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• Setting serial RS232 port settings; any in C# alternatives to SerialPort class ?

  - by adrin

  In my .NET application I need to achieve serial port setup equivalent to this C++ managed code: ::SetCommMask(m_hCOMM, EV_RXCHAR); ::SetupComm(m_hCOMM, 9*2*128*10, 400); ::PurgeComm(m_hCOMM, PURGE_TXABORT|PURGE_RXABORT|PURGE_TXCLEAR|PURGE_RXCLEAR); COMMTIMEOUTS timeOut; timeOut.ReadIntervalTimeout = 3; timeOut.ReadTotalTimeoutConstant = 3; timeOut.ReadTotalTimeoutMultiplier = 1; timeOut.WriteTotalTimeoutConstant = 0; timeOut.WriteTotalTimeoutMultiplier= 0; int nRet= ::SetCommTimeouts(m_hCOMM, &timeOut); ::EscapeCommFunction(m_hCOMM, SETDTR); ::EscapeCommFunction(m_hCOMM, SETRTS); DCB dcb; memset(&dcb, 0, sizeof(DCB)); dcb.BaudRate= m_nSpeed; dcb.ByteSize= 8; dcb.fParity = FALSE; dcb.Parity = NOPARITY; dcb.StopBits= ONESTOPBIT; dcb.fBinary = TRUE; dcb.fDsrSensitivity= FALSE; dcb.fOutxDsrFlow= FALSE; dcb.fOutxCtsFlow= FALSE; dcb.fDtrControl = DTR_CONTROL_HANDSHAKE; dcb.fRtsControl = RTS_CONTROL_TOGGLE; nRet= ::SetCommState(m_hCOMM, &dcb); Is it possible at all? How do I approach this problem? Are there any (preferable free) libraries that allow such low level serial port control or should I create my own wrapper on top of Win32 api? Anyone did anything similar or has an idea how to 'glue' win32 serial port api with .net so that I can use neat .NET DataReceived() events ? Or maybe I can create .NET SerialPort instance and then modify it using managed API?

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• Are there any ASP.NET MVC subscription-based starter kits or examples?

  - by Wayne M

  Basically something that handles the low-level "plumbing" code for a subscription-based service. I see a lot of things dealing with basic membership, but nothing that handles the subscription aspect (recurring billing, automated jobs for setting up billing, notification for billing, etc). This might be the one thing that keeps me from using ASP.NET MVC for my SaaS idea, since it would take a fair amount of development time to write my own; if I go with my other option, Ruby on Rails, I can buy a kit that does all of this for $250. I haven't found anything even remotely close to this for .NET - all of the SaaS sample apps I've seen are more like StackOverflow et all where you have one site that multiple people log on to, not the web application model where you have subscribers who are billed monthly, each of whom has users and other entities (e.g. Customers, Tasks, etc) for their own site. Is there anything similar for ASP.NET, or some kind of guidelines for writing my own if I have to, so I don't waste too much time? As a startup that means that I'm doing all the coding myself. I've found this, but it seems to only be for billing and didn't seem to have much (any?) documentation on exactly how to set it up.

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• Flash "visible" issue

  - by justkevin

  I'm writing a tool in Flex that lets me design composite sprites using layered bitmaps and then "bake" them into a low overhead single bitmapData. I've discovered a strange behavior I can't explain: toggling the "visible" property of my layers works twice for each layer (i.e., I can turn it off, then on again) and then never again for that layer-- the layer stays visible from that point on. If I override "set visible" on the layer as such: override public function set visible(value:Boolean):void { if(value == false) this.alpha = 0; else {this.alpha = 1;} } The problem goes away and I can toggle "visibility" as much as I want. Any ideas what might be causing this? Edit: Here is the code that makes the call: private function onVisibleChange():void { _layer.visible = layerVisible.selected; changed(); } The changed() method "bakes" the bitmap: public function getBaked():BitmapData { var w:int = _composite.width + (_atmosphereOuterBlur * 2); var h:int = _composite.height + (_atmosphereOuterBlur * 2); var bmpData:BitmapData = new BitmapData(w,h,true,0x00000000); var matrix:Matrix = new Matrix(); var bounds:Rectangle = this.getBounds(this); matrix.translate(w/2,h/2); bmpData.draw(this,matrix,null,null,new Rectangle(0,0,w,h),true); return bmpData; } Incidentally, while the layer is still visible, using the Flex debugger I can verify that the layer's visible value is "false".

