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• Searching for patterns to create a TCP Connection Pool for high performance messaging

  - by JoeGeeky

  I'm creating a new Client / Server application in C# and expect to have a fairly high rate of connections. That made me think of database connection pools which help mitigate the expense of creating and disposing connections between the client and database. I would like to create a similar capability for my application and haven't been able to find any good examples of how to apply this pattern. Do I really need to spin up an instance of a TcpClient every time I want to send a message to the server and receive a receipt message? Each connection is expected to transport between 1-5KB with each receiving a 1KB response message. I realize this question is somewhat vague, but I am starting from scratch so I am open to suggestions. Even if that means my suppositions are all wrong.

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• geom_tile heatmap with different high fill colours based on factor

  - by Michael

  I'm interested in building a heatmap with geom_tile in ggplot2 that uses a different gradient high color based on a factor. The plot below creates the plot where the individual tiles are colored blue or red based on the xy_type, but there is no gradient. ggplot() + geom_tile(data=mydata, aes(x=factor(myx), y=myy, fill=factor(xy_type))) + scale_fill_manual(values=c("blue", "red")) The plot below does not use the xy_type factor to choose the color, but I get a single group gradient based on the xy_avg_value. ggplot() + geom_tile(data=mydata, aes(x=factor(myx), y=myy, fill=xy_avg_value)) Is there a technique to blend these two plots? I can use a facet_grid(xy_type ~ .) to create separate plots of this data, with the gradient. As this is ultimately going to be a map (x~y coordinates), I'd like to find a way to display the different gradient together in a single geom_tile map.

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• Android MapView with High Res tiles?

  - by Nemi

  I have created a simple map app that shows the local garage sales in my town. It was simple enough to create and I parse out the Google Maps (html) xml doc that the local paper uses on their google maps mashup on their website. I have noticed that the Map Tiles used in the MapView class are not as high-res as the tiles used in the real Android Google Maps app (I have a Droid). I have searched the docs and google, but I cannot find any info on this. Actually, I can't even find anyone mentioning this, which surprises me and makes me think I am missing something simple. Is this a case of Google making the APIs available, but at a lower quality, or am I missing some setting that enables higher quality map tiles?

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• Database storage for high sample rate data in web app

  - by Jim

  I've got multiple sensors feeding data to my web app. Each channel is 5 samples per second and the data gets uploaded bundled together in 1 minute json messages (containing 300 samples). The data will be graphed using flot at multiple zoom levels from 1 day to 1 minute. I'm using Amazon SimpleDB and I'm currently storing the data in the 1 minute chunks that I receive it in. This works well for high zoom levels, but for full days there will be simply be too many rows to retrieve. The idea I've currently got is that every hour I can crawl through the data and collect together 300 samples for the last hour and store them in an hour Domain (table if you like). Does this sound like a reasonable solution? How have others implemented the same sort of systems?

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• Android MapView High Res tiles?

  - by Nemi

  I have created a simple map app that shows the local garage sales in my town. It was simple enough to create and I parse out the Google Maps (html) xml doc that the local paper uses on their google maps mashup on their website. I have noticed that the Map Tiles used in the MapView class are not as high-res as the tiles used in the real Android Google Maps app (I have a Droid). I have searched the docs and google, but I cannot find any info on this. Actually, I can't even find anyone mentioning this, which surprises me and makes me think I am missing something simple. Is this a case of Google making the APIs available, but at a lower quality, or am I missing some setting that enables higher quality map tiles?

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• High level audio crossfading library for python

  - by tcoopman

  I am looking for a high level audio library that supports crossfading for python (and that works in linux). In fact crossfading a song and saving it is about the only thing I need. I tried pyechonest but I find it really slow. Working with multiple songs at the same time is hard on memory too (I tried to crossfade about 10 songs in one, but I got out of memory errors and my script was using 1.4Gb of memory). So now I'm looking for something else that works with python. I have no idea if there exists anything like that, if not, are there good command line tools for this, I could write a wrapper for the tool.

