hi,
i am running a very big code on my pc using redhat linux.
when i try to increase my array size, compile and run, i get
segmentation fault. i go into the debugger, run it, it crashes
right away. i can't even trace where it happens.
i have no idea what is the problem. any idea ???
Nov 14 '05
11  2229  tw*********@yah oo.com (mike) writes:
[...] ok...i declare all my variables with static array sizes. (a while back,
i did try the dynamic allocations as Emmanuel suggested below, but
since there is a huge number of variables with O(1e5-1e6) degrees of
freedom with complicate relationships, i decided to abandon this).
one of my variables:
double q[2650000][10][5] -> this is fine, but when i try:
double q[4530000][10][5] -> here is the error i got from the ddd debugger:
Program received signal SIGSEGV, Segmentation fault.
0x40000be0 in q ()
you guys are right, it looks like the memory is messed up.
so there is a limit on the array size?
Assuming sizeof(double) is 8, the first declaration gives you an array
whose size is nearly one gigabyte; the second is nearly 1.7 gigabytes.
If that's just *one* of your variables, you're dealing with a whole
lot of data, and I'm not surprised that your OS doesn't let you
allocate it all at once.
You may be able to increase the limit using the "limit" or "ulimit"
command (please don't ask for further details here; if you can't find
documentation, try a newsgroup appropriate to your operating system).
But you should consider whether it's all going to fit into physical
memory anyway. You might have better luck using files.
--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.
mike wrote: i am running a very big code on my pc using redhat linux.
when i try to increase my array size, compile and run, i get
segmentation fault. i go into the debugger, run it, it crashes
right away. i can't even trace where it happens.
i have no idea what is the problem. any idea ???
The large stack-based allocation screws up your stack. Shoving large
arrays on the stack is a bad idea if you ask me. Use malloc instead of a
static allocated array.
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