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• Getting a job in the games industry as a developer, just knowing a game engine

  - by numerical25

  I recently enrolled in a community college for games developement. But I am skeptical about the curriculum. I have no experience in the gaming industry so I wouldn't be able to tell whether it's a good investment or not. So I am asking you. I don't want to get too much into the details of all the classes I am taking so I will try to be brief. By the time I graduate, I should have a understanding of how a game engine works. I will be working with the Unreal Engine to develop a Multiplayer game from scratch. So in the process of my final project, I will learn how to work within the Unreal Engine, learn Python and learn how to use its API to connect to a remote server and build game mechanics. Overall I will also recieve an associates degree in game development. I learn C++ but not C. The director said he was trying to implement C in the program as well. What I notice is I will not learn how to build a 3D game engine from scratch. They do not teach any artificial intelligence (AI). I will not learn how to work with the graphics card using a graphics API such as DirectX or OpenGL. I know building a game engine from scratch is a little complex, but at the same time the track is requiring me to take some advanced mathematics courses such as calculus and geometry 1 and 2. I also got to take a physics class. I just think that's a little much for just learning how to use the Unreal Engine but not actually build one or try to learn the anatomy of a games engine. Is this good enough to possibly land my a job in the industry? If I left anything out or was not detail, please feel free to ask more questions. Edit: I do learn data structures and algorithms.

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• Scalable / Parallel Large Graph Analysis Library?

  - by Joel Hoff

  I am looking for good recommendations for scalable and/or parallel large graph analysis libraries in various languages. The problems I am working on involve significant computational analysis of graphs/networks with 1-100 million nodes and 10 million to 1+ billion edges. The largest SMP computer I am using has 256 GB memory, but I also have access to an HPC cluster with 1000 cores, 2 TB aggregate memory, and MPI for communication. I am primarily looking for scalable, high-performance graph libraries that could be used in either single or multi-threaded scenarios, but parallel analysis libraries based on MPI or a similar protocol for communication and/or distributed memory are also of interest for high-end problems. Target programming languages include C++, C, Java, and Python. My research to-date has come up with the following possible solutions for these languages: C++ -- The most viable solutions appear to be the Boost Graph Library and Parallel Boost Graph Library. I have looked briefly at MTGL, but it is currently slanted more toward massively multithreaded hardware architectures like the Cray XMT. C - igraph and SNAP (Small-world Network Analysis and Partitioning); latter uses OpenMP for parallelism on SMP systems. Java - I have found no parallel libraries here yet, but JGraphT and perhaps JUNG are leading contenders in the non-parallel space. Python - igraph and NetworkX look like the most solid options, though neither is parallel. There used to be Python bindings for BGL, but these are now unsupported; last release in 2005 looks stale now. Other topics here on SO that I've looked at have discussed graph libraries in C++, Java, Python, and other languages. However, none of these topics focused significantly on scalability. Does anyone have recommendations they can offer based on experience with any of the above or other library packages when applied to large graph analysis problems? Performance, scalability, and code stability/maturity are my primary concerns. Most of the specialized algorithms will be developed by my team with the exception of any graph-oriented parallel communication or distributed memory frameworks (where the graph state is distributed across a cluster).

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• sample java code for approximate string matching or boyer-moore extended for approximate string matc

  - by Dolphin

  Hi I need to find 1.mismatch(incorrectly played notes), 2.insertion(additional played), & 3.deletion (missed notes), in a music piece (e.g. note pitches [string values] stored in a table) against a reference music piece. This is either possible through exact string matching algorithms or dynamic programming/ approximate string matching algos. However I realised that approximate string matching is more appropriate for my problem due to identifying mismatch, insertion, deletion of notes. Or an extended version of Boyer-moore to support approx. string matching. Is there any link for sample java code I can try out approximate string matching? I find complex explanations and equations - but I hope I could do well with some sample code and simple explanations. Or can I find any sample java code on boyer-moore extended for approx. string matching? I understand the boyer-moore concept, but having troubles with adjusting it to support approx. string matching (i.e. to support mismatch, insertion, deletion). Also what is the most efficient approx. string matching algorithm (like boyer-moore in exact string matching algo)? Greatly appreciate any insight/ suggestions. Many thanks in advance

