizes() and VecSetFromOptions(), the vector format
35: (currently parallel, shared, or sequential) is determined at runtime. Also, the
36: parallel partitioning of the vector is determined by PETSc at runtime.
38: Routines for creating particular vector types directly are:
39: VecCreateSeq() - uniprocessor vector
40: VecCreateMPI() - distributed vector, where the user can
41: determine the parallel partitioning
42: VecCreateShared() - parallel vector that uses shared memory
43: (available only on the SGI); otherwise,
44: is the same as VecCreateMPI()
46: With VecCreate(), VecSetSizes() and VecSetFromOptions() the option -vec_type mpi or
47: -vec_type shared causes the particular type of vector to be formed.
49: */
51: VecCreate(PETSC_COMM_WORLD,&x);
52: VecSetSizes(x,PETSC_DECIDE,n);
53: VecSetFromOptions(x);
54: /*
55: Duplicate some work vectors (of the same format and
56: partitioning as the initial vector).
57: */
58: VecDuplicate(x,&y);
59: VecDuplicate(x,&w);
61: /*
62: Duplicate more work vectors (of the same format and
63: partitioning as the initial vector). Here we duplicate
64: an array of vectors, which is often more convenient than
65: duplicating individual ones.
66: */
67: VecDuplicateVecs(x,3,&z);
68: /*
69: Set the vectors to entries to a constant value.
70: */
71: VecSet(x,one);
72: VecSet(y,two);
73: VecSet(z[0],one);
74: VecSet(z[1],two);
75: VecSet(z[2],three);
76: /*
77: Demonstrate various basic vector routines.
78: */
79: MPI_Barrier(PETSC_COMM_WORLD);
80: VecDot(x,y,&dot);
81: VecMDot(x,3,z,dots);
83: /*
84: Note: If using a complex numbers version of PETSc, then
85: PETSC_USE_COMPLEX is defined in the makefiles; otherwise,
86: (when using real numbers) it is undefined.
87: */
89: PetscPrintf(PETSC_COMM_WORLD,"Vector length %D\n",n);
90: VecMax(x,&maxind,&maxval);
91: PetscPrintf(PETSC_COMM_WORLD,"VecMax %g, VecInd %D\n",(double)maxval,maxind);
93: VecMin(x,&maxind,&maxval);
94: PetscPrintf(PETSC_COMM_WORLD,"VecMin %g, VecInd %D\n",(double)maxval,maxind);
95: PetscPrintf(PETSC_COMM_WORLD,"All other values should be near zero\n");
98: VecScale(x,two);
99: VecNorm(x,NORM_2,&norm);
100: v = norm-2.0*PetscSqrtReal((PetscReal)n); if (v > -PETSC_SMALL && v < PETSC_SMALL) v = 0.0;
101: PetscPrintf(PETSC_COMM_WORLD,"VecScale %g\n",(double)v);
104: VecCopy(x,w);
105: VecNorm(w,NORM_2,&norm);
106: v = norm-2.0*PetscSqrtReal((PetscReal)n); if (v > -PETSC_SMALL && v < PETSC_SMALL) v = 0.0;
107: PetscPrintf(PETSC_COMM_WORLD,"VecCopy %g\n",(double)v);
109: VecAXPY(y,three,x);
110: VecNorm(y,NORM_2,&norm);
111: v = norm-8.0*PetscSqrtReal((PetscReal)n); if (v > -PETSC_SMALL && v < PETSC_SMALL) v = 0.0;
112: PetscPrintf(PETSC_COMM_WORLD,"VecAXPY %g\n",(double)v);
114: VecAYPX(y,two,x);
115: VecNorm(y,NORM_2,&norm);
116: v = norm-18.0*PetscSqrtReal((PetscReal)n); if (v > -PETSC_SMALL && v < PETSC_SMALL) v = 0.0;
117: PetscPrintf(PETSC_COMM_WORLD,"VecAYPX %g\n",(double)v);
119: VecSwap(x,y);
120: VecNorm(y,NORM_2,&norm);
121: v = norm-2.0*PetscSqrtReal((PetscReal)n); if (v > -PETSC_SMALL && v < PETSC_SMALL) v = 0.0;
122: PetscPrintf(PETSC_COMM_WORLD,"VecSwap %g\n",(double)v);
123: VecNorm(x,NORM_2,&norm);
124: v = norm-18.0*PetscSqrtReal((PetscReal)n); if (v > -PETSC_SMALL && v < PETSC_SMALL) v = 0.0;
125: PetscPrintf(PETSC_COMM_WORLD,"VecSwap %g\n",(double)v);
127: VecWAXPY(w,two,x,y);
128: VecNorm(w,NORM_2,&norm);
129: v = norm-38.0*PetscSqrtReal((PetscReal)n); if (v > -PETSC_SMALL && v < PETSC_SMALL) v = 0.0;
130: PetscPrintf(PETSC_COMM_WORLD,"VecWAXPY %g\n",(double)v);
132: VecPointwiseMult(w,y,x);
133: VecNorm(w,NORM_2,&norm);
134: v = norm-36.0*PetscSqrtReal((PetscReal)n); if (v > -PETSC_SMALL && v < PETSC_SMALL) v = 0.0;
135: PetscPrintf(PETSC_COMM_WORLD,"VecPointwiseMult %g\n",(double)v);
137: VecPointwiseDivide(w,x,y);
138: VecNorm(w,NORM_2,&norm);
139: v = norm-9.0*PetscSqrtReal((PetscReal)n); if (v > -PETSC_SMALL && v < PETSC_SMALL) v = 0.0;
140: PetscPrintf(PETSC_COMM_WORLD,"VecPointwiseDivide %g\n",(double)v);
142: dots[0] = one;
143: dots[1] = three;
144: dots[2] = two;
146: VecSet(x,one);
147: VecMAXPY(x,3,dots,z);
148: VecNorm(z[0],NORM_2,&norm);
149: v = norm-PetscSqrtReal((PetscReal)n); if (v > -PETSC_SMALL && v < PETSC_SMALL) v = 0.0;
150: VecNorm(z[1],NORM_2,&norm);
151: v1 = norm-2.0*PetscSqrtReal((PetscReal)n); if (v1 > -PETSC_SMALL && v1 < PETSC_SMALL) v1 = 0.0;
152: VecNorm(z[2],NORM_2,&norm);
153: v2 = norm-3.0*PetscSqrtReal((PetscReal)n); if (v2 > -PETSC_SMALL && v2 < PETSC_SMALL) v2 = 0.0;
154: PetscPrintf(PETSC_COMM_WORLD,"VecMAXPY %g %g %g \n",(double)v,(double)v1,(double)v2);
156: /*
157: Free work space. All PETSc objects should be destroyed when they
158: are no longer needed.
159: */
160: VecDestroy(&x);
161: VecDestroy(&y);
162: VecDestroy(&w);
163: VecDestroyVecs(3,&z);
164: PetscFinalize();
165: return 0;
166: }