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• Need to find latitude and longitude of postcodes and store into my database

  - by Matt

  Hey guys, Ive got a database full of UK Postcodes, now i'd like to be able to store the latitude and longitude of these specific postcodes along with the record with the database. Is there anyway that i can obtain this data free without violating any T&C's? I know i could do this using google maps api for each postcode, but i have way over 20,000 postcodes in this database and to get the lat and lng for each of these postcodes each time is not an option really. Thanks in advance, M

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• How to save big "database-like" class in python

  - by Rafal

  Hi there, I'm doing a project with reasonalby big DataBase. It's not a probper DB file, but a class with format as follows: DataBase.Nodes.Data=[[] for i in range(1,1000)] f.e. this DataBase is all together something like few thousands rows. Fisrt question - is the way I'm doing efficient, or is it better to use SQL, or any other "proper" DB, which I've never used actually. And the main question - I'd like to save my DataBase class with all record, and then re-open it with Python in another session. Is that possible, what tool should I use? cPickle - it seems to be only for strings, any other? In matlab there's very useful functionality named save workspace - it saves all Your variables to a file that You can open at another session - this would be vary useful in python!

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• Computationally simple Pseudo-Gaussian Distribution with varying mean and standard deviation?

  - by mstksg

  This picture from wikipedia has a nice example of the sort of functions I'd ideally like to generate http://en.wikipedia.org/wiki/File:Normal_Distribution_PDF.svg Right now I'm using the Irwin-Hall Distribution, which is more or less a Polynomial approximation of the Gaussian distribution...basically, you use uniform random number generator and iterate it x times, and take the average. The more iterations, the more like a Gaussian Distribution it is. It's pretty nice; however I'd like to be able to have one where I can vary the mean. For example, let's say I wanted a number between the range 0 and 10, but around 7. Like, the mean (if I repeated this function multiple times) would turn out to be 7, but the actual range is 0-10. Is there one I should look up, or should I work on doing some fancy maths with standard Gaussian Distributions?

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• Examples of useful or non-trival dual interfaces

  - by Scott Weinstein

  Recently Erik Meijer and others have show how IObservable/IObserver is the dual of IEnumerable/IEnumerator. The fact that they are dual means that any operation on one interface is valid on the other, thus providing a theoretical foundation for the Reactive Extentions for .Net Do other dual interfaces exist? I'm interested in any example, not just .Net based.

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• Create My own language with "Functional Programming Language"

  - by esehara

  I prefer Haskell. I already know How to create my own language with Procedural Language (for example: C, Java, Python, etc). But, I know How to create my own language with Functional Language (for example Haskell, Clojure and Scala). I've already read: Internet Resources Write Yourself a Scheme in 48 Hours Real World Haskell - Chapter 16.Using Persec Writing A Lisp Interpreter In Haskell Parsec, a fast combinator parser Implementing functional languages: a tutorial Books Introduction Functional Programming Using Haskell 2nd Edition -- Haskell StackOverflow (but with procedural language) Learning to write a compiler create my own programming language Source Libraries and tools/HJS -- Haskell Are there any other good sources? I wants to get more links,or sources.

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• Finding the heaviest length-constrained path in a weighted Binary Tree

