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• Are all the system's floating points operations the same?

  - by Jj

  We're making this web app in PHP and when working in the reports we have Excel files to compare our results to make sure our coding is doing the right operations. Now we're running into some differences due floating point arithmetics. We're doing the same divisions and multiplications and running into slightly different numbers, that add up to a notable difference. My question is if Excel is delegating it's floating point arithmetic to the CPU and PHP is also relying in the CPU for it's operations. Or does each application implements its own set of math algorithms?

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• Use the [Serializable] attribute or subclassing from MarshalByRefObject?

  - by Theo Lenndorff

  I'd like to use an object across AppDomains. For this I can use the [Serializeable] attribute: [Serializable] class MyClass { public string GetSomeString() { return "someString" } } Or subclass from MarshalByRefObject: class MyClass: MarshalByRefObject { public string GetSomeString() { return "someString" } } In both cases I can use the class like this: AppDomain appDomain = AppDomain.CreateDomain("AppDomain"); MyClass myObject = (MyClass)appDomain.CreateInstanceAndUnwrap( typeof(MyClass).Assembly.FullName, typeof(MyClass).FullName); Console.WriteLine(myObject.GetSomeString()); Why do both approaches seem to have the same effect? What is the difference in both approaches? When should I favor the one approach over the other? EDIT: At the surface I know that there are differences between both mechanisms, but if someone jumped out of a bush and asked me the question I couldn't give him a proper answer. The questions are quite open questions. I hoped that someone can explain it better than I could do.

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• Library for polygon operations

  - by AJM

  I've recently encountered a need for a library or set of libraries to handle operations on 2D polygons. I need to be able to perform boolean/clipping operations (difference and union) and triangulation. So far the libraries I've found are poly2tri, CGAL, and GPC. Poly2tri looks good for triangulation but I'm still left with boolean operations, and I'm unsure about its maturity. CGAL and GPC are only free if my own project is free. My particular project isn't commercial, so I'm hesitant to pay or request for any licenses. But I may want to use my code for a future commercial project, so I'm hesitant about CGAL's open source licenses and GPC's freeware-only restriction. There doesn't seem to be any polygon clipping libraries with nice BSD-style licenses.

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• Memcache localhost connection oddity

  - by MatW

  When I try to connect to memcache using this code: $memcache = new Memcache; $memcache->connect('localhost', 11211) or die ("Could not connect"); The call dies with the "Could not connect" error, but if I use localhost's IP: $memcache = new Memcache; $memcache->connect('127.0.0.1', 11211) or die ("Could not connect"); It works! So what's my problem? Well, this new computer is the only development environment I've setup that's been sensitive to that difference. I'm not about to go changing the settings on any code for what seems to be a computer specific issue, but I can't figure out what could be causing this behaviour... Any ideas? I'm running XP, memcached 1.2.4, and wampserver 2. I've checked the hosts file and it does have an entry for localhost.

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• C# ASP.Net The type or namespace name 'iAnywhere' could not be found

  - by Louis Russell

  Morning all, I know that this sounds like a simple referencing problem from the title this is becoming a nightmare! I have a code class that uses the "iAnywhere.Data.AsaClient.dll". This Dll is referenced in the project and in the code class I have added this dll in the Using section. Everything seems fine at build with no errors at all but when I go to run the application it comes up with the following Compilation Error: Compiler Error Message: CS0246: The type or namespace name 'iAnywhere' could not be found (are you missing a using directive or an assembly reference?) The line that the Error points to this line in the class: using iAnywhere.Data.AsaClient; I have set the dll to copy local and it makes no difference, the Dll is installed on my PC so is in the GAC, I use this Dll with many other C# projects and have no problems. I have scoured Google looking for an answer and haven't found anything that points me to an answer to my problem. Any help would be brilliant!

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• GIS: When and why to use ArcObjects over GDAL programming to work with ArcGIS rasters and vectors?

  - by anotherobject

  Im just starting off with GDAL + python to support operations that cannot be done with ArcGIS python geoprocessing scripting. Mainly I am doing spatial modeling/analysis/editing of raster and vector data. I am a bit confused when ArcObject development is required versus when GDAL can be used? Is there functionality of ArcObjects that GDAL does not do? Is the opposite true too? I am assuming that ArcObjects are more useful in developing online tools versus Desktop analysis and modeling where the difference is more to do with preference? In my case i prefer GDAL because of python support, which I believe ArcObjects lack. thanks!

