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  • Best way to get a reasonably random key for MYSQL records

    - by Steve N
    Hi there, I need to generate a reasonably random unique key for a table. It should be something like a GUID for MYSQL. I've tried UUID, but it looks like only the first few characters are actually random- the rest are the same every time I insert them. Essentially, it is desirable for this key field to be very difficult to guess, even if you already have one known value in the column. What is the best way to do this, and how should I set up the field data type to store the value efficiently? Thank you, Steve

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  • Looking for a clear and concise web page explaining why lower bits of random numbers are usually not

    - by Hamish Grubijan
    I am putting together an internal "every developer should know" wiki page. I saw many discussions regarding rand() % N, but not a single web page that explains it all. For instance, I am curious if this problem is only C- and Linux-specific, or if it also applies to Windows, C++,. Java, .Net, Python, Perl. Please help me get to the bottom of this. Also, just how non-random do the numbers get? Thank you!

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  • Code Golf: Ghost Leg

    - by Anax
    The challenge The shortest code by character count that will output the numeric solution, given a number and a valid string pattern, using the Ghost Leg method. Examples Input: 3, "| | | | | | | | |-| |=| | | | | |-| | |-| |=| | | |-| |-| | |-|" Output: 2 Input: 2, "| | |=| | |-| |-| | | |-| | |" Output: 1 Clarifications Do not bother with input. Consider the values as given somewhere else. Both input values are valid: the column number corresponds to an existing column and the pattern only contains the symbols |, -, = (and [space], [LF]). Also, two adjacent columns cannot both contain dashes (in the same line). The dimensions of the pattern are unknown (min 1x1). Clarifications #2 There are two invalid patterns: |-|-| and |=|=| which create ambiguity. The given input string will never contain those. The input variables are the same for all; a numeric value and a string representing the pattern. Entrants must produce a function. Test case Given pattern: "|-| |=|-|=|LF| |-| | |-|LF|=| |-| | |LF| | |-|=|-|" |-| |=|-|=| | |-| | |-| |=| |-| | | | | |-|=|-| Given value : Expected result 1 : 6 2 : 1 3 : 3 4 : 6 5 : 5 6 : 2

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  • Fastest Way to generate 1,000,000+ random numbers in python

    - by Sandro
    I am currently writing an app in python that needs to generate large amount of random numbers, FAST. Currently I have a scheme going that uses numpy to generate all of the numbers in a giant batch (about ~500,000 at a time). While this seems to be faster than python's implementation. I still need it to go faster. Any ideas? I'm open to writing it in C and embedding it in the program or doing w/e it takes. Constraints on the random numbers: A Set of numbers 7 numbers that can all have different bounds: eg: [0-X1, 0-X2, 0-X3, 0-X4, 0-X5, 0-X6, 0-X7] Currently I am generating a list of 7 numbers with random values from [0-1) then multiplying by [X1..X7] A Set of 13 numbers that all add up to 1 Currently just generating 13 numbers then dividing by their sum Any ideas? Would pre calculating these numbers and storing them in a file make this faster? Thanks!

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  • C++ code parser/processor library

    - by uray
    is there any library that parse a source code of C++ to produce lets say, call graph, class inheritance tree, flow control, class member list or anything as a ready to use graph or structure in code (not in diagram image). to make it more clear, suppose to generate call graph image, there will be a process like this: ` C++ source -> parser -> intermediate structure -> renderer -> call graph image ^ | [i need this] `

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  • [ASP.NET] Generating images: Alternate font by User Agent (OS)

    - by sinni800
    Hello, I need to generate small images for certain parts of text. Those will have to fit into the text seamlessly. I know I can not make up for every browser font settings available, but how do I have to check for Linux, Mac and Windows users depending on the user agent? I want to use the right font (of the three "Verdana, Arial, Helvetiva") for the right user agent OS. So: How do I check for the OS? What do I have to compare to in the user agent? Where can I get the other two fonts. Does the Windows-included Verdana look the same as the one used on Linux (or, is it free anyway? I don't know much about fonts)? Where do I get Helvetica? Is it Mac OS licensed? Any code examples can be in either c# or VB.NET. I can read both. Thank you in advance.

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  • Using system time directly to get random numbers

    - by Richard Mar.
    I had to return a random element from an array so I came up with this placeholder: return codes[(int) (System.currentTimeMillis() % codes.length - 1)]; Now than I think of it, I'm tempted to use it in real code. The Random() seeder uses system time as seed in most languages anyway, so why not use that time directly? As a bonus, I'm free from the worry of non-random lower bits of many RNGs. It this hack coming back to bite me? (The language is Java if that's relevant.)

