Set Covering : Runtime hang\error at function call in c
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Thread: Set Covering : Runtime hang\error at function call in c

  1. #1
    Join Date
    Nov 2011
    Posts
    1

    Lightbulb Set Covering : Runtime hang\error at function call in c

    I am implementing a set covering application which uses cover function

    int cover(set *skill_list,set *player_list,set *covering)
    Suppose skill_set={a,b,c,d,e}, player_list={s1,s2,s3} then output coverin ={s1,s3} where say s1={a,b,c}, s3={d,e} and s2={b,d}.

    Now when I am calling this function it's hanging at run (set_cover.exe stopped working).

    Here is my cover function:

    typedef struct Spst_{
    void *key;
    set *st;
    }Spst;

    int cover(set *skill_list,set *player_list,set *covering)
    {
    Liste *member,*max_member;
    Spst *subset;
    set *intersection;
    void **data;
    int max_size;

    set_init(covering); //to initialize set covering initially

    while(skill_list->size>0&&player_list->size>0)
    {
    max_size=0;
    for(member=player_list->head;member!=NULL;member=member->next)
    {
    if(set_intersection(intersection,((Spst *)(member->data))->st,skill_list)!=0)
    return -1;

    if(intersection->size>max_size)
    {
    max_member=member;
    max_size=intersection->size;
    }

    set_destroy(intersection); //at the end of iteration
    }

    if(max_size==0) //to check for no covering
    return -1;

    subset=(Spst *)max_member->data; //to insert max subset from play list to covering set
    set_inselem(covering,subset);

    for(member=(((Spst *)max_member->data)->st->head);member!=NULL;member=member->next) //to rem elem from skill list
    {
    data=(void **)member->data;
    set_remelem(skill_list,data);
    }

    set_remelem(player_list,(void **)subset); //to rem subset from set of subsets play list
    }

    if(skill_list->size>0)
    return -1;

    return 0;
    }


    Now assuming I have defined three set type sets(as stated above) and calling from main as

    cover(skills,subsets,covering);=> runtime hang Here
    Please give inputs on the missing link in this or the prerequisites for a proper call to this function type required.

    Assume other functions used in cover are tested and working fine.

  2. #2
    Join Date
    Nov 2011
    Posts
    6

    Re: Set Covering : Runtime hang\error at function call in c

    Hi , you have not given the complete code as
    set_intersection(intersection,((Spst *)(member->data))->st,skill_list);
    function what it do we dont know ..infact i am not getting the idea about what the whole function cover is doing .. one more thing .. why using so many pointer .

  3. #3
    Join Date
    Apr 1999
    Posts
    27,422

    Re: Set Covering : Runtime hang\error at function call in c

    Quote Originally Posted by bitme View Post
    I am implementing a set covering application which uses cover function

    int cover(set *skill_list,set *player_list,set *covering)
    Suppose skill_set={a,b,c,d,e}, player_list={s1,s2,s3} then output coverin ={s1,s3} where say s1={a,b,c}, s3={d,e} and s2={b,d}.

    Now when I am calling this function it's hanging at run (set_cover.exe stopped working).
    You are using pointers all over the place in your code. By doing this, it is assumed you know how to debug a problem when you get a pointer related problem. So have you debugged your code?
    Assume other functions used in cover are tested and working fine.
    No. We cannot just assume that the other functions are working.

    When you write a C program that is highly based on pointers, a "working" program may not be working at all. It could be corrupting memory, and you wouldn't know it.

    To properly diagnose these issues, you must provide all your code to us, not just a few functions. We would then need to run your program on our machine to duplicate the problem. Trying to debug a program that has pointers like this is not possible with just a few functions being shown us and we are just to look at them.

    But the bottom line is that you wrote this program, therefore you should be able to debug it yourself. Otherwise, don't undertake writing such complex and hard-to-maintain functions.

    Last, please use code tags when posting code, as your code is practically unreadable:
    Code:
    typedef struct Spst_{           
        void *key;
        set *st;
    }Spst;
    
    int cover(set *skill_list,set *player_list,set *covering)       
    {
        Liste *member,*max_member;          
        Spst *subset;
        set *intersection;          
        void **data;
        int max_size;                   
    
        set_init(covering);         //to initialize set covering initially  
    
        while(skill_list->size>0&&player_list->size>0)
        {
            max_size=0;
            for(member=player_list->head;member!=NULL;member=member->next)
            {
                if(set_intersection(intersection,((Spst *)(member->data))->st,skill_list)!=0)
                    return -1;
    
                if(intersection->size>max_size)
                {
                    max_member=member;
                    max_size=intersection->size;
                }
    
                set_destroy(intersection);              //at the end of iteration
            }
    
            if(max_size==0)                 //to check for no covering
                return -1;
    
            subset=(Spst *)max_member->data;            //to insert max subset from play list to covering set
            set_inselem(covering,subset);
    
            for(member=(((Spst *)max_member->data)->st->head);member!=NULL;member=member->next)     //to rem elem from skill list
            {
                data=(void **)member->data;
                set_remelem(skill_list,data);
             }
    
            set_remelem(player_list,(void **)subset);           //to rem subset from set of subsets play list
        }
    
        if(skill_list->size>0)
            return -1;
    
        return 0;
    }
    That is an example of using code tags.

    Regards,

    Paul McKenzie

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