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• What's the best practice for handling system-specific information under version control?

  - by Joe

  I'm new to version control, so I apologize if there is a well-known solution to this. For this problem in particular, I'm using git, but I'm curious about how to deal with this for all version control systems. I'm developing a web application on a development server. I have defined the absolute path name to the web application (not the document root) in two places. On the production server, this path is different. I'm confused about how to deal with this. I could either: Reconfigure the development server to share the same path as the production Edit the two occurrences each time production is updated. I don't like #1 because I'd rather keep the application flexible for any future changes. I don't like #2 because if I start developing on a second development server with a third path, I would have to change this for every commit and update. What is the best way to handle this? I thought of: Using custom keywords and variable expansion (such as setting the property $PATH$ in the version control properties and having it expanded in all the files). Git doesn't support this because it would be a huge performance hit. Using post-update and pre-commit hooks. Possibly the likely solution for git, but every time I looked at the status, it would report the two files as being changed. Not really clean. Pulling the path from a config file outside of version control. Then I would have to have the config file in the same location on all servers. Might as well just have the same path to begin with. Is there an easy way to deal with this? Am I over thinking it?

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• Why can’t I create a database in an empty ASP MVC 2 project using Project->Add->New Item->SQL Server

  - by Dr Dork

  I'm diving head first into ASP MVC and am playing around with creating and manipulating a database. I did a search and found this tutorial for creating a database, however when I follow it, I get this error right at the start when trying to add a new database to my fresh, empty ASP MVC 2 project... A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified) The only requirement the tutorial mentioned was SQL Server Express, but when I went to download it, it said it was already installed. I'm assuming it was part of the VS 2010 RC I installed and am running. So I don't know what else I need if I am missing something. This is all new to me, so I'm sure I'm missing something obvious here and after I'm done posting this question, I plan to do some more research into the topic of databases and how they work with ASP MVC. In the meantime, I was you could help me answer a couple high level questions... What am I missing/forgetting to do that is causing this error? Any suggestions for good resources/tutorials that focus on using databases with ASP MVC? I've done a lot of database programming in the past, so I'm familiar with the concepts of relational databases and the SQL language. I wish I could find a good resource for learning how to work with them in an ASP dev environment, as well as a good breakdown of all the related technologies used for working with them (i.e. LINQ to SQL). Thanks so much in advance for all your help! I'm going to start researching these questions right now.

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• CI + Joomla 1.5

  - by DMin

  Hi, This is something that I just cooked up with Joomla and CodeIgniter(CI). I Wrote my database intensive application in CodeIgniter and frontend is Joomla. I'm using Jumi(Joomla Extention) so I can include the CI files inside joomla to basically insert the content generated by CI into Joomla articles. Problem is, you can't include CI files directly using JUMI from joomla because CI tends to route the pages so instead of seeing your joomla page with the CI content, you be redirected to the CI page itself. I did a little work around for this : Made an additional page that just basically does cURL to the CI page - gets the data and echos it out. From jumi, I include this cURL page instead. Couple of questions: I've seen at least a few posts that CI + Joomla is difficult to do(link). 1) Do you see any glaring security issues or possible performance issues? 2) Do you know of a better way to implement this? 3) What do you think of this? Do you think this is a good way to do this? There is one component out there that plugs CI with Joomla but it requires you to have a fresh CI install. It allows only one controller & the download link is down as well.

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• Why can't we just use a hash of passphrase as the encryption key (and IV) with symmetric encryption algorithms?