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• Post High Score and Retrieve Position

  - by majman

  I'm not so savvy with MYSQL, so my apologies in advance is this is a dumb question. I've created a super basic PHP High Scores table. Upon inserting a new score into the DB Table, I'd like to retrieve the position of that score so that I can get 10 results with the persons score falling within that range. My INSERT Query looks something like: $stmt = $mysqli->prepare("INSERT INTO highscores (name, time, score) VALUES (?, ?, ?)"); $stmt->bind_param('sdi', $name, $time, $score); UPDATE - I'm looking for a way to do this with as few queries as possible. I recall reading something about getting an INSERT ID when making an insert, but I would then still have to make a second query to get those results.

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• Application.Idle causes high CPU usage

  - by Neal

  Hello, I use the Application.Idle event to handle toolbar status (enable/disable) etc. quite extensively. As I'm beta testing Norton AntiVirus 2011, it brought to my attention that my app that I'm developing triggered a high CPU usage warning on at least one CPU. Sure enough, I opened the task manager and watched one of the four CPU's (quad core system) go to near 100%. I thought Application.Idle was the way to handle things when the application wasn't performing CPU tasks. Why is Application.Idle spiking the CPU? Here is how I attach to the event: AddHandler Application.Idle, AddressOf OnAppIdle Been using Application.Idle for a long time, never knew it would have this issue. Using VS 2010 .NET 4 Thank you.

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• High level programming logic, design, pattern

  - by Muhammad Shahzad

  I have been doing programming from last 7 years, getting better and better, but still i think that am lacking something. I have been doing work in JOOMLA, MAGENTO, WP, Custom PHP, Opencart, laravel, codeignitor. Sometimes i need to design logic for a huge database application, in the applications we need nesting loops and queries, although i follow OOPS standards, ORM etc, still i feel i need more robust coding designs. I need to know how can i improve these things, so that code remain neat, efficient and faster. Also how big webapps like facebook twitter tests there code speed? How high level programmers choose design patterns. If you can help me find something useful with examples?

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• High quality software examples

  - by Francisco Garcia

  One of the best ways to learn about programming is reading high quality code/projects from great engineers. Which open-source projects do you think is worth looking at? I mean, that code that you can print and sit under a tree with a glass of wine and enjoy reading. If you can, also specify if the software is great to look at because its documentation, design, UML diagrams or just plain code. I believe UML is not very common within open-source projects. Is there such a thing as a project branch that polishes code and design with the sole objective to give other programmers a great example of great software?

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• Single page app with high number of images working extremely slow on iOS8 safari/Webview

  - by NikhilWanpal

  We are working on a WebView (not WKWebView, yet) app, are are observing that the app runs extremely slow on iOS 8. The same app runs smooth on lower versions of OS like iOS7 and iOS6. So we tried it in safari on iOS8 and the performance is similar to iOS6 and 7. The app is filled with images and many are high resolution. While trying to trace the issue (trial and error!) we reduced the sizes and resolutions of the images and the performance improved, but it is still not at par with versions 6 and 7. We are unable to find any such issues reported elsewhere and are stuck. It would be great if we could get some pointers on this one.

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• How to sort numbers in array from low to high

  - by Louie

  Hello all, I am trying to sort an array of prices from low to high. I have it working but not the way I want it to. Long story short, the sorter is putting numbers in order like this: 100 10900 200 290 instead of sorting like this 100 200 290 10900 here is my code I am doing this with. -(void)filterPriceLowHigh { NSSortDescriptor *sortDescriptor; sortDescriptor = [[[NSSortDescriptor alloc] initWithKey:@"ListPrice" ascending:YES] autorelease]; NSArray *sortDescriptors = [NSArray arrayWithObject:sortDescriptor]; NSArray *sortedArray; sortedArray = [app.vehiclesArrayToDisplay sortedArrayUsingDescriptors:sortDescriptors]; [app.vehiclesArrayToDisplay removeAllObjects]; [app.vehiclesArrayToDisplay addObjectsFromArray:sortedArray]; } Could someone tell me what I need to do here? thanks in advance.

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• C# - .WAV Playback Randomly High Pitch

  - by Nate Shoffner

  For some reason, when a WAV file is played back using the snippet below, it randomly plays back screwy, like a high pitch noise. It doesn't happen all the time, just randomly. It seems to happen more often when it is played back more frequently. The WAV properties are below along with the code snippet I am using. WAV Properties: Bit Rate - 750kbps Audio Sample Size - 16 bit Channels - 1 (mono) Audio Sample Rate - 44kHz Audio Format - PCM Snippet: System.Media.SoundPlayer myPlayer = new System.Media.SoundPlayer(Captcha.Properties.Resources.sound1); myPlayer.Play(); Is this because of the way I am playing the file or the file itself? Thank you.

