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POC random tree pointer warning (and sometimes crashing)
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2013-05-05T10:42:20.893
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I'm writing a program to create a trinary tree of random size. That is, I add 0-3 branches for each node randomly, then see how large the tree is. The goal is to run this a few thousand times and then do statistics -- size, diameter, depth, etc. I use a basic tree structure, and then a pointer of pointers to be able to order the nodes (0,1,2,3) based on when they were created, called tab_of_order. The current code, however, crashes randomly (maybe 1 time out of 5). At the bottom I give an example of what a crash looks like. The ArbreAlea() seems to run fine, but crashes on the return. I can't see why, either. Until it stops crashing I can't conceivably do a loop for 1000 cases. On another note, at the beginning of the function to create the random tree, I get a pointer warning "warning: assignment from incompatible pointer type [enabled by default]". Would this lead to my function crashing? Any idea how to fix it? The two functions I didn't paste are just functions to create a random number (0,1,2,3,4) with changing probabilities. Any help greatly appreciated! <pre><code>#include<stdlib.h> #include<stdio.h> // Structure of the tree. Position is the value of the node. The nodes are // numbered 1 to n thus the number gives it's position struct tree_el { int position; struct tree_el * first, * second, * third, * fourth; }; typedef struct tree_el myNode; //Structure of the data to be analysed struct donnees { int nb_vertices; int nb_feuilles; int profondeur; int largeur; int diametre; }; //Simplified queue structure struct queue { int debut; int fin; }; //initialize functions int get_rnd_value (int min, int max); int rand_loi1 (int iteration); void add_node (int nb_node_to_add, myNode **tab_of_order, struct queue *arbreQ); struct donnees * ArbreAlea (void); int main(void) { srand((unsigned)time(NULL)); //seed random number generator int nb_node=0; struct donnees *resultat; resultat=(struct donnees*)malloc(sizeof(struct donnees)*1); resultat = ArbreAlea(); printf("\n\nNombre Vertices : %d \n",resultat->nb_vertices); return 0; } void add_node(int nb_node_to_add, myNode **tab_of_order, struct queue *arbreQ){ int i; int next = arbreQ->debut; for (i=1; i <= nb_node_to_add; i++){ myNode *tmp_node; tmp_node = (myNode*) malloc(sizeof(myNode)*1); tmp_node->position = arbreQ->fin + i; if(i==1){ tab_of_order[next]->first = tmp_node; } else if(i==2) { tab_of_order[next]->second = tmp_node; } else if(i==3) { tab_of_order[next]->third = tmp_node; } else if(i==4) { tab_of_order[next]->fourth = tmp_node; } tab_of_order[tmp_node->position] = tmp_node; //printf("Tab_of_order[ %d ] %d connected to node %d\n", next , i, tab_of_order[tmp_node->position]->position); } //printf("add to node %d, %d node(s) is/are added\n", next , nb_node_to_add); arbreQ->fin = arbreQ->fin + nb_node_to_add; arbreQ->debut +=1; tab_of_order[arbreQ->fin + 1] = NULL; //printf("\nDebut %d Fin %d\n",arbreQ->debut,arbreQ->fin); return; } struct donnees * ArbreAlea (void) { struct donnees *data; //Here i get "warning: assignment from incompatible pointer type [enabled by default]" data = (struct donnnes *)malloc(sizeof(struct donnees)*1); struct queue *arbreQ; arbreQ = (struct queue *)malloc(sizeof(struct queue)*1); arbreQ->debut=0; arbreQ->fin=0; int nb_node = 0; //nb_node is the number total of nodes in tree. int nb_node_to_add; // nb_node_to_add is how many nodes you have to add for each node. // this table keeps track of the order of nodes to quickly look up where to add the next node. myNode ** tab_of_order; tab_of_order = (myNode **) malloc(sizeof(myNode*) * nb_node); // First we make the begninning of the tree. This is the only time it can have 4 branches. // There is a 1/4 chance of having a tree of size one. myNode *tree; tree = (myNode*) malloc(sizeof(myNode) * 1 ) ; tree->position = 0; tab_of_order[0] = tree; //next = 0; nb_node_to_add = rand_loi1(arbreQ->debut); if (nb_node_to_add == 0){ data->nb_vertices=1; data->nb_feuilles=0; data->profondeur=0; data->largeur=0; data->diametre=0; printf("\nZero Tree"); return(data); } else { do { nb_node_to_add=rand_loi1(arbreQ->debut); printf("\nAdding %d nodes, debut %d, fin %d",nb_node_to_add,arbreQ->debut,arbreQ->fin); if (nb_node_to_add==0) arbreQ->debut += 1; else if (nb_node_to_add>=1) add_node(nb_node_to_add, tab_of_order, arbreQ); nb_node = nb_node + nb_node_to_add; if (tab_of_order[arbreQ->debut]==NULL) printf("\n Next is null : %d",arbreQ->debut); }while (tab_of_order[arbreQ->debut]!=NULL); } data->nb_vertices=nb_node+1; data->profondeur=0; data->largeur=0; printf("\nTree debut %d fin %d nodes %d",arbreQ->debut,arbreQ->fin,nb_node+1); return (data); } </code></pre>
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<c><pointers><struct><tree><crash>
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C random tree pointer warning (and sometimes crashing)
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