  - by TX_

  Inspired by my previous question, now I have a very interesting idea: Do you really ever need to use Rfc2898DeriveBytes or similar classes to "securely derive" the encryption key and initialization vector from the passphrase string, or will just a simple hash of that string work equally well as a key/IV, when encrypting the data with symmetric algorithm (e.g. AES, DES, etc.)? I see tons of AES encryption code snippets, where Rfc2898DeriveBytes class is used to derive the encryption key and initialization vector (IV) from the password string. It is assumed that one should use a random salt and a shitload of iterations to derive secure enough key/IV for the encryption. While deriving bytes from password string using this method is quite useful in some scenarios, I think that's not applicable when encrypting data with symmetric algorithms! Here is why: using salt makes sense when there is a possibility to build precalculated rainbow tables, and when attacker gets his hands on hash he looks up the original password as a result. But... with symmetric data encryption, I think this is not required, as the hash of password string, or the encryption key, is never stored anywhere. So, if we just get the SHA1 hash of password, and use it as the encryption key/IV, isn't that going to be equally secure? What is the purpose of using Rfc2898DeriveBytes class to generate key/IV from password string (which is a very very performance-intensive operation), when we could just use a SHA1 (or any other) hash of that password? Hash would result in random bit distribution in a key (as opposed to using string bytes directly). And attacker would have to brute-force the whole range of key (e.g. if key length is 256bit he would have to try 2^256 combinations) anyway. So either I'm wrong in a dangerous way, or all those samples of AES encryption (including many upvoted answers here at SO), etc. that use Rfc2898DeriveBytes method to generate encryption key and IV are just wrong.

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• Merging two arrays in PHP

  - by Industrial

  Hi everyone, I am trying to create a new array from two current arrays. Tried array_merge, but it will not give me what I want. $array1 is a list of keys that I pass to a function. $array2 holds the results from that function, but doesn't contain any non-available resuls for keys. So, I want to make sure that all requested keys comes out with 'null':ed values, as according to the shown $result array. It goes a little something like this: $array1 = array('item1', 'item2', 'item3', 'item4'); $array2 = array( 'item1' => 'value1', 'item2' => 'value2', 'item3' => 'value3' ); Here's the result I want: $result = array( 'item1' => 'value1', 'item2' => 'value2', 'item3' => 'value3', 'item4' => '' ); It can be done this way, but I don't think that it's a good solution - I really don't like to take the easy way out and suppress PHP errors by adding @:s in the code. This sample would obviously throw errors since 'item4' is not in $array2, based on the example. foreach ($keys as $k => $v){ @$array[$v] = $items[$v]; } So, what's the fastest (performance-wise) way to accomplish the same result?

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• C++ AMP, for loops to parallel_for_each loop

  - by user1430335

  I'm converting an algorithm to make use of the massive acceleration that C++ AMP provides. The stage I'm at is putting the for loops into the known parallel_for_each loop. Normally this should be a straightforward task to do but it appears more complex then I first thought. It's a nested loop which I increment using steps of 4 per iterations: for(int j = 0; j < height; j += 4, data += width * 4 * 4) { for(int i = 0; i < width; i += 4) { The trouble I'm having is the use of the index. I can't seem to find a way to properly fit this into the parallel_for_each loop. Using an index of rank 2 is the way to go but manipulating it via branching will do harm to the performance gain. I found a similar post: Controlling the index variables in C++ AMP. It also deals about index manipulation but the increment aspect doesn't cover my issue. With kind regards, Forcecast

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• Using map() on a _set in a template?

  - by Stuart Grimshaw

  I have two models like this: class KPI(models.Model): """KPI model to hold the basic info on a Key Performance Indicator""" title = models.CharField(blank=False, max_length=100) description = models.TextField(blank=True) target = models.FloatField(blank=False, null=False) group = models.ForeignKey(KpiGroup) subGroup = models.ForeignKey(KpiSubGroup, null=True) unit = models.TextField(blank=True) owner = models.ForeignKey(User) bt_measure = models.BooleanField(default=False) class KpiHistory(models.Model): """A historical log of previous KPI values.""" kpi = models.ForeignKey(KPI) measure = models.FloatField(blank=False, null=False) kpi_date = models.DateField() and I'm using RGraph to display the stats on internal wallboards, the handy thing is Python lists get output in a format that Javascript sees as an array, so by mapping all the values into a list like this: def f(x): return float(x.measure) stats = map(f, KpiHistory.objects.filter(kpi=1) then in the template I can simply use {{ stats }} and the RGraph code sees it as an array which is exactly what I want. [87.0, 87.5, 88.5, 90] So my question is this, is there any way I can achieve the same effect using Django's _set functionality to keep the amount of data I'm passing into the template, up until now I've been passing in a single KPI object to be graphed but now I want to pass in a whole bunch so is there anything I can do with _set {{ kpi.kpihistory_set }} dumps the whole model out, but I just want the measure field. I can't see any of the built in template methods that will let me pull out just the single field I want. How have other people handled this situation?