  - by Hristo

  UPDATE I worked out an algorithm that I think runs in O(n*k) running time. Below is the pseudo-code: routine heaviestKPath( T, k ) // create 2D matrix with n rows and k columns with each element = -8 // we make it size k+1 because the 0th column must be all 0s for a later // function to work properly and simplicity in our algorithm matrix = new array[ T.getVertexCount() ][ k + 1 ] (-8); // set all elements in the first column of this matrix = 0 matrix[ n ][ 0 ] = 0; // fill our matrix by traversing the tree traverseToFillMatrix( T.root, k ); // consider a path that would arc over a node globalMaxWeight = -8; findArcs( T.root, k ); return globalMaxWeight end routine // node = the current node; k = the path length; node.lc = node’s left child; // node.rc = node’s right child; node.idx = node’s index (row) in the matrix; // node.lc.wt/node.rc.wt = weight of the edge to left/right child; routine traverseToFillMatrix( node, k ) if (node == null) return; traverseToFillMatrix(node.lc, k ); // recurse left traverseToFillMatrix(node.rc, k ); // recurse right // in the case that a left/right child doesn’t exist, or both, // let’s assume the code is smart enough to handle these cases matrix[ node.idx ][ 1 ] = max( node.lc.wt, node.rc.wt ); for i = 2 to k { // max returns the heavier of the 2 paths matrix[node.idx][i] = max( matrix[node.lc.idx][i-1] + node.lc.wt, matrix[node.rc.idx][i-1] + node.rc.wt); } end routine // node = the current node, k = the path length routine findArcs( node, k ) if (node == null) return; nodeMax = matrix[node.idx][k]; longPath = path[node.idx][k]; i = 1; j = k-1; while ( i+j == k AND i < k ) { left = node.lc.wt + matrix[node.lc.idx][i-1]; right = node.rc.wt + matrix[node.rc.idx][j-1]; if ( left + right > nodeMax ) { nodeMax = left + right; } i++; j--; } // if this node’s max weight is larger than the global max weight, update if ( globalMaxWeight < nodeMax ) { globalMaxWeight = nodeMax; } findArcs( node.lc, k ); // recurse left findArcs( node.rc, k ); // recurse right end routine Let me know what you think. Feedback is welcome. I think have come up with two naive algorithms that find the heaviest length-constrained path in a weighted Binary Tree. Firstly, the description of the algorithm is as follows: given an n-vertex Binary Tree with weighted edges and some value k, find the heaviest path of length k. For both algorithms, I'll need a reference to all vertices so I'll just do a simple traversal of the Tree to have a reference to all vertices, with each vertex having a reference to its left, right, and parent nodes in the tree. Algorithm 1 For this algorithm, I'm basically planning on running DFS from each node in the Tree, with consideration to the fixed path length. In addition, since the path I'm looking for has the potential of going from left subtree to root to right subtree, I will have to consider 3 choices at each node. But this will result in a O(n*3^k) algorithm and I don't like that. Algorithm 2 I'm essentially thinking about using a modified version of Dijkstra's Algorithm in order to consider a fixed path length. Since I'm looking for heaviest and Dijkstra's Algorithm finds the lightest, I'm planning on negating all edge weights before starting the traversal. Actually... this doesn't make sense since I'd have to run Dijkstra's on each node and that doesn't seem very efficient much better than the above algorithm. So I guess my main questions are several. Firstly, do the algorithms I've described above solve the problem at hand? I'm not totally certain the Dijkstra's version will work as Dijkstra's is meant for positive edge values. Now, I am sure there exist more clever/efficient algorithms for this... what is a better algorithm? I've read about "Using spine decompositions to efficiently solve the length-constrained heaviest path problem for trees" but that is really complicated and I don't understand it at all. Are there other algorithms that tackle this problem, maybe not as efficiently as spine decomposition but easier to understand? Thanks.

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• What is an XYZ-complete problem?

  - by TheMachineCharmer

  EDIT: Diagram: http://www.cs.umass.edu/~immerman/complexity_theory.html There must be some meaning to the word "complete" its used every now and then. Look at the diagram. I tried reading previous posts about NP- My question is what does the word "COMPLETE" mean? Why is it there? What is its significance? N- Non-deterministic - makes sense' P- Polynomial - makes sense but the "COMPLETE" is still a mystery for me.

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• curious ill conditioned numerical problem

  - by aaa

  hello. somebody today showed me this curious ill conditioned problem (apparently pretty famous), which looks relatively simple ƒ = (333.75 - a^2)b^6 + a^2 (11a^2 b^2 - 121b^4 - 2) + 5.5b^8 + a/(2^b) where a = 77617 and b = 33096 can you determine correct answer?

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• Gaining information from nodes of tree

  - by jainp

  I am working with the tree data structure and trying to come up with a way to calculate information I can gain from the nodes of the tree. I am wondering if there are any existing techniques which can assign higher numerical importance to a node which appears less frequently at lower level (Distance from the root of the tree) than the same nodes appearance at higher level and high frequency. To give an example, I want to give more significance to node Book, at level 2 appearing once, then at level 3 appearing thrice. Will appreciate any suggestions/pointers to techniques which achieve something similar. Thanks, Prateek

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• Opening read-only OLEDB connection to MS Access back-end database while allowing updates via separat

  - by djdilicious

  I have a back-end MS Access 2002-2003 database which stores blog entries. I created a separate front-end database with the forms for entering blog posts into the backend database. Finally, I have a website utilizing ASP to display the blog entries. The website connects directly to the backend database using an OLEDB connection object. Whenever I open the form for creating a new post in MS Access, loading the blog post page on the website displays the error: Could not use "; file already in use. I would like to be able to display the older blog posts even though the newest one is in the process of being added.

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• What exactly are administrative redexes after CPS conversion?

  - by eljenso

  In the context of Scheme and CPS conversion, I'm having a little trouble deciding what administrative redexes (lambdas) exactly are: all the lambda expressions that are introduced by the CPS conversion only the lambda expressions that are introduced by the CPS conversion but you wouldn't have written if you did the conversion "by hand" or through a smarter CPS-converter If possible, a good reference would be welcome.