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• Optimal Serialization of Primitive Types

  - by Greg Dean

  We are beginning to roll out more and more WAN deployments of our product (.Net fat client w/ IIS hosted Remoting backend). Because of this we are trying to reduce the size of the data on the wire. We have overridden the default serialization by implementing ISerializable (similar to this), we are seeing anywhere from 12% to 50% gains. Most of our efforts focus on optimizing arrays of primitive types. I would like to know if anyone knows of any fancy way of serializing primitive types, beyond the obvious? For example today we serialize an array of ints as follows: [4-bytes (array length)][4-bytes][4-bytes] Can anyone do significantly better? The most obvious example of a significant improvement, for boolean arrays, is putting 8 bools in each byte, which we already do. Note: Saving 7 bits per bool may seem like a waste of time, but when you are dealing with large magnitudes of data (which we are), it adds up very fast. Note: We want to avoid general compression algorithms because of the latency associated with it. Remoting only supports buffered requests/responses(no chunked encoding). I realize there is a fine line between compression and optimal serialization, but our tests indicate we can afford very specific serialization optimizations at very little cost in latency. Whereas reprocessing the entire buffered response into new compressed buffer is too expensive.

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• P6 Architecture - Register renaming aside, does the limited user registers result in more ops spent

  - by mrjoltcola

  I'm studying JIT design with regard to dynamic languages VM implementation. I haven't done much Assembly since the 8086/8088 days, just a little here or there, so be nice if I'm out of sorts. As I understand it, the x86 (IA-32) architecture still has the same basic limited register set today that it always did, but the internal register count has grown tremendously, but these internal registers are not generally available and are used with register renaming to achieve parallel pipelining of code that otherwise could not be parallelizable. I understand this optimization pretty well, but my feeling is, while these optimizations help in overall throughput and for parallel algorithms, the limited register set we are still stuck with results in more register spilling overhead such that if x86 had double, or quadruple the registers available to us, there may be significantly less push/pop opcodes in a typical instruction stream? Or are there other processor optmizations that also optimize this away that I am unaware of? Basically if I've a unit of code that has 4 registers to work with for integer work, but my unit has a dozen variables, I've got potentially a push/pop for every 2 or so instructions. Any references to studies, or better yet, personal experiences?

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• How Random is System.Guid.NewGuid()? (Take two)

  - by Vilx-

  Before you start marking this as a duplicate, read me out. The other question has a (most likely) incorrect accepted answer. I do not know how .NET generates its GUIDs, probably only Microsoft does, but there's a high chance it simply calls CoCreateGuid(). That function however is documented to be calling UuidCreate(). And the algorithms for creating an UUID are pretty well documented. Long story short, be as it may, it seems that System.Guid.NewGuid() indeed uses version 4 UUID generation algorithm, because all the GUIDs it generates matches the criteria (see for yourself, I tried a couple million GUIDs, they all matched). In other words, these GUIDs are almost random, except for a few known bits. This then again raises the question - how random IS this random? As every good little programmer knows, a pseudo-random number algorithm is only as random as its seed (aka entropy). So what is the seed for UuidCreate()? How ofter is the PRNG re-seeded? Is it cryptographically strong, or can I expect the same GUIDs to start pouring out if two computers accidentally call System.Guid.NewGuid() at the same time? And can the state of the PRNG be guessed if sufficiently many sequentially generated GUIDs are gathered?

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• ai: Determining what tests to run to get most useful data

