slope_limiter.c

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#include <stdio.h>
#include <stdarg.h>
 
#include "../include/var_struc.h"
#include "../include/tools.h"
 
 
void minmod_limiter(const _Bool NO_h, const int m, const _Bool find_bound, double s[],
            const double U[], const double UL, const double UR, const double HL, ...)
{
    va_list ap;
    va_start(ap, HL);
    int j;
    double const alpha = config[41]; // the paramater in slope limiters.
    double s_L, s_R; // spatial derivatives in coordinate x (slopes) 
    double h = HL, HR, * X;
    if (NO_h)
    {
        HR = va_arg(ap, double);
        X  = va_arg(ap, double *);
    }
 
    for(j = 0; j < m; ++j) // Reconstruct slopes
    { /*
       *  j-1          j          j+1
       * j-1/2  j-1  j+1/2   j   j+3/2  j+1
       *   o-----X-----o-----X-----o-----X--...
       */
        if(j)
        {
            if (NO_h)
            h = 0.5 * (X[j+1] - X[j-1]);
            s_L = (U[j] - U[j-1]) / h;
        }
        else
        {
            if (NO_h)
            h = 0.5 * (X[j+1] - X[j] + HL);
            s_L = (U[j] - UL) / h;
        }
        if(j < m-1)
        {
            if (NO_h)
            h = 0.5 * (X[j+2] - X[j]);
            s_R = (U[j+1] - U[j]) / h;
        }
        else
        {
            if (NO_h)
            h = 0.5 * (X[j+1] - X[j] + HR);
            s_R = (UR - U[j]) / h;
        }
        if (find_bound)
        s[j] = minmod3(alpha*s_L, alpha*s_R, s[j]);
        else
        s[j] = minmod2(s_L, s_R);
    }
    va_end(ap);
}