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• Windows Azure Worldwide availability

  - by Insomniac

  Hi, I've been reviewing Windows Azure platform for some time, and can't find answer to one very important question. If I deploy my application within a cloud, how it will be reached from different places worldwide? For example if I have a web application with a database and want it to be accessible to users in UK, US, China and etc. Can I be sure that any user in the world will get almost the same request processing time? I think of it this way. 1. User sends request (navigates in browser to my web site) 2. This request gets in a cloud in a nearest location (closest to user MS Data Center?) 3. It is processed by an instance of my web application (in nearest location, with request to my centralized DB which can be far away but SQL request goes via MS internal network, which I believe should be very fast). 4. Response sent to user. Please let me know if I'm wrong. Thanks.

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• Fixing an SQL where statement that is ugly and confusing

  - by Mike Wills

  I am directly querying the back-end MS SQL Server for a software package. The key field (vehicle number) is defined as alpha though we are entering numeric value in the field. There is only one exception to this, we place an "R" before the number when the vehicle is being retired (which means we sold it or the vehicle is junked). Assuming the users do this right, we should not run into a problem using this method. (Right or wrong isn't the issue here) Fast forward to now. I am trying to query a subset of these vehicle numbers (800 - 899) for some special processing. By doing a range of '800' to '899' we also get 80, 81, etc. If I cast the vehicle number into an INT, I should be able to get the right range. Except that these "R" vehicles are kicking me in the butt now. I have tried where vehicleId not like 'R%' and cast(vehicleId as int) between 800 and 899 however, I get a casting error on one of these "R" vehicles. What does work is where vehicleId not between '800' and '899' and cast(vehicleId as int) between 800 and 899', but I feel there has to be a better way and less confusing way. I have also tried other variations with HAVING and a sub-query all producing a casting error.

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• Optimization of a c++ matrix/bitmap class

  - by Andrew

  I am searching a 2D matrix (or bitmap) class which is flexible but also fast element access. The contents A flexible class should allow you to choose dimensions during runtime, and would look something like this (simplified): class Matrix { public: Matrix(int w, int h) : data(new int[x*y]), width(w) {} void SetElement(int x, int y, int val) { data[x+y*width] = val; } // ... private: // symbols int width; int* data; }; A faster often proposed solution using templates is (simplified): template <int W, int H> class TMatrix { TMatrix() data(new int[W*H]) {} void SetElement(int x, int y, int val) { data[x+y*W] = val; } private: int* data; }; This is faster as the width can be "inlined" in the code. The first solution does not do this. However this is not very flexible anymore, as you can't change the size anymore at runtime. So my question is: Is there a possibility to tell the compiler to generate faster code (like when using the template solution), when the size in the code is fixed and generate flexible code when its runtime dependend? I tried to achieve this by writing "const" where ever possible. I tried it with gcc and VS2005, but no success. This kind of optimization would be useful for many other similar cases.

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• optimized search using ajax and keypress

  - by ooo

  i have the following code as i want to search a database as a user is typing into a textbox. This code below works fine but it seems a little inefficient as if a user is typing really fast, i am potentially doing many more searches than necessary. So if a user is typing in "sailing" i am searching on "sail", "saili", "sailin", and "sailing" i wanted to see if there was a way to detect any particular time between keypresses so only search if user stops typing for 500 milliseconds or something like this. is there a best practices for something like this? $('#searchString').keypress(function(e) { if (e.keyCode == 13) { var url = '/Tracker/Search/' + $("#searchString").val(); $.get(url, function(data) { $('div#results').html(data); $('#results').show(); }); } else { var existingString = $("#searchString").val(); if (existingString.length > 2) { var url = '/Tracker/Search/' + existingString; $.get(url, function(data) { $('div#results').html(data); $('#results').show(); }); } }

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• Iphone -- maintaining a list of strings and a corresponding typedef enum

  - by William Jockusch

  Suppose I have the following: typedef enum functionType {ln, sin, sqrt} functionType; NSArray *functions = [NSArray arrayWithObjects: @"ln", @"sin", @"sqrt", nil]; Suppose further that *functions will not change at runtime. Question -- is there any way to set up a single structure which updates both of these? So that I only have to keep track of one list, instead of two. To explain what is going on -- the idea is that string input from the user will be stored in a variable of type functionType. Later on, I will have code like this: double valueOfFunction: (functionType) function withInput: (double) input switch (function) { case ln: return ln(input); case sin: return sin(input); case sqrt: return sqrt(input); //etc . . . could grow to include a lot of functions. } And valueOfFunction needs to be fast. So I don't want to be doing string comparisons there.