  - by Sai Emrys

  This is for http://cssfingerprint.com I have a system (see about page on site for details) where: I need to output a ranked list, with confidences, of categories that match a particular feature vector the binary feature vectors are a list of site IDs & whether this session detected a hit feature vectors are, for a given categorization, somewhat noisy (sites will decay out of history, and people will visit sites they don't normally visit) categories are a large, non-closed set (user IDs) my total feature space is approximately 50 million items (URLs) for any given test, I can only query approx. 0.2% of that space I can only make the decision of what to query, based on results so far, ~10-30 times, and must do so in <~100ms (though I can take much longer to do post-processing, relevant aggregation, etc) getting the AI's probability ranking of categories based on results so far is mildly expensive; ideally the decision will depend mostly on a few cheap sql queries I have training data that can say authoritatively that any two feature vectors are the same category but not that they are different (people sometimes forget their codes and use new ones, thereby making a new user id) I need an algorithm to determine what features (sites) are most likely to have a high ROI to query (i.e. to better discriminate between plausible-so-far categories [users], and to increase certainty that it's any given one). This needs to take into balance exploitation (test based on prior test data) and exploration (test stuff that's not been tested enough to find out how it performs). There's another question that deals with a priori ranking; this one is specifically about a posteriori ranking based on results gathered so far. Right now, I have little enough data that I can just always test everything that anyone else has ever gotten a hit for, but eventually that won't be the case, at which point this problem will need to be solved. I imagine that this is a fairly standard problem in AI - having a cheap heuristic for what expensive queries to make - but it wasn't covered in my AI class, so I don't actually know whether there's a standard answer. So, relevant reading that's not too math-heavy would be helpful, as well as suggestions for particular algorithms. What's a good way to approach this problem?

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• Simulating pass by reference for an array in Java

  - by Leif Andersen

  I was wondering, in java, is it possible to in anyway, simulate pass by reference for an array? Yes, I know the language doesn't support it, but is there anyway I can do it. Say, for example, I want to create a method that reverses the order of all the elements in an array. (I know that this code snippet isn't the best example, as there is a better algorithms to do this, but this is a good example of the type of thing I want to do for more complex problems). Currently, I need to make a class like this: public static void reverse(Object[] arr) { Object[] tmpArr = new Object[arr.length]; count = arr.length - 1; for(Object i : arr) tmpArr[count--] = i; // I would like to do arr = tmpArr, but that will only make the shallow // reference tmpArr, I would like to actually change the pointer they passed in // Not just the values in the array, so I have to do this: count = arr.length - 1; for(Object i : tmpArr) arr[count--] = i; return; } Yes, I know that I could just swap the values until I get to the middle, and it would be much more efficient, but for other, more complex purposes, is there anyway that I can manipulate the actual pointer? Again, thank you.

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• How can I load file into web app through certain periods?

  - by Elena

  Hi all! I have next task: I need to load the same file into my web app several times, for example - twice a day! Suppose in that file I have information, that changes, and I need to load this info into my app to change the statistics for example. How can I load file several times (twice an hour, or twice a day)? What should I use? Is any algorithm to do that? I am not allowed to use external libraries like Quartz Scheduler. So I need to do it with Thread and/or Timer. Can anybody give me some example or algorithm how to do it. Where can I create the entry point to my Thread, can I do it in managed bean or I need some sort of filter/listener/servlet. I works with jsf and richFaces. Maybe in this technologies there are some algorithms to solve my problem. Any ideas? Thanks very much for help!

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• Simulating pass by reference for an array reference (i.e. a reference to a reference) in Java

  - by Leif Andersen

  I was wondering, in java, is it possible to in anyway, simulate pass by reference for an array? Yes, I know the language doesn't support it, but is there anyway I can do it. Say, for example, I want to create a method that reverses the order of all the elements in an array. (I know that this code snippet isn't the best example, as there is a better algorithms to do this, but this is a good example of the type of thing I want to do for more complex problems). Currently, I need to make a class like this: public static void reverse(Object[] arr) { Object[] tmpArr = new Object[arr.length]; count = arr.length - 1; for(Object i : arr) tmpArr[count--] = i; // I would like to do arr = tmpArr, but that will only make the shallow // reference tmpArr, I would like to actually change the pointer they passed in // Not just the values in the array, so I have to do this: count = arr.length - 1; for(Object i : tmpArr) arr[count--] = i; return; } Yes, I know that I could just swap the values until I get to the middle, and it would be much more efficient, but for other, more complex purposes, is there anyway that I can manipulate the actual pointer? Again, thank you.

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• What is a good standard exercise to learn the OO features of a language?