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• How do i implement tag searching with lucene?

  - by acidzombie24

  I havent used lucene. Last time i ask (many months ago, maybe a year) people suggested lucene. As am example say there are 3 items tag like this apples carrots apples carrots apple banana if a user search apples i dont care if there is any preference from 1,2 and 4. However i seen many forums do this which i hated is when a user search apple carrots 2 and 3 are get high results while 1 is hard to find even though it matches my search more closely. I HATED this in forums. Also i would like the ability to do search carrots -apples which will only get me 3. I am not sure what should happen if i search carrots banana but anyways as long as more 2 and 3 results are lower priority then 1 when i search apples carrots i'll be happy. Can lucene do this? and where do i start? i see a lot of classes and many of them talk about docs. What should i use for tagging?

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• jQuery Fancy - popup window doesn't fully expand

  - by fmz

  I am using jQuery Fancybox to display a number of Flash videos on a site and I am having trouble with the window not opening fully on the first click in Firefox. It works fine in other browsers. Here is the jQuery: <script type="text/javascript"> $(document).ready(function() { $("a.videoLink").fancybox({ 'titleShow' : false, 'autoscale' : true, 'width' : '820', 'height' : '620', 'transitionIn' : 'elastic', 'transitionOut' : 'elastic' }); }); </script> Here is the html: <tr> <td class="title"><a class="videoLink" href="#video-content30">CPR Lesson 1 Movie</a></td> <td class="time">38:39</td> <td class="video" style="display:none"> <div id="video-content30"> <script type='text/javascript'> var flashvars = { file: 'http://www.stockmarketcpr.com/smsys/link/CPR-Lesson-1-Movie.flv', id: '30' }; var params = { wmode: 'opaque', bgcolor: '#CCCCCC', allowfullscreen: 'true', allowscriptaccess: 'always' }; swfobject.embedSWF('http://www.stockmarketcpr.com/_flash/player.swf', 'player30','800','600', '9.0.0','expressInstall.swf', flashvars, params); </script> <div id="player30"></div> </div> </td> </tr> I end up getting a quarter inch high, full-width window on the first click. The second click plays fine. I would appreciate any assistance. Thank you!

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• Why do I get this exception? {An item with the same key has already been added."})

  - by Alan

  Aknittel NewSellerID is the result of a lookup on tblSellers. These tables (tblSellerListings and tblSellers) are not "officially" joined with a foreign key relationship, either in the model or in the database, but I want some referential integrity maintained for the future. So my issue remains. Why do I get the exception ({"An item with the same key has already been added."}) with this code, if I don't begin each iteration of the foreach loop with a new ObjectContext and end it with SaveChanges, which I think will affect performance. Also, could you tell me why ORCSolutionsDataService.tblSellerListings (An ADO.NET DataServices/WCF object is not IDisposable, like LINQ to Entities?? ============================================== // Add listings to previous seller int NewSellerID = 0; // Look up existing Seller key using SellerUniqueEBAYID var qryCurrentSeller = from s in service.tblSellers where s.SellerEBAYUserID == SellerUserID select s; foreach (var s in qryCurrentSeller) NewSellerID = s.SellerID; // Save the selected listings for this seller foreach (DataGridViewRow dgr in dgvRows) { ORCSolutionsDataService.tblSellerListings NewSellerListing = new ORCSolutionsDataService.tblSellerListings(); NewSellerListing.ItemID = dgr.Cells["txtSellerItemID"].Value.ToString(); NewSellerListing.Title = dgr.Cells["txtSellerItemTitle"].Value.ToString(); NewSellerListing.CurrentPrice = Convert.ToDecimal(dgr.Cells["txtSellerItemPrice"].Value); NewSellerListing.QuantitySold = Convert.ToInt32(dgr.Cells["txtSellerItemSold"].Value); NewSellerListing.EndTime = Convert.ToDateTime(dgr.Cells["txtSellerItemEnds"].Value); NewSellerListing.CategoryName = dgr.Cells["txtSellerItemCategory"].Value.ToString(); NewSellerListing.ExtendedPrice = Convert.ToDecimal(dgr.Cells["txtExtendedReceipts"].Value); NewSellerListing.RetrievedDtime = Convert.ToDateTime(dtSellerDataRetrieved.ToString()); NewSellerListing.SellerID = NewSellerID; service.AddTotblSellerListings(NewSellerListing); } service.SaveChanges(); } catch (Exception ex) { MessageBox.Show("Unable to add a new case. Exception: " + ex.Message); }

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• Is there a faster way to access a property member of a class using reflection?

