| --- Log opened Mon Jan 25 00:00:28 2010 |
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| 01:25 | <@McMartin> | Sigh. I've got my solution for #148, but I can't seem to stop leaking 20 times my RAM. |
| 02:02 | < gnolam> | McMartin: http://imgur.com/quoWk.gif |
| 02:03 | <@McMartin> | gnolam: This is a "I'm maintaining a pointer to something secretly and I can't figure out where" thing |
| 02:04 | <@McMartin> | I'm going to have to wait for MCV and consult with his wisdom |
| 02:07 | | * gnolam should get into Project Euler some day. |
| 02:08 | <@McMartin> | I suspect I could re-do everything to make my solution more contained and rely less on infinite lists |
| 02:08 | <@McMartin> | But the solution is so elegant, I want to keep it =( |
| 02:24 | <@Derakon> | McM: language? |
| 02:29 | <@McMartin> | Haskell |
| 02:29 | <@McMartin> | Hence why I need to wait for MCV~ |
| 02:29 | <@Derakon> | Right, right. |
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| 03:01 | <@McMartin> | Hup, there's the circular reference, I think |
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| 04:34 | | * Vornicus fiddles with a random ridiculous puzzle: longest two-word heterogram. |
| 04:39 | <@Vornicus> | (a heterogram is a word/phrase with no repeated letters; "uncopyrightables" is the longest one-word heterogram |
| 05:04 | <@McMartin> | Memory usage has gone from approx 60GB to approx 10MB. |
| 05:04 | <@Derakon> | ...60GB memory usage? |
| 05:05 | <@McMartin> | Yeah, uh, I had ten lazily evaluated infinite lists that was supposed to get garbage collected as it was processed? |
| 05:05 | <@McMartin> | They weren't because I had some stale pointers to the heads of them. |
| 05:05 | <@McMartin> | I'd shut it off after three seconds as the 1-GB machine doing the computation started thrashing (it took a few seconds to build up, so if I was fast with top I could see it carreeening towards the brick wall), but that's my estimate of the required RAM as-was. |
| 05:06 | <@McMartin> | Memory usage is now at 0.3% and stable, and I'm estimating the basic runtime as being about 20MB. |
| 05:07 | <@McMartin> | I don't see any way to solve this though that doesn't in some way involve a loop from one to a billion. |
| 05:09 | <@McMartin> | Granted, the brute force one is a loop more like 10^20. |
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| 06:16 | <@McMartin> | woot, level 4 \o/ |
| 06:20 | <@Vornicus> | woot |
| 06:21 | < Serah> | Wheee. |
| 06:28 | <@McMartin> | It's even continguous |
| 06:28 | <@Derakon> | How many level-4s are there? |
| 06:30 | <@Derakon> | Ahh. 470. |
| 06:31 | | Derakon is now known as Derakon[AFK] |
| 06:31 | <@Vornicus> | (and another 358 level 5s and 6s, for a total of 828 who have achieved that goal.) |
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| 06:40 | <@McMartin> | http://projecteuler.net/index.php?section=profile&profile=McMartin |
| 06:41 | <@Vornicus> | DODECAHEDRON~ |
| 06:41 | <@Vornicus> | _ |
| 06:41 | <@Vornicus> | rather. |
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| 13:39 | < Tarinaky> | I'm looking for suggestions on PRNGs. |
| 13:39 | < Tarinaky> | I could just use an off the shelf Mersenne Twister but I'm kindof put off by the fact that I don't understand it. |
| 13:40 | | * TheWatcher tends to use knuth's subtractive method |
| 13:42 | | * TheWatcher digs out his code |
| 13:44 | < Tarinaky> | I should specify it's for a game. Which I'm informed simplifies things. |
| 13:45 | <@TheWatcher> | Tarinaky: http://pastebin.starforge.co.uk/105 - the .cpp http://pastebin.starforge.co.uk/106 - the .h |
| 13:45 | < Tarinaky> | Cheers. |
| 13:45 | <@TheWatcher> | http://alexandria.starforge.co.uk/wiki/Random_Number_Generator - the discussion |
| 13:51 | < Tarinaky> | What's abs? |
| 13:52 | <@TheWatcher> | absolute. |
| 13:52 | < Tarinaky> | Oh. Sorry. Brain fart. |
| 13:53 | <@TheWatcher> | (it's in cstdlib, or it bloody should be) |
| 13:54 | < Tarinaky> | "for(i = 1; i < 56; ++i) {" shouldn't this be i < 55? |
| 13:54 | < Tarinaky> | Or am I missing something? |
| 13:55 | < Tarinaky> | Line 20 in the discussion ;x |
| 13:57 | <@TheWatcher> | Nope, 56 is right. The primer loop wants to cover the whole array, rather than the whole thing except the last element like the initialiser |
| 13:59 | < Tarinaky> | But ma only has 55 elements. |
