section of my code is:
Code:printf(" i am upto here %d %d\n", i, j); payoffs[i][j] = (double *) malloc(sizeof(double)*temp); if( payoffs[i][j] == NULL) { printf("Mem Error \n"); exit(-1); } printf("but not upto here\n", i,j);
When value of temps 10^4 this works fine but when temp is 20^4, i get segmentation fault and also error message is not printed. If malloc was not able to allocate meory i should have got Mem Error, why is it only giving segmentation fault.
Are you running this on Linux, by any chance?
By the way, do not cast the return value of malloc unless you need the code to be compilable as C++.
Look up a C++ Reference and learn How To Ask Questions The Smart WayOriginally Posted by Bjarne Stroustrup (2000-10-14)
Yes, I am using Fedora 13, x_86
I removed the casting but it made no difference. In other general case why does casting do potential harm?By the way, do not cast the return value of malloc unless you need the code to be compilable as C++.
How is payoff declared ?
(Guessing) Shouldn't you assign the result of malloc to payoff and not payoff[i][j] ?
Thats not the issue, its working for all values of temp less than 10^4.. anyway. My declaration and allocation is ; ( here MEM_ERROR is macro)
Code:double ***payoffs = NULL; ................................... for(i =0; i < players; i++) { temp = profile/actions[i]; payoffs[i]= (double**)malloc(sizeof(double*)); if( payoffs[i] == NULL) MEM_ERROR maximum[i]= (char **)malloc(sizeof(char *)); if( maximum[i] == NULL) MEM_ERROR for(j = 0; j < actions[i]; j++) { maximum[i][j] = (char *) malloc(sizeof(char*)*temp); if ( maximum[i][j] ==NULL) MEM_ERROR printf(" i am upto here %d %d %d\n", i, j, temp); payoffs[i][j] = malloc(sizeof(double)*temp); if( payoffs[i][j] == NULL) MEM_ERROR printf("but not upto here\n", i,j); } }
I don't know if this is the problem that you're facing, but you may be interested to read: What is Optimistic Memory Allocation? How does it affect me?
When you forget to #include <stdlib.h>
Look up a C++ Reference and learn How To Ask Questions The Smart Way
thank you.. Seems like optimisitc memory alocation in linux is the problem. I am working out. Its a fairly large program, will take some time.... its a new information whatsoever. thanks
> double ***payoffs = NULL;
So do you do this at some point before trying to use it?
payoffs = malloc( players * sizeof(*payoffs) );
And what about this?
> payoffs[i]= (double**)malloc(sizeof(double*));
You do payoffs[i][j] later on, so this simply isn't enough memory.
Try say
payoffs[i] = malloc( actions[i] * sizeof(*payoffs[i]) );
If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
If at first you don't succeed, try writing your phone number on the exam paper.
I have done this before use:
I think they are same, isnt it?Code:payoffs = (double ***)malloc(sizeof(double **)*players);
If everything is correct, then yes. Otherwise, the version without the cast and which takes the sizeof based on the object rather than the type is correct.
Look up a C++ Reference and learn How To Ask Questions The Smart Way