  - by Ross Goddard

  I am currently using the following code to access the property of an object using reflection: Dim propInfo As Reflection.PropertyInfo = myType.GetProperty(propName) Dim objValue As Object = propInfo.GetValue(myObject, Nothing) I am having some issues with the speed since this type of code is being called many times and is causing some slowdown. I have been looking into using Refelction.Emit or dynamic methods, but I am not sure exactly how to make use of them. Background Information: I am creating a list of a subset of the properties of the object, associating then with some meta information (such as if they can be loaded from the database or xml, if they are editable, can the user see them). This is for later consumption so we can write code such as : foreach prop as BaseWrapper in graphNode.NodeProperties prop.LoadFromDataRow(dr) next The application makes heavy use of having access to this list. The problem is that on the initial load of a project, a larger number of objects are being created that make use of this, so for each object created it is looping through this code a number of times. I initially tried adding each property to the list manually, but this ran into problems with not everything being initialized at the correct time and some other issues. If there is no other good way, then I may have to rethink some of the design and see what else can be done to improve the performance.

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• Getting the Item Count of a large sharepoint list in fastest way

  - by sooraj

  I am trying to get the count of the items in a sharepoint document library programatically. The scale I am working with is 30-70000 items. We have usercontrol in a smartpart to display the count . Ours is a TEAM site. This is the code to get the total count SPList VoulnterrList = web.Lists[ListTitle]; SPQuery query = new SPQuery(); query.ViewAttributes = "Scope=\"Recursive\""; string queries = "<Where><Eq><FieldRef Name='ApprovalStatus' /><Value Type='Choice'>Pending</Value></Eq></Where>"; query.Query = queries; SPListItemCollection lstitemcollAssoID = VoulnterrList.GetItems(query); lblCount.Text = "Total Proofs: " + VoulnterrList.Items.Count.ToString() + " Pending Proofs: " + lstitemcollAssoID.Count.ToString(); The problem is this has serious performance issue it takes 75 to 80 sec to load the page. if we comment this page load will decrees to 4 sec. Any better approch for this problem Ours is sharepoint 2007

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• Stable/repeatable random sort (MySQL, Rails)

  - by Matt Rogish

  I'd like to paginate through a randomly sorted list of ActiveRecord models (rows from MySQL database). However, this randomization needs to persist on a per-session basis, so that other people that visit the website also receive a random, paginate-able list of records. Let's say there are enough entities (tens of thousands) that storing the randomly sorted ID values in either the session or a cookie is too large, so I must temporarily persist it in some other way (MySQL, file, etc.). Initially I thought I could create a function based on the session ID and the page ID (returning the object IDs for that page) however since the object ID values in MySQL are not sequential (there are gaps), that seemed to fall apart as I was poking at it. The nice thing is that it would require no/minimal storage but the downsides are that it is likely pretty complex to implement and probably CPU intensive. My feeling is I should create an intersection table, something like: random_sorts( sort_id, created_at, user_id NULL if guest) random_sort_items( sort_id, item_id, position ) And then simply store the 'sort_id' in the session. Then, I can paginate the random_sorts WHERE sort_id = n ORDER BY position LIMIT... as usual. Of course, I'd have to put some sort of a reaper in there to remove them after some period of inactivity (based on random_sorts.created_at). Unfortunately, I'd have to invalidate the sort as new objects were created (and/or old objects being removed, although deletion is very rare). And, as load increases the size/performance of this table (even properly indexed) drops. It seems like this ought to be a solved problem but I can't find any rails plugins that do this... Any ideas? Thanks!!

