Issue
I'm trying to pass the slice of the output of one function slice to another function, however I receive Segmentation fault error at line 93 in append_2d_slice slice function. I commented line which causes the problem. I suspect I'm passing slice variable to the function in a wrong way, but I'm not sure.
Here is the code:
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
//Works on Collab
void awe_2d_heterogeneous_8th_order_data_time_reverse(
double** UUo, double** UUm, int nx, int ny, double dx, double dy,
double dt, double** v, double** slice, int it, double rx
) {
// Get dimensions of the wavefield
int irx = (int)(rx / dx); // Force to be integer
// Inject wavelet
for (int i = 0; i < ny; i++) {
// printf("i: %d\n", i);
UUo[irx][i] += dt * dt * slice[i][it];
}
// Define Courant numbers (squared)
double dtdx2 = (dt / dx) * (dt / dx);
double dtdy2 = (dt / dy) * (dt / dy);
// Update solution
for (int i = 4; i < nx - 4; i++) {
for (int j = 4; j < ny - 4; j++) {
UUm[i][j] = 2 * UUo[i][j] - UUm[i][j] + dtdx2 * v[i][j] * v[i][j] * (
-1.0/560 * UUo[i - 4][j]
+ 8.0/315 * UUo[i - 3][j]
- 1.0/5 * UUo[i - 2][j]
+ 8.0/5 * UUo[i - 1][j]
- 205.0/72 * UUo[i][j]
+ 8.0/5 * UUo[i + 1][j]
- 1.0/5 * UUo[i + 2][j]
+ 8.0/315 * UUo[i + 3][j]
- 1.0/560 * UUo[i + 4][j]) + dtdy2 * v[i][j] * v[i][j] * (
-1.0/560 * UUo[i][j - 4]
+ 8.0/315 * UUo[i][j - 3]
- 1.0/5 * UUo[i][j - 2]
+ 8.0/5 * UUo[i][j - 1]
- 205.0/72 * UUo[i][j]
+ 8.0/5 * UUo[i][j + 1]
- 1.0/5 * UUo[i][j + 2]
+ 8.0/315 * UUo[i][j + 3]
- 1.0/560 * UUo[i][j + 4]);
}
}
}
void awe_2d_explicit_solver_heterogeneous_8th_order(
double** UUo, double** UUm, int nx, int ny, double dx, double dy,
double dt, double** v, double* F, int it, double sx, double sy
) {
// Define Courant numbers (squared)
double dtdx2 = (dt / dx) * (dt / dx);
double dtdy2 = (dt / dy) * (dt / dy);
// Source location
int isx = (int)(sx / dx);
int isy = (int)(sy / dy);
// Inject wavelet
UUo[isx][isy] += dt * dt * F[it];
// Update solution without using slicing
for (int i = 4; i < nx - 4; i++) {
for (int j = 4; j < ny - 4; j++) {
UUm[i][j] = 2 * UUo[i][j] - UUm[i][j] + dtdx2 * v[i][j] * v[i][j] * (
-1.0/560 * UUo[i - 4][j]
+ 8.0/315 * UUo[i - 3][j]
- 1.0/5 * UUo[i - 2][j]
+ 8.0/5 * UUo[i - 1][j]
- 205.0/72 * UUo[i][j]
+ 8.0/5 * UUo[i + 1][j]
- 1.0/5 * UUo[i + 2][j]
+ 8.0/315 * UUo[i + 3][j]
- 1.0/560 * UUo[i + 4][j]) + dtdy2 * v[i][j] * v[i][j] * (
-1.0/560 * UUo[i][j - 4]
+ 8.0/315 * UUo[i][j - 3]
- 1.0/5 * UUo[i][j - 2]
+ 8.0/5 * UUo[i][j - 1]
- 205.0/72 * UUo[i][j]
+ 8.0/5 * UUo[i][j + 1]
- 1.0/5 * UUo[i][j + 2]
+ 8.0/315 * UUo[i][j + 3]
- 1.0/560 * UUo[i][j + 4]);
}
}
}
void append_2d_slice(double*** dest, double** src, int nx, int ny, int nt) {
for (int i = 0; i < nx; i++) {
for (int j = 0; j < ny; j++) {
dest[i][j][nt] = src[i][j]; // Debugger Points here Segmenation fault
}
}
}
void write_text_file_slice(double** slice, int nx, int ny, const char* filename) {
FILE *file = fopen(filename, "w");
if (file == NULL) {
fprintf(stderr, "Error opening file for writing.\n");
exit(1);
}
// Write slice data to the text file
for (int i = 0; i < nx; i++) {
for (int j = 0; j < ny; j++) {
fprintf(file, "%.50lf ", slice[i][j]);
}
fprintf(file, "\n");
}
fclose(file);
}
int main() {
// Define constants and arrays
int nz = 300;
int nx = 298;
double dz = 5.0;
double dx = 5.0;
double t0 = 0.05;
double CC = 0.5;
int nt = 2000;
double F[nt];
double sx = 25;
double sy = 800;
// Initialize UUo and UUm with zeros
double **UUo = malloc(nz * sizeof *UUo);
double **UUm = malloc(nz * sizeof *UUm);
double **UUo1 = malloc(nz * sizeof *UUo1);
double **UUm1 = malloc(nz * sizeof *UUm1);
double **v = malloc(nz * sizeof *v);
for (int i = 0; i < nz; i++) {
