如何使用C中的函数生成随机数组

我试图将程序从Matlab移植到C，以便改善执行时间和内存使用。 由于C中没有生成0和1统一填充数组的函数（或者我找不到它们），因此我创建了一个函数来相应地填充相关概率的数组。

示例 ：如果概率为0.3（30％），我希望有一个包含100个元素的数组，随机填充零和1 ，并且数组的总和必须接近30。

而不是100我使用N =试验数，所以如果N = 10000那么数组之和应该接近3000，等等。

Matlab中的function只是：

function [y] = rand_gen(N,Prob) for i=1:N y(i,1) = binornd(1,Prob); end end 

该函数将被称为：

 array = rand_gen(N, Probability); 

现在，这是C中的问题：当我运行程序时，我可以生成一些数组，但最大试验次数（N）非常低，我不认为它是内存问题。 如果我运行N = 100000的程序一切正常，但在100000（和其他东西）崩溃后。 C中的程序是：

 #include  #include  #include  int * rand_gen(int N, double Prob); // Function declaration int sum_array(int a[], int num_elements); // Function declaration int main() // Main function { int N; // Declaration: Number of trials printf("Number of trials: "); scanf("%d", &N); // Asks for Number of trials double Prob_a = 0.5; // Probability (50%) int i; // Declaration: Index int sum; // Declaration: sum of elements of arrays int bin_array_0[N]; // Declaration: array populated randomly by 0 and 1 int bin_array_1[N]; // Declaration: array populated randomly by 0 and 1 int bin_array_2[N]; // Declaration: array populated randomly by 0 and 1 int bin_array_3[N]; // Declaration: array populated randomly by 0 and 1 int *ptrnd = NULL; // Declaration: pointer to array int seed = time(NULL); // Declaration: random number generator seed (based on current time) srand(seed); ptrnd = rand_gen(N, Prob_a); // Populate a temporary array with 0 and 1 using the rand_gen function for(i=0 ; i<N ; i++) { bin_array_0[i] = *(ptrnd + i); } /* Print the sum of ones in the array * in order to check the rand_gen probability * reliability and compare to the temp array */ sum = sum_array(bin_array_0, N); printf("\n The sum of the bin_array_0 is %d\n", sum); ptrnd = rand_gen(N, Prob_a); // Populate a temporary array with 0 and 1 using the rand_gen function for(i=0 ; i<N ; i++) { bin_array_1[i] = *(ptrnd + i); } /* Print the sum of ones in the array * in order to check the rand_gen probability * reliability and compare to the temp array */ sum = sum_array(bin_array_1, N); printf("\n The sum of the bin_array_1 is %d\n", sum); ptrnd = rand_gen(N, Prob_a); // Populate a temporary array with 0 and 1 using the rand_gen function for(i=0 ; i<N ; i++) { bin_array_2[i] = *(ptrnd + i); } /* Print the sum of ones in the array * in order to check the rand_gen probability * reliability and compare to the temp array */ sum = sum_array(bin_array_2, N); printf("\n The sum of the bin_array_2 is %d\n", sum); ptrnd = rand_gen(N, Prob_a); // Populate a temporary array with 0 and 1 using the rand_gen function for(i=0 ; i<N ; i++) { bin_array_3[i] = *(ptrnd + i); } /* Print the sum of ones in the array * in order to check the rand_gen probability * reliability and compare to the temp array */ sum = sum_array(bin_array_3, N); printf("\n The sum of the bin_array_3 is %d\n", sum); return(0); } // Function: generate an array populated by 0 and 1 according to a uniformed distribution int * rand_gen(int N, double Prob) { int sum; // Declaration: sum of elements of arrays int *array; array = (int *)malloc(sizeof(int)*N); if(array == NULL) { printf("\nRun out of memory!\n"); exit(1); } int j; double x; for(j=0; j<N; j++) { x=rand(); x=x/RAND_MAX; if (x < Prob) { array[j]=1; } else { array[j]=0; } } /* Print the sum of ones in the array * in order to check the rand_gen probability * reliability and compare to the bin_array_* */ sum = sum_array(array, N); printf("\n The sum of the temp array is %d\n", sum); return array; } // Function: sum elements of array and return the sum. int sum_array(int a[], int num_elements) { int k, sum=0; for (k=0; k<num_elements; k++) { sum = sum + a[k]; } return(sum); } 

请给我一些如何解决问题的提示。 我已经尝试过不同类型的值（ long而不是int和double而不是float ）但没有任何结果。 先感谢您！

干杯，

Pullo86

Answer 1

你几乎肯定想要做的是传递rand_gen()一个指向它要填充的数组的指针，并让它写入，而不是让它分配大型数组然后复制和泄漏。 （这是一个应用程序，C ++ STL， 和 ，可能更适合。）

但是，如果要使用此基本结构，请声明：

 #include  #include  #include  /* Set N. */ bool *binarray[] = { rand_gen( N, prob_a ), // binarray[0] rand_gen( N, prob_a ), rand_gen( N, prob_a ), rand_gen( N, prob_a ) // binarray[3] }; static const size_t m = sizeof(binarray)/sizeof(binarray[0]); /* Do stuff with binarray[0] through binarray[m-1]. */ for ( size_t i = 0; i < m; ++i ) { free(binarray[i]); binarray[i] = NULL; } 

但实际上，您可能需要随机生成器更新的数组数组，例如：

 bool *fill_arrays( size_t m, size_t n, bool to_fill[m][n], double prob ) { for ( size_t i = 0; i < m; ++i ) rand_gen_in_place( to_fill[i], n, prob ); return to_fill; } void do_stuff_with( size_t m, size_t n, bool binarray[m][n] ); int main(void) { /* … */ bool* arrayp = calloc( M*N, sizeof(bool) ); fill_arrays( M, N, arrayp, prob_a ); do_stuff_with( M, N, arrayp ); free(arrayp); /* … */ }