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  • How can I generate an "unlimited" world?

    - by snowlord
    I would like to create a game with an endless (in reality an extremely large) world in which the player can move about. Whether or not I will ever get around to implement the game is one matter, but I find the idea interesting and would like some input on how to do it. The point is to have a world where all data is generated randomly on-demand, but in a deterministic way. Currently I focus on a large 2D map from which it should be possible to display any part without knowledge about the surrounding parts. I have implemented a prototype by writing a function that gives a random-looking, but deterministic, integer given the x and y of a pixel on the map (see my recent question about this function). Using this function I populate the map with "random" values, and then I smooth the map using a simple filter based on the surrounding pixels. This makes the map dependent on a few pixels outside its edge, but that's not a big problem. The final result is something that at least looks like a map (especially with a good altitude color map). Given this, one could maybe first generate a coarser map which is used to generate bigger differences in altitude to create mountain ranges and seas. Anyway, that was my idea, but I am sure that there exist ways to do this already and I also believe that given the specification, many of you can come up with better ideas. EDIT: Forgot the link to my question.

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  • Is there a more efficent way to randomise a set of linq results?

    - by Matthew De'Loughry
    Hi just wondering if you could help I've produced a function to get back a random set of submission depnding on the amount passed to it, but I worry that even though it works now with a small amount of data when the a large amount is passed through it would become efficent and cause problems. Just wondering if you could suggest a more efficent way of doing the following: public List<Submission> GetRandomWinners(int id) { List<Submission> submissions = new List<Submission>(); int amount = (DbContext().Competitions .Where(s => s.CompetitionId == id).FirstOrDefault()).NumberWinners; for(int i = 1 ; i <= amount; i++) { bool added = false; while (!added) { bool found = false; var randSubmissions = DbContext().Submissions .Where(s => s.CompetitionId == id && s.CorrectAnswer).ToList(); int count = randSubmissions.Count(); int index = new Random().Next(count); foreach (var sub in submissions ) { if (sub == randSubmissions.Skip(index).FirstOrDefault()) found = true; } if (!found) { submissions.Add(randSubmissions.Skip(index).FirstOrDefault()); added = true; } } } return submissions; } As I say I have this fully working and bringing back the wanted result just I'm not liking the foreach and while checks in there and my head has just turned to mush now try to come up with the above soloution. Thanks Matt

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  • modprobe amd-rng fails, No such device

    - by CrackerJack9
    When trying to install hw_random to a 2.6 kernel, modprobe returns a FATAL error "No such device" on both CentOS 5.7 and Fedora 15. Both are using the latest kernel, respectively. The .ko file exists, and config- contains CONFIG_RTC=y and CONFIG_CRYPTO_RNG=m Both servers are x86_64 AMD processors. The only google results are very old, often reference the kernel module 'hw_random' (which has been replaced with processor specific modules and don't offer much help. Has anyone been able to install hw_random? Am I missing a step while installing the module?

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  • Only some motherboards can support faster RAM?

    - by Wesley
    This is a question relating to one of my builds. Here are the specs: ECS P4VXASD2+ V5.0 motherboard Intel P4 Northwood 2.8 GHz (533 MHz FSB, 512 KB L2) 2x 1GB PC3200 DDR RAM Maxtor 300GB IDE HDD 16 MB NVIDIA TNT2 Pro AGP OKIA 300W ATX PSU Gigabyte 52x CD-ROM The issue right now is that I'm trying to install Windows XP from the CD drive but the computer randomly restarts partway through installation. My other build was BSODing due to RAM latency errors. This ECS board manual states that memory modules "up to 333 MHz" (i.e. PC2700) is supported. However, I am running PC3200 modules, which is clearly faster than PC2700. Would this be causing the computer from randomly restarting? EDIT 1: I also wanted to mention that my Emachines T2482 is actually running 2x 512MB PC3200 DDR RAM when it should only be supporting PC1600 and PC2100 DDR RAM. Yet there are no issues with it.

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  • Computer randomly reboots during "intensive activity".

    - by Reznor
    My friend has been playing games on his new build for some time now. However, lately, his computer will randomly reboot out of nowhere, so far only happening in game, and presumably only to happen in game as it happens nowhere else. This can happen in game during play or even in the options. Note, it isn't a crash or blue screen. It's just a normal reboot. This started today, I believe, and has only occured in two games: Dead Space and Stalker: Shadow of Chernobyl. He has played a handful of games before these, for about a week or so, without this problem. We theorized on two possibilities: Maybe something is overheating? Maybe the power supply is inadequate? These two were quickly dismissed, as all his components were operating at normal temperatures when he got back to his desktop from the reboot, and we all know these parts don't exactly cool down quickly, especially if they get hot enough to trigger a reboot. Besides, I know at-least my motherboard reports processor overheating at start-up, and requests I press f1 to continue into boot. The PSU one was dismissed too. He has an 850w power supply on a rig that was estimated to take only 720 some watts, that's with some overcompensating to be safe. He opened up his case to make sure nothing was seated wrong or in the way. All was fine, but he did notice a sticker on his video card. It had a giant barcode on it and some numbers. Now, I'm used to seeing these stickers, they're the warranty stickers, right, and removal voids the warranty? Yeah, well, we find it odd because this sticker is slapped right over the circuits of the video card, not on a block or anything. Is this normal? Should he remove it? Right now, I am concerned with the memory. Could that be at fault? Here are his specs: Windows 7 Home Premium, 64-Bit Intel i7 950 EVGA GeForce 570 GTX 4 GB DDR3 PC10666 dual-channel Corsair RAM Corsair 850w PSU Gigabyte GA-X58A-UD3R Western Digital 1 TB WD1001FALS