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• Fastest reliable way for Clojure (Java) and Ruby apps to communicate

  - by jkndrkn

  Hi There, We have cloud-hosted (RackSpace cloud) Ruby and Java apps that will interact as follows: Ruby app sends a request to Java app. Request consists of map structure containing strings, integers, other maps, and lists (analogous to JSON). Java app analyzes data and sends reply to Ruby App. We are interested in evaluating both messaging formats (JSON, Buffer Protocols, Thrift, etc.) as well as message transmission channels/techniques (sockets, message queues, RPC, REST, SOAP, etc.) Our criteria: Short round-trip time. Low round-trip-time standard deviation. (We understand that garbage collection pauses and network usage spikes can affect this value). High availability. Scalability (we may want to have multiple instances of Ruby and Java app exchanging point-to-point messages in the future). Ease of debugging and profiling. Good documentation and community support. Bonus points for Clojure support. What combination of message format and transmission method would you recommend? Why? I've gathered here some materials we have already collected for review: Comparison of various java serialization options Comparison of Thrift and Protocol Buffers (old) Comparison of various data interchange formats Comparison of Thrift and Protocol Buffers Fallacies of Protocol Buffers RPC features Discussion of RPC in the context of AMQP (Message-Queueing) Comparison of RPC and message-passing in distributed systems (pdf) Criticism of RPC from perspective of message-passing fan Overview of Avro from Ruby programmer perspective

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• Tracking a fragment of a file in two places with git

  - by mabraham

  Hi, I have code such as void myfunc() { introduction(); while(condition()) { complex(); loop(); interior(); code(); } cleanup(); } which I wish to duplicate into two versions, viz: void myfuncA() { introduction(); minorchangeA(); while(condition()) { complex(); loop(); interior(); code(); } cleanup(); } void myfuncB() { introduction(); minorchangeB(); while(condition()) { complex(); modifiedB(); loop(); interior(); code(); } cleanup(); extracleanupB(); } git claims to track content rather than files, so do I need to tell it that there are chunks here that are common to both myfuncA and myfuncB so that when merging with upstream changes to myfunc that those changes should propagate to both myfuncA and myfuncB? If so, how? The code could be written so that myfuncAB did the correct thing at each point by testing for condition A or B, but that could seriously hinder readability or performance.

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• Parallelizing L2S Entity Retrieval

  - by MarkB

  Assuming a typical domain entity approach with SQL Server and a dbml/L2S DAL with a logic layer on top of that: In situations where lazy loading is not an option, I have settled on a convention where getting a list of entities does not also get each item's child entities (no loading), but getting a single entity does (eager loading). Since getting a single entity also gets children, it causes a cascading effect in which each child then gets its children too. This sounds bad, but as long as the model is not too deep, I usually don't see performance problems that outweigh the benefits of the ease of use. So if I want to get a list in which each of the items is fully hydrated with children, I combine the GetList and GetItem methods. So I'll get a list and then loop through it getting each item with the full cascade. Even this is generally acceptable in many of the projects I've worked on - but I have recently encountered situations with larger models and/or more data in which it needs to be more efficient. I've found that partitioning the loop and executing it on multiple threads yields excellent results. In my first experiment with a list of 50 items from one particular project, I did 5 threads of 10 items each and got a 3X improvement in time. Of course, the mileage will vary depending on the project but all else being equal this is clearly a big opportunity. However, before I go further, I was wondering what others have done that have already been through this. What are some good approaches to parallelizing this type of thing?

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• C# specifying generic delegate type param at runtime

  - by smerlin

  following setup, i have several generic functions, and i need to choose the type and the function identified by two strings at runtime. my first try looked like this: public static class FOOBAR { public delegate void MyDelegateType(int param); public static void foo<T>(int param){...} public static void bar<T>(int param){...} public static void someMethod(string methodstr, string typestr) { MyDelegateType mydel; Type mytype; switch(typestr) { case "int": mytype = typeof(int); break; case "double": mytype = typeof(double); break; default: throw new InvalidTypeException(typestr); } switch(methodstr) { case "foo": mydel = foo<mytype>; //error break; case "bar": mydel = bar<mytype>; //error break; default: throw new InvalidTypeException(methodstr); } for(int i=0; i<1000; ++i) mydel(i); } } since this didnt work, i nested those switchs (a methodstr switch inside the typestr switch or viceversa), but that solution is really ugly and unmaintainable. The number of types is pretty much fixed, but the number of functions like foo or bar will increase by high numbers, so i dont want nested switchs. So how can i make this working without using nested switchs ?

