[英]How should I declare global variables in my C++ project?
I have two matrices as global variables. 我有两个矩阵作为全局变量。 However, when I run my project, I get a apache Mach-O linker error in xCode that says that my global variables are declared more than once.
但是,当我运行项目时,在xCode中出现了一个Apache Mach-O链接器错误,该错误表明我的全局变量被声明了多次。 I've determined the problem to be the placement of my global variables and the imports of the header files.
我确定问题出在我的全局变量的位置和头文件的导入。
My svd.h is here: 我的svd.h在这里:
#ifndef __netflix_project__svd__
#define __netflix_project__svd__
#include <stdio.h>
#include "dataManager.h"
const float GLOBAL_AVG_SET1 = 3.608609;
const float GLOBAL_AVG_SET2 = 3.608859;
const int TOTAL_USERS = 458293;
const int TOTAL_MOVIES = 17770;
double **user_feature_table = new double *[TOTAL_USERS];
double **movie_feature_table = new double *[TOTAL_MOVIES];
void initialize(int num_features);
void train();
double predictRating(int user, int movie);
#endif /* defined(__netflix_project__svd__) */
My svd.cpp is here: 我的svd.cpp在这里:
#include "svd.h"
void initialize(int num_features) {
for(int i = 0; i < TOTAL_USERS; i++) {
user_feature_table[i] = new double[num_features];
for(int k = 0; k < num_features; k++) {
user_feature_table[i][k] = GLOBAL_AVG_SET2 / num_features;
}
}
for(int i = 0; i < TOTAL_MOVIES; i++) {
movie_feature_table[i] = new double[num_features];
for(int k = 0; k < num_features; k++) {
movie_feature_table[i][k] = GLOBAL_AVG_SET2 / num_features;
}
}
}
My main.cpp looks like this: 我的main.cpp看起来像这样:
#include <iostream>
#include "svd.h"
int main(int argc, const char * argv[]) {
// Parse file and store test points as testPoint objects
std::vector<testPoint*> dataSet = fillTestPoints();
// Get global average of data set
/*
double avg = getGlobalAverage(dataSet);
printf("%f", avg);
*/
initialize(30);
for(int i = 0; i < TOTAL_USERS; i++) {
printf("%f\n", user_feature_table[i][0]);
}
return 0;
}
I ran into this problem before, but fixed it by taking out the global variables. 我之前遇到过这个问题,但是通过取出全局变量来解决了。 However, I do need to optimize this code, and using global variables is the way to do it so I do need to figure this out.
但是,我确实需要优化此代码,并且使用全局变量是实现此目的的方法,因此我需要弄清楚这一点。 Thanks!
谢谢!
In header file, only declare them. 在头文件中,仅声明它们。
extern const float GLOBAL_AVG_SET1;
extern const float GLOBAL_AVG_SET2;
extern const int TOTAL_USERS;
extern const int TOTAL_MOVIES;
extern double **user_feature_table;
extern double **movie_feature_table;
In one of your .cpp files, define and initialize them: 在您的一个.cpp文件中,定义并初始化它们:
const float GLOBAL_AVG_SET1 = 3.608609;
const float GLOBAL_AVG_SET2 = 3.608859;
const int TOTAL_USERS = 458293;
const int TOTAL_MOVIES = 17770;
double **user_feature_table = new double *[TOTAL_USERS];
double **movie_feature_table = new double *[TOTAL_MOVIES];
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