FDTD_2D_Maxwell/snapshot2d.c

/*
    2D FDTD simulator
    Copyright (C) 2019 Emilia Blåsten

    This program is free software: you can redistribute it and/or
    modify it under the terms of the GNU Affero General Public License
    as published by the Free Software Foundation, either version 3 of
    the License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public
    License along with this program.  If not, see
    <http://www.gnu.org/licenses/>.
*/
/* snapshot2d.c: Function to record the 2D field to a file. The data
 * is stored as binary data. */

#include <stdio.h>
#include <stdlib.h>
#include "gridtmz.h"
#include "snapshot2d.h"

static int temporalStride = -2, frame = 0, startTime,
           startNodeX, endNodeX, spatialStrideX,
           startNodeY, endNodeY, spatialStrideY;

static char basename[80];

void snapshotInit2d(Grid *g) {
  int choice;

  printf("Do you want 2D snapshots? (1=yes, 0=no) ");
  scanf("%d", &choice);
  if(choice == 0) {
    temporalStride = -1;
    return;
  }

  printf("Duration of simulation is %d steps.\n", g->maxTime);
  printf("Enter start time and temporal stride: ");
  scanf(" %d %d", &startTime, &temporalStride);

  printf("In x direction grid has %d total nodes"
         " (ranging from 0 to %d).\n", g->sizeX, g->sizeX-1);
  printf("Enter first node, last node, and spatial stride: ");
  scanf(" %d %d %d", &startNodeX, &endNodeX, &spatialStrideX);

  printf("In y direction grid has %d total nodes"
         " (ranging from 0 to %d).\n", g->sizeY, g->sizeY-1);
  printf("Enter first node, last node, and spatial stride: ");
  scanf(" %d %d %d", &startNodeY, &endNodeY, &spatialStrideY);

  printf("Enter the base name: ");
  scanf(" %s", basename);

  return;
}

void snapshot2d(Grid *g) {
  int mm, nn;
  float dim1, dim2, temp;
  char filename[100];
  FILE *out;

  // ensure temporal stride set to a reasonable value
  if(temporalStride == -1) return;
  if(temporalStride < -1) {
    fprintf(stderr,
      "snapshot2d: snapshotInit2d must be called before snapshot.\n"
      "            Temporal stride must be set to positive value.\n");
    exit(-1);
  }

  // get snapshot is temporal conditions met
  if(g->time >= startTime && (g->time - startTime) % temporalStride == 0) {
    sprintf(filename, "%s.%d", basename, frame++);
    out = fopen(filename, "wb");

    // write dimensions to output file --
    // express dimensions as floats
    dim1 = (endNodeX - startNodeX) / spatialStrideX + 1;
    dim2 = (endNodeY - startNodeY) / spatialStrideY + 1;
    fwrite(&dim1, sizeof(float), 1, out);
    fwrite(&dim2, sizeof(float), 1, out);

    // write remaining data
    for(nn = endNodeY; nn >= startNodeY; nn -= spatialStrideY) {
      for(mm = startNodeX; mm <= endNodeX; mm += spatialStrideX) {
        temp = (float)g->ez[mm][nn]; //store data as a float
        fwrite(&temp, sizeof(float), 1, out); // write the float
      }
    }

    fclose(out);  // close the file
  }

  return;
}