UUo[i] = calloc(nx, sizeof *UUo[i]);
UUm[i] = calloc(nx, sizeof *UUm[i]);
UUo1[i] = calloc(nx, sizeof *UUo1[i]);//addition
UUm1[i] = calloc(nx, sizeof *UUm1[i]);//addition
v[i] = calloc(nx, sizeof *v[i]);
}
// Initialize fff with zeros
double ***fff = malloc(nz * sizeof *fff);
for (int i = 0; i < nz; i++) {
fff[i] = calloc(nx, sizeof *fff[i]);
for (int j = 0; j < nx; j++) {
fff[i][j] = calloc(nt, sizeof *fff[i][j]);
}
}
// Initialize mmm with zeros
double ***mmm = malloc(nz * sizeof *mmm);
for (int i = 0; i < nz; i++) {
mmm[i] = calloc(nx, sizeof *mmm[i]);
for (int j = 0; j < nx; j++) {
mmm[i][j] = calloc(nt, sizeof *mmm[i][j]);
}
}
// Time stepping parameters
double dt = CC * dz / 5560.328125; // Assuming 'v' is the maximum value
double t[nt];
for (int i = 0; i < nt; i++) {
t[i] = i * dt;
}
// Define forcing function
double ss = 0.01;
for (int i = 0; i < nt; i++) {
F[i] = (1.0 - ((t[i] - t0) / ss) * ((t[i] - t0) / ss)) * exp(-((t[i] - t0) * (t[i] - t0)) / (2 * ss * ss));
}
// Read 'v' from the file
FILE *file = fopen("marmousi.txt", "r");
if (file == NULL) {
fprintf(stderr, "Error opening file.\n");
perror("fopen");
return 1; // Exit with an error code
}
for (int i = 0; i < nz; i++) {
for (int j = 0; j < nx; j++) {
if (fscanf(file, "%lf", &v[i][j]) != 1) {
fprintf(stderr, "Error reading from file.\n");
fclose(file);
return 1; // Exit with an error code
}
}
}
fclose(file);
printf("Forward Propagation...\n");
for (int it = 0; it < nt; it++) {
awe_2d_explicit_solver_heterogeneous_8th_order(UUo1, UUm1, nz, nx, dz, dx, dt, v, F, it, sx, sy);
// Swap UUo and UUm
double** tmp = UUo1;
UUo1 = UUm1;
UUm1 = tmp;
append_2d_slice(fff, UUo1, nz, nx, it);
}
printf("Forward Propagation Done !\n");
double** slice = fff[5];
write_text_file_slice(slice, nx, nt, "slice.txt");
printf("Backward Propagation...\n");
for (int it = nt - 1; it > 0; it--) {
//printf("%d\n",it);
awe_2d_heterogeneous_8th_order_data_time_reverse(UUo, UUm, nz, nx, dz, dx, dt, v, slice, it, sx);
double** tmp = UUo;
UUo = UUm;
UUm = tmp;
append_2d_slice(mmm, UUo, nz, nx, nt - 1 - it);// When I uncomment this part the code stops working and Debugger Points at line 93 on Windows Machine
}
printf("Backward Propagation Done !\n");
double** slicep = mmm[5];
write_text_file_slice(slicep, nx, nt, "slicep.txt");
// Free allocated memory
for (int i = 0; i < nz; i++) {
free(UUo[i]);
free(UUm[i]);
free(UUo1[i]);
free(UUm1[i]);
free(v[i]);
}
free(UUo);
free(UUm);
free(UUo1);
free(UUm1);
free(v);
for (int i = 0; i < nz; i++) {
for (int j = 0; j < nx; j++) {
free(fff[i][j]);
free(mmm[i][j]);
}
free(fff[i]);
free(mmm[i]);
}
free(fff);
free(mmm);
return 0;
}
Here is the link to txt file used in script : https://drive.google.com/drive/folders/1pmSkKrxS7IWDGyPiyl0SuNEh3gidmyFS?usp=drive_link
Edit_0:
The code above with uncommented line append_2d_slice(mmm, UUo, nz, nx, nt - 1 - it); works on Colab and wsl (Windows Subsystem for Linux) , however it does not work on Windows . The question is Why ? Could it be version of gcc ?
gcc version on Windows : gcc.exe (MinGW.org GCC-6.3.0-1) 6.3.0 gcc version on Linux: gcc (Ubuntu 9.4.0-1ubuntu1~20.04.2) 9.4.0
Edit_1: Okay, I configured runner so that code runs on WSL Terminal and it solves the issue, but I'm still not sure why it doesn't work on Windows I suspect version of gcc.
Solution
If someone else has similar issue, C code running without issues on Linux, WSL, Colab but not on Windows machine.Configure your code_runner so that it runs on WSL Terminal. In my case I'm using Visual Studio Code. I include here the link which shows how to configure that on Visual Studio Code.
Answered By - Fearless_Wolf Answer Checked By - Gilberto Lyons (WPSolving Admin)