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• [MySQL, InnoDb] Rating place

  - by Pavel

  I'm trying to generate rating place table using following receipt http://stackoverflow.com/questions/1776821/assign-places-in-the-rating-mysql-php but my database is high loaded. I tried not to create table, but use MEMORY TABLE and update it using following SQL query insert into tops (uid) select uid from users order by exp desc; but got the following MySQL error Deadlock found when trying to get lock; try restarting transaction because there are too many queries until SQL select is being executed. How to solve this problem? P.S. CREATE TABLE tops as SELECT work almost fine except high server load... up to load average: 50 if tops are non-memory table. My table users has near 4.5 millions of rows. Thanks for any advices.

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• Javascript : where are high level data structures?

  - by user355056

  Hi! I'm writing a client program for a game in Javascript but I'm new in Javascript world. Core Javascript lack of high level data structures. I've found code snippets on internet but I'm looking for a reference library (like commons-collection or google-collection in java world). I found this post: http://stackoverflow.com/questions/2523436/javascript-implementation-of-a-set-data-structure which refers to jshashtable and closure. Are they reference implementations? Do you know something else? Thanks

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• Choosing an alternative ( visual basic) high level programming language

  - by user370244

  I used to be visual basic 6 programmer, i was pleased with visual basic : it is high level language that do stuff fast,easy to learn, easy to do stuff in,you can drag and drop stuff to the form and write your code,it is simply amazing.however microsoft buried VB6 and pointed us to VB.NET which is so different that it is not the old VB anymore.I didn't like what microsoft did and would like to look somewhere AWAY from microsoft and from any other proprietary language . I would like to look into a similar language that is easy,cross platform (windows / Linux), object oriented, visual design, non proprietary and compile (for some guarding against reverse engineering). i am freelancer so the choice is entirely mine,i don't care about performance of programs, the time taken to develop a given programs is much more important. desktop / database / GUI /networking programming is what i am looking for. so any such language offered by our open source community ? thank you so much

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• Will high reputation in Programmers help to get a good job?

  - by Lorenzo

  In reference to this question, do you think that having a high reputation on this site will help to get a good job? Aside silly and humorous questions, on Programmers we can see a lot of high quality theory questions. I think that, if Stack Overflow will eventually evolve in "strictly programming related" (which usually is "strictly coding related"), the questions on Programmers will be much more interesting and meaningful ("Stack Overflow" = "I have this specific coding/implementation issue"; "Programmers" = "Best practices, team shaping, paradigms, CS theory"). So could high reputation on this site help (or at least be a good reference)? And then, more o less than Stack Overflow?

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• implementing a high level function in a script to call a low level function in the game engine

  - by eat_a_lemon

  In my 2d game engine I have a function that does pathfinding, find_shortest_path. It executes for each time step in the game loop and calculates the next coordinate pair in the series of coordinates to reach the destination object. Now I want to call this function in a scripting language and have it only return the last coordinate pair result. I want the game engine to go about the business of rendering the incremental steps but I don't want the high level script to care about the rendering. The high level script is only for ai game logic. Now I know how to bind a method from C to python but how can I signal and coordinate the wait time between the incremental steps without the high level function returning until its time for the last step?

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• Language+IDE for teaching high school students?

  - by daveagp

  I'm investigating languages and IDEs for a project involving teaching high-school students (around grade 11). It will teach basics of programming as an introduction to computer science (e.g., including how numbers/strings/characters are represented, using procedures and arrays, control flow, a little bit of algorithms, only very basic I/O). The non-negotiable requirements for this project are: a free up-to-date cross-platform IDE (Win & Mac incl. 64-bit) with debug a compiler where it's easy to learn from your mistakes together with the IDE, a gentle installation+learning curve So far, the best options I see are the following. Are there others I should know about? I am giving a short explanation with each one to generally show what I am looking for. In order from most to least promising: Pascal + FreePascal IDE (it seems a little buggy but actively developed?) Python + Eclipse + PyDev (good but features are overwhelming/hard to navigate) Groovy + Eclipse ('') Python + IDLE (looks unnatural to do debugging, to me) Pascal + Lazarus (IDE overwhelming, e.g. not obvious how to "start from scratch") Preferably, as a rule of thumb, the language should be direct enough that you don't need to wrap every program in a class, don't need to reference a System object to println, etc. I tried a little bit to see if there is something in JavaScript or (non-Visual) Basic along the lines of what I want, but found nothing so far. I would say that C/C++/C#, Java, Ruby, Lisp, VB do not fit my criteria for languages for this project. To reiterate my questions: are any of those 5 options really awesome or un-awesome? Are there other options which are even MORE awesome? Anything for Basic or JavaScript which meets all of the criteria? Thanks!