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• Memory Bandwidth Performance for Modern Machines

  - by porgarmingduod

  I'm designing a real-time system that occasionally has to duplicate a large amount of memory. The memory consists of non-tiny regions, so I expect the copying performance will be fairly close to the maximum bandwidth the relevant components (CPU, RAM, MB) can do. This led me to wonder what kind of raw memory bandwidth modern commodity machine can muster? My aging Core2Duo gives me 1.5 GB/s if I use 1 thread to memcpy() (and understandably less if I memcpy() with both cores simultaneously.) While 1.5 GB is a fair amount of data, the real-time application I'm working on will have have something like 1/50th of a second, which means 30 MB. Basically, almost nothing. And perhaps worst of all, as I add multiple cores, I can process a lot more data without any increased performance for the needed duplication step. But a low-end Core2Due isn't exactly hot stuff these days. Are there any sites with information, such as actual benchmarks, on raw memory bandwidth on current and near-future hardware? Furthermore, for duplicating large amounts of data in memory, are there any shortcuts, or is memcpy() as good as it will get? Given a bunch of cores with nothing to do but duplicate as much memory as possible in a short amount of time, what's the best I can do?

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• c# web extracting programming, which libraries, examples samples please

  - by user287745

  I have just started programming and have made a few small applications in C and C#. My understanding is that programming for web and thing related to web is nowadays a very easy task. Please note this is for personnel learning, not for rent a coder or any money making. An application which can run on any Windows platform even Windows 98. The application should start automatically at a scheduled time and do the following. Connect to a site which displays stock prices summary (high low current open). Capture the data (excluding the other things in the site.) And save it to disk (an SQL database) Please note:- Internet connection is assumed to be there always. Do not want to know how to make database schema or database. The stock exchange has no law prohibiting the use of the data provided on its site, but I do not want to mention the name in case I am wrong, but it's for personal private use only. The data of summary of pricing is arranged in a table such that when copied pasted to MS Excel it automatically forms a table. need steps guidance please, examples, lbraries

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• Normalize whitespace and other plain-text formatting routines

  - by dreftymac

  Background: The language is JavaScript. The goal is to find a library or pre-existing code to do low-level plain-text formatting. I can write it myself, but why re-invent the wheel. The issue is: it is tough to determine if a "wheel" is out there, since any search for JavaScript libraries pulls up an ocean of HTML-centric stuff. I am not interested in HTML necessarily, just text. Example: I need a JavaScript function that changes this: BEFORE: nisi ut aliquip | ex ea commodo consequat duis |aute irure dolor in esse cillum dolore | eu fugiat nulla pariatur |excepteur sint occa in culpa qui | officia deserunt mollit anim id |est laborum ... into this ... AFTER: nisi ut aliquip | ex ea commodo consequat duis | aute irure dolor in esse cillum dolore | eu fugiat nulla pariatur | excepteur sint occa in culpa qui | officia deserunt mollit anim id | est laborum Question: Does it exist, a JavaScript library that is non-html-web-development-centric that has functions for normalizing spaces in delimited plain text, justifying and spacing plain text? Rationale: Investigating JavaScript for use in a programmer's text editor.

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• Going from small to medium sized websites.

  - by Landitus

  I've been coding websites for a couple of years now, mostly in php and xhtml. I come from the design world, but I'm proud of doing standart compliant websites and great interfaces. Also used Wordpress and loved it. Most of the time there were really simple commercial websites, with no database included, where everything is done from scratch. Every page is parsed through an index?page=xxx and But I have a few prospects that are larger websites (let's call them 'medium sized websites') where I feel I'm lacking the following: How to dispach or render the pages (MVC controller instead of index?page=???) Proper page hierarchy and easy breadcrumbs implementation Auto generation of navigation menu, or an easy way to maintain them? Clean URLs Form validation Easy database support I really don't know if I should be looking into php scripts, and refine my skills or get into a CMS (like drupal) or a PHP framework. I found Wordpress very assuring and didn't feel trapped into crazy conventions, but I feel is not the right tool for this. I hate the CMS Page with the big textbox as I am used to code every page by hand my pages are not a title and a textbox. Got the feeling? My php skills are sort of medium/low still, but I would like to hear some thoughts of what I should learn to take the next step!

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• How to nest shapes in a DSL Tools diagram?