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  • Help for creating a random String

    - by Max
    I need to create a random string which should be between the length of 6 to 10 but it sometimes generates only about the length of 3 to 5. Here's my code. Can anyone would be able to find out the problem? :( int lengthOfName = (int)(Math.random() * 4) + 6; String name = ""; /* randomly choosing a name*/ for (int j = 0; j <= lengthOfName; j++) { int freq = (int)(Math.random() * 100) + 1; if(freq <= 6){ name += "a"; }if(freq == 7 && freq == 8){ name += "b"; }if(freq >= 9 && freq <= 11){ name += "c"; }if(freq >= 12 && freq <= 15){ name += "d"; }if(freq >= 16 && freq <= 25){ name += "e"; }if(freq == 26 && freq == 27){ name += "f"; }if(freq == 28 && freq == 29){ name += "g"; }if(freq >= 30 && freq <= 33){ name += "h"; }if(freq >= 34 && freq <= 48){ name += "i"; }if(freq == 49 && freq == 50){ name += "j"; }if(freq >= 51 && freq <= 55){ name += "k"; }if(freq >= 56 && freq <= 60){ name += "l"; }if(freq == 61 && freq == 62){ name += "m"; }if(freq >= 63 && freq <= 70){ name += "n"; }if(freq >= 71 && freq <= 75){ name += "o"; }if(freq == 76 && freq == 77){ name += "p"; }if(freq == 78){ name += "q"; }if(freq >= 79 && freq <= 84){ name += "r"; }if(freq == 85 && freq == 86){ name += "s"; }if(freq == 87 && freq == 88){ name += "t"; }if(freq >= 89 && freq <= 93){ name += "u"; }if(freq == 94){ name += "v"; }if(freq == 95 && freq == 96){ name += "w"; }if(freq == 97){ name += "x"; }if(freq == 98 && freq == 99){ name += "y"; }if(freq == 100){ name += "z"; } }

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  • Set seed on Math.random()

    - by Kevin
    Hi - I need to write some junit tests on java code that calls Math.random(). I know that I can set the seed if I was instantiating my own Random object to produce repeatable results. Is there a way to do this also for Math.random() ?

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  • Latest stream cipher considered reasonably secure & easy to implement?

    - by hythlodayr
    (A)RC4 used to fit the bill, since it was so simple to write. But it's also less-than-secure these days. I'm wondering if there's a successor that's: Code is small enough to write & debug within an hour or so, using pseudo code as a template. Still considered secure, as of 2010. Optimized for software. Not encumbered by licensing issues. I can't use crypto libraries, otherwise all of this would be moot. Also, I'll consider block algorithms though I think most are pretty hefty. Thanks.

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  • How do i generate random data with RSA?

    - by acidzombie24
    After loading my RSACryptoServiceProvider rsa object i would like to create a key for my AES object. Since i dont need to store the AES key (i only need it to decrypt on my prv side) i figure i dont need to store it and i can generate it with my public key. I thought doing rsa.Encrypt(byte[] with 4 hardcoded bytes); would generate the data i need. It turns out everytime i call this function even with the same data i get different results. So theres no way for me to recreate the AES key if its different everytime. How can i generate data with RSA in a way that i can recreate anytime i need?

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  • Any tools can randomly generate the source code according to a language grammar?

    - by wbsun
    A C program source code can be parsed according to the C grammar(described in CFG) and eventually turned into many ASTs. I am considering if such tool exists: it can do the reverse thing by firstly randomly generating many ASTs, which include tokens that don't have the concrete string values, just the types of the tokens, according to the CFG, then generating the concrete tokens according to the tokens' definitions in the regular expression. I can imagine the first step looks like an iterative non-terminals replacement, which is randomly and can be limited by certain number of iteration times. The second step is just generating randomly strings according to regular expressions. Is there any tool that can do this?

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  • How to add precedence to LALR parser like in YACC?

    - by greenoldman
    Please note, I am asking about writing LALR parser, not writing rules for LALR parser. What I need is... ...to mimic YACC precedence definitions. I don't know how it is implemented, and below I describe what I've done and read so far. For now I have basic LALR parser written. Next step -- adding precedence, so 2+3*4 could be parsed as 2+(3*4). I've read about precedence parsers, however I don't see how to fit such model into LALR. I don't understand two points: how to compute when insert parenthesis generator how to compute how many parenthesis the generator should create I insert generators when the symbols is taken from input and put at the stack, right? So let's say I have something like this (| denotes boundary between stack and input): ID = 5 | + ..., at this point I add open, so it gives ID = < 5 | + ..., then I read more input ID = < 5 + | 5 ... and more ID = < 5 + 5 | ; ... and more ID = < 5 + 5 ; | ... At this point I should have several reduce moves in normal LALR, but the open parenthesis does not match so I continue reading more input. Which does not make sense. So this was when problem. And about count, let's say I have such data < 2 + < 3 * 4 >. As human I can see that the last generator should create 2 parenthesis, but how to compute this? After all there could be two scenarios: ( 2 + ( 3 *4 )) -- parenthesis is used to show the outcome of generator or (2 + (( 3 * 4 ) ^ 5) because there was more input Please note that in both cases before 3 was open generator, and after 4 there was close generator. However in both cases, after reading 4 I have to reduce, so I have to know what generator "creates".

