typedef char            schar;
typedef short		int2;
typedef int 		int4;



int itlap(int argc,void *argv[])
{

    int i,j;
    int c=0;
    double *phi   = (double *)argv[c++] ;
    double *dr_2r = (double *)argv[c++] ;
    int4    n     = *((int4 *)argv[c++]) ;
    int4   *wi    = (int4 *)argv[c++] ;
    int4   *w0    = (int4 *)argv[c++] ;
    int4   *w1    = (int4 *)argv[c++] ;
    int4   *w2    = (int4 *)argv[c++] ;
    int4   *w3    = (int4 *)argv[c++] ;
    
#if 0
    printf("argc=%d\n",argc);
    printf("n=%d\n",n);
    for(i=0;i<n;i++)
       printf(" %d ",wi[i]);
#endif

    
    for(i=0;i<n;i++){
       phi[wi[i]] = (phi[w0[i]]+phi[w1[i]]+phi[w2[i]]+phi[w3[i]]  
            - dr_2r[wi[i]]*(phi[w0[i]]-phi[w1[i]]))/4.;
    }
    
    for(i=n-1;i>=0;i--){
       phi[wi[i]] = (phi[w0[i]]+phi[w1[i]]+phi[w2[i]]+phi[w3[i]]  
            - dr_2r[wi[i]]*(phi[w0[i]]-phi[w1[i]]))/4.;
    }

    return(1);
}

/*     phi[wi] = k*(phi[w0]+phi[w1]+phi[w2]+phi[w3] - dr_2r*(phi[w0]-phi[w1]))/4.d+(1-k)*phi[wi]
*/