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• Design for fastest page download

  - by mexxican

  I have a file with millions of URLs/IPs and have to write a program to download the pages really fast. The connection rate should be at least 6000/s and file download speed at least 2000 with avg. 15kb file size. The network bandwidth is 1 Gbps. My approach so far has been: Creating 600 socket threads with each having 60 sockets and using WSAEventSelect to wait for data to read. As soon as a file download is complete, add that memory address(of the downloaded file) to a pipeline( a simple vector ) and fire another request. When the total download is more than 50Mb among all socket threads, write all the files downloaded to the disk and free the memory. So far, this approach has been not very successful with the rate at which I could hit not shooting beyond 2900 connections/s and downloaded data rate even less. Can somebody suggest an alternative approach which could give me better stats. Also I am working windows server 2008 machine with 8 Gig of memory. Also, do we need to hack the kernel so as we could use more threads and memory. Currently I can create a max. of 1500 threads and memory usage not going beyond 2 gigs [ which technically should be much more as this is a 64-bit machine ]. And IOCP is out of question as I have no experience in that so far and have to fix this application today. Thanks Guys!

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• 2-column table with two foreign keys. Performance/design question.

  - by Emanuel

  Hello everyone! I recently ran into a quite complex problem and after looking around a lot I couldn't find a solution to it. I've found answers to my questions many times before on stackoverflow.com, so I decided to post here. So I'm making a user/group managment system for a web-based project, and I'm storing all related data into a postgreSQL database. This system relies on three tables: USERS GROUPS GROUP_USERS The two first tables simply define all the users and all the groups on the site, and the last table, GROUP_USERS, stores the groups every user is part of. It only has two columns: USER_ID GROUP_ID Since every user can be a member of several groups, I decided to make a separate table for this purpose, rather than storing a comma separated column in the USERS-table. Now, both columns are foreign keys, and I want to make them both primary keys as well, this since each combination of USER_ID and GROUP_ID has to be unique, and if I give them the constraint UNIQUE pgAdmin tells me that each table should have at least one Primary key. But now I am stuck with what seems to be a lot of indexes and relations to a very small table only containing numbers. In the end, I want this table to be as fast as possible, even if containing tens of thousands of rows. Size on disk shouldn't be a problem since its just all numbers anyway, but it feels quite stupid to have a full-sized index refering to a smaller table. Should I stick with my current solution, store comma-separated values in a column in the USERS-table or is there any other solution I should be aware of. PS. I don't want to use an array-column, even if they are supported by postgreSQL. I want to be as generic as possible so I can switch database later on, if necessary. EDIT: I other words, will using a compound primary key and two foreign keys in one table with only two columns have a negative impact on performance rather than the opposite due to the size of the generated index? Thank you!

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• sql queries slower than expected

  - by neubert

  Before I show the query here are the relevant table definitions: CREATE TABLE phpbb_posts ( topic_id mediumint(8) UNSIGNED DEFAULT '0' NOT NULL, poster_id mediumint(8) UNSIGNED DEFAULT '0' NOT NULL, KEY topic_id (topic_id), KEY poster_id (poster_id), ); CREATE TABLE phpbb_topics ( topic_id mediumint(8) UNSIGNED NOT NULL auto_increment ); Here's the query I'm trying to do: SELECT p.topic_id, p.poster_id FROM phpbb_topics AS t LEFT JOIN phpbb_posts AS p ON p.topic_id = t.topic_id AND p.poster_id <> ... WHERE p.poster_id IS NULL; Basically, the query is an attempt to find all topics where the number of times someone other than the target user has posted in is zero. In other words, the topics where the only person who has posted is the target user. Problem is that query is taking a super long time. My general assumption when it comes to SQL is that JOINs of any are super fast and can be done in no time at all assuming all relevant columns are primary or foreign keys (which in this case they are). I tried out a few other queries: SELECT COUNT(1) FROM phpbb_topics AS t JOIN phpbb_posts AS p ON p.topic_id = t.topic_id; That returns 353340 pretty quickly. I then do these: SELECT COUNT(1) FROM phpbb_topics AS t JOIN phpbb_posts AS p ON p.topic_id = t.topic_id AND p.poster_id <> 77198; SELECT COUNT(1) FROM phpbb_topics AS t JOIN phpbb_posts AS p ON p.topic_id = t.topic_id WHERE p.poster_id <> 77198; And both of those take quite a while (between 15-30 seconds). If I change the < to a = it takes no time at all. Am I making some incorrect assumptions? Maybe my DB is just foobar'd?

