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  • How can I create an array of random numbers in C++

    - by Nick
    Instead of The ELEMENTS being 25 is there a way to randomly generate a large array of elements....10000, 100000, or even 1000000 elements and then use my insertion sort algorithms. I am trying to have a large array of elements and use insertion sort to put them in order and then also in reverse order. Next I used clock() in the time.h file to figure out the run time of each algorithm. I am trying to test with a large amount of numbers. #define ELEMENTS 25 void insertion_sort(int x[],int length); void insertion_sort_reverse(int x[],int length); int main() { clock_t tStart = clock(); int B[ELEMENTS]={4,2,5,6,1,3,17,14,67,45,32,66,88, 78,69,92,93,21,25,23,71,61,59,60,30}; int x; cout<<"Not Sorted: "<<endl; for(x=0;x<ELEMENTS;x++) cout<<B[x]<<endl; insertion_sort(B,ELEMENTS); cout <<"Sorted Normal: "<<endl; for(x=0;x<ELEMENTS;x++) cout<< B[x] <<endl; insertion_sort_reverse(B,ELEMENTS); cout <<"Sorted Reverse: "<<endl; for(x=0;x<ELEMENTS;x++) cout<< B[x] <<endl; double seconds = clock() / double(CLK_TCK); cout << "This program has been running for " << seconds << " seconds." << endl; system("pause"); return 0; }

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  • generating random enums

    - by null_radix
    How do I randomly select a value for an enum type in C++? I would like to do something like this. enum my_type(A,B,C,D,E,F,G,h,J,V); my_type test(rand() % 10); But this is illegal... there is not an implicit conversion from int to an enum type.

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  • Python: Random integer

    - by user3696440
    I been hitting a wall thats been keeping me from tinkering on a game. class Damage: def shortsword(): shortsword=randint(1,6)+1 shortsword=int(shortsword) return shortsword I been wanting this number to pop up as part of a message on print and then use the same number as part of another function to help with subtracting of health on the target. Though each time I grab this it is always going to change.

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  • Get a random folder C# .NET

    - by Joshua
    Hi. public sealed static class FolderHelper { public static string GetRandomFolder() { // do work } } But.... How? Like start at c:\ (or whatever the main drive is) and then randomly take routes? Not even sure how to do that.

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  • Stochastic calculus library in python

    - by LeMiz
    Hello, I am looking for a python library that would allow me to compute stochastic calculus stuff, like the (conditional) expectation of a random process I would define the diffusion. I had a look a at simpy (simpy.sourceforge.net), but it does not seem to cover my needs. This is for quick prototyping and experimentation. In java, I used with some success the (now inactive) http://martingale.berlios.de/Martingale.html library. The problem is not difficult in itself, but there is a lot non trivial, boilerplate things to do (efficient memory use, variable reduction techniques, and so on). Ideally, I would be able to write something like this (just illustrative): def my_diffusion(t, dt, past_values, world, **kwargs): W1, W2 = world.correlated_brownians_pair(correlation=kwargs['rho']) X = past_values[-1] sigma_1 = kwargs['sigma1'] sigma_2 = kwargs['sigma2'] dX = kwargs['mu'] * X * dt + sigma_1 * W1 * X * math.sqrt(dt) + sigma_2 * W2 * X * X * math.sqrt(dt) return X + dX X = RandomProcess(diffusion=my_diffusion, x0 = 1.0) print X.expectancy(T=252, dt = 1./252., N_simul= 50000, world=World(random_generator='sobol'), sigma1 = 0.3, sigma2 = 0.01, rho=-0.1) Does someone knows of something else than reimplementing it in numpy for example ?

