# PetIGA / demo / AdaptiveL2Projection.c

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239``` ```/* This code computes the L2 projection of a function defined in Function to a B-spline space. The space is adaptively refined by a brute force strategy: which knot do we insert such that the global L2 error is reduced the most? keywords: scalar, linear */ #include "petiga.h" #define SQ(A) (A)*(A) PetscScalar Function(PetscReal x, PetscReal y, PetscReal z) { PetscScalar x0=0.85,y0=0.45; PetscScalar sigx=0.125,sigy=0.2; return exp( -( SQ(x-x0) / (2.*SQ(sigx)) + SQ(y-y0) / (2.*SQ(sigy) ) ) ); } #undef __FUNCT__ #define __FUNCT__ "System" PetscErrorCode System(IGAPoint p,PetscScalar *K,PetscScalar *F,void *ctx) { PetscInt nen = p->nen; PetscReal x[3] = {0,0,0}; IGAPointFormPoint(p,x); PetscScalar f = Function(x[0],x[1],x[2]); const PetscReal *N; IGAPointGetShapeFuns(p,0,(const PetscReal**)&N); PetscInt a,b; for (a=0; ai+1) Ur[idim][j] = U[idim][j-1]; } PetscReal error; ierr = ComputeError(dim,p,C,&Ur[0],&Nr[0],&error);CHKERRQ(ierr); if(error < *min_error){ *min_error = error; *insert = i; } } return 0; } #undef __FUNCT__ #define __FUNCT__ "main" int main(int argc, char *argv[]) { PetscErrorCode ierr; ierr = PetscInitialize(&argc,&argv,0,0);CHKERRQ(ierr); PetscReal U[3][MAX_BREAKS]; PetscInt N[3]; PetscInt i,j; PetscInt dim = 2, p = 2, C = 1; ierr = PetscOptionsBegin(PETSC_COMM_WORLD,"","Options","IGA");CHKERRQ(ierr); ierr = PetscOptionsInt("-dim","dimension",__FILE__,dim,&dim,NULL);CHKERRQ(ierr); ierr = PetscOptionsInt("-p","polynomial order", __FILE__,p,&p,NULL);CHKERRQ(ierr); ierr = PetscOptionsInt("-C","global continuity order",__FILE__,C,&C,NULL);CHKERRQ(ierr); ierr = PetscOptionsEnd();CHKERRQ(ierr); // initial breaks (2x2 mesh) for (i=0; i 1e-9){ PetscInt insert[3],imin=-1; PetscReal error[3]; min_error = 1.e20; for(i=0;iinsert[imin];j--) U[imin][j] = U[imin][j-1]; U[imin][insert[imin]+1] = in; N[imin] += 1; printf("Step %d: Error %.16e\n",step,min_error); step += 1; } IGA iga; ierr = IGACreate(PETSC_COMM_WORLD,&iga);CHKERRQ(ierr); ierr = IGASetDim(iga,dim);CHKERRQ(ierr); ierr = IGASetDof(iga,1);CHKERRQ(ierr); for (i=0; i