Calculate the integral using Monte Carlo method

#include "stdio.h"
#include "stdlib.h"
#include "math.h"

double rnd1(double *r)  //the definition body of rnd1
{ int m;
  double s, u, v, p;
  s=65536.0; u=2053.0; v=13849.0;
  m=(int)(*r/s); *r=*r-m*s;
  *r=u*(*r)+v; m=(int)(*r/s);
  *r=*r-m*s; p=*r/s;
  return(p);
}

double mtml(int n, double a[], double b[], double (*f)())  /*n为积分的维度,数组a保存着积分下限，
                                                                                                                        数组b保存着积分上限，f为函数指针，指向被积函数*/
{
    int m, i;
    double r, s, d, *x;
    x=malloc(n*sizeof(double));
    r=1.0; d=10000.0; s=0.0;
    for (m=0; m<=9999; m++)
    {
        for (i=0; i<=2-1; i++)
            x[i]=a[i]+(b[i]-a[i])*rnd1(&r);
        s=s+(*f)(n, x)/d;
    }
    for (i=0; i<=n-1; i++)
        s=s*(b[i]-a[i]);
    free(x);
    return(s);
}


main()
{
    static double a[3]={1.0, 1.0, 1.0};
    static double b[3]={2.0, 2.0, 2.0};
    double mtmlf(int, double []);
    printf("\n");
    printf("s=%e\n", mtml(3, a, b, mtmlf));
    printf("\n");
}

double mtmlf(int n, double x[])//mtmlf为被积函数，这里是定值1
{
    int i;
    double f;
    f=0.0;
    for(i=0; i<=n-1; i++)
      f=f+x[i]*x[i];
    return(f);
}