  - by Paul Lalonde

  I have a DSL containing two main domain classes: Area and Entity. Areas are represented visually by a GeometryShape, whereas entities are represented by a CompartmentShape. Entities can be embedded in an Area, or not (in this case they are embedded in the root object, which is a kind of Area). There may be relationships between entities, including between entities in different areas. Areas cannot be embedded inside of other areas, nor entities embedded inside of other entities. My problem is that I cannot get the behavior I want from the diagram. The embedding of entities in areas works perfectly well at the model level, but the visual representation behaves erratically. For example, if I drag an entity that was created in an area outside of that area, it no longer responds to mouse clicks (I have code that performs the re-parenting, but somehow the diagram side of things is broken). I have searched high and low for samples of how to do this, and come up empty. Every example I've found on the web simulates nesting via "references" relationships, whereas I am performing true embedding of the domain classes (and therefore of their associated shape classes). Does anyone have an example of how to do this? While I'm venting, am I the only one who thinks the diagram/shape classes are massively under-documented?

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• Caching sitemaps in django

  - by michuk

  I implemented a simple sitemap class using django's default sitemap app. As it was taking a long time to execute, I added manual caching: class ShortReviewsSitemap(Sitemap): changefreq = "hourly" priority = 0.7 def items(self): # try to retrieve from cache result = get_cache(CACHE_SITEMAP_SHORT_REVIEWS, "sitemap_short_reviews") if result!=None: return result result = ShortReview.objects.all().order_by("-created_at") # store in cache set_cache(CACHE_SITEMAP_SHORT_REVIEWS, "sitemap_short_reviews", result) return result def lastmod(self, obj): return obj.updated_at The problem is that memcache allows only max 1MB object. This one was bigger that 1MB, so storing into cache failed: >7 SERVER_ERROR object too large for cache The problem is that django has an automated way of deciding when it should divide the sitemap file into smalled ones. According to the docs (http://docs.djangoproject.com/en/dev/ref/contrib/sitemaps/): You should create an index file if one of your sitemaps has more than 50,000 URLs. In this case, Django will automatically paginate the sitemap, and the index will reflect that. What do you think would be the best way to enable caching sitemaps? - Hacking into django sitemaps framework to restrict a single sitemap size to, let's say, 10,000 records seems like the best idea. Why was 50,000 chosen in the first place? Google advice? random number? - Or maybe there is a way to allow memcached store bigger files? - Or perhaps onces saved, the sitemaps should be made available as static files? This would mean that instead of caching with memcached I'd have to manually store the results in the filesystem and retrieve them from there next time when the sitemap is requested (perhaps cleaning the directory daily in a cron job). All those seem very low level and I'm wondering if an obvious solution exists...

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• Query on object id in VQL

  - by Banang

  I'm currently working with the versant object database (using jvi), and have a case where I need to query the database based on an object id. What I'm trying to achieve is something along the lines of Employee employee = new Employee("Mr. Pickles"); session.commit(); FundVQLQuery q = new FundVQLQuery(session, "select * from Employee employee where employee = $1"); q.bind(employee); q.execute(); However, I'm finding out the hard way (I get an EVJ_NOT_A_VALID_KEY_TYPE error thrown at me) that this is infact not the way to do it. Anyone got any experience in working with VQL? Your help is much apreciated! A small clarification: The problem is I'm running some performance tests on the database using the pole position framework, and one of the tests in that framework requires me to fetch an object from the database using either an object reference or a low level object id. Thus, I'm not allowed to reference specific fields in the employee object, but must perform the query on the object in its entirety. So, it's not allowed for me to go "select * from Employee e where e.id = 4", I need it to use the entire object. Accepted answer: Since there is some sort of lunacy magic built into SO that prevents me to mark an accepted answer after a bounty has run out, readers should know that the answer posted by Chris Holmes solves this issue. Readers are encouraged to up-vote his post to further signalize the correctness of his answer to any future readers of this thread.