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• Worth website that a web developer must surf daily?

  - by I Like PHP

  Hello All, this may be not a right place to ask this question, but i can get best answer only from here, so i m posting here. i m a web developer and working with technology PHP,MySQL, JavaScript,jQuery,AJAX, CSS, HTML, JSON i daily surf few websites regarding web development , i know there are a lot of website with very good knowledge but we are not aware of that so i think we have to share with each other.i m mentioning some useful links that we must surf daily for gaining knowledge and do better/fast development. please you also suggest some good links which you surf regularly and best in their field. i surf belows links regularly - [Stack Overflow][1] // No doubt, it is best - [Delicious][2]// best social bookmarking website - [Smashing Magazine][3] // Best site to improve knowledege for a web developer - [Net tuts][4] // Best tutorail wesbsite with full explanation - [Official PHP site ][5] // i think nothing to mention about it( just superb) - [Javascript Debugger][6] // U can filter your javascript/jquery code here - [jQuery Official site][7] // best to learn jQuery i m waiting for you great response. i also need any good and trusted website on mysql, i think mysql officail website is very confusing, i had to search a lot to find a single thing, if u have any good regarding mysql then share please. Thanks alwayz.

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• log activity. intrusion detection. user event notification ( interraction ). messaging

  - by Julian Davchev

  Have three questions that I somehow find related so I put them in same place. Currently building relatively large LAMP system - making use of messaging(activeMQ) , memcache and other goodies. I wonder if there are best practices or nice tips and tricks on howto implement those. System is user aware - meaning all actions done can be bind to particular logged user. 1. How to log all actions/activities of users? So that stats/graphics might be extracted later for analysing. At best that will include all url calls, post data etc etc. Meaning tons of inserts. I am thinking sending messages to activeMQ and later cron dumping in DB and cron analysing might be good idea here. Since using Zend Framework I guess I may use some request plugin so I don't have to make the log() call all over the code. 2.How to log stuff so may be used for intrusion detection? I know most things might be done on http level using apache mods for example but there are also specific cases like (5 failed login attempts in a row (leads to captcha) etc etc..) This also would include tons of inserts. Here I guess direct usage of memcache might be best approach as data don't seem vital to be permanantly persisted. Not sure if cannot use data from point 1. 3.System will notify users of some events. Like need approval , something broke..whatever.Some events will need feedback(action) from user, others are just informational. Wonder if there is common solutions for needs like this. Example: Based on occuring event(s) user will be notifed (user inbox for example) what happend. There will be link or something to lead him to details of thingy that happend and take action accordingly. Those seem trivial at first look but problem I see if coding it directly is becoming really fast hard to maintain.

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• Storing large numbers of varying size objects on disk

  - by Foredecker

  I need to develop a system for storing large numbers (10's to 100's of thousands) of objects. Each object is email-like - there is a main text body, and several ancillary text fields of limited size. A body will be from a few bytes, to several KB in size. Each item will have a single unique ID (probably a GUID) that identifies it. The store will only be written to when an object is added to it. It will be read often. Deletions will be rare. The data is almost all human readable text so it will be readily compressible. A system that lets me issue the I/Os and mange the memory and caching would be ideal. I'm going to keep the indexes in memory, using it to map indexes to the single (and primary) key for the objects. Once I have the key, then I'll load it from disk, or the cache. The data management system needs to be part of my application - I do not want to depend on OS services. Or separately installed packages. Native (C++) would be best, but a manged (C#) thing would be ok. I believe that a database is an obvious choice, but this needs to be super-fast for look up and loading into memory of an object. I am not experienced with data base tech and I'm concerned that general relational systems will not handle all this variable sized data efficiently. (Note, this has nothing to do with my job - its a personal project.) In your experience, what are the viable alternatives to a traditional relational DB? Or would a DB work well for this?

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• Is it possible to cache all the data in a SQL Server CE database using LinqToSql?