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  • How to create a random string of characters in C#?

    - by Keltex
    I'm trying to create random strings of characters. I'm wondering if there might be a more efficient way. Here's my algorithm: string RANDOM = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz#@$^*()"; StringBuilder sb = new StringBuilder(); int length = rand.Next(10) + 1; for (int idx = 0; idx < length; ++idx) { sb.Append(RANDOM[rand.Next(RANDOM.Length)]); } string RandomString = sb.ToString(); I'm wondering if the StringBuilder is the best choice. Also if selecting a random character from my RANDOM string is the best way.

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  • Matlab - binary vector with high concentration of 1s (or 0s)

    - by JohnIdol
    What's the best way to generate a number X of random binary vectors of size N with concentration of 1s (or, simmetrically, of 0s) that spans from very low to very high? Using randint or unidrnd (as in this question) will generate binary vectors with uniform distributions, which is not what I need in this case. Any help appreciated!

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  • Example about crypto/rand in Go

    - by nevalu
    Could put a little example about the use of crypto/rand [1]? The function Read has as parameter an array of bytes. Why? If it access to /dev/urandom to get the random data. func Read(b []byte) (n int, err os.Error) [1] http://golang.org/pkg/crypto/rand/

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  • How does MySQL's ORDER BY RAND() work?

    - by Eugene
    Hi, I've been doing some research and testing on how to do fast random selection in MySQL. In the process I've faced some unexpected results and now I am not fully sure I know how ORDER BY RAND() really works. I always thought that when you do ORDER BY RAND() on the table, MySQL adds a new column to the table which is filled with random values, then it sorts data by that column and then e.g. you take the above value which got there randomly. I've done lots of googling and testing and finally found that the query Jay offers in his blog is indeed the fastest solution: SELECT * FROM Table T JOIN (SELECT CEIL(MAX(ID)*RAND()) AS ID FROM Table) AS x ON T.ID >= x.ID LIMIT 1; While common ORDER BY RAND() takes 30-40 seconds on my test table, his query does the work in 0.1 seconds. He explains how this functions in the blog so I'll just skip this and finally move to the odd thing. My table is a common table with a PRIMARY KEY id and other non-indexed stuff like username, age, etc. Here's the thing I am struggling to explain SELECT * FROM table ORDER BY RAND() LIMIT 1; /*30-40 seconds*/ SELECT id FROM table ORDER BY RAND() LIMIT 1; /*0.25 seconds*/ SELECT id, username FROM table ORDER BY RAND() LIMIT 1; /*90 seconds*/ I was sort of expecting to see approximately the same time for all three queries since I am always sorting on a single column. But for some reason this didn't happen. Please let me know if you any ideas about this. I have a project where I need to do fast ORDER BY RAND() and personally I would prefer to use SELECT id FROM table ORDER BY RAND() LIMIT 1; SELECT * FROM table WHERE id=ID_FROM_PREVIOUS_QUERY LIMIT 1; which, yes, is slower than Jay's method, however it is smaller and easier to understand. My queries are rather big ones with several JOINs and with WHERE clause and while Jay's method still works, the query grows really big and complex because I need to use all the JOINs and WHERE in the JOINed (called x in his query) sub request. Thanks for your time!

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  • Diehard test only integers?

    - by emmy
    i want to test some "random" numbers in (0 1). i will test them with the diehard tests battery, but i dont know if it tests numbers in (0 1). so diehard test any kind of numbers, or it just test intergers?

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  • Rearranging a sequence

    - by sarah
    I'm have trouble rearranging sequences so the amount of letters in the given original sequence are the same in the random generated sequences. For example: If i have a string 'AAAC' I need that string rearranged randomly so the amount of A's and C's are the same.

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  • How to generate irregular ball shapes?

    - by tomato
    What kind of algorithms would generate random "goo balls" like those in World of Goo. (btw, if you haven't played it yet, highly recommended). I'm using Proccesing, but any generic algorithm would do. I guess it boils down to how to "randomly" make balls that are kind of round, but not perfectly round, and still looking realistic. Thanks in advance!