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• java distributed cache for low latency, high availability

  - by Shahbaz

  I've never used distributed caches/DHTs like memcached, jboss cache, ehcache, etc. I'm wondering which, if any, is appropriate for my use. First, I'm not doing web applications (as most of these project seem to be geared towards web apps). I write servers (Order Management Systems actually) for financial trading firms. The servers themselves are not too complicated. They need to receive information (market data, orders, executions, etc.) rout them to their destination while possibly transforming some of these messages. I am looking at these products to solve the following problems: * Safe repository of the state of the server. I'd rather build the logic of my application as a bunch of transformers (similar to Apache Camel) and store the state in a 'safe' place * This repository should be distributed: in case one of these data stores crashes, one or two more should be up and I should be able to switch to them seamlessly * This repository should be fast. Single digits milliseconds count here, in other words, systems which consume/process this data are automated systems, not humans clicking on links. This system needs to have high-throughput and low latency. By sending my data outside the process, I am necessarily slowing performance, but I am trying to balance absolute raw speed and absolute protection of data. * This repository should be safe. Similar to the point about several on-line backups, this system needs to write data to disk (potentially more than one disk). I'd really like to stop writing my own 'transaction servers.' Am I correct to be looking into projects such as jboss cache, ehcache, etc.? Thanks

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• Optimising RSS parsing on App Engine to avoid high CPU warnings

  - by Danny Tuppeny

  I'm pulling some RSS feeds into a datastore in App Engine to serve up to an iPhone app. I use cron to schedule updating the RSS every x minutes. Each task only parses one RSS feed (which has 15-20 items). I frequently get warnings about high CPU usage in the App Engine dashboard, so I'm looking for ways to optimise my code. Currently, I use minidom (since it's already there on App Engine), but I suspect it's not very efficient! Here's the code: dom = minidom.parseString(urlfetch.fetch(url).content) if dom: items = [] for node in dom.getElementsByTagName('item'): item = RssItem( key_name = self.getText(node.getElementsByTagName('guid')[0].childNodes), title = self.getText(node.getElementsByTagName('title')[0].childNodes), description = self.getText(node.getElementsByTagName('description')[0].childNodes), modified = datetime.now(), link = self.getText(node.getElementsByTagName('link')[0].childNodes), categories = [self.getText(category.childNodes) for category in node.getElementsByTagName('category')] ); items.append(item); db.put(items); def getText(self, nodelist): rc = '' for node in nodelist: if node.nodeType == node.TEXT_NODE: rc = rc + node.data return rc There isn't much going on, but the scripts often take 2-6 seconds CPU time, which seems a bit excessive for looping through 20ish items and reading a few attributes. What can I do to make this faster? Is there anything particularly bad in the above code, or should I change to another way of parsing? Are there are any libraries (that work on App Engine) that would be better, or would I be better parsing the RSS myself?

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• Threads, Sockets, and Designing Low-Latency, High Concurrency Servers

  - by lazyconfabulator

  I've been thinking a lot lately about low-latency, high concurrency servers. Specifically, http servers. http servers (fast ones, anyway) can serve thousands of users simultaneously, with very little latency. So how do they do it? As near as I can tell, they all use events. Cherokee and Lighttpd use libevent. Nginx uses it's own event library performing much the same function of libevent, that is, picking a platform optimal strategy for polling events (like kqueue on *bsd, epoll on linux, /dev/poll on Solaris, etc). They all also seem to employ a strategy of multiprocess or multithread once the connection is made - using worker threads to handle the more cpu intensive tasks while another thread continues to listen and handle connections (via events). This is the extent of my understanding and ability to grok the thousand line sources of these applications. What I really want are finer details about how this all works. In examples of using events I've seen (and written) the events are handling both input and output. To this end, do the workers employ some sort of input/output queue to the event handling thread? Or are these worker threads handling their own input and output? I imagine a fixed amount of worker threads are spawned, and connections are lined up and served on demand, but how does the event thread feed these connections to the workers? I've read about FIFO queues and circular buffers, but I've yet to see any implementations to work from. Are there any? Do any use compare-and-swap instructions to avoid locking or is locking less detrimental to event polling than I think? Or have I misread the design entirely? Ultimately, I'd like to take enough away to improve some of my own event-driven network services. Bonus points to anyone providing solid implementation details (especially for stuff like low-latency queues) in C, as that's the language my network services are written in.