  - by DanM

  I'm using LinqToSql to query a small, simple SQL Server CE database. I've noticed that any operations involving sub-properties are disappointingly slow. For example, if I have a Customer table that is referenced by an Order table, LinqToSql will automatically create an EntitySet<Order> property. This is a nice convenience, allowing me to do things like Customer.Order.Where(o => o.ProductName = "Stopwatch"), but for some reason, SQL Server CE hangs up pretty bad when I try to do stuff like this. One of my queries, which isn't really that complicated takes 3-4 seconds to complete. I can get the speed up to acceptable, even fast, if I just grab the two tables individually and convert them to List<Customer> and List<Order>, then join then manually with my own query, but this is throwing out a lot of what makes LinqToSql so appealing. So, I'm wondering if I can somehow get the whole database into RAM and just query that way, then occasionally save it. Is this possible? How? If not, is there anything else I can do to boost the performance besides resorting to doing all the joins manually? Note: My database in its initial state is about 250K and I don't expect it to grow to more than 1-2Mb. So, loading the data into RAM certainly wouldn't be a problem from a memory point of view. Update Here are the table definitions for the example I used in my question: create table Order ( Id int identity(1, 1) primary key, ProductName ntext null ) create table Customer ( Id int identity(1, 1) primary key, OrderId int null references Order (Id) )

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• getting string.substring(N) not to choke when N > string.length

  - by aape

  I'm writing some code that takes a report from the mainframe and converts it to a spreadsheet. They can't edit the code on the MF to give me a delimited file, so I'm stuck dealing with it as fixed width. It's working okay now, but I need to get it more stable before I release it for testing. My problem is that in any given line of data, say it could have three columns of numbers, each five chars wide at positions 10, 16, and 22. If on this one particular row, there's no data for the last two cols, it won't be padded with spaces; rather, the length of the string will be only 14. So, I can't just blindly have dim s as string = someStream.readline a = s.substring(10, 5) b = s.substring(16, 5) c = s.substring(22, 5) because it'll choke when it substrings past the length of the string. I know I could test the length of the string before processing each row, and I have automated the filling of some of the vsariables using a counter and a loop, and using the counter*theWidthOfTheGivenVariable to jump around, but this project was a dog to start with (come on! turning a report into a spreadsheet?), but there are many different types of rows (it's not just a grid), and the code's getting ugly fast. I'd like this to be clean, clear, and maintainable for the poor sucker that gets this after me. If it matters, here's my code so far (it's really crufty at the moment). You can see some of my/its idiocy in the processSection#data subs So, I'm wondering 1) is there a way baked in to .NET to have string.substring not error when reading past the end of a string without wrapping it in a try...catch? and 2) would it be appropriate in this situation to write a new string class that inherits from string that has a more friendly substring function in it? ETA: Thanks for all the advice and knowledge everyone. I'll go with the extension. Hopefully one of these years, I'll get my chops up enough to pay someone back in kind. :)

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• Logic: Best way to sample & count bytes of a 100MB+ file

  - by Jami

  Let's say I have this 170mb file (roughly 180 million bytes). What I need to do is to create a table that lists: all 4096 byte combinations found [column 'bytes'], and the number of times each byte combination appeared in it [column 'occurrences'] Assume two things: I can save data very fast, but I can update my saved data very slow. How should I sample the file and save the needed information? Here're some suggestions that are (extremely) slow: Go through each 4096 byte combinations in the file, save each data, but search the table first for existing combinations and update it's values. this is unbelievably slow Go through each 4096 byte combinations in the file, save until 1 million rows of data in a temporary table. Go through that table and fix the entries (combine repeating byte combinations), then copy to the big table. Repeat going through another 1 million rows of data and repeat the process. this is faster by a bit, but still unbelievably slow This is kind of like taking the statistics of the file. NOTE: I know that sampling the file can generate tons of data (around 22Gb from experience), and I know that any solution posted would take a bit of time to finish. I need the most efficient saving process

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• Why is DivMod Limited to Words (<=65535)?

