数字集成的C代码在一台计算机上运行，​​但在另一台计算机上运行

Question

我使用rk4方法编写了一个简单摆锤的代码，并使用数值积分。 Here's an image of expected result. 它可以在我的笔记本电脑上运行，运行Ubuntu 14.04,64位（结果会产生正弦波），但在我的PC上无法运行，它运行Debian 8并且也是64位。 Here's an image of the wrong plot. 有什么理由会发生这种情况吗？

以下是代码：

#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <string.h>

int N = 2;

float h = 0.001;

struct t_y_couple {
  float t;
  float *y;
};


struct t_y_couple integrator_rk4(float dt, float t, float *p1);

void oscnetwork_opt(float t, float *y, float *dydt);

int main(void) {
  /* initializations*/
  struct t_y_couple t_y;

  int i, iter, j;

  //  time span for which to run simulation
  int tspan = 20;

  //  total number of time iterations = tspan*step_size
  int tot_time = (int)ceil(tspan / h);

  //  Time array
  float T[tot_time];

  //  pointer definitions
  float *p, *q;

  //  vector to hold values for each differential variable for all time
  //  iterations
  float Y[tot_time][2];
  //  N = total number of coupled differential equations to solve

  //  initial conditions vector for time = 0

  Y[0][0] = 0;
  Y[0][1] = 3.14;
  //  set the time array
  T[0] = 0;

  //  This loop calls the RK4 code
  for (i = 0; i < tot_time - 1; i++) {
    p = &Y[i][0];     // current time
    q = &Y[i + 1][0]; // next time step
                      //      printf("\n\n");
                      //      for (j=0;j<N;j++)

    //      call the RK4 integrator with current time value, and current
    //      values of voltage
    t_y = integrator_rk4(h, T[i], p);

    //      Return the time output of integrator into the next iteration of time
    T[i + 1] = t_y.t;

    //      copy the output of the integrator into the next iteration of voltage
    q = memcpy(q, t_y.y, (2) * sizeof(float));

    printf("%f ", T[i + 1]);
    for (iter = 0; iter < N; iter++)
      printf("%f ", *(p + iter));
    printf("\n");
  }

  return 0;
}

struct t_y_couple integrator_rk4(float dt, float t, float y[2]) {
  //  initialize all the pointers
  float y1[2], y2[2], y3[2], yout[2];
  float tout, dt_half;
  float k1[2], k2[2], k3[2], k4[2];
  //  initialize iterator
  int i;
  struct t_y_couple ty1;
  tout = t + dt;
  dt_half = 0.5 * dt;
  float addition[2];

  //  return the differential array into k1
  oscnetwork_opt(t, y, k1);
  //  multiply the array k1 by dt_half
  for (i = 0; i < 2; i++)
    y1[i] = y[i] + (k1[i]) * dt_half;
  //  add k1 to each element of the array y

  //  do the same thing 3 times
  oscnetwork_opt(t + dt_half, y1, k2);
  for (i = 0; i < 2; i++)
    y2[i] = y[i] + (k2[i]) * dt_half;

  oscnetwork_opt(t + dt_half, y2, k3);
  for (i = 0; i < 2; i++)
    y3[i] = y[i] + (k3[i]) * dt_half;
  oscnetwork_opt(tout, y3, k4);

  //  Make the final additions with k1,k2,k3 and k4 according to the RK4 code
  for (i = 0; i < 2; i++) {
    addition[i] = ((k1[i]) + (k2[i]) * 2 + (k3[i]) * 2 + (k4[i])) * dt / 6;

  }
  //  add this to the original array
  for (i = 0; i < 2; i++)
    yout[i] = y[i] + addition[i];
  //  return a struct with the current time and the updated voltage array
  ty1.t = tout;
  ty1.y = yout;

  return ty1;
}

// function to return the vector with coupled differential variables for each
// time iteration
void oscnetwork_opt(float t, float y[2], float *dydt) {
  int i;
  dydt[0] = y[1];
  dydt[1] = -(1) * sin(y[0]);
}

Answer 1

yout中的变量integrator_rk4()存在生命周期问题。您将yout的地址分配给ty1.y，但您在此功能之外使用它。这是未定义的行为。

快速修复：

struct t_y_couple {
  float t;
  float y[2];
};

struct t_y_couple integrator_rk4(float dt, float t, float y[2]) {
  float y1[2], y2[2], y3[2], yout[2];

  // ...

  ty1.t = tout;
  ty1.y[0] = yout[0];
  ty1.y[1] = yout[1];

  return ty1;
}

你有很多无用的分配，你制作了＃34; spaghetti code＆＃34;与您的全局变量。 You should not cast the return of malloc