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• Do I need to using locking against integers in c++ threads

  - by Shane MacLaughlin

  The title says it all really. If I am accessing a single integer type (e.g. long, int, bool, etc...) in multiple threads, do I need to use a synchronisation mechanism such as a mutex to lock them. My understanding is that as atomic types, I don't need to lock access to a single thread, but I see a lot of code out there that does use locking. Profiling such code shows that there is a significant performance hit for using locks, so I'd rather not. So if the item I'm accessing corresponds to a bus width integer (e.g. 4 bytes on a 32 bit processor) do I need to lock access to it when it is being used across multiple threads? Put another way, if thread A is writing to integer variable X at the same time as thread B is reading from the same variable, is it possible that thread B could end up a few bytes of the previous value mixed in with a few bytes of the value being written? Is this architecture dependent, e.g. ok for 4 byte integers on 32 bit systems but unsafe on 8 byte integers on 64 bit systems? Edit: Just saw this related post which helps a fair bit.

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• Detecting well behaved / well known bots

  - by Simon_Weaver

  I found this question very interesting : Programmatic Bot Detection I have a very similar question, but I'm not bothered about 'badly behaved bots'. I am tracking (in addition to google analytics) the following per visit : Entry URL Referer UserAgent Adwords (by means of query string) Whether or not the user made a purchase etc. The problem is that to calculate any kind of conversion rate I'm ending up with lots of 'bot' visits that are greatly skewing my results. I'd like to ignore as many as possible bot visits, but I want a solution that I don't need to monitor too closely, and that won't in itself be a performance hog and preferably still work if someone has javascript disabled. Are there good published lists of the top 100 bots or so? I did find a list at http://www.user-agents.org/ but that appears to contain hundreds if not thousands of bots. I don't want to check every referer against thousands of links. Here is the current googlebot UserAgent. How often does it change? Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)

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• jQuery : how to determine that a div is scrolled down

  - by subtenante

  I have a div with defined height, and overflow:scroll;. Its content is too long so scrollbars appear. Now for the ichy part. Some of its inner HTML strangely appears all the time (to be precise, the footer of a table generated by the tableFilter plugin). I'd like to make this footer disappear when it is not needed (it actually appears out of the containing <div>'s border). I resolved to make it disappear but setting its z-index to -1000. But I want to make it appear when the containing <div> is totally scrolled down. How can I know the user has scrolled at the bottom ? Using the help from answers below, I used scrollTop attribute but the difference between scrollTop and innerHeight is the size of the scrollbar plus some unidentified delta. A scrollbar is 16 pixels high in most browsers under Windows, but I get a difference of 17 in Firefox and something like 20 in IE, where my <div> content's borders seems to be rendered bigger. A way (actually two ways...) to compute the scrollbar size has been given there.

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• How often should network traffic/collisions cause SNMP Sets to fail?

  - by A. Levy

  My team has a situation where an SNMP SET will fail once every two weeks or so. Since this set happens automatically, we don't necessarily notice it immediately when it fails, and this can result in an inconsistent configuration and associated wailing and gnashing of teeth. The plan is to fix this by having our software automatically retry the SET when it fails. The problem is, we aren't sure why the failure is happening. My (extremely limited) knowledge of SNMP isn't particularly helpful in diagnosing this problem, so I thought I'd ask StackOverflow for some advice. We think that every so often a spike in network traffic will cause the SET to fail. Since SNMP uses UDP for communication, I would think it would be relatively easy for a command to be drowned out if traffic was high for a short period of time. However, I have no idea how common this is. We have a small network with a single cisco router and there are less than a dozen SNMP controlled devices on that network. In addition to the SNMP traffic, there are some status web pages being loaded from the various devices. In case it makes a difference, I believe we are using the AdventNet SNMP API version 4.0.4 for Java. Does it sound reasonable that there will be some SET commands dropped occasionally, or should we be looking for other causes?

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• Using an unencoded key vs a real Key, benefits?