  - by FarmBoy

  When I'm learning a new language, I often program some mathematical functions to get used to the control flow syntax. After that, I like to implement some sorting algorithms to get used to the array/list constructs. But I don't have a standard exercise for exploring the languages OO features. Does anyone have a stock exercise for this? A good answer would naturally lend to inheritance, polymorphism, etc., for a programmer already comfortable with these concepts. An ideal answer would be one that could be communicated in a few words, without ambiguity, in the way that "implement mergesort" is completely unambiguous. (As an example, answering "design a game" is so vague as to be useless.) Any ideas? EDIT: I have to remark that the results here are somewhat ironic. 10 upvotes and (originally) 5 favorites suggest that this is a question others are interested in. Yet the most upvoted answer is one that says there is no good answer. Oh well. I think I'll look at the textbook below, I've found games useful in the past for OO.

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• Can you force a crash if a write occurs to a given memory location with finer than page granularity?

  - by Joseph Garvin

  I'm writing a program that for performance reasons uses shared memory (alternatives have been evaluated, and they are not fast enough for my task, so suggestions to not use it will be downvoted). In the shared memory region I am writing many structs of a fixed size. There is one program responsible for writing the structs into shared memory, and many clients that read from it. However, there is one member of each struct that clients need to write to (a reference count, which they will update atomically). All of the other members should be read only to the clients. Because clients need to change that one member, they can't map the shared memory region as read only. But they shouldn't be tinkering with the other members either, and since these programs are written in C++, memory corruption is possible. Ideally, it should be as difficult as possible for one client to crash another. I'm only worried about buggy clients, not malicious ones, so imperfect solutions are allowed. I can try to stop clients from overwriting by declaring the members in the header they use as const, but that won't prevent memory corruption (buffer overflows, bad casts, etc.) from overwriting. I can insert canaries, but then I have to constantly pay the cost of checking them. Instead of storing the reference count member directly, I could store a pointer to the actual data in a separate mapped write only page, while keeping the structs in read only mapped pages. This will work, the OS will force my application to crash if I try to write to the pointed to data, but indirect storage can be undesirable when trying to write lock free algorithms, because needing to follow another level of indirection can change whether something can be done atomically. Is there any way to mark smaller areas of memory such that writing them will cause your app to blow up? Some platforms have hardware watchpoints, and maybe I could activate one of those with inline assembly, but I'd be limited to only 4 at a time on 32-bit x86 and each one could only cover part of the struct because they're limited to 4 bytes. It'd also make my program painful to debug ;)

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• Better ways to implement a modulo operation (algorithm question)

  - by ryxxui

  I've been trying to implement a modular exponentiator recently. I'm writing the code in VHDL, but I'm looking for advice of a more algorithmic nature. The main component of the modular exponentiator is a modular multiplier which I also have to implement myself. I haven't had any problems with the multiplication algorithm- it's just adding and shifting and I've done a good job of figuring out what all of my variables mean so that I can multiply in a pretty reasonable amount of time. The problem that I'm having is with implementing the modulus operation in the multiplier. I know that performing repeated subtractions will work, but it will also be slow. I found out that I could shift the modulus to effectively subtract large multiples of the modulus but I think there might still be better ways to do this. The algorithm that I'm using works something like this (weird pseudocode follows): result,modulus : integer (n bits) (previously defined) shiftcount : integer (initialized to zero) while( (modulus<result) and (modulus(n-1) != 1) ){ modulus = modulus << 1 shiftcount++ } for(i=shiftcount;i>=0;i++){ if(modulus<result){result = result-modulus} if(i!=0){modulus = modulus << 1} } So...is this a good algorithm, or at least a good place to start? Wikipedia doesn't really discuss algorithms for implementing the modulo operation, and whenever I try to search elsewhere I find really interesting but incredibly complicated (and often unrelated) research papers and publications. If there's an obvious way to implement this that I'm not seeing, I'd really appreciate some feedback.

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• Why is my multithreaded Java program not maxing out all my cores on my machine?