  - by Andreas Rejbrand

  In Delphi, the declaration of the DivMod function is procedure DivMod(Dividend: Cardinal; Divisor: Word; var Result, Remainder: Word); Thus, the divisor, result, and remainder cannot be grater than 65535, a rather severe limitation. Why is this? Why couldn't the delcaration be procedure DivMod(Dividend: Cardinal; Divisor: Cardinal; var Result, Remainder: Cardinal); The procedure is implemented using assembly, and is therefore probably extremely fast. Would it not be possible for the code PUSH EBX MOV EBX,EDX MOV EDX,EAX SHR EDX,16 DIV BX MOV EBX,Remainder MOV [ECX],AX MOV [EBX],DX POP EBX to be adapted to cardinals? How much slower is the naïve attempt procedure DivModInt(const Dividend: integer; const Divisor: integer; out result: integer; out remainder: integer); begin result := Dividend div Divisor; remainder := Dividend mod Divisor; end; that is not (?) limited to 16-bit integers?

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• How to correctly pass a float from C# to C++ (dll)

  - by RavelT

  I'm getting huge differences when I pass a float from C# to C++. I'm passing a dynamic float wich changes over time. With a debuger I get this: c++ lonVel -0.036019072 float c# lonVel -0.029392920 float I did set my MSVC++2010 floating point model to /fp:fast wich should be the standard in .NET if I'm not mistaken, but this didnt help. Now I cant give out the code but I can show a fraction of it. From C# side it looks like this: namespace Example { public class Wheel { public bool loging = true; #region Members public IntPtr nativeWheelObject; #endregion Members public Wheel() { this.nativeWheelObject = Sim.Dll_Wheel_Add(); return; } #region Wrapper methods public void SetVelocity(float lonRoadVelocity,float latRoadVelocity){Sim.Dll_Wheel_SetVelocity(this.nativeWheelObject,lonRoadVelocity,latRoadVelocity);} #endregion Wrapper methods } internal class Sim { #region PInvokes [DllImport(pluginName, CallingConvention=CallingConvention.Cdecl)] public static extern void Dll_Wheel_SetVelocity(IntPtr wheel,float lonRoadVelocity,float latRoadVelocity); #endregion PInvokes } } And in C++ side @ exportFunctions.cpp: EXPORT_API void Dll_Wheel_SetVelocity(CarWheel* wheel,float lonRoadVelocity,float latRoadVelocity){ wheel->SetVelocity(lonRoadVelocity,latRoadVelocity);} So any sugestions on what I should do in order to get 1:1 results or atleast 99% correct results.

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• SQL: find entries in 1:n relation that don't comply with condition spanning multiple rows

  - by milianw

  I'm trying to optimize SQL queries in Akonadi and came across the following problem that is apparently not easy to solve with SQL, at least for me: Assume the following table structure (should work in SQLite, PostgreSQL, MySQL): CREATE TABLE a ( a_id INT PRIMARY KEY ); INSERT INTO a (a_id) VALUES (1), (2), (3), (4); CREATE TABLE b ( b_id INT PRIMARY KEY, a_id INT, name VARCHAR(255) NOT NULL ); INSERT INTO b (b_id, a_id, name) VALUES (1, 1, 'foo'), (2, 1, 'bar'), (3, 1, 'asdf'), (4, 2, 'foo'), (5, 2, 'bar'), (6, 3, 'foo'); Now my problem is to find entries in a that are missing name entries in table b. E.g. I need to make sure each entry in a has at least the name entries "foo" and "bar" in table b. Hence the query should return something similar to: a_id = 3 is missing name "bar" a_id = 4 is missing name "foo" and "bar" Since both tables are potentially huge in Akonadi, performance is of utmost importance. One solution in MySQL would be: SELECT a.a_id, CONCAT('|', GROUP_CONCAT(name ORDER BY NAME ASC SEPARATOR '|'), '|') as names FROM a LEFT JOIN b USING( a_id ) GROUP BY a.a_id HAVING names IS NULL OR names NOT LIKE '%|bar|foo|%'; I have yet to measure the performance tomorrow, but severly doubt it's any fast for tens of thousand of entries in a and thrice as many in b. Furthermore we want to support SQLite and PostgreSQL where to my knowledge the GROUP_CONCAT function is not available. Thanks, good night.

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• Parallelize or vectorize all-against-all operation on a large number of matrices?