  - by user246114

  Hi, I am reading the docs for Key generation in app engine. I'm not sure what effect using a simple String key has over a real Key. For example, when my users sign up, they must supply a unique username: class User { /** Key type = unencoded string. */ @PrimaryKey private String name; } now if I understand the docs correctly, I should still be able to generate named keys and entity groups using this, right?: // Find an instance of this entity: User user = pm.findObjectById(User.class, "myusername"); // Create a new obj and put it in same entity group: Key key = new KeyFactory.Builder( User.class.getSimpleName(), "myusername") .addChild(Goat.class.getSimpleName(), "baa").getKey(); Goat goat = new Goat(); goat.setKey(key); pm.makePersistent(goat); the Goat instance should now be in the same entity group as that User, right? I mean there's no problem with leaving the User's primary key as just the raw String? Is there a performance benefit to using a Key though? Should I update to: class User { /** Key type = unencoded string. */ @PrimaryKey private Key key; } // Generate like: Key key = KeyFactory.createKey( User.class.getSimpleName(), "myusername"); user.setKey(key); it's almost the same thing, I'd still just be generating the Key using the unique username anyway, Thanks

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• Stopping at my Front-End abilities... good career move?

  - by R. H.

  Just curious about what other front-end and back-end people think, career wise. Here's the details: I'm a 30 yr old mom who is pretty good at front end development - that's my day job at an interactive agency. Don't have the money or time to go back to school or lots of high priced training sessions. I started out as a graphic designer ten years ago or so, then moved into database-backed web stuff, like CMS. I'm great at transforming PSD to a working html and css structure, especially for Wordpress themes. I enjoy this part of the process, probably because it's easy and fun, and as I learn a little more about jQuery and PHP, I can make it even better if I want or need. I'm not sure where I should stop though, as far as my career goes. I don't know that I'll ever get to the point that I'm a great PHP developer or jQuery master. Is it lame to just be a front-end designer/developer? Can that be a successful career all its own? Or, should I obligate myself to learning the harder programming, if I'm capable? Any advice or points any of you may have is appreciated!

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• Do I need a spatial index in my database?

  - by Sanoj

  I am designing an application that needs to save geometric shapes in a database. I haven't choosen the database management system yet. In my application, all database queries will have an bounding box as input, and as output I want all shapes within that database. I know that databases with a spatial index is used for this kind of application. But in my application there will not be any queries of type "give me objects nearby x/y" or other more complex queries that are useful in a GIS application. I am planning of having a database without a spatial index and have queries looking like: SELECT * FROM shapes WHERE x < max_x AND x > min_x AND y < max_y AND y > min_y And have an index on the columns x (double) and y (double). As long I can see, I don't really need a database with an spatial index, howsoever my application is close to that kind of applications. And even if I would like to have nearby queries, then I could create a big enough bounding box around that point. Or will this lead to poor performance? Do I really need a spatial database? And when is a spatial index needed?

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• What is better for a student programming in C++ to learn for writing GUI: C# vs QT?

  - by flashnik

  I'm a teacher(instructor) of CS in the university. The course is based on Cormen and Knuth and students program algorithms in C++. But sometimes it is good to show how an algorithm works or just a result of task through GUI. Also in my opinion it's very imporant to be able to write full programs. They will have courses concerning GUI but a three years, later, in fact, before graduatuion. I think that they should be able to write simple GUI applications earlier. So I want to teach them it. How do you think, what is more useful for them to learn: programming GUI with QT or writing GUI in C# and calling unmanaged C++ library? Update. For developing C++ applications students use MS Visual studio, so C# is already installed. But QT AFAIK also can be integrated into VS. I have following pros of C# (some were suggested there in answers): The need to make an additional layer. It's more work, but it forces you explicitly specify contract between GUI and processing data. The border between GUI and algorithms becomes very clear. It's more popular among employers. At least, in Russia where we live. It's rather common to write performance-critical algorithms in C++ and PInvoke them from well-looking C# application/ASP.Net website. Maybe it is not so widespread in the rest of the world but in Russia Windows is very popular, especially in companies and corporations due to some reasons, so most of b2b applications are Windows applications. Rapid development. It's much quicker to code in .Net then in C++ due to many reasons. And the con is that it's a new language with own specific for students. And the mess with invoking calls to library.

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