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• what's a good way to synchronize a sql server 2008 database from a 2005 database automatically?

  - by Keith Nicholas

  Ok, the scenario is... two servers, on completely different parts of the internet. The sql 2008 database just needs to get data updates and schema changes. It doesn't need to send anything to the 2005 database. Basically just suck data and schema as efficiently as possible automatically as a scheduled task. The database is quite huge.... but the changes per day are probablly around 20/30 megabytes of data/ I can't run any of the inbuilt replication on the 2005 database. I've had a wee look at the Sync Framework, I think that might do what I want, but seems a bit painful and requires a bit of work to get going. I'm wondering if there is tooling out there to make this easier? or?? not quite sure what my options are.

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• How does a compiler first compile itself in the same language?

  - by jdk

  I recently read the Mono C# compiler is able to compile itself using the C# language. Cool. In the past I've heard of other languages doing the same. It twists my mind - at inception seems like a chicken and egg problem: syntax vs compiler. What comes first, second and third, etc?...

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• count of distinct acyclic paths from A[a,b] to A[c,d]?

  - by Sorush Rabiee

  I'm writing a sokoban solver for fun and practice, it uses a simple algorithm (something like BFS with a bit of difference). now i want to estimate its running time ( O and omega). but need to know how to calculate count of acyclic paths from a vertex to another in a network. actually I want an expression that calculates count of valid paths, between two vertices of a m*n matrix of vertices. a valid path: visits each vertex 0 or one times. have no circuits for example this is a valid path: but this is not: What is needed is a method to find count of all acyclic paths between the two vertices a and b. comments on solving methods and tricks are welcomed.

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• What is a data structure for quickly finding non-empty intersections of a list of sets?

  - by Andrey Fedorov

  I have a set of N items, which are sets of integers, let's assume it's ordered and call it I[1..N]. Given a candidate set, I need to find the subset of I which have non-empty intersections with the candidate. So, for example, if: I = [{1,2}, {2,3}, {4,5}] I'm looking to define valid_items(items, candidate), such that: valid_items(I, {1}) == {1} valid_items(I, {2}) == {1, 2} valid_items(I, {3,4}) == {2, 3} I'm trying to optimize for one given set I and a variable candidate sets. Currently I am doing this by caching items_containing[n] = {the sets which contain n}. In the above example, that would be: items_containing = [{}, {1}, {1,2}, {2}, {3}, {3}] That is, 0 is contained in no items, 1 is contained in item 1, 2 is contained in itmes 1 and 2, 2 is contained in item 2, 3 is contained in item 2, and 4 and 5 are contained in item 3. That way, I can define valid_items(I, candidate) = union(items_containing[n] for n in candidate). Is there any more efficient data structure (of a reasonable size) for caching the result of this union? The obvious example of space 2^N is not acceptable, but N or N*log(N) would be.

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• How to associate static entity instances in a Session without database retrieval

  - by Michael Hedgpeth

  I have a simple Result class that used to be an Enum but has evolved into being its own class with its own table. public class Result { public static readonly Result Passed = new Result(StatusType.Passed) { Id = [Predefined] }; public static readonly Result NotRun = new Result(StatusType.NotRun) { Id = [Predefined] }; public static readonly Result Running = new Result(StatusType.Running) { Id = [Predefined] }; } Each of these predefined values has a row in the database at their predefined Guid Id. There is then a failed result that has an instance per failure: public class FailedResult : Result { public FailedResult(string description) : base(StatusType.Failed) { . . . } } I then have an entity that has a Result: public class Task { public Result Result { get; set; } } When I save a Task, if the Result is a predefined one, I want NHibernate to know that it doesn't need to save that to the database, nor does it need to fetch it from the database; I just want it to save by Id. The way I get around this is when I am setting up the session, I call a method to load the static entities: protected override void OnSessionOpened(ISession session) { LockStaticResults(session, Result.Passed, Result.NotRun, Result.Running); } private static void LockStaticResults(ISession session, params Result[] results) { foreach (var result in results) { session.Load(result, result.Id); } } The problem with the session.Load method call is it appears to be fetching to the database (something I don't want to do). How could I make this so it does not fetch the database, but trusts that my static (immutable) Result instances are both up to date and a part of the session?

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• What does the q in a q-grammar stand for?

  - by Aru

  So I've been reading sites and the classic books on compilers, reading about s-grammar and q-grammars I wondered what the s and q stand for, I think the s stands for simple grammar. While the q...well, I have no idea. What does the q in a q-grammar stand for?