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  • How do you efficiently generate a list of K non-repeating integers between 0 and an upper bound N

    - by tucuxi
    The question gives all necessary data: what is an efficient algorithm to generate a sequence of K non-repeating integers within a given interval. The trivial algorithm (generating random numbers and, before adding them to the sequence, looking them up to see if they were already there) is very expensive if K is large and near enough to N. The algorithm provided here seems more complicated than necessary, and requires some implementation. I've just found another algorithm that seems to do the job fine, as long as you know all the relevant parameters, in a single pass.

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  • Generating n statements from context-free grammars

    - by Dervin Thunk
    Hello, So not to reinvent the wheel, I would like to know what has already been done about generating random statements from a context-free language (like those produced by yacc, etc.). These grammars are primarily for parsing, but maybe someone has done some generation for testing the parsers? Thanks

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  • Is rand() predictable in C++

    - by singh
    When I run the below program I always get the same values each time. Is rand not a true random function? int main() { while(1) { getch(); cout<<rand()<<endl; } } In each run I am getting the below values. 41 18467 6334 26500 19169 15724 ......

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  • How do I randomly select from a list in Python?

    - by Liam Block
    Basically, I've got a homework task of programming a text based battle simulator in Python. Obviously I've gone with pokémon... I would like the enemy to be randomly selected, however I don't know how to randomly select from a list... foo = ['a', 'b', 'c', 'd', 'e'] from random import choice print choice(foo) This is what I've been told to try but I've got no modules or anything imported... How can I make this work, appreciated.

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  • is rand() is perdicatable in C++

    - by singh
    Hi When i run below program i always get same values each time..Is rand is not a true random function. int main() { while(1) { getch(); cout<<rand()<<endl; } } In each run i am getting below values. 41 18467 6334 26500 19169 15724 ......

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  • How to generate correlated binary variables

    - by jonalm
    Dear All I need to generate a series of N random binary variables with a given correlation function. Let x = {x_i} be a series of binary variables (taking the value 0 or 1, i running form 1 to N). The marginal probability is given Pr(x_i = 1) = p, and the values should be correlated in the following way E[ x_i x_j ] = const * |i-j|^-alfa where alfa is a positive number. Is it possible to generate a series like this? preferably in python.

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  • MySQL ORDER BY rand(), name ASC

    - by Josh K
    I would like to take a database of say, 1000 users and select 20 random ones (ORDER BY rand(),LIMIT 20) then order the resulting set by the names. I came up with the following query which is not working like I hoped. SELECT * FROM users WHERE 1 ORDER BY rand(), name ASC LIMIT 20

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  • Multi-threaded random_r is slower than single threaded version.

    - by Nixuz
    The following program is essentially the same the one described here. When I run and compile the program using two threads (NTHREADS == 2), I get the following run times: real 0m14.120s user 0m25.570s sys 0m0.050s When it is run with just one thread (NTHREADS == 1), I get run times significantly better even though it is only using one core. real 0m4.705s user 0m4.660s sys 0m0.010s My system is dual core, and I know random_r is thread safe and I am pretty sure it is non-blocking. When the same program is run without random_r and a calculation of cosines and sines is used as a replacement, the dual-threaded version runs in about 1/2 the time as expected. #include <pthread.h> #include <stdlib.h> #include <stdio.h> #define NTHREADS 2 #define PRNG_BUFSZ 8 #define ITERATIONS 1000000000 void* thread_run(void* arg) { int r1, i, totalIterations = ITERATIONS / NTHREADS; for (i = 0; i < totalIterations; i++){ random_r((struct random_data*)arg, &r1); } printf("%i\n", r1); } int main(int argc, char** argv) { struct random_data* rand_states = (struct random_data*)calloc(NTHREADS, sizeof(struct random_data)); char* rand_statebufs = (char*)calloc(NTHREADS, PRNG_BUFSZ); pthread_t* thread_ids; int t = 0; thread_ids = (pthread_t*)calloc(NTHREADS, sizeof(pthread_t)); /* create threads */ for (t = 0; t < NTHREADS; t++) { initstate_r(random(), &rand_statebufs[t], PRNG_BUFSZ, &rand_states[t]); pthread_create(&thread_ids[t], NULL, &thread_run, &rand_states[t]); } for (t = 0; t < NTHREADS; t++) { pthread_join(thread_ids[t], NULL); } free(thread_ids); free(rand_states); free(rand_statebufs); } I am confused why when generating random numbers the two threaded version performs much worse than the single threaded version, considering random_r is meant to be used in multi-threaded applications.

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  • How could I generate instances of an object randomly at the top of the screen and make them "fall"?

    - by Custard
    I am making a game in Flash CS4 (actionscript 3) and I would like to be able to make "copies" of an instance that would randomly appear at the top of the screen and fall. For example, multiple objects(that are the same one) are falling from the top of the screen continuously, starting at random X positions. (i think this would be considered Real-Time effect). P.S., please tell me if the information is insufficient for an answer, I couldn't think of much more to add to it. Thanks for your time and answers, -Custard

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