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• "Scheduling restart of crashed service", but no call to onStart() follows

  - by kostmo

  In the 1.6 API, is there a way to ensure that the onStart() method of a Service is called after the service is killed due to memory pressure? From the logs, it seems that the "process" that the service belongs to is restarted, but the service itself is not. I have placed a Log.d() call in the onStart() method, and this is not reached. To test my service under memory pressure, I spawn it from an activity, then launch the web browser and visit some Javascript-heavy websites like Slashdot until my service is killed. The logcat reads: 03-07 16:44:13.778: INFO/ActivityManager(52): Process com.kostmo.charbuilder.full (pid 2909) has died. 03-07 16:44:13.778: WARN/ActivityManager(52): Scheduling restart of crashed service com.kostmo.charbuilder.full/com.kostmo.charbuilder.DownloadImagesService in 5000ms 03-07 16:44:13.778: INFO/ActivityManager(52): Low Memory: No more background processes. 03-07 16:44:13.778: ERROR/ActivityThread(52): Failed to find provider info for android.server.checkin 03-07 16:44:13.778: WARN/Checkin(52): Can't log event SYSTEM_SERVICE_LOOPING: java.lang.IllegalArgumentException: Unknown URL content://android.server.checkin/events 03-07 16:44:18.908: INFO/ActivityManager(52): Start proc com.kostmo.charbuilder.full for service com.kostmo.charbuilder.full/com.kostmo.charbuilder.DownloadImagesService: pid=3560 uid=10027 gids={3003, 1015} 03-07 16:44:19.868: DEBUG/ddm-heap(3560): Got feature list request 03-07 16:44:20.128: INFO/ActivityThread(3560): Publishing provider com.kostmo.charbuilder.full.provider.character: com.kostmo.charbuilder.provider.ImageFileContentProvider

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• [Java] Cluster Shared Cache

  - by GuiSim

  Hi everyone. I am searching for a java framework that would allow me to share a cache between multiple JVMs. What I would need is something like Hazelcast but without the "distributed" part. I want to be able to add an item in the cache and have it automatically synced to the other "group member" cache. If possible, I'd like the cache to be sync'd via a reliable multicast (or something similar). I've looked at Shoal but sadly the "Distributed State Cache" seems like an insufficient implementation for my needs. I've looked at JBoss Cache but it seems a little overkill for what I need to do. I've looked at JGroups, which seems to be the most promising tool for what I need to do. Does anyone have experiences with JGroups ? Preferably if it was used as a shared cache ? Any other suggestions ? Thanks ! EDIT : We're starting tests to help us decide between Hazelcast and Infinispan, I'll accept an answer soon. EDIT : Due to a sudden requirements changes, we don't need a distributed map anymore. We'll be using JGroups for a low level signaling framework. Thanks everyone for you help.

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• iPhone - Memory Management - Using Leaks tool and getting some bizarre readings.

  - by Robert

  Hey all, putting the finishing touches on a project of mine so I figured I would run through it and see if and where I had any memory leaks. Found and fixed most of them but there are a couple of things regarding the memory leaks and object alloc that I am confused about. 1) There are 2 memory leaks that do not show me as responsible. There are 8 leaks attributed to AudioToolbox with the function being RegisterEmbeddedAudioCodecs(). This accounts for about 1.5 kb of leaks. The other one is detected immediately when the app begins. Core Graphics is responsible with the extra info being open_handle_to_dylib_path. For the audio leak I have looked over my audio code and to me it seems ok. self.musicPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL fileURLWithPath:songFilePath] error:NULL]; [musicPlayer prepareToPlay]; [musicPlayer play] is called later on in a function. 2) Is it normal for there to be a spike in Object Allocation whenever a new view or controller is presented? My total memory usage is very, very low except for whenever I present a view controller. It spikes then immediately goes back down. I am guessing that this is just the phone handling all the information for switching or something. Blegh. Wall of text. Thanks in advance to anyone who helps! =)

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• Creating spotlight in OpenGL scene