  - by reve_etrange

  I have approximately 5,000 matrices with the same number of rows and varying numbers of columns (20 x ~200). Each of these matrices must be compared against every other in a dynamic programming algorithm. In this question, I asked how to perform the comparison quickly and was given an excellent answer involving a 2D convolution. Serially, iteratively applying that method, like so list = who('data_matrix_prefix*') H = cell(numel(list),numel(list)); for i=1:numel(list) for j=1:numel(list) if i ~= j eval([ 'H{i,j} = compare(' char(list(i)) ',' char(list(j)) ');']); end end end is fast for small subsets of the data (e.g. for 9 matrices, 9*9 - 9 = 72 calls are made in ~1 s). However, operating on all the data requires almost 25 million calls. I have also tried using deal() to make a cell array composed entirely of the next element in data, so I could use cellfun() in a single loop: # who(), load() and struct2cell() calls place k data matrices in a 1D cell array called data. nextData = cell(k,1); for i=1:k [nextData{:}] = deal(data{i}); H{:,i} = cellfun(@compare,data,nextData,'UniformOutput',false); end Unfortunately, this is not really any faster, because all the time is in compare(). Both of these code examples seem ill-suited for parallelization. I'm having trouble figuring out how to make my variables sliced. compare() is totally vectorized; it uses matrix multiplication and conv2() exclusively (I am under the impression that all of these operations, including the cellfun(), should be multithreaded in MATLAB?). Does anyone see a (explicitly) parallelized solution or better vectorization of the problem?

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• How to get VC# to rebuild auto-generated .cs files?

  - by Jive Dadson

  I imagine this question has been asked and answered, but I cannot find it. I wanted to make a simple GUI to interface to a windows 7 command. I usually use Wx, but since this was to be a windows-only thing, I decided to see if I could whip it out real fast using Visual C# 2010 Express, which I had never used before. Things started off just great. I created a form, put a few buttons and text boxes and such on it, and hit Debug. It came up and ran just like that. No muss, no fuss. So I then designed the form just the way I wanted it, renamed the controls from "Button1" and so forth to meaningful names. But now it's a mess. By clicking around, I discovered that VC# had auto-generated two files called Form1.cs and Form1.Designer.cs. The later contains the bindings between functions and the events generated from user-clicks etc., and the former contains no-op code for those functions, for me to complete. Problem is, the names are all still the original "Button1" and so forth, not the new ones, and the new controls I added after running the first time do not appear at all. I want it to regenerate all that stuff afresh from the finished form. How to?

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• custom sorting or ordering a table without resorting the whole shebang

  - by fuugus

  for ten years we've been using the same custom sorting on our tables, i'm wondering if there is another solution which involves fewer updates, especially since today we'd like to have a replication/publication date and would'nt like to have our replication replicate unnecessary entries. i had a look into nested sets, but it does'nt seem to do the job for us. base table: id | a_sort ---+------- 1 10 2 20 3 30 after inserting insert into table (a_sort) values(15) an entry at the second position. id | a_sort ---+------- 1 10 2 20 3 30 4 15 ordering the table with select * from table order by a_sort and resorting all the a_sort entries, updating at least id=(2,3,4) will of course produce the desired output id | a_sort ---+------- 1 10 4 20 2 30 3 40 the column names, the column count, datatypes, a possible join, possible triggers or the way the resorting is done is/are irrelevant to the problem. also we've found some pretty neat ways to do this task fast. only; how the heck can we reduce the updates in the db to 1 or 2 max. seems like an awfully common problem. the captain obvious in me thougth once "use an a_sort float(53), insert using a fixed value of ordervaluefirstentry+abs(ordervaluefirstentry-ordervaluenextentry)/2".. but this would only allow around 1040 "in between" entries - so never resorting seems a bit problematic ;)

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• Faster way to convert from a String to generic type T when T is a valuetype?

  - by Kumba

  Does anyone know of a fast way in VB to go from a string to a generic type T constrained to a valuetype (Of T as Structure), when I know that T will always be some number type? This is too slow for my taste: Return DirectCast(Convert.ChangeType(myStr, GetType(T)), T) But it seems to be the only sane method of getting from a String -- T. I've tried using Reflector to see how Convert.ChangeType works, and while I can convert from the String to a given number type via a hacked-up version of that code, I have no idea how to jam that type back into T so it can be returned. I'll add that part of the speed penalty I'm seeing (in a timing loop) is because the return value is getting assigned to a Nullable(Of T) value. If I strongly-type my class for a specific number type (i.e., UInt16), then I can vastly increase the performance, but then the class would need to be duplicated for each numeric type that I use. It'd almost be nice if there was converter to/from T while working on it in a generic method/class. Maybe there is and I'm oblivious to its existence?