| 14:00 | < Tarinaky> | For 1...56 ignores the first and goes out of bounds at the end. |
| 14:00 | <@TheWatcher> | int ma[56]; |
| 14:00 | <@TheWatcher> | so < 56 is fine |
| 14:00 | < Tarinaky> | Oh! |
| 14:00 | < Tarinaky> | 6 ma[55] = mj; confused me. |
| 14:01 | < Tarinaky> | Why're you ignoring ma[0] though? |
| 14:02 | <@TheWatcher> | Makes the initialise maths less messy, basically. |
| 14:06 | < Tarinaky> | I see. |
| 14:06 | < Tarinaky> | Part of my requirement is I need to be able to save the PRNG's state to a file. |
| 14:07 | <@TheWatcher> | So, save ma[], inext, and inextp - you can trivially add functions to get them |
| 14:08 | < Tarinaky> | If I save the values of ma then read them back in that'll work? |
| 14:08 | <@TheWatcher> | and then, you can just.. yep |
| 14:08 | < Tarinaky> | Heh, that's what I was going to ask >.> |
| 14:08 | < Tarinaky> | As for initial seed - I assume time() would be satisfactory? |
| 14:09 | <@TheWatcher> | you'll need inext and inextp as well as ma, otherwise you'll break the seqeuence, but yes. And yes, time'll be fine. |
| 14:09 | < Tarinaky> | Alright. |
| 14:09 | | * Tarinaky goes off and attempts to reimplement it. |
| 14:09 | <@TheWatcher> | (hell, you could add load() and save() which take file streams to read/write to *shrug*) |
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| 14:11 | < Tarinaky> | That was the notion. |
| 14:12 | <@TheWatcher> | Have fun :) |
| 14:15 | < Tarinaky> | What's the significance of 56 btw? |
| 14:16 | <@TheWatcher> | In complete honesty, I'm not sure. That's something knuth's discussion of the algorithm kinda glosses over a bit. |
| 14:16 | < Tarinaky> | And the internal seed? |
| 14:17 | | * TheWatcher digs out his copy of the text, one moment |
| 14:17 | < Tarinaky> | Heh. |
| 14:19 | <@TheWatcher> | That number is a side effect of allowing the algorithm to work nicely with floats on systems with <32bit ints. You can use any number provided that it is less than MBIG there. |
| 14:20 | <@TheWatcher> | I left it because *shrug* whynot. |
| 14:21 | < Tarinaky> | It just has to be 0<internal seed < MBIG, aye? |
| 14:21 | <@TheWatcher> | Aye |
| 14:24 | <@TheWatcher> | You could set it to something like 1723 or something similarly appropriate. |
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| 14:35 | < Tarinaky> | I don't really understand what would be appropriate :/ |
| 14:35 | < Tarinaky> | ma[i] -= ma[i + (i + 30) % 55]; << Won't this run out of bounds? |
| 14:36 | < Tarinaky> | When i is 55 for example... 55+30 :/ |
| 14:37 | <@TheWatcher> | Precedence, old bean |
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| 14:38 | | * Tarinaky looks up the precedence. |
| 14:38 | < Tarinaky> | If it doesn't run out of bound why're there brackets around i+30? |
| 14:38 | <@TheWatcher> | Wate |
| 14:38 | <@TheWatcher> | that should be 1 + (i + 30) % 55 |
| 14:39 | < Tarinaky> | Ah. That makes much more sense. |
| 14:39 | | * TheWatcher fixes |
| 14:41 | | * TheWatcher does vaguely wonder when he messed that one up though, hohums |
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| 15:00 | < Tarinaky> | TheWatcher: I have no idea how you got the stats you did. |
| 15:00 | < Tarinaky> | http://tarinaky.pastebin.com/m23040a9a |
| 15:00 | < Tarinaky> | I'm getting considerably less random output than you did. |
| 15:02 | <@TheWatcher> | huh. Did you change anything other than that s/i+/1+/ ? |
| 15:02 | < Tarinaky> | Not that I'm aware of. |
| 15:02 | < Tarinaky> | I used slightly more verbose variable names. |
| 15:02 | | * Tarinaky pastebins full source. |
| 15:03 | <@TheWatcher> | How many numbers are you generating, too?# |
| 15:03 | < Tarinaky> | http://tarinaky.pastebin.com/m39727f00 |
| 15:03 | < Tarinaky> | 1E3. |
| 15:03 | < Tarinaky> | My test program is: for(int i=0;i<1E3;i++) { |
| 15:03 | < Tarinaky> | cout << PRNG() << " "; |
| 15:03 | < Tarinaky> | } |
| 15:04 | < Tarinaky> | Well, prng PRNG then the for-loop. |
| 15:07 | <@TheWatcher> | Well, there's one mistale note - 49 should be miArray[55]= iCurrent; |
| 15:09 | <@TheWatcher> | *mistake I |
| 15:10 | < Tarinaky> | That change hasn't had any appreciable effect on the statistics. |
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| 15:14 | <@TheWatcher> | hm |
| 15:15 | | * TheWatcher cinfuseds |
| 15:15 | <@TheWatcher> | *o |