  - by Victor Oliveira

  Im studying OpenGL and trying to create a spot light at my application. The code that Im using for my #vertex-shader is below: #:vertex-shader #{ #version 150 core in vec3 in_pos; in vec2 in_tc; out vec2 tc; glLightf(GL_LIGHT0, GL_SPOT_CUTOFF, 20.0f); GLfloat spot_direction[] = { -1.0, -1.0, 0.0 }; glLightfv(GL_LIGHT0, GL_SPOT_DIRECTION, spot_direction); glEnable(GL_LIGHT0); void main() { vec4 pos= vec4(vec3(1.0)*in_pos - vec3(1.0), 1.0); pos.z=0.0; gl_Position = pos; tc = in_tc; } } The thing is, everytime Im trying to run the code an Error that says: Type: other, Source: api, ID: 131169, Severity: low Message: Framebuffer detailed info: The driver allocated storage for renderbuffer 1. len = 157, written = 0 failed to compile vertex shader of deferred: directional info log for shader deferred: directional vertex info log for shader deferred: directional: ERROR: Unbound variable: when Specifications: Renderer: GeForce GTX 580/PCIe/SSE2 Version: 3.3.0 NVIDIA 319.17 GLSL: 3.30 NVIDIA via Cg compiler Status: Using GLEW 1.9.0 1024 x 768 OS: Linux debian I guess to create this spotlight is pretty much simple, but since Im really new to OpenGL I dont have a clue how to do it until now, even reading sources like: http://www.glprogramming.com/red/chapter05.html#name3 Read also in some place that light spots can get really hard to understand, but I cant avoid this step right now since Im following my lecture schedule. Could anybody help me?

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• How to test a struts 2.1.x developer?

  - by Jason Pyeron

  We employ test to filter out those who can't. The tests are designed to be very low effort for those who can and too much effort for those who can't. Here is an example for java web application developer on an Oracle project: We only work with contractors who can use the tools we use, to determine if you can use the tools we have devised some very simple tests. Instructions If you are prepared and knowledgeable this will take you about 2-5 minutes. Suggested knowledge and tools: * subversion 1.6 see http://subversion.tigris.org/ or http://cygwin.com/setup.exe * java 1.6 see http://java.sun.com/javase/downloads/index.jsp * oracle >=10g see http://www.oracle.com/technology/software/products/jdev/index.html * j2ee server see http://tomcat.apache.org/download-55.cgi or http://www.jboss.org/jbossas/downloads/ Steps 1. check out svn://statics32.pdinc.us/home/subversion/guest 2. deploy the war file found at trunk/test.war 3. browse to the web application you installed from the war file and answer the one SQL question: How many rows are in the table 'testdata' where column 'value' ends with either an 'A' or an 'a'? The login credentials are in trunk/doc/oracle.txt 4. make a RESULTS HASH by submitting your answer to the form. 5. create a file in tmp/YourUserName.txt and put the RESULTS HASH in it, not the answer. 6. check in your file (don't forget to add the file first). 7. message me with the revision number of your check in. As such I am looking for ideas on how to test for someone to be a struts 2.1 w/ annotations.

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• Saving complex aggregates using Repository Pattern

  - by Kevin Lawrence

  We have a complex aggregate (sensitive names obfuscated for confidentiality reasons). The root, R, is composed of collections of Ms, As, Cs, Ss. Ms have collections of other low-level details. etc etc R really is an aggregate (no fair suggesting we split it!) We use lazy loading to retrieve the details. No problem there. But we are struggling a little with how to save such a complex aggregate. From the caller's point of view: r = repository.find(id); r.Ps.add(factory.createP()); r.Cs[5].updateX(123); r.Ms.removeAt(5); repository.save(r); Our competing solutions are: Dirty flags Each entity in the aggregate in the aggregate has a dirty flag. The save() method in the repository walks the tree looking for dirty objects and saves them. Deletes and adds are a little trickier - especially with lazy-loading - but doable. Event listener accumulates changes. Repository subscribes a listener to changes and accumulates events. When save is called, the repository grabs all the change events and writes them to the DB. Give up on repository pattern. Implement overloaded save methods to save the parts of the aggregate separately. The original example would become: r = repository.find(id); r.Ps.add(factory.createP()); r.Cs[5].updateX(123); r.Ms.removeAt(5); repository.save(r.Ps); repository.save(r.Cs); repository.save(r.Ms); (or worse) Advice please! What should we do?

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• ASP.NET MVC View ReRenders Part of Itself