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• Hibernate overriding database modifications with detached object state

  - by EugeneP

  I'm gonna go with this design: create an object and keep it alive during all web-app session. And I need to synchronize its state with database state. What I want to achieve is that : IF between my db operations, that is, modifications that I persist to a db someone intentionally spoils table rows, then on next saving to a database all those changes WOULD BE OVERWRITTEN with the object state, that always contains valid data. What Hibernate methods do you recommend me to use to persist the modifications in a database? saveOrUpdate() is a possible solution, but maybe there's anything better? Again, I repeat how it looks. First I create an object without collections. Persist it (save()). Then user provides us with additional data. In a serviceLayer, again, we modify our object in memory (say, populate it with collections) and then, persist it again. So every serviceLayer operation of the next step must simply guarantee that database contains the exact persistent copy of this object that we have in memory. If data in a database differ, it MUST BE OVERRIDDEN with the object (kept in memory) state. What Session operations do you recommend?

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• How do I create a good evaluation function for a new board game?

  - by A. Rex

  I write programs to play board game variants sometimes. The basic strategy is standard alpha-beta pruning or similar searches, sometimes augmented by the usual approaches to endgames or openings. I've mostly played around with chess variants, so when it comes time to pick my evaluation function, I use a basic chess evaluation function. However, now I am writing a program to play a completely new board game. How do I choose a good or even decent evaluation function? The main challenges are that the same pieces are always on the board, so a usual material function won't change based on position, and the game has been played less than a thousand times or so, so humans don't necessarily play it enough well yet to give insight. (PS. I considered a MoGo approach, but random games aren't likely to terminate.) Any ideas? Game details: The game is played on a 10-by-10 board with a fixed six pieces per side. The pieces have certain movement rules, and interact in certain ways, but no piece is ever captured. The goal of the game is to have enough of your pieces in certain special squares on the board. The goal of the computer program is to provide a player which is competitive with or better than current human players.

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• efficacy of register allocation algorithms!

  - by aksci

  i'm trying to do a research/project on register allocation using graph coloring where i am to test the efficiency of different optimizing register allocation algorithms in different scenarios. how do i start? what are the prerequisites and the grounds with which i can test them. what all algos can i use? thank you!

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• Check for Duplicates in a Database Before Entering Data

  - by gamerzfuse

  Before Entering data into a database, I just want to check that the database doesn't have the same username in the database already. I have the username in SQL set as a key, so it can't be duplicated on that end, but I am looking at finding a more user-friendly error message then "KEY already exists". Is there are simple way to check if the variable value already exists in a row? Thanks!

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• .NET TDD with a Database and ADO.NET Entity Framework - Integration Tests

  - by Brian

  Hello, I'm using ADO.NET entity framework, and am using an AdventureWorks database attached to my local database server. For unit testing, what approaches have people taken to work with a database? Obviously, the database has to be in a pre-defined state of change so that the tests can have some isolation from each other... so I need to be able to run through the inserts and updates, then rollback either between tests or after the batch of tests are done. Any advice? Thanks.

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• Issue in Adding data into database using hibernate

  - by sarah

  Hi , I am getting the following exception "org.hibernate.HibernateException: The database returned no natively generated identity value "while adding data into database i am using the following code.Please let me know what is wrong Sesion session=HibernateUtil.getSession(); Transaction tx = session.beginTransaction(); session.save(user); logger.info("Successfully data insert in database"); tx.commit(); isSaved=true; Thankx

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• Git dirctet acyclic graph - children know their parents but not the other way around

  - by dayscott

  Git is implemented as a directed acyclic graph. Children know their parents but not the other way round. This makes sense because i can reach every commit only through a branch or a tag ( generally speaking through a reference). That's how i traverse the tree. What other reasons had the developers of Git to make "the children know their parents but not the other way around"?/ What are the key benefits of this?

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• Throughput measurements

  - by dotsid

  I wrote simple load testing tool for testing performance of Java modules. One problem I faced is algorithm of throughput measurements. Tests are executed in several thread (client configure how much times test should be repeated), and execution time is logged. So, when tests are finished we have following history: 4 test executions 2 threads 36ms overall time - idle * test execution 5ms 9ms 4ms 13ms T1 |-*****-*********-****-*************-| 3ms 6ms 7ms 11ms T2 |-***-******-*******-***********-----| <-----------------36ms---------------> For the moment I calculate throughput (per second) in a following way: 1000 / overallTime * threadCount. But there is problem. What if one thread will complete it's own tests more quickly (for whatever reason): 3ms 3ms 3ms 3ms T1 |-***-***-***-***----------------| 3ms 6ms 7ms 11ms T2 |-***-******-*******-***********-| <--------------32ms--------------> In this case actual throughput is much better because of measured throughput is bounded by the most slow thread. So, my question is how should I measure throughput of code execution in multithreaded environment.

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