main() for ``physics.C''

 

main() {
  int n,N;
  double d,V,U,shift;

  // Scan grid size (n) and grid spacing (d)
  printf("n:  "); scanf("%d",&n);
  printf("dx: "); scanf("%lf",&d);

  // Compute total number of points in and volume of cell
  N=n*n*n; V=pow(n*d,3);
  printf("%d^3 grid of size %f^3=%lf (bohr^3)...\n",n,n*d,V);

  // Initialize physics vectors on n^3 grid with spacing d in each direction 
  pvector ones(i3vec(n,n,n),d3vec(d,d,d));
  pvector v1(i3vec(n,n,n),d3vec(d,d,d));
  pvector v2(i3vec(n,n,n),d3vec(d,d,d));
  pvector v3(i3vec(n,n,n),d3vec(d,d,d));

  // Set pvector ones to all 1's.
  ones.evalr(constant,1.);

  // Does b_{G=0}(x_i)=ones?
  v1.evalr(constant,0.); // Set v1=all zeros
  v1.dat[0][0][0]=Complex(1.,0.); // Set G=[0][0][0] component to 1

  v2=I(v1)-ones; // Compute difference
  printf("b_{G=(0,0,0)}(x_i)=ones?  %e\n",v2^v2); // Print magnitude of error

}