2 * ising.c - visualization of ising spins in an N x N lattice
6 * author: hackbard@hackdaworld.dyndns.org
22 int main(int argc, char **argv)
29 int max_x,x_c,max_y,y_c;
44 /* we will parse argv later ... */
48 d2_lattice_init(&argc,argv,&d2_l,max_x,max_y);
50 atom=(unsigned char *)(malloc(max_x*max_y*sizeof(unsigned char)));
54 /* begin at T=0 M=1 situation */
55 memset(atom,0,max_x*max_y*sizeof(unsigned char));
57 S=1; /* i have no idea! */
61 beta=5.0/T; /* k_B = 1 */
62 /* do 100 itterations, we will need more */
67 for(x_c=0;x_c<max_x;x_c++)
69 for(y_c=0;y_c<max_y;y_c++)
72 if((*(atom+x_c+((y_c+max_y+1)%max_y)*max_x))&1) ++count_p;
73 if((*(atom+x_c+((y_c+max_y-1)%max_y)*max_x))&1) ++count_p;
74 if((*(atom+((max_x+x_c+1)%max_x)+y_c*max_x))&1) ++count_p;
75 if((*(atom+((max_x+x_c-1)%max_x)+y_c*max_x))&1) ++count_p;
76 if(((*(atom+x_c+y_c*max_x))&1)==0) count_p=4-count_p;
77 delta_e=(2*count_p-4)*S;
78 if(delta_e<0) *(atom+x_c+y_c*max_x)=(*(atom+x_c+y_c*max_x)+1)&1;
81 if(1.0*rand()/RAND_MAX<exp(-1.0*delta_e*beta))
82 *(atom+x_c+y_c*max_x)=(*(atom+x_c+y_c*max_x)+1)&1;
84 if((*(atom+x_c+y_c*max_x))&1) ++M;
87 sprintf(t_text,"temp = %d",T);
89 sprintf(b_text,"beta = %f",beta);
91 sprintf(m_text,"magn = %f",1.0-2.0*M/(max_x*max_y));
93 d2_lattice_draw(&d2_l,0,0,3,arg_v);