| 15:16 | < Tarinaky> | Would it help to try compiling it on your box to see if it's something hardware? |
| 15:16 | < Tarinaky> | :/ |
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| 15:18 | <@TheWatcher> | give me a few, I'm fighting phpbb3 updates that don't want to stick |
| 15:18 | < Tarinaky> | Sure. I need to think about food anyway. |
| 15:19 | < Tarinaky> | I may just pull MT19973 off the shelf and use that :/ |
| 15:19 | < Tarinaky> | I'm just put off by the fact that I don't really understand it. |
| 15:19 | < Tarinaky> | But then I don't really understand this one either >.> |
| 15:20 | < Tarinaky> | At least, not in terms of the statistics. |
| 15:31 | <@TheWatcher> | Tarinaky: hm. This /is/ odd - I'm getting different stats than either yours or my old ones from the wiki. Bizarre |
| 15:32 | <@TheWatcher> | I must've changes something at some point, hm |
| 15:32 | <@TheWatcher> | *d |
| 15:32 | | * Tarinaky changes the 1 back to an i. |
| 15:33 | < Tarinaky> | Nope. Didn't help. |
| 15:37 | < Tarinaky> | Hunh. The off-the-shelf Mersenne Twister I have doesn't give me better stats. |
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| 15:40 | <@TheWatcher> | Bloody frustrating though |
| 15:41 | <@TheWatcher> | Ooooh |
| 15:41 | <@TheWatcher> | That's how I did it I think |
| 15:41 | | * TheWatcher fiddles |
| 15:45 | < Tarinaky> | A friend of mine told me they had a PRNG where they iterated over a list of pi's digits. |
| 15:45 | < Tarinaky> | Which amused me slightly. |
| 15:45 | < Tarinaky> | Well, a subset of the digits of pi anyway. |
| 15:48 | <@TheWatcher> | Okay |
| 15:48 | <@TheWatcher> | I worked out the problem |
| 15:49 | < Tarinaky> | You were secretly feeding ent the results of casino dice? |
| 15:50 | <@TheWatcher> | nope, we were both feeding ascii data to ent |
| 15:50 | <@TheWatcher> | http://pastebin.starforge.co.uk/108 |
| 15:50 | <@TheWatcher> | Try code similar to that for yours |
| 15:55 | < Tarinaky> | Yeah. -much- better. |
| 15:55 | < Tarinaky> | Cheers for that. |
| 16:32 | < gnolam> | Dammit. Now you've gotten me hooked on Project Euler. :( |
| 16:35 | | * TheWatcher patpats gnolam |
| 16:39 | < gnolam> | Of course, I'm mostly using it as an excuse to learn Python beyond the "handy shell script" level. |
| 16:45 | | * TheWatcher updates the number generator page on his wiki so the issue does not arise again |
| 17:01 | < Tarinaky> | :/ Why am I having difficulty erasing a stringstream :/ |
| 17:02 | < Tarinaky> | stringstream_foo.str().clear() doesn't work. Neither does str() = string() |
| 17:07 | <@TheWatcher> | clear just clears the error state flags. Tried foo << ""; ? |
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| 17:07 | < Tarinaky> | I wasn't trying stringstream::clear() |
| 17:08 | < Tarinaky> | I mean stringstream::str().clear() |
| 17:08 | <@TheWatcher> | oh, right, I'm paying attention |
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| 17:09 | <@TheWatcher> | I'd still say try foo.str("") or foo << ""; |
| 17:11 | < Tarinaky> | foo.str("") works. |
| 17:11 | < Tarinaky> | Thanks. |
| 17:13 | | * Tarinaky wonders if there's a way of counting the number of line-break characters there are in a given string. |
| 17:16 | <@TheWatcher> | What's wrong with `int count = 0; for(int i =0; i < str.length(); ++i) { if(str[i] = '\n') ++count; }` ? |
| 17:16 | <@TheWatcher> | *== |
| 17:17 | < Tarinaky> | Oooo. |
| 17:17 | < Tarinaky> | Cheers. I was seriously struggling to come up with that :/ |
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| 17:50 | | * Tarinaky wibbles - my code is such a mess. |
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| 18:02 | <@Vornicus-Latens> | Tarinaky: then refactor it! |
| 18:03 | < Tarinaky> | I'm not sure I really can tbh. |
| 18:11 | | * AbuDhabi tries to understand how this piece of code happened. |
| 18:11 | < AbuDhabi> | Basically, it checks whether an uninitialized variable is not equal 1/true. |
| 18:12 | < AbuDhabi> | Was I too lazy to get rid of the if statement from some earlier code? |
| 18:13 | < Tarinaky> | Git has a blame file. |
| 18:13 | < Tarinaky> | That would likely answer your question. |
| --- Log closed Mon Jan 25 18:24:35 2010 |
| --- Log opened Mon Jan 25 18:25:01 2010 |
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| --- Log closed Tue Jan 26 00:00:29 2010 |