  - by James B

  Hi, I have a program that starts up and creates an in-memory data model and then creates a (command-line-specified) number of threads to run several string checking algorithms against an input set and that data model. The work is divided amongst the threads along the input set of strings, and then each thread iterates the same in-memory data model instance (which is never updated again, so there are no synchronization issues). I'm running this on a Windows 2003 64-bit server with 2 quadcore processors, and from looking at Windows task Manager they aren't being maxed-out, (nor are they looking like they are being particularly taxed) when I run with 10 threads. Is this normal behaviour? It appears that 7 threads all complete a similar amount of work in a similar amount of time, so would you recommend running with 7 threads instead? Should I run it with more threads?...Although I assume this could be detrimental as the JVM will do more context switching between the threads. Alternatively, should I run it with fewer threads? Alternatively, what would be the best tool I could use to measure this?...Would a profiling tool help me out here - indeed, is one of the several profilers better at detecting bottlenecks (assuming I have one here) than the rest? Note, the server is also running SQL Server 2005 (this may or may not be relevant), but nothing much is happening on that database when I am running my program. Note also, the threads are only doing string matching, they aren't doing any I/O or database work or anything else they may need to wait on. Thanks in advance, -James

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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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• Graph drawing for the Web 2.0

  - by tokel

  Hi. There are a lot of chart drawing libraries out there, but what I am looking for is an interactive(!) graph (nodes and edges) drawing library. At best some kind of AJAX, but I am also open for other technologies (Java, Flash). However I would really prefer an AJAX implementation. Also only Open Source framework suggestions please (I already know about yFiles). The thing I have in mind is a bit like GWTUML. That is quite nice already, but misses an API for their graph drawing. It seems that it is an custom implementation for their product. Also some layout algorithms would be nice. Is there really no library around for that task? I wonder a bit as there are so many chart libraries available. Let me emphasize again (seems to be necessary cause of the first two comments): I am NOT looking for another chart library! Regards, Kai P.S. Things I know about already: JUNG (Java), Prefuse (Java), GINY (Java), yFiles (AJAX, but not Open Source). Just another graph library I found (Javascript, not sure if it is still maintained): Graph Gear

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• Solving problems involving more complex data structures with CUDA

  - by Nils

  So I read a bit about CUDA and GPU programming. I noticed a few things such that access to global memory is slow (therefore shared memory should be used) and that the execution path of threads in a warp should not diverge. I also looked at the (dense) matrix multiplication example, described in the programmers manual and the nbody problem. And the trick with the implementation seems to be the same: Arrange the calculation in a grid (which it already is in case of the matrix mul); then subdivide the grid into smaller tiles; fetch the tiles into shared memory and let the threads calculate as long as possible, until it needs to reload data from the global memory into shared memory. In case of the nbody problem the calculation for each body-body interaction is exactly the same (page 682): bodyBodyInteraction(float4 bi, float4 bj, float3 ai) It takes two bodies and an acceleration vectors. The body vector has four components it's position and the weight. When reading the paper, the calculation is understood easily. But what is if we have a more complex object, with a dynamic data structure? For now just assume that we have an object (similar to the body object presented in the paper) which has a list of other objects attached and the number of objects attached is different in each thread. How could I implement that without having the execution paths of the threads to diverge? I'm also looking for literature which explains how different algorithms involving more complex data structures can be effectively implemented in CUDA.

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• Bored with CS. What can I study that will make an impact?

  - by Eric Martinez

  So I'm going to an average university, majoring in CS. I haven't learned a damn thing and am in my third year. I've come to be really bored with studying CS. Initially, I was kind of misinformed and thought majoring in CS would make me a good "product creator". I make my money combining programming and business/marketing. But I have always done programming for the love of the art. I find things like algorithms interesting and want to be able to use CS to solve real world problems. I like the idea of bioinformatics and other hybrid studies. I'm not good enough, yet I hope, to really make a significant effort in those areas but I aspire to be. What are some other fields, open problems, and otherwise cool stuff to apply CS knowledge to in the real world? I'm really looking for something that will motivate me and re-excite me to continue studying CS. Edit: Like someone mentioned below. I am very interesting in the idea of being able to use computer science to help answer fundamental questions of life and the universe. But I'm not sure what is possible or how to begin.

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• Open source gravatar-like implementations?

