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➜ Programming
➜ General
➜ random_range
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| Posted by
| Zeno
USA (2,871 posts) Bio
|
| Date
| Thu 23 Jun 2005 06:13 PM (UTC) Amended on Thu 23 Jun 2005 06:39 PM (UTC) by Zeno
|
| Message
| I'm using SocketMUD and I seem to be having an issue with random_range. It crashes:
(gdb) f 4
#4 0x0804fe46 in pre_battle (acct=0xbfffe680, arg=0x80512b8 "") at battle.c:259
259 sprintf ( buf3, "Interesting fact #%d: %s", number+1, fact_table[number].text );
(gdb) p number
$1 = 544501582
number = random_range( 0, MAX_FACTS);
sprintf ( buf3, "Interesting fact #%d: %s", number+1, fact_table[number].text );
communicate(acct, buf3, COMM_INFO);
I have no idea why number is that high. It shouldn't go past 5.
/* returns a random number between a and b */
int random_range(int a, int b)
{
return ((int)(rand_seed() * ((double) (b) - (a) + 1))) + (a);
}
The whole random.c file can be found here:
http://www.daimi.au.dk/~jobo/socketmud/download/snippets/random.tar.gz
Anyone know why it's such a high number? My fact_table has 5 facts so it should go up to only 5.
This doesn't happen everytime. About 1 in 10 times. |
Zeno McDohl,
Owner of Bleached InuYasha Galaxy
http://www.biyg.org | | Top |
|
| Posted by
| David Haley
USA (3,881 posts) Bio
|
| Date
| Reply #1 on Thu 23 Jun 2005 07:07 PM (UTC) |
| Message
| There could be a bug in the random number generation code or you misusing it somehow. Are you initializing it using its init functions?
If you write a for loop in a separate program printing out 100 random numbers between 0 and 5, are they all between 0 and 5? |
David Haley aka Ksilyan
Head Programmer,
Legends of the Darkstone
http://david.the-haleys.org | | Top |
|
| Posted by
| Zeno
USA (2,871 posts) Bio
|
| Date
| Reply #2 on Thu 23 Jun 2005 07:16 PM (UTC) |
| Message
| Well there's never been a problem with it before. I used it for a damage function. It always did the range.
dam = random_range( 1, 5 );
I tested this just now. It never did anything outside of 1 - 5. |
Zeno McDohl,
Owner of Bleached InuYasha Galaxy
http://www.biyg.org | | Top |
|
| Posted by
| David Haley
USA (3,881 posts) Bio
|
| Date
| Reply #3 on Thu 23 Jun 2005 07:24 PM (UTC) |
| Message
| Well, if the function works and you know it works, there must be a problem in your code somewhere. A stack overflow that's corrupting memory, a bad type that's causing overflow, who knows.
I'd still recommend however that you write a for loop to exactly replicate your situation that is random_range(0, 5).
I'd also recommend actually stepping through the function in question and seeing if values are sane all the way through. |
David Haley aka Ksilyan
Head Programmer,
Legends of the Darkstone
http://david.the-haleys.org | | Top |
|
| Posted by
| Zeno
USA (2,871 posts) Bio
|
| Date
| Reply #4 on Thu 23 Jun 2005 07:36 PM (UTC) |
| Message
| Well this is odd.
(gdb)
259 number = random_range( 0, MAX_FACTS);
(gdb) p number
$5 = 134586728
(gdb) next
261 sprintf ( buf3, "Interesting fact #%d: %s", number+1, fact_table[number].text );
(gdb) p number
$7 = 4
Did I print number before it was set the first time? |
Zeno McDohl,
Owner of Bleached InuYasha Galaxy
http://www.biyg.org | | Top |
|
| Posted by
| David Haley
USA (3,881 posts) Bio
|
| Date
| Reply #5 on Thu 23 Jun 2005 07:41 PM (UTC) |
| Message
| | Yes. When it shows you a statement, that's what it's about to execute, so printing out 'number' will give you the previous (uninitialized) value. |
David Haley aka Ksilyan
Head Programmer,
Legends of the Darkstone
http://david.the-haleys.org | | Top |
|
| Posted by
| Zeno
USA (2,871 posts) Bio
|
| Date
| Reply #6 on Thu 23 Jun 2005 07:44 PM (UTC) |
| Message
| | Okay that's what I thought. I'll check more later into this with gdb and step after work. |
Zeno McDohl,
Owner of Bleached InuYasha Galaxy
http://www.biyg.org | | Top |
|
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