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• Why should i use EJB?

  - by Nitesh Panchal

  Hello, As we all know that EJB's in 3.1 or 3.0 are simple POJOs. You just need to give annotations here and there and it gets converted to EJB from simple class. So, now my question is why should i use EJBs at all? Can i not do without them? In .Net i created class library and got things done. I never felt the need for anything like EJB. Simple classes were enough. Then, why in Java people stress on EJB? What is difference between a simple POJO and EJB in terms of execution and memory? Further which function should i write in EJB and which should i write in simple class? Should i dump every function in EJB only? or there is some kind of strategy? Does EJB provide anything special?

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• Enumerate Class Properties in C#

  - by user275561

  I have a class Similar to this public class Model { public TimeSpan Time1 {get; set;} public TimeSpan Time2 { get; set; } public TimeSpan Time3 { get; set; } public TimeSpan Time4 { get; set; } } Now Let's Imagine I have to populate the times during runtime and then Figure out the time remaining between Time 1 and Time 2, then when that passes Find the time remaining between Time2 and Time3 and so on. However, I need to take into account what the time is right now. For Example: Now it is 1:00 PM Time1=5:00 AM Time 2 = 12:00 PM Time 3= 4:00 PM Time 4 = 6:00 PM So since the time is 1:00PM, I need to find the difference between Time 2 and Time 3 Now is there a smarter way other than reflection to determine this? Should i add something in my class

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• (My)SQL performance: updating one field vs many unneccesary fields

  - by changokun

  i'm processing a form that has a lot of fields for a user who is editing an existing record. the user may have only changed one field, and i would typically do an update query that sets the values of all the fields, even though most of them don't change. i could do some sort of tracking to see which fields have actually changed, and only update the few that did. is there a performance difference between updating all fields in a record vs only the one that changed? are there other reasons to go with either method? the shotgun method is pretty easy...

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• How to handle similar items in rails MVC?

  - by mocker

  I'm working on building a pretty simple site mainly as an exercise in learning more about rails. You can see my rough progress at statific.com. It's working pretty much as I wanted it for keeping track of server information, but now I'd like to expand it to other things, next on the list being firewalls. I can pretty easily duplicate all the models, views, etc.. that I have for my servers. The problem I see with that is that it isn't very DRY since most of the code would look the same, the only difference would be the attributes I have setup for firewalls would be different than for servers. I know in plain ruby this is pretty simple, you can have a 'Product' w/ common attributes ('manufacturer', 'model') and then have children with more specific attributes. Does the same type of concept exist for rails, or am I just over thinking this?

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• Why am I getting "Enter Parameter Value" when running my MS Access query?

  - by DanM

  In my query, I use the IIF function to assign either "Before" or "After" to a field named BeforeOrAfter using AS. When I run this query, however, the "Enter Parameter Value" dialog appears, requesting a value for BeforeOrAfter. If I remove BeforeOrAfter DESC from the ORDER BY clause, I don't get the dialog. Here is the offending query: SELECT d.Scenario, e.Event, IIF(d.LogTime < e.Time, 'Before','After') AS BeforeOrAfter, d.HeartRate FROM Data d INNER JOIN Events e ON d.Scenario = e.Scenario WHERE e.Include = Yes ORDER BY d.Scenario, e.Id, BeforeOrAfter DESC Question: Why is my AS BeforeOrAfter not being recognized by the ORDER BY clause? Why does it ask me to enter a parameter value for "BeforeOrAfter" when I run this query? Note: I tried using brackets, single quotes, double quotes, etc., but none of that made any difference.

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• Metro + Jetty + OSGi = pain

  - by mjgp2

  I am trying to swap out Sun's HTTPServer for the much better Jetty server, within an OSGi bundle, running on Equinox. I have tried this: System.setProperty("com.sun.net.httpserver.HttpServerProvider","org.mortbay.jetty.j2se6.JettyHttpServerProvider"); but when endpoint.publish(url) is called, and the server is spawned, it complains of a ClassNotFoundException for org.mortbay.jetty.j2se6.JettyHttpServerProvider. However, the correct jars are in the bundle, and indeed in the Activator I can instantiate a org.mortbay.jetty.j2se6.JettyHttpServerProvider. I think that this is a some kind of classpath issue - the spawned server is in a different classpath maybe? I have tried adding the JARs in at the JDK level, but this doesn't make any difference. Can oanyone shed any light how on earth to get this working? P.S. Maybe hideous System.setProperty calls will vanish from the world one day. Hopefully :)

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• Thread vs ThreadPool - .Net 2.0

  - by NLV

  Hello I'm not able to understand the difference between Thread vs ThreadPool. Consider i've to manipulate 50,000 records using threads. In case of threads i need to either predefine no of threads or no of records per threads. Either of them has to be constant. In case of threadpool we dont need to set any of them theoretically. But practically we need to assign the number of records per thread, because the no of threads may grow extremely large if the input no of records is huge. Any insights on this?