  - by Tauren

  I'm already using gravatar icons for the users of my web service. However, I'm finding several problems with this approach: Only a small percentage of the users take the time to set up a gravatar profile. My users are not tech-savvy, but would be likely to add a dedicated photo to my site. Users of my service are encouraged to use images that depict them in proper uniform for the industry my service relates to. They wouldn't want that same picture to be used for personal purposes throughout the internet. They would not take the time or effort to manage a separate email address and gravatar account just to have an "in-uniform" profile photo for my service. Before I implement my own profile image feature, I was wondering if there are any open-source solutions that I could leverage with similar features to gravatar. Specifically: The ability to display any size thumbnail (up to 512px would be fine) Takes care of caching different sized thumbnails Has support for something like identicons, preferably pluggable with different style algorithms (monsters, etc.), even better if I can customize these Ability to fall-back to gravatar if no photo found Does anything like this exist? I haven't found it yet if it does.

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• Any book on designing and implementing a CRPG engine?

  - by Fabzter

  Hi! First, let me tell you, I am not really interested in making my own rpg engine (at least not in the near future, hehe), but I do feel like I want to understand the internals of how a rpg engine works. Why? Well, because I like to read about programming and design, It keeps me motivated and excited, and because I know I will learn a lot, for, even when I have been programming for some years now, I never stop considering myself an ignorant... there are simply SO many things involving a game engine (specially rpg ones, like branching storylines, and items and economics!) I'm eager to know. I've been searching (and thus, finding) lots of info online, but it is never focused in what I'm interested (most of it talks about the mathematics and AI algorithms implementation, which I know quite well), which is the design of overall structure, patterns, scripting engine, decision engine... damn, so many things I can't even imagine, since I've never done any game programming. I hope you know have an idea of how I feel, and how I want to learn for the sake of learning, and why would I want you to tell me if you know if there exist books touching the topics that interest me the most.

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• Mathematics for Computer Science Students

  - by Ender

  To cut a long story short, I am a CS student that has received no formal Post-16 Maths education for years. Right now even my Algebra is extremely rusty and I have a couple of months to shape up my skills. I've got a couple of video lectures in my bookmarks, consisting of: Pre-Calculus Algebra Calculus Probability Introduction to Statistics Differential Equations Linear Algebra My aim as of today is to be able to read the CLRS book Introduction to Algorithms and be able to follow the Mathematical notation in that, as well as being able to confidently read and back-up any arguments written in Mathematical notation. Aside from these video lectures, can anyone recommend any good books to help teach someone wishing to go from a low-foundation level to a more advanced level of Mathematics? Just as a note, I've taken a first-year module in Analytical Modelling, so I understand some of the basic concepts of Discrete Mathematics. EDIT: Just a note to those that are looking to learn Linear Algebra using the Video Lectures I have posted up. Peteris Krumins' Blog contains a run-through of these lecture notes as well as his own commentary and lecture notes, an invaluable resource for those looking to follow the lectures too.

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• simple Java "service provider frameworks"?

  - by Jason S

  I refer to "service provider framework" as discussed in Chapter 2 of Effective Java, which seems like exactly the right way to handle a problem I am having, where I need to instantiate one of several classes at runtime, based on a String to select which service, and an Configuration object (essentially an XML snippet): But how do I get the individual service providers (e.g. a bunch of default providers + some custom providers) to register themselves? interface FooAlgorithm { /* methods particular to this class of algorithms */ } interface FooAlgorithmProvider { public FooAlgorithm getAlgorithm(Configuration c); } class FooAlgorithmRegistry { private FooAlgorithmRegistry() {} static private final Map<String, FooAlgorithmProvider> directory = new HashMap<String, FooAlgorithmProvider>(); static public FooAlgorithmProvider getProvider(String name) { return directory.get(serviceName); } static public boolean registerProvider(String name, FooAlgorithmProvider provider) { if (directory.containsKey(name)) return false; directory.put(name, provider); return true; } } e.g. if I write custom classes MyFooAlgorithm and MyFooAlgorithmProvider to implement FooAlgorithm, and I distribute them in a jar, is there any way to get registerProvider to be called automatically, or will my client programs that use the algorithm have to explicitly call FooAlgorithmRegistry.registerProvider() for each class they want to use?

