/* 1D FDTD simulation with an additive source. 
 * All snapshots are written to a single output file. */

#include <stdio.h>
#include <math.h>

#define SIZE 200

int main()
{
  double ez[SIZE] = {0.}, hy[SIZE] = {0.}, imp0 = 377.0;
  int qTime, maxTime = 200, mm;

  char filename[100] = "sim.dat";     
  FILE *snapshots;

  snapshots=fopen(filename, "w");      


  /* do time stepping */
  for (qTime = 0; qTime < maxTime; qTime++) {

    /* update magnetic field */              
    for (mm = 0; mm < SIZE - 1; mm++)
      hy[mm] = hy[mm] + (ez[mm + 1] - ez[mm]) / imp0;
                                                
    /* update electric field */                
    for (mm = 1; mm < SIZE; mm++)
      ez[mm] = ez[mm] + (hy[mm] - hy[mm - 1]) * imp0;

    /* use additive source at node 50 */
    ez[50] += exp(-(qTime - 30.) * (qTime - 30.) / 100.); 

    /* write snapshot if time a multiple of 2 */
    if (qTime % 2 == 0) {                     
      for (mm = 0; mm < SIZE; mm++)
        fprintf(snapshots, "%g ", ez[mm]);
      fprintf(snapshots, "\n");               
    }
  } /* end of time-stepping */             
  

  fclose(snapshots);                     

  return 0;
}