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• What does "infinity" really mean on a connection timeout? Does it retry the connection?

  - by corgrath

  The difference between connection and read timeout, is that read specifies how long the data connection can be open until it automatically closesc, correct? A connection timeout specifies how long the socket should wait until a connection is established, correct? So if a connection timeout is set to "infinity" what does that really mean? Will it try to establish a connection and if no response is given (as on packets are lost? or port is down?) it will just idle? or will Could someone please explain the basics of network/socket timeouts? and in what situation can a client socket wait infinity?

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• Performance of fopen vs stat

  - by Alex Marshall

  Hello, I'm writing several C programs for an embedded system where every bit of performance we can squeeze out will matter. Part of that is accessing log files. When determining if a file exists, is there any performance difference between using open / fopen, and stat ? I've been using stat on the assumption that it only has to do a quick check against the file system, whereas fopen would have to actually gain access to a file and manipulate internal data structures before returning. Is there any merit to this ?

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• Different execution plan for similar queries

  - by Graham Clements

  I am running two very similar update queries but for a reason unknown to me they are using completely different execution plans. Normally this wouldn't be a problem but they are both updating exactly the same amount of rows but one is using an execution plan that is far inferior to the other, 4 secs vs 2 mins, when scaled up this is causing me a massive problem. The only difference between the two queries is one is using the column CLI and the other DLI. These columns are exactly the same datatype, and are both indexed exactly the same, but for the DLI query execution plan, the index is not used. Any help as to why this is happening is much appreciated. -- Query 1 UPDATE a SET DestKey = ( SELECT TOP 1 b.PrefixKey FROM refPrefixDetail AS b WHERE a.DLI LIKE b.Prefix + '%' ORDER BY len(b.Prefix) DESC ) FROM CallData AS a -- Query 2 UPDATE a SET DestKey = ( SELECT TOP 1 b.PrefixKey FROM refPrefixDetail b WHERE a.CLI LIKE b.Prefix + '%' ORDER BY len(b.Prefix) DESC ) FROM CallData AS a

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• SilverLight WebApp Calling Webservice in the same solution

  - by Ben

  Hi, I have a website solution that is composed of a SilverLight Project and an ASP Site that contains an asmx Webservice. The SilverLight project calls various methods in the Webservice, and this works fine on my home PC. When i publish the site (using 123-Reg if that makes a difference), it appears that the SilverLight app is no longer able to call the webservice. I have tried debugging the app by pointing my local version of the site to my published webservice and i get a "policy" issue. I know that 123 Reg have .Net 3.5 running on their servers, so i would assume that the site should "just work" when i publish it. Am i making a hugely stupid assumption there? Is there anything that i can do to change the "policies" within my app? Or is there another way around what i am trying to do ( i need to keep the webservice, as i want for it to be used from other places, and dont really want to duplicate code and create the same methods within the SilverLight project). Thanks

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• malloc()/free() behavior differs between Debian and Redhat

  - by StasM

  I have a Linux app (written in C) that allocates large amount of memory (~60M) in small chunks through malloc() and then frees it (the app continues to run then). This memory is not returned to the OS but stays allocated to the process. Now, the interesting thing here is that this behavior happens only on RedHat Linux and clones (Fedora, Centos, etc.) while on Debian systems the memory is returned back to the OS after all freeing is done. Any ideas why there could be the difference between the two or which setting may control it, etc.?