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  • Huge procedurally generated 'wilderness' worlds

    - by The Communist Duck
    Hi. I'm sure you all know of games like Dwarf Fortress - massive, procedural generated wilderness and land. Something like this, taken from this very useful article. However, I was wondering how I could apply this to a much larger scale; the scale of Minecraft comes to mind (isn't that something like 8x the size of the Earth's surface?). Pseudo-infinite, I think the best term would be. The article talks about fractal perlin noise. I am no way an expert on it, but I get the general idea (it's some kind of randomly generated noise which is semi-coherent, so not just random pixel values). I could just define regions X by X in size, add some region loading type stuff, and have one bit of noise generating a region. But this would result in just huge amounts of islands. On the other extreme, I don't think I can really generate a supermassive sheet of perlin noise. And it would just be one big island, I think. I am pretty sure Perlin noise, or some noise, would be the answer in some way. I mean, the map is really nice looking. And you could replace the ascii with tiles, and get something very nice looking. Anyone have any ideas? Thanks. :D -TheCommieDuck

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  • Huge procedurally generated 'wilderness' worlds

    - by The Communist Duck
    I'm sure you all know of games like Dwarf Fortress - massive, procedural generated wilderness and land. Something like this, taken from this very useful article. However, I was wondering how I could apply this to a much larger scale; the scale of Minecraft comes to mind (isn't that something like 8x the size of the Earth's surface?). Pseudo-infinite, I think the best term would be. The article talks about fractal perlin noise. I am no way an expert on it, but I get the general idea (it's some kind of randomly generated noise which is semi-coherent, so not just random pixel values). I could just define regions X by X in size, add some region loading type stuff, and have one bit of noise generating a region. But this would result in just huge amounts of islands. On the other extreme, I don't think I can really generate a supermassive sheet of perlin noise. And it would just be one big island, I think. I am pretty sure Perlin noise, or some noise, would be the answer in some way. I mean, the map is really nice looking. And you could replace the ascii with tiles, and get something very nice looking. Anyone have any ideas? Thanks. :D

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  • How can I deal with actor translations and other "noise" in third-party motion capture data?

    - by Charles
    I'm working on a game, and I've run into a problem with motion capture data. My team is using 3DS Max 2011 and trying to put free motion capture files on our models. The problem we're having is it has become extremely hard to find motion capture data that stays in place. We've found some great motion captures of things like walking and jumping but the actors themselves move within the data, so when we attach these animations to our models and bring them into XNA, the models walk forward even when they should technically be standing still (and then there's also the problem of them resetting at the end of the animation). How can we clean up, at runtime or asset-processing time, the animation in these motion capture files?

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  • How to reduce fan noise with some latest Dell laptops, Desktop PC's?

    - by YumYumYum
    I have a few new Dell laptops and desktop PC's. Some of them have extremely noisy fans. The technicians who are sent by Dell refuse to attempt to fix things when they see that the OS is Ubuntu. They seem to be comfortable dealing with machines running MS Windows. For Linux, is there any way to slow or lower the fan speed? Please can anyone advise how it should be done. I have tried lm_sensors but failed.

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  • Is there a (family of) monotonically non-decreasing noise function(s)?

    - by Joe Wreschnig
    I'd like a function to animate an object moving from point A to point B over time, such that it reaches B at some fixed time, but its position at any time is randomly perturbed in a continuous fashion, but never goes backwards. The objects move along straight lines, so I only need one dimension. Mathematically, that means I'm looking for some continuous f(x), x ? [0,1], such that: f(0) = 0 f(1) = 1 x < y ? f(x) = f(y) At "most" points f(x + d) - f(x) bears no obvious relation to d. (The function is not uniformly increasing or otherwise predictable; I think that's also equivalent to saying no degree of derivative is a constant.) Ideally, I would actually like some way to have a family of these functions, providing some seed state. I'd need at least 4 bits of seed (16 possible functions), for my current use, but since that's not much feel free to provide even more. To avoid various issues with accumulation errors, I'd prefer the function not require any kind of internal state. That is, I want it to be a real function, not a programming "function".

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  • Big noise from Power Supply Unity Fa? Should I replace it immediately?

    - by EApubs
    Recently, I started to get a large noise from my PC when switched on. After some time, it disappears. I discovered that the issue is with the Power Supply Unit. Does this mean I have a failing PSU? Will it harm the PC if I didn't replace it immediately? Several years ago I bought a new computer casing which is very weird. Its small and compact. Normally, we have the PSU in the top. But in here, the PSU is on the bottom and right below the hard drive. Recently, two of my hard drives started to show problems. Read errors and bad sectors. Can it be the PSU and the design of the casing? Here's an image of the PSU and the hard drive :

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  • CPU fan making noise. heat sink or replace...

    - by user32185
    CPU fan is making noise ...i figured out reasons: Cable is hitting the fan causing a vibration. And may be also CPU fan is loose causing vibration... suggest options... i cleaned the fan ...but found that there is no heatsink compound /paste between processor and the fan..is it ok ..should i apply heat sink compound. How to correct the cable vibration... My processor is p4 2.4 ghz motherboard intel 845gvsr if i have to buy new fan ..which brand should i go for ..and estimated cost ?!

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