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• Which linear programming package should I use for high numbers of constraints and "warm starts"

  - by davidsd

  I have a "continuous" linear programming problem that involves maximizing a linear function over a curved convex space. In typical LP problems, the convex space is a polytope, but in this case the convex space is piecewise curved -- that is, it has faces, edges, and vertices, but the edges aren't straight and the faces aren't flat. Instead of being specified by a finite number of linear inequalities, I have a continuously infinite number. I'm currently dealing with this by approximating the surface by a polytope, which means discretizing the continuously infinite constraints into a very large finite number of constraints. I'm also in the situation where I'd like to know how the answer changes under small perturbations to the underlying problem. Thus, I'd like to be able to supply an initial condition to the solver based on a nearby solution. I believe this capability is called a "warm start." Can someone help me distinguish between the various LP packages out there? I'm not so concerned with user-friendliness as speed (for large numbers of constraints), high-precision arithmetic, and warm starts. Thanks!

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• Alternatives to LINQ To SQL on high loaded pages

  - by Alex

  To begin with, I LOVE LINQ TO SQL. It's so much easier to use than direct querying. But, there's one great problem: it doesn't work well on high loaded requests. I have some actions in my ASP.NET MVC project, that are called hundreds times every minute. I used to have LINQ to SQL there, but since the amount of requests is gigantic, LINQ TO SQL almost always returned "Row not found or changed" or "X of X updates failed". And it's understandable. For instance, I have to increase some value by one with every request. var stat = DB.Stats.First(); stat.Visits++; // .... DB.SubmitChanges(); But while ASP.NET was working on those //... instructions, the stats.Visits value stored in the table got changed. I found a solution, I created a stored procedure UPDATE Stats SET Visits=Visits+1 It works well. Unfortunately now I'm getting more and more moments like that. And it sucks to create stored procedures for all cases. So my question is, how to solve this problem? Are there any alternatives that can work here? I hear that Stackoverflow works with LINQ to SQL. And it's more loaded than my site.

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• How to convert string with double high/wide characters to normal string [VC++6]

  - by Shaitan00

  My application typically recieves a string in the following format: " Item $5.69 " Some contants I always expect: - the LENGHT always 20 characters - the start index of the text always [5] - and most importantly the index of the DECIMAL for the price always [14] In order to identify this string correctly I validate all the expected contants listed above .... Some of my clients have now started sending the string with Doube-High / Double-Wide values (pair of characters which represent a single readable character) similar to the following: " Item $x80x90.x81x91x82x92 " For testing I simply scan the string character-by-character, compare char[i] and char[i+1] and replace these pairs with their corresponding single character when a match is found (works fine) as follows: [Code] for (int i=0; i < sData.length(); i++) { char ch = sData[i] & 0xFF; char ch2 = sData[i+1] & 0xFF; if (ch == '\x80' && ch2 == '\x90') zData.replace("\x80\x90", "0"); else if (ch == '\x81' && ch2 == '\x91') zData.replace("\x81\x91", "1"); else if (ch == '\x82' && ch2 == '\x92') zData.replace("\x82\x92", "2"); ... ... ... } [/Code] But the result is something like this: " Item $5.69 " Notice how this no longer matches my expectation: the lenght is now 17 (instead of 20) due to the 3 conversions and the decimal is now at index 13 (instead of 14) due to the conversion of the "5" before the decimal point. Ideally I would like to convert the string to a normal readable format keeping the constants (length, index of text, index of decimal) at the same place (so the rest of my application is re-usable) ... or any other suggestion (I'm pretty much stuck with this)... Is there a STANDARD way of dealing with these type of characters? Any help would be greatly appreciated, I've been stuck on this for a while now ... Thanks,

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