  - by Jason

  In all my years of .NET programming I have not run across a bug as weird as this one. I discovered the problem because some elements on the page were getting double-bound by jQuery. After some (ridiculous) debugging, I finally discovered that once the view is completely done rendering itself and all its children partial views, it goes back to an arbitrary yet consistent location and re-renders itself. I have been pulling my hair out about this for two days now and I simply cannot get it to render itself only once! For lack of any better debugging idea, I've painstakingly added logging tracers throughout the HTML just so I can pin down what may be causing this. For instance, this code ($log just logs to the console): ... <script type="text/javascript">var x = 0; $log('1');</script> <div id="new-ad-form"> <script type="text/javascript">x++;$log('1.5', x);</script> ... will yield ... <--- this happens before this snippet 1 1.5 1 ... 10 <--- bottom of my form, after snippet 1.5 2 <--- beginning of part that runs again! ... 9 <--- this happens after this snippet I've searched my codebase high and low, but there is NOTHING that says that it should re-render part of a page. I'm wondering if the jQueryUI has anything to do with it, as #new-ad-form is the container for a jQueryUI dialog box. If this is potentially the case, here's my init code for that: $('#new-ad-form').dialog({ autoOpen: false, modal: true, width: 470, title: 'Create A New Ad', position: ['center', 35], close: AdEditor.reset });

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• C#.NET DataGridView - update database

  - by Geo Ego

  I know this is a basic function of the DataGridView, but for some reason, I just can't get it to work. I just want the DataGridView on my Windows form to submit any changes made to it to the database when the user clicks the "Save" button. On form load, I populate the DataGridView and that's working fine. In my save function, I basically have the following (I've trimmed out some of the code around it to get to the point): using (SqlDataAdapter ruleTableDA = new SqlDataAdapter("SELECT rule.fldFluteType AS [Flute], rule.fldKnife AS [Knife], rule.fldScore AS [Score], rule.fldLowKnife AS [Low Knife], rule.fldMatrixScore AS [Matrix Score], rule.fldMatrix AS [Matrix] FROM dbo.tblRuleTypes rule WHERE rule.fldMachine_ID = '1003'", con)) { SqlCommandBuilder commandBuilder = new SqlCommandBuilder(ruleTableDA); DataTable dt = new DataTable(); dt = RuleTable.DataSource as DataTable; ruleTableDA.Fill(dt); ruleTableDA.Update(dt); } Okay, so I edited the code to do the following: build the commands, create a DataTable based on the DataGridView (RuleTable), fill the DataAdapter with the DataTable, and update the database. Now ruleTableDA.Update(dt) is throwing the exception "Concurrency violation: the UpdateCommand affected 0 of the expected 1 records." Thanks very much!

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• Generate a set of strings with maximum edit distance

  - by Kevin Jacobs

  Problem 1: I'd like to generate a set of n strings of fixed length m from alphabet s such that the minimum Levenshtein distance (edit distance) between any two strings is greater than some constant c. Obviously, I can use randomization methods (e.g., a genetic algorithm), but was hoping that this may be a well-studied problem in computer science or mathematics with some informative literature and an efficient algorithm or three. Problem 2: Same as above except that adjacent characters cannot repeat; the i'th character in each string may not be equal to the i+1'th character. E.g., 'CAT', 'AGA' and 'TAG' are allowed, 'GAA', 'AAT', and 'AAA' are not. Background: The basis for this problem is bioinformatic and involves designing unique DNA tags that can be attached to biologically derived DNA fragments and then sequenced using a fancy second generation sequencer. The goal is to be able to recognize each tag, allowing for random insertion, deletion, and substitution errors. The specific DNA sequencing technology has a relatively low error rate per base (~1%), but is less precise when a single base is repeated 2 or more times (motivating the additional constraints imposed in problem 2).

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• Altruistic network connection bandwidth estimation

  - by datenwolf

  Assume two peers Alice and Bob connected over a IP network. Alice and Bob are exchanging packets of lossy compressed data which are generated and to be consumes in real time (think a VoIP or video chat application). The service is designed to cope with as little bandwidth available, but relies on low latencies. Alice and Bob would mark their connection with an apropriate QoS profile. Alice and Bob want use a variable bitrate compression and would like to consume all of the leftover bandwidth available for the connection between them, but would voluntarily reduce the consumed bitrate depending on the state of the network. However they'd like to retain a stable link, i.e. avoid interruptions in their decoded data stream caused by congestion and the delay until the bandwidth got adjusted. However it is perfectly possible for them to loose a few packets. TL;DR: Alice and Bob want to implement a VoIP protocol from scratch, and are curious about bandwidth and congestion control. What papers and resources do you suggest for Alice and Bob to read? Mainly in the area of bandwidth estimation and congestion control.

