OpenMP并没有改善性能

Question

所以，我相信下面的代码，即使我没有看到任何错误，也无法并行化我的性能，并且就好像它是一个普通的单线程程序。

在 C 中使用OpenMP，我试图找到从文件读取的邻接列表之间的交叉点。我不知道我的代码是否是I / O绑定，或者我的指令放置不正确，循环不正确，我记录时间的方式还是由于某些系统要求？ omp_set_num_threads()似乎工作正常。

你们认为我应该检查一下这可能是OpenMP的问题，我很高兴知道。我知道它与OMP有关，因为我在MPI中编写了类似的代码，它提供了预期的性能。谢谢！

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

#define MAX 20000    //number of vertices we are working with
#define EACHLINE 99000  //max chars each line of file could possess

int *allLines[MAX];        //stores all the lines, hopefully
int lengths[MAX];
int lines = 0;

//function for getting intersecton of two arrays
void getIntersections(int *one, int *two, int l1, int l2){   
//arrays and their sizes
    #pragma omp critical
    {
        printf("%d & %d: [ ", *one, *two);
        for(int o=1; o<l1; o++){
            for(int t=1; t<l2; t++){
                if(*(one+o)==*(two+t)){
                     printf("%d ", *(one+o));
                     break;
                }
            }
        }
        printf("]\n");
    }
}

//getting common ones out of the adjacency lists with vertices v1 & v2
void getLists(int v1, int v2){
    int r, s, length1, length2;
    int *arr1, *arr2; 
    int done = 0;
    for(r=0; r<lines; r++){
        if( *(allLines[r]) == v1){
            int *arr11 = malloc(sizeof(int)*lengths[r]);
            length1 = lengths[r];
            arr11 = allLines[r];
            arr1 = arr11;
            if(done>0)
                break;
            done = 1;
        }
        else if( *(allLines[r]) == v2){
            int *arr22 = malloc(sizeof(int)*lengths[r]);
            length2 = lengths[r];
            arr22 = allLines[r];
            arr2 = arr22;
            if(done>0)
                break;
            done = 1;
        }    
    }
    getIntersections(arr1, arr2, length1, length2);
}

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

    //getting number of lines in file
    FILE *tp = fopen("r2.txt","r");
    int ch=0;
    while ((ch = fgetc(tp)) != EOF){
        if (ch == '\n')
            lines++;
    }
    fclose(tp);

    FILE* fp;
    if((fp = fopen("r2.txt", "r")) == NULL){        //opens file
        perror("Error opening file!");
        return 1;
    }

    char input[EACHLINE];
    for(int g = 0; g < lines; g++){   //dividing task among processes
        int arr[MAX], length = 0, c, bytesread;

        fgets(input, sizeof(input), fp);
        char* str = input;               //list buffer
        while (sscanf(str, "%d%n", &c, &bytesread) > 0) {  \
        //changing string of spaced numbers to int array
            arr[length++] = c;
            str += bytesread;
        }
        int *rr = malloc(sizeof(int)*length);
        for(int i=0; i < length; i++) {
            *(rr+i) = arr[i];       
        }
        allLines[g] = rr;
        lengths[g] = length;        
    }       

    clock_t start, end;     //clocks
    double cpu_time_used;   //time recorder
    start = clock();

    omp_set_num_threads(81);
    int r, s;
    #pragma omp parallel private(r, s) shared(lengths, allLines, lines)
    {   
        #pragma omp for
        for(r=0; r<lines; r++){
            for(s=0; s < lengths[r]; s++){  
                if( *(allLines[r]) < *(allLines[r]+s) ){
                    getLists( *(allLines[r]), *(allLines[r]+s) );
                }
            }      
        }
    }
    end = clock();  //timer stop
    cpu_time_used = ((double) (end - start)) / CLOCKS_PER_SEC;   
    //time taken
    printf("Time: %f\n", cpu_time_used);

    for(int k=0; k<lines; k++)
        free(allLines[k]);  

    fclose(fp);
    return 0;
}