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Рабочая версия

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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <malloc.h>
  4. #include <math.h>
  5.  
  6. int N=5;
  7. typedef double (*mytype)(double, double); //тип указывающий на функцию
  8.  
  9. double f0(double x, double y)
  10. {
  11.     return cos(x)/x+(-1.0)*(y+0)/x;
  12. }
  13.  
  14. double f1(double x, double y)
  15. {
  16.     return x/50;
  17. }
  18.  
  19. double f2 (double x, double y)
  20. {
  21.     return (-2.0)* (y+2)/ x;
  22. }
  23.  
  24. double f3 (double x, double y)
  25. {
  26.     return -cos(x);
  27. }
  28.  
  29. double f4 (double x, double y)
  30. {
  31.     return sin (x);
  32. }
  33.  
  34.  
  35. double* StepEuler (double x, double *y, double step, int N, double (*func[])(double, double ))
  36. {
  37.     for (int i=0; i<N; i++)
  38.     {
  39.         y[i]=y[i]+func[i](x, y[i])*step;
  40.     }
  41.     return y;
  42. }
  43. double* StepRK(double x, double *y, double step, int N, double (*func[])(double, double))
  44. {
  45.     double *k1, *k2, *k3, *k4;
  46.     k1 = malloc(N * sizeof(double));
  47.     k2 = malloc(N * sizeof(double));
  48.     k3 = malloc(N * sizeof(double));
  49.     k4 = malloc(N * sizeof(double));
  50.  
  51.     for (int i = 0; i < N; ++i)
  52.         k1[i] = func[i](x,y[i]);
  53.  
  54.     double *dop = malloc(N * sizeof(double));
  55.     for (int i = 0; i < N; ++i)
  56.     {
  57.         dop[i] = y[i] + k1[i]*step/2;
  58.         k2[i] = func[i]((x+step/2),(dop[i]));
  59.  
  60.     }
  61.  
  62.     for (int i = 0; i < N; ++i)
  63.     {
  64.         dop[i] = y[i] + k2[i]*step/2;
  65.         k3[i] = func[i]((x+step/2),(dop[i]));
  66.  
  67.     }
  68.  
  69.     for (int i = 0; i < N; ++i)
  70.     {
  71.         dop[i] = y[i] + k1[i]*step;
  72.         k4[i] = func[i]((x+step),(dop[i]));
  73.  
  74.     }
  75.  
  76.     for (int i = 0; i < N; ++i)
  77.         y[i] = y[i]+ step*(k1[i]+2*k2[i]+2*k3[i]+k4[i])/6;
  78.  
  79.     return y;
  80. }
  81.  
  82. void main()
  83. {
  84.     mytype *mass = malloc(N * sizeof(mytype));
  85.     mass[0]=f0;
  86.     mass[1]=f1;
  87.     mass[2]=f2;
  88.     mass[3]=f3;
  89.     mass[4]=f4;
  90.     FILE *fe, *fk;
  91.     fe=fopen ("Euler.txt", "w");
  92.  
  93.     //double (*mass[]) (double, double*, int) ={f0, f1, f3, f2, f4};
  94.     double x, xk, h, x0, y1, y2, y3, y4, y5;
  95.     printf("Input interval");
  96.     scanf("%lf%lf", &x, &xk);
  97.     x0=x;
  98.     printf("Input step");
  99.     scanf("%lf", &h);
  100.     printf("Input start conditions");
  101.     scanf("%lf%lf%lf%lf%lf", &y1, &y2,&y3,&y4,&y5);
  102.     double *y = malloc(N * sizeof(double));
  103.     *y=y1;
  104.     *(y+1)=y2;
  105.     *(y+2)=y3;
  106.     *(y+3)=y4;
  107.     *(y+4)=y5;
  108.     for (;x < xk; x =x+ h) {
  109.         printf("%lf\t", x);
  110.         fprintf(fe, "%lf\t", x);
  111.         for (int i = 0; i < N; ++i) {
  112.             printf("%lf\t", y[i]);
  113.             fprintf(fe, "%lf\t", y[i]);
  114.         }
  115.         y = StepEuler(x, y, h, N, mass);
  116.         printf("\n");
  117.         fprintf(fe, "\n");
  118.     }
  119.     fclose(fe);
  120.     *y=y1;
  121.     *(y+1)=y2;
  122.     *(y+2)=y3;
  123.     *(y+3)=y4;
  124.     *(y+4)=y5;
  125.     x=x0;
  126.     fk=fopen ("RK.txt", "w");
  127.     for (;x < xk; x =x + h) {
  128.         printf("%lf\t", x);
  129.         fprintf(fk, "%lf\t", x);
  130.         for (int i = 0; i < N; i++) {
  131.             printf("%lf\t", y[i]);
  132.             fprintf(fk, "%lf\t", y[i]);
  133.         }
  134.         y = StepRK(x, y, h, N, mass);
  135.         printf("\n");
  136.         fprintf(fk, "\n");
  137.     }
  138.     fclose(fe);
  139.     fclose(fk);
  140. }
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