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ising2d.c
160 lines (127 loc) · 2.77 KB
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ising2d.c
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#include<stdio.h>
#include<stdlib.h>
#include<math.h>
#include"twist.c"
typedef struct conf{
int spin;
int up;
int down;
int left;
int right;
}Ising;
void initialize(int N, Ising **S);
void mcstep(int N, double T, Ising **S);
double magnetization(int N, Ising **S);
double energy(int N, Ising **S);
int main(int argc, char **argv)
{
double T=0;;
double mag=0.0;
int N;
int i;
Ising **S;
double tot_Erg=0;
double capacity=0.0;
double kai=0.0;
init_rnd(gus());
N=atoi(argv[1]);
S=(Ising **)malloc(sizeof(Ising *) * N);
for(i=0; i<N; i++)
S[i]=(Ising *)malloc(sizeof(Ising) * N);
initialize(N, S);
for(T=3.01; T>=0.01; T-=0.01)
{
mag=0.0;
tot_Erg=0.0;
kai=0.0;
capacity=0.0;
for(i=0; i<200000; i++)
mcstep(N, T, S);
for(i=0; i<200000; i++)
{
mcstep(N, T, S);
mag+=magnetization(N, S);
tot_Erg+=energy(N, S);
kai+=pow(magnetization(N, S), 2);
capacity+=pow(energy(N,S), 2);
}
mag=mag/200000;
tot_Erg=tot_Erg/200000;
kai=kai/200000;
capacity=capacity/200000;
kai=(kai-mag*mag)/T;
capacity=(capacity - tot_Erg*tot_Erg)/(T*T);
kai=kai*N*N;
capacity=capacity*N*N;
printf("%lf\t%lf\t%lf\t%lf\t%lf\n", T, mag, tot_Erg, kai, capacity);
}
free(S);
return 0;
}
void initialize(int N, Ising **S)
{
int i,j;
for(i=0; i<N; i++)
for(j=0; j<N; j++)
{
if(drnd() < 0.5)
S[i][j].spin=1;
else
S[i][j].spin=-1;
}
for(i=0; i<N; i++)
for(j=0; j<N; j++)
{
S[i][j].up=i-1;
S[i][j].down=i+1;
S[i][j].left=j-1;
S[i][j].right=j+1;
}
for(j=0; j<N; j++)
{
S[0][j].up=N-1;
S[N-1][j].down=0;
}
for(i=0; i<N; i++)
{
S[i][0].left=N-1;
S[i][N-1].right=0;
}
}
void mcstep(int N, double T, Ising **S)
{
int i,j,k;
double E_flip;
double E1, E2;
for(k=0; k<N*N; k++)
{
i=(int)(drnd()*N);
j=(int)(drnd()*N);
E1=-S[i][j].spin * (S[ S[i][j].up ][j].spin + S[ S[i][j].down ][j].spin + S[i][ S[i][j].left ].spin + S[i][ S[i][j].right ].spin );
E2=-(-S[i][j].spin) * (S[ S[i][j].up ][j].spin + S[ S[i][j].down ][j].spin + S[i][ S[i][j].left ].spin + S[i][ S[i][j].right ].spin );
E_flip=E2-E1;
if(E_flip<0 || drnd() < exp(-E_flip/T))
S[i][j].spin=-S[i][j].spin;
}
}
double magnetization(int N, Ising **S)
{
int i, j;
double mag=0.0;
for(i=0; i<N; i++)
for(j=0; j<N; j++)
mag+=S[i][j].spin;
mag=mag/(N*N);
return fabs(mag);
}
double energy(int N, Ising **S)
{
int i, j;
double E_tot;
E_tot=0.0;
for(i=0; i<N; i++)
for(j=0; j<N; j++)
E_tot+=-S[i][j].spin * ( S[ S[i][j].up ][j].spin + S[ S[i][j].down ][j].spin + S[i][ S[i][j].left ].spin + S[i][ S[i][j].right ].spin );
E_tot=E_tot/(N*N);
return E_tot;
}