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  • take out objects from randomizer obj c

    - by David Pollak
    hello everyone, I'm a new "developer" trying to build some iPhone app I'm making an app which gets text from a list of objects in a NSArray and then randomizes them and display one in a TextView, here's the code: - (IBAction)azione{ NSArray *myArray= [NSArray arrayWithObjects: @"Pasta",@"Pizza",@"Wait",@"Go", nil]; int length = [myArray count]; int chosen = arc4random() % length; testo.text = [myArray objectAtIndex: chosen]; } what I want to do now, is when I open the app and get a random object, to take it out from the list, so that it won't be picked again ex. I open the appI get "Pizza"Do the action againI don't get "Pizza" anymore, only "Pasta" "Wait" and "Go" What should I do ? Which code should I use ? Thanks for answers

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  • Simple hardware RNG

    - by roygbiv
    I made a tongue-in-cheek comment to this question about making a hardware RNG. Does anyone know of any simple plans or can anyone descibe a simple hardware based RNG and the software to drive it? Go to Radio Shack. Buy a diode, an NTR resistor, a capacitor and serial cable. Cut off the end of the serial cable that does not fit on your computer. Solder the diode and resistor in series between pins DTR and DSR of the cable. Solder the capacitor between DSR and TXD pins. Write a small C program to do the following: Set DTR to 1. Start Timer. Monitor DSR until it goes to 1. Stop Timer. Calculate resistance from elapsed time. Retreive serveral bits from that value to use as part of random number. Repeat until enough bits have accumulated.

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  • Efficient banner rotation with PHP

    - by reggie
    I rotate a banner on my site by selecting it randomly from an array of banners. Sample code as demonstration: <?php $banners = array( '<iframe>...</iframe>', '<a href="#"><img src="#.jpg" alt="" /></a>', //and so on ); echo $banners(rand(0, count($banners))); ?> The array of banners has become quite big. I am concerned with the amount of memory that this array adds to the execution of my page. But I can't figure out a better way of showing a random banner without loading all the banners into memory...

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  • ideas for algorithm? sorting a list randomly with emphasis on variety

    - by Steve Eisner
    I have a table of items with [ID,ATTR1,ATTR2,ATTR3]. I'd like to select about half of the items, but try to get a random result set that is NOT clustered. In other words, there's a fairly even spread of ATTR1 values, ATTR2 values, and ATTR3 values. This does NOT necessarily represent the data as a whole, in other words, the total table may be generally concentrated on certain attribute values, but I'd like to select a subset with more variety. The attributes are not inter-related, so there's not really a correlation between ATTR1 and ATTR2. Any ideas for an efficient algorithm? Thanks! I don't really even know how to search for this :)

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  • How to always return a set number of records when using find_related_tags with acts-as-taggable-on

    - by hadees
    I'm using the acts-as-taggable-on gem and I need to use find_related_tags on my survey model to get back 3 surveys every time. In the event there aren't always 3 related I need to pick how ever many are related plus some random ones to get to 3. Additionally I have a method I wrote called completed_survey_ids which return an array of survey_ids that shouldn't be used because the user has already completed them. Also there is a rare case that there won't be enough surveys because the user has completed them all so in that event it is okay to return less surveys then requested. I did write a named_scope to handle getting rid of the completed_survey_ids that I think works named_scope :not, lambda { |survey_ids| {:conditions => "id NOT IN (#{survey_ids.join(',')})" } }

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  • Most efficient way to randomly "sort" (Shuffle) a list of integers in C#

    - by Carl
    I need to randomly 'sort' a list of integers (0-1999) in the most efficient way possible. Any ideas? Currently, I am doing something like this: bool[] bIndexSet = new bool[iItemCount]; for (int iCurIndex = 0; iCurIndex < iItemCount; iCurIndex++) { int iSwapIndex = random.Next(iItemCount); if (!bIndexSet[iSwapIndex] && iSwapIndex != iCurIndex) { int iTemp = values[iSwapIndex]; values[iSwapIndex] = values[iCurIndex]; values[iCurIndex] = values[iSwapIndex]; bIndexSet[iCurIndex] = true; bIndexSet[iSwapIndex] = true; } }

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  • Randomize numbers within a subset

    - by Samuel
    I have a array of integer numbers (say 1,2,3,4,5 or 1,2,3, ... 10 or 1,2,3, ... 50) from which I would like to get a random set of numbers ordered differently every time. Is there a utility method to do this? e.g. for 1,2,3,4,5 post randomization it might be either [1,5,4,2,3 or 2,1,3,5,4 or 3,1,2,4,5 or ...] I would like to know if there is a java utility method / class which already provides this capability?