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• search engine crawling frequency

  - by Aditya Pratap Singh

  I want to design a search engine for news websites ie. download various article pages from these websites, index the pages, and answer search queries on the index. I want a short pseudocode to find an appropriate crawling frequency -- i do not want to crawl too often because the website may not have changed, and do not want to crawl too infrequently because index would then be out of date. Assume that crawling code looks as follows while(1) { sleep(sleep_interval); // sleep for sleep_interval crawl(website); // crawls the entire website diff = diff(currently_crawled_website, previously_crawled_website); // returns a % value of difference between the latest and previous crawls of the website sleep_interval = infer_sleep_interval(diff, sleep_interval); } looking for a pseudocode for the infer_sleep_interval method: long sleep_interval infer_sleep_interval(int diff_percentage,long previous_sleep_interval) { ... ... ... } i want to design method which adaptively alters the sleeping interval based on the update frequency of the website.

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• CouchDB Map/Reduce raises execption in reduce function?

  - by fuzzy lollipop

  my view generates keys in this format ["job_id:1234567890", 1271430291000] where the first key element is a unique key and the second is a timestamp in milliseconds. I run my view with this elapsed_time?startkey=["123"]&endkey=["123",{}]&group=true&group_level=1 and here is my reduce function, the intention is to reduce the output to get the earliest and latest timestamps and return the difference between them and now function(keys,values,rereduce) { var now = new Date().valueOf(); var first = Number.MIN_VALUE; var last = Number.MAX_VALUE; if (rereduce) { first = Math.max(first,values[0].first); last = Math.min(last,values[0].last); } else { first = keys[0][0][1]; last = keys[keys.length-1][0][1]; } return {first:now - first, last:now - last}; } and when processing a query it constantly raises the following execption: function raised exception (new TypeError("keys has no properties", "", 1)) I am making sure not to reference keys inside my rereduce block. Why does this function constantly raise this exception?

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• 500 INTERNAL SERVER ERROR

  - by jude

  Hi, I have and old content database which i restored in my sharepoint 2007. But whenver i try to access web sites in my sharepoint i get error : 500 INTERNAL SERVER ERROR. I can see the old content database at :- Sharepoint Centre Admin-Application Management-Content databases. There is no difference in the version of the old content database. My current content database is working fine.Its just the old content database is not. What could be the reason? Thanks, Jude Aloysius.

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• Storing script files outside web root

  - by memilanuk

  I've seen recommendations to store some or all php include files some place other than in the web document root directory (username/public_html in my case) for the specific reason of protecting php files with sensitive information (like database connection and login info) in the event that the web server hiccups and stops protecting php files and they become 'visible' to outsiders who know where to look. It seems somewhat paranoid to me, but I'm guessing people have gotten burned badly on this before so I'm willing to go along. The suggestion usually takes the form of having the include files in something like '../include_files/' so its not directly in the document root and not directly accessible to outsiders through the web server. My question is this: is there a significant difference in security between that way and just putting your 'include_files' directory under the document root and sticking an .htaccess file in there (with the appropriate entries)? Would putting an .htaccess file in '../include_files/' make any significant improvement there? TIA, Monte

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• Repository vs Data Access

  - by vdh_ant

  Hi guys In the context of the n-tier application, is there a difference between what you would consider your data access classes to be and your repositories? I tend to think yes but I just wanted to see what other thought. My thinking is that the job of the repository is just to contain and execute the raw query itself, where as the data access class would create the context, execute the repository (passing in the context), handle mapping the data model to the domain model and return the result back up... What do you guys think? Also do you see any of this changing in a Linq to XML scenario (assuming that you change the context for the relevant XDocument)? Cheers Anthony

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• jQuery Event Keypress: Which key was pressed?

  - by BlaM

  With jQuery, how do I find out which key was pressed when I bind to the keypress event? $('#searchbox input').bind('keypress', function(e) {}); I want to trigger an submit when ENTER is pressed. [Update] Even though I found the (or better: one) answer myself, there seems to be some room for variation ;) Is there a difference between keyCode and which - especially if I'm just looking for ENTER, which will never be a unicode key? Do some browsers provide one property and others provide the other one?

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• Adding additional components to a web page after rendering by Wicket

  - by Andrew Fielden

  I have a requirement to create a web page using Wicket 1.5, which can present a variable number of panels to capture user input. All the panels have the same structure. The page would start off with one panel, and includes a button to dynamically add more as required. So the number of panels is unknown at the time the page is initially rendered. Effectively I'd be altering the structure of the page dynamically. This is possible in Javascript, using document.addElement() I've done a similar thing in the past by creating all the components on page load, and selectively showing/hiding components. The difference here is that the number of components (panels) is initially unknown. I'm unsure as to how this would be achieved with Wicket.

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