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• Custom listbox sorting

  - by Arcadian

  I need to sort the data contained within a number of listboxes. The user will be able to select between two different types of sorting using radio boxes, one of which is checked by default on form load. I have created the IF statements needed in order to test whether the checked condition is true for that radio button. but i need some help to create the custom sort algorithms. Each list with contain similar looking data, the only difference in the prefix with which each line starts. For example each line in the first listbox starts with the prefix "G30" and the second listbox will be "G31" and so on. There are 10 listboxes in total (G30-G39 in terms of prefixes). The first search algorithm has to sort the lines by the number order of the first 13 chars. Example: This is how the data looks before sorting G35:45:58:11 JG07 G35:45:20:41 JG01 G35:58:20:21 JG03 G35:66:22:20 JG05 G35:45:85:21 JG02 G35:64:56:11 JG03 G35:76:35:11 JG02 G35:77:97:12 JG03 G35:54:29:11 JG01 G35:55:51:20 JG01 G35:76:24:20 JG06 G35:76:55:11 JG01 and this is how it should look after sorting G35:45:20:41 JG01 G35:45:58:11 JG07 G35:45:85:21 JG02 G35:54:29:11 JG01 G35:55:51:20 JG01 G35:58:20:21 JG03 G35:64:56:11 JG03 G35:66:22:20 JG05 G35:76:24:20 JG06 G35:76:35:11 JG02 G35:76:55:11 JG01 G35:77:97:12 JG03 as you can see, the prefixes are the same. so it is sorted, lowest first, by the next pair integers, then the next pair and the next but not by the value after "JG". the second sort algorithm will ignore the first 13 chars and sort by order of the value after "JG", highest first. any help? theres some rep in it for you :) thanks in advance

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• Is there an algorithm to securely split a message into x parts requiring at least y parts to reassem

  - by Aaron

  Is there an algorithm to securely split a message into x parts requiring at least y parts to reassemble? Obviously, y <= x. An example: Say that I have a secret message that I only want to be read in the event of my death. As a way to ensure this, I give a fraction of the message to ten friends. Now, I can't guaranty that all my friends will be able to put their messages together to recover the original. So, I construct each message fraction in such a way so as to only require any 5 friends to put their parts together to reconstruct the whole. However, owning less than 5 parts will not give anything away about the message, except possibly the length. My question is, is this possible? What algorithms might I look at to accomplish this? Clarification edit: The important part of this is the cryptographic strength. An attacker should not be able to recover the message, either in whole or in part with less than y parts.

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• Calculate total batch upload transfer percent with limited information

  - by GONeale

  Hi there, I have a system which uploads to a server file by file and displays a progress bar on file upload progress, then underneath a second progress bar which I want to indicate percentage of batch complete across all files queued to upload. Information and algorithms I can work out are: Bytes Sent / Total Bytes To Send = First progress bar (eg. 512KB of 1024KB (50%)) That works fine. However supposing I have two other files left to upload, but both file sizes are unknown (as this is only known once the file is about to commence upload, at which point it is compressed and file size is determined) how would I go about making my third progress bar? I didn't think this would be possible as I would need "Total Bytes Sent" / "Total Bytes To Send", to replicate the logic of my first progress bar on a larger scale, however I did get a version working: "Current file number we are on" / "total number of files to send" returning the percentage through the batch, however obviously will not incrementally update and it's pretty crude. So on further thinking I thought if I could incorporate the current file % with this algorithm I could perhaps get the correct progress percentage of my batch's current point. I tried this algorithm, but alas to no such avail (sorry to any math heads, it's probably quite apparent why it won't work) ("Current file number we are on" / "total number of files to send") * ("Bytes Sent" / "Total Bytes To Send") For example I thought I was on the right track when testing with this example: 2/3 (2nd of 3rd file) = 66% (this is right so far) but then when I added * 0.20 (for indicating only 20% of 2nd file has uploaded) we went back to 13%. What I need is only a little over 33%! I did try the inverse at 0.80 and a (2/3 * (2/3 * 0.2)) Can this be done without knowing entire bytes in batch to upload? Please help! Thank you!

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