PhuongTrinhNhiet2D.c

#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#include <math.h>
#include <time.h>

#define  m       20
#define  n       20
#define  T       2
#define  dt      0.01
#define  dx      0.1
#define  D       0.1
//=========================

void DisplayMatrix(float *A, int row, int col) {
    int i, j;
    for (i = 0; i < row; i++) {
        for (j = 0; j < col; j++) printf("  %.2f", *(A + i * col + j));
        printf("\n");
    }
}
//=========================

void Write2File(float *C) {
    FILE *result = fopen("result2.txt", "a");
    int i, j;

    for (i = 0; i < m; i++) {
        for (j = 0; j < n; j++) {
            fprintf(result, "%lf\t", *(C + i * n + j));
        }
        fprintf(result, "\n");
    }

    fclose(result);
}
//=========================

void KhoiTao(float *C) {
    int i, j;
    for (i = 0; i < m; i++)
        for (j = 0; j < n; j++) {
            if (i >= (m / 2 - 5) && i < (m / 2 + 5) && j >= (n / 2 - 5) && j < (n / 2 + 5))
                *(C + i * n + j) = 80.0;
            else
                *(C + i * n + j) = 25.0;
        }
}
//=========================

void FD(float *C, float *dC) {
    int i, j;
    float c, u, d, l, r;
    for (i = 0; i < m; i++)
        for (j = 0; j < n; j++) {
            c = *(C + i * n + j);
            u = (i == 0) ? *(C + i * n + j) : *(C + (i - 1) * n + j);
            d = (i == m - 1) ? *(C + i * n + j) : *(C + (i + 1) * n + j);
            l = (j == 0) ? *(C + i * n + j) : *(C + i * n + j - 1);
            r = (j == n - 1) ? *(C + i * n + j) : *(C + i * n + j + 1);
            *(dC + i * n + j) = (D / (dx * dx))*(u + d + l + r - 4 * c);
        }
}
//=========================

int main() {
    int i, j, count;
    float t;
    time_t t1, t2;
    t = 0;
    float *C, *dC;
    C = (float *) malloc((m * n) * sizeof (float));
    dC = (float *) malloc((m * n) * sizeof (float));
    KhoiTao(C);
    Write2File(C);
    printf("Gia tri khoi tao:\n");
    DisplayMatrix(C, m, n);
    count = 0;
    t1 = time(NULL);
    while (t <= T) {
        FD(C, dC);
        for (i = 0; i < m; i++)
            for (j = 0; j < n; j++)
                *(C + i * n + j) = *(C + i * n + j) + dt * (*(dC + i * n + j));
        t = t + dt;
        count = count + 1;
//        if (count % 5 == 0) Write2File(C);
    }
    t2 = time(NULL);
    //FD(C, dC);
    printf("Gia tri cuoi cung:\n");
    DisplayMatrix(C, m, n);
    //
    printf("\tThe Calculation time:%ld\n", (long) (t2 - t1));
    return 0;
}