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  • jQuery: how to pick unique IDs ?

    - by Seerumi
    Hello. New to whole this jQuery (and javascript altogether, heh) and so far it's been excellent, but now I'm in a small pickle. Let's say I have list of forms generated from SQL database and every single one of them has to have unique id, so how I can select the specific item that is to be manipulated (changing values via php). the $("#submit").click(function()) will trigger every submit buttons on the page, so how I can the #submit to be some random id that I clicked. There might be a smarter way, but I'm new to this so try to bear with me. thought of passing the unique value with onClick="myfunction(unique_id)", but don't know how it goes with jQuery. hope this made any sense

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  • PHP: read all files but randomly?

    - by mathiregister
    hi there, i wonder if there's a way of reading a directory in a random order. With the following code i'm running through the directory thumbs and it's printing images on my website. However, they are always read alphabetically and i wonder if there's a way in doing this randomly? <?php $path = 'thumbs'; if ($handle = opendir($path)) { while (false !== ($file = readdir($handle))) { if ($file != '.' && $file != '..' && $file != '.DS_Store' && $file != 'Thumbs.db') { print "<img class='thumb' src='$path/$file'/>"; } else { //no proper file } } closedir($handle); } ?> thank you for your suggestions! regards

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  • Distributing players to tables

    - by IVlad
    Consider N = 4k players, k tables and a number of clans such that each member can belong to one clan. A clan can contain at most k players. We want to organize 3 rounds of a game such that, for each table that seats exactly 4 players, no 2 players sitting there are part of the same clan, and, for the later rounds, no 2 players sitting there have sat at the same table before. All players play all rounds. How can we do this efficiently if N can be about ~80 large? I thought of this: for each table T: repeat until 4 players have been seated at T: pick a random player X that is not currently seated anywhere if X has not sat at the same table as anyone currently at T AND X is not from the same clan as anyone currently at T seat X at T break I am not sure if this will always finish or if it can get stuck even if there is a valid assignment. Even if this works, is there a better way to do it?

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  • C++ Program performs better when piped

