| 1 | = Ex23.c = |

| 2 | {{{#!C |

| 3 | /* |

| 4 | Large Scale Computing |

| 5 | Convective Heat/Mass Transfer |

| 6 | ex23.c : Gauss-Seidel |

| 7 | |

| 8 | duphi/dx = d2phi/dx2 |

| 9 | */ |

| 10 | #include<stdio.h> |

| 11 | #include<stdlib.h> |

| 12 | #include<math.h> |

| 13 | |

| 14 | /* min and max macros */ |

| 15 | #define max(a,b) (((a) > (b)) ? (a) : (b)) |

| 16 | #define min(a,b) (((a) < (b)) ? (a) : (b)) |

| 17 | |

| 18 | int main(int argc, char **argv){ |

| 19 | double a,b,d,u; |

| 20 | double *phi; |

| 21 | double w; |

| 22 | double dx,x,sol; |

| 23 | double err; |

| 24 | double ae,aw,ap; |

| 25 | double tol = 1.0e-10; |

| 26 | int i,num,itc; |

| 27 | FILE *fp; |

| 28 | |

| 29 | if (argc < 6){ |

| 30 | printf("Usage:%s [NUM] [A] [B] [D] [U]\n",argv[0]); |

| 31 | exit(-1); |

| 32 | } |

| 33 | |

| 34 | /* set parameters */ |

| 35 | num = atoi(argv[1]); |

| 36 | a = atof(argv[2]); |

| 37 | b = atof(argv[3]); |

| 38 | d = atof(argv[4]); |

| 39 | u = atof(argv[5]); |

| 40 | |

| 41 | printf("num=%d A=%e B=%e D=%e U=%e\n",num,a,b,d,u); |

| 42 | |

| 43 | /* Memory Allocation and Check*/ |

| 44 | phi = (double *)calloc(num, sizeof(double)); |

| 45 | if (phi == (double *)NULL){ |

| 46 | printf("Memory Allocation Failed\n"); |

| 47 | exit(-1); |

| 48 | } |

| 49 | |

| 50 | /** Setup **/ |

| 51 | dx = 1.0 / (double)(num - 1); |

| 52 | for (i = 0 ; i < num ; i++){ |

| 53 | phi[i] = 0.0; |

| 54 | } |

| 55 | ae = d / dx + max(-u,0.0); |

| 56 | aw = d / dx + max(u,0.0); |

| 57 | ap = ae + aw; |

| 58 | |

| 59 | /* Boundary Condition*/ |

| 60 | phi[0] = a; |

| 61 | phi[num-1] = b; |

| 62 | |

| 63 | /* Solve with Gauss-Seidel Method*/ |

| 64 | itc = 0; |

| 65 | while(1){ |

| 66 | /* update phi & Check Convergence */ |

| 67 | err = 0.0; |

| 68 | for (i = 1 ; i < (num - 1) ; i++){ |

| 69 | w = (ae * phi[i + 1] + aw * phi[i - 1]) / ap; |

| 70 | err += (w - phi[i]) * (w - phi[i]); |

| 71 | phi[i] = w; |

| 72 | } |

| 73 | |

| 74 | itc++; |

| 75 | if (err < tol) break; |

| 76 | if ((itc % 100) == 0) printf("itc=%d err=%e\n",itc,err); |

| 77 | } |

| 78 | |

| 79 | printf("Number of Iteration=%d\n",itc); |

| 80 | |

| 81 | /* Output Result */ |

| 82 | fp = fopen("res.dat","w"); |

| 83 | if (fp == NULL){ |

| 84 | printf("File could not create\n"); |

| 85 | exit(-1); |

| 86 | } |

| 87 | |

| 88 | for (i = 0 ; i < num ; i++){ |

| 89 | x = dx * (double)i; |

| 90 | sol = a + (b - a) * (exp(x * u / d) - 1.0) / (exp(u / d) - 1.0); |

| 91 | fprintf(fp,"%e %e %e\n",x,phi[i],sol); |

| 92 | } |

| 93 | fclose(fp); |

| 94 | |

| 95 | /* END : Deallocate Memory */ |

| 96 | free(phi); |

| 97 | printf("Done\n"); |

| 98 | } |

| 99 | }}} |