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• What is the most efficient way to handle points / small vectors in JavaScript?

  - by Chris

  Currently I'm creating an web based (= JavaScript) application thata is using a lot of "points" (= small, fixed size vectors). There are basically two obvious ways of representing them: var pointA = [ xValue, yValue ]; and var pointB = { x: xValue, y: yValue }; So translating my point a bit would look like: var pointAtrans = [ pointA[0] + 3, pointA[1] + 4 ]; var pointBtrans = { x: pointB.x + 3, pointB.y + 4 }; Both are easy to handle from a programmer point of view (the object variant is a bit more readable, especially as I'm mostly dealing with 2D data, seldom with 3D and hardly with 4D - but never more. It'll allways fit into x,y,z and w) But my question is now: What is the most efficient way from the language perspective - theoretically and in real implementations? What are the memory requirements? What are the setup costs of an array vs. an object? ... My target browsers are FireFox and the Webkit based ones (Chromium, Safari), but it wouldn't hurt to have a great (= fast) experience under IE and Opera as well...

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• Java: multi-threaded maps: how do the implementations compare?

  - by user346629

  I'm looking for a good hash map implementation. Specifically, one that's good for creating a large number of maps, most of them small. So memory is an issue. It should be thread-safe (though losing the odd put might be an OK compromise in return for better performance), and fast for both get and put. And I'd also like the moon on a stick, please, with a side-order of justice. The options I know are: HashMap. Disastrously un-thread safe. ConcurrentHashMap. My first choice, but this has a hefty memory footprint - about 2k per instance. Collections.sychronizedMap(HashMap). That's working OK for me, but I'm sure there must be faster alternatives. Trove or Colt - I think neither of these are thread-safe, but perhaps the code could be adapted to be thread safe. Any others? Any advice on what beats what when? Any really good new hash map algorithms that Java could use an implementation of? Thanks in advance for your input!

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• User to be validated against nested security groups in Windows.

  - by user412272

  Hi, This is my first post here and after much looking around I have come here with my question. Will really appreciate a fast response. I am faced with a problem to validate user credentials of the currently logged on user against a group in Windows. The user membership to a group can be through other groups also ie nested membership. Eg. User U is a part of group G1. Group G1 is a part of another group G2. The requirement is that when the user is validated against group G2, the validations should succeed. The user can be a local or AD user but the group will always be a local group ( or domain local group if created directly on a DC). I have tried using WindowsPrincipal.IsInRole() method, but it seems to be checking only for direct membership to a group. I also tried UserPrincipal.GetAuthorizationGroups() for the current user, but it also doesnt seem to be doing recursive search. I am posting a code snippet of the working code below, but this code is taking much more than acceptable time. bool CheckUserPermissions(string groupName) { WindowsIdentity currentUserIdentity = System.Security.Principal.WindowsIdentity.GetCurrent(); bool found = false; PrincipalContext context= new PrincipalContext(ContextType.Machine); GroupPrincipal group = GroupPrincipal.FindByIdentity(context, IdentityType.Name, groupName); if (group!= null) { foreach (Principal p in group.GetMembers(true)) { if (p.Sid == currentUserIdentity.User) { found = true; break; } } group.Dispose(); } return found; }

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• .NET Development of iPhone App with MonoTouch - which development environment?

  - by Click Ahead

  Hi All, I'm a .NET developer (C#) with several years developing Windows Mobile Apps. I would like to get into developing iPhone Apps and MonoTouch looks good based on reviews I've read. So I'm going to go with MonoTouch. My understanding is that I'll need a new Mac, but as it happens I also need a new PC for my .NET windows development. My question is should I (a) Purchase a Mac Book Pro and dual boot with Windows 7 (b) Purchase a Mac Pro and dual boot with Windows 7 (c) Purchase a good Dev PC and a slighlty less well spec'd Mac Book Pro or Mac Pro Bear in mind I'm only doing MonoTouch development with the Mac, most of my development (approx. 80% initially) will be done on the Windows side. My budget is approx. €3,000 / $4,000 and I'd like a good, fast development environment.It's purely for development so on the windows side installing SQL 2008/VS 2010/Office and on the OS X side installing MonoTouch. BTW - my budget excludes licensing for VS/MonoTouch/etc, I have a MonoTouch and MSDN license. Any opinions are greatly appreciated. I'm a newbie to Mac's !

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