    - by ET1 Nerd
    I haven't done any programming in a decade. I wanted to get back into it, so I made this little pointless program as practice. The easiest way to describe what it does is with output of my --help codeblock: ./prng_bench --help ./prng_bench: usage: ./prng_bench $N $B [$T] This program will generate an N digit base(B) random number until all N digits are the same. Once a repeating N digit base(B) number is found, the following statistics are displayed: -Decimal value of all N digits. -Time & number of tries taken to randomly find. Optionally, this process is repeated T times. When running multiple repititions, averages for all N digit base(B) numbers are displayed at the end, as well as total time and total tries. My "problem" is that when the problem is "easy", say a 3 digit base 10 number, and I have it do a large number of passes the "total time" is less when piped to grep. ie: command ; command |grep took : ./prng_bench 3 10 999999 ; ./prng_bench 3 10 999999|grep took .... Pass# 999999: All 3 base(10) digits = 3 base(10). Time: 0.00005 secs. Tries: 23 It took 191.86701 secs & 99947208 tries to find 999999 repeating 3 digit base(10) numbers. An average of 0.00019 secs & 99 tries was needed to find each one. It took 159.32355 secs & 99947208 tries to find 999999 repeating 3 digit base(10) numbers. If I run the same command many times w/o grep time is always VERY close. I'm using srand(1234) for now, to test. The code between my calls to clock_gettime() for start and stop do not involve any stream manipulation, which would obviously affect time. I realize this is an exercise in futility, but I'd like to know why it behaves this way. Below is heart of the program. Here's a link to the full source on DB if anybody wants to compile and test. https://www.dropbox.com/s/6olqnnjf3unkm2m/prng_bench.cpp clock_gettime() requires -lrt. for (int pass_num=1; pass_num<=passes; pass_num++) { //Executes $passes # of times. clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &temp_time); //get time start_time = timetodouble(temp_time); //convert time to double, store as start_time for(i=1, tries=0; i!=0; tries++) { //loops until 'comparison for' fully completes. counts reps as 'tries'. <------------ for (i=0; i<Ndigits; i++) //Move forward through array. | results[i]=(rand()%base); //assign random num of base to element (digit). | /*for (i=0; i<Ndigits; i++) //---Debug Lines--------------- | std::cout<<" "<<results[i]; //---a LOT of output.---------- | std::cout << "\n"; //---Comment/decoment to disable/enable.*/ // | for (i=Ndigits-1; i>0 && results[i]==results[0]; i--); //Move through array, != element breaks & i!=0, new digits drawn. -| } //If all are equal i will be 0, nested for condition satisfied. -| clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &temp_time); //get time draw_time = (timetodouble(temp_time) - start_time); //convert time to dbl, subtract start_time, set draw_time to diff. total_time += draw_time; //add time for this pass to total. total_tries += tries; //add tries for this pass to total. /*Formated output for each pass: Pass# ---: All -- base(--) digits = -- base(10) Time: ----.---- secs. Tries: ----- (LINE) */ std::cout<<"Pass# "<<std::setw(width_pass)<<pass_num<<": All "<<Ndigits<<" base("<<base<<") digits = " <<std::setw(width_base)<<results[0]<<" base(10). Time: "<<std::setw(width_time)<<draw_time <<" secs. Tries: "<<tries<<"\n"; } if(passes==1) return 0; //No need for totals and averages of 1 pass. /* It took ----.---- secs & ------ tries to find --- repeating -- digit base(--) numbers. (LINE) An average of ---.---- secs & ---- tries was needed to find each one. (LINE)(LINE) */ std::cout<<"It took "<<total_time<<" secs & "<<total_tries<<" tries to find " <<passes<<" repeating "<<Ndigits<<" digit base("<<base<<") numbers.\n" <<"An average of "<<total_time/passes<<" secs & "<<total_tries/passes <<" tries was needed to find each one. \n\n"; return 0;

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  • Randomly generating sequence of ints in a specific range

    - by vvv
    Hi, I am unsure how to put this and my math skills aren't that strong. But here's what I need. I want to generate a list of all the 16bit integers (0-65535). But everytime I do so I want to seed the algorithm randomly that each time the list starts with a different integer and all the subsequent integers will be generated once but also in random order. small example (1-5): ... 1, 5, 3, 2, 4 4, 3, 1, 5, 2 2, 1, 4, 5, 3 ... Any help?

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  • Text + randomchar dosn't work [JavaScript]

    - by user558773
    <script> function makeid() { var text = "var text = document.write(lastNumber);"; var possible = "*+-/"; for( var i=0; i < 1; i++ ) document.write(lastNumber + possible.charAt(Math.floor(Math.random() * possible.length)); return text; } document.write(makeid(1))</script> How do i make this to type for ex: 23* 45- 13/ and so on. What is wrong? It just show me 2 numbers and no char after.

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  • A function where small changes in input always result in large changes in output

    - by snowlord
    I would like an algorithm for a function that takes n integers and returns one integer. For small changes in the input, the resulting integer should vary greatly. Even though I've taken a number of courses in math, I have not used that knowledge very much and now I need some help... An important property of this function should be that if it is used with coordinate pairs as input and the result is plotted (as a grayscale value for example) on an image, any repeating patterns should only be visible if the image is very big. I have experimented with various algorithms for pseudo-random numbers with little success and finally it struck me that md5 almost meets my criteria, except that it is not for numbers (at least not from what I know). That resulted in something like this Python prototype (for n = 2, it could easily be changed to take a list of integers of course): import hashlib def uniqnum(x, y): return int(hashlib.md5(str(x) + ',' + str(y)).hexdigest()[-6:], 16) But obviously it feels wrong to go over strings when both input and output are integers. What would be a good replacement for this implementation (in pseudo-code, python, or whatever language)?