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• DSP - Filtering frequencies using DFT

  - by Trap

  I'm trying to implement a DFT-based 8-band equalizer for the sole purpose of learning. To prove that my DFT implementation works I fed an audio signal, analyzed it and then resynthesized it again with no modifications made to the frequency spectrum. So far so good. I'm using the so-called 'standard way of calculating the DFT' which is by correlation. This method calculates the real and imaginary parts both N/2 + 1 samples in length. To attenuate a frequency I'm just doing: float atnFactor = 0.6; Re[k] *= atnFactor; Im[k] *= atnFactor; where 'k' is an index in the range 0 to N/2, but what I get after resynthesis is a slighty distorted signal, especially at low frequencies. The input signal sample rate is 44.1 khz and since I just want a 8-band equalizer I'm feeding the DFT 16 samples at a time so I have 8 frequency bins to play with. Can someone show me what I'm doing wrong? I tried to find info on this subject on the internet but couldn't find any. Thanks in advance.

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• Handling XMLHttpRequest to call external application

  - by Ian

  I need a simple way to use XMLHttpRequest as a way for a web client to access applications in an embedded device. I'm getting confused trying to figure out how to make something thin and light that handles the XMLHttpRequests coming to the web server and can translate those to application calls. The situation: The web client using Ajax (ExtJS specifically) needs to send and receive asynchronously to an existing embedded application. This isn't just to have a thick client/thin server, the client needs to run background checking on the application status. The application can expose a socket interface, with a known set of commands, events, and configuration values. Configuration could probably be transmitted as XML since it comes from a SQLite database. In between the client and app is a lighttpd web server running something that somehow handles the translation. This something is the problem. What I think I want: Lighttpd can use FastCGI to route all XMLHttpRequest to an external process. This process will understand HTML/XML, and translate between that and the application's language. It will have custom logic to simulate pushing notifications to the client (receive XMLHttpRequest, don't respond until the next notification is available). C/C++. I'd really like to avoid installing Java/PHP/Perl on an embedded device. So I'll need more low level understanding. How do I do this? Are there good C++ libraries for interpreting the CGI headers and HTML so that I don't have to do any syntax processing, I can just deal with the request/response contents? Are there any good references to exactly what goes on, server side, when handling the XMLHttpRequest and CGI interfaces? Is there any package that does most of this job already, or will I have to build the non-HTTP/CGI stuff from scratch? Thanks for any help! I am really having trouble learning about the server side of these technologies.

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• DVCS with a Windows central repository

  - by Mikko Rantanen

  We are currently using VSS for version control. Quite few of our developers are interested in a distributed model (And want to get rid of VSS). Our network is full of Windows machines and while our IT department has experience maintaining Linux machines they would prefer not to. What DVCS systems can host their central repository on Windows while providing.. Push access to the repository. Basic authentication. Mostly just a way to allow or deny access to the whole repository. No need for fine grained access. Server process so users don't need write right to the repository reducing the risk of accidentally messing with it. On the client side a GUI such as Tortoise would be more or less a requirement (Sorry, Windows shell sucks. :|). Ease of installation would be a huge plus as our IT department is already quite low on resources. And using windows credentials for authentication would be an advantage but not a requirement as long as the client is able to store the credentials. I have had a (really) quick look at Git, Mercurial and Bazaar. Git seemed to use ssh or simple WebDAV for repository access, requiring write permission for the users. Mercurial had a built in http server, but this seemed to be only for pull purposes. Update: Mercurial supports push as well. Bazaar Seemed to use sftp for repository access, again requiring a write permission for the users. Are there windows server processes for any DVCS systems and has anyone managed to set one up in a Windows land? And apologies if this is a duplicate question. I couldn't find one. Update Got Mercurial working for push purposes! Detailed list what was required can be found as an answer below.

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• Payment Processors - What do I need to know if I want to accept credit cards on my website?

  - by Michael Pryor

  This question talks about different payment processors and what they cost, but I'm looking for the answer to what do I need to do if I want to accept credit card payments? Assume I need to store credit card numbers for customers, so that the obvious solution of relying on the credit card processor to do the heavy lifting is not available. PCI Data Security, which is apparently the standard for storing credit card info, has a bunch of general requirements, but how does one implement them? And what about the vendors, like Visa, who have their own best practices? Do I need to have keyfob access to the machine? What about physically protecting it from hackers in the building? Or even what if someone got their hands on the backup files with the sql server data files on it? What about backups? Are there other physical copies of that data around? Tip: If you get a merchant account, you should negotiate that they charge you "interchange-plus" instead of tiered pricing. With tiered pricing, they will charge you different rates based on