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  • How can I randomly iterate through a large Range?

    - by void
    I would like to randomly iterate through a range. Each value will be visited only once and all values will eventually be visited. For example: class Array def shuffle ret = dup j = length i = 0 while j > 1 r = i + rand(j) ret[i], ret[r] = ret[r], ret[i] i += 1 j -= 1 end ret end end (0..9).to_a.shuffle.each{|x| f(x)} where f(x) is some function that operates on each value. A Fisher-Yates shuffle is used to efficiently provide random ordering. My problem is that shuffle needs to operate on an array, which is not cool because I am working with astronomically large numbers. Ruby will quickly consume a large amount of RAM trying to create a monstrous array. Imagine replacing (0..9) with (0..99**99). This is also why the following code will not work: tried = {} # store previous attempts bigint = 99**99 bigint.times { x = rand(bigint) redo if tried[x] tried[x] = true f(x) # some function } This code is very naive and quickly runs out of memory as tried obtains more entries. What sort of algorithm can accomplish what I am trying to do? [Edit1]: Why do I want to do this? I'm trying to exhaust the search space of a hash algorithm for a N-length input string looking for partial collisions. Each number I generate is equivalent to a unique input string, entropy and all. Basically, I'm "counting" using a custom alphabet. [Edit2]: This means that f(x) in the above examples is a method that generates a hash and compares it to a constant, target hash for partial collisions. I do not need to store the value of x after I call f(x) so memory should remain constant over time. [Edit3/4/5/6]: Further clarification/fixes.

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  • Best way to store list of numbers and to retrieve them

    - by bingoNumbers
    Hi. What is the best way to store a list of random numbers (like lotto/bingo numbers) and retrieve them? I'd like to store on a Database a number of rows, where each row contains 5-10 numbers ranging from 0 to 90. I will store a big number of those rows. What I'd like to be able is to retrieve the rows that have at least X number in common to a newly generated row. Example: [3,4,33,67,85,99] [55,56,77,89,98,99] [3,4,23,47,85,91] Those are on the DB I will generate this: [1,2,11,45,47,88] and now I want to get the rows that have at least 1 number in common with this one. The easiest (and dumbest?) way is to make 6 select and check for similar results. I thought to store numbers with a large binary string like 000000000000000000000100000000010010110000000000000000000000000 with 99 numbers where each number represent a number from 1 to 99, so if I have 1 at the 44th position, it means that I have 44 on that row. This method is probably shifting the difficult tasks to the Db but it's again not very smart. Any suggestion?

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  • Python multiprocessing doesn't play nicely with uuid.uuid4().

    - by yig
    I'm trying to generate a uuid for a filename, and I'm also using the multiprocessing module. Unpleasantly, all of my uuids end up exactly the same. Here is a small example: import multiprocessing import uuid def get_uuid( a ): ## Doesn't help to cycle through a bunch. #for i in xrange(10): uuid.uuid4() ## Doesn't help to reload the module. #reload( uuid ) ## Doesn't help to load it at the last minute. ## (I simultaneously comment out the module-level import). #import uuid ## uuid1() does work, but it differs only in the first 8 characters and includes identifying information about the computer. #return uuid.uuid1() return uuid.uuid4() def main(): pool = multiprocessing.Pool( 20 ) uuids = pool.map( get_uuid, range( 20 ) ) for id in uuids: print id if __name__ == '__main__': main() I peeked into uuid.py's code, and it seems to depending-on-the-platform use some OS-level routines for randomness, so I'm stumped as to a python-level solution (to do something like reload the uuid module or choose a new random seed). I could use uuid.uuid1(), but only 8 digits differ and I think there are derived exclusively from the time, which seems dangerous especially given that I'm multiprocessing (so the code could be executing at exactly the same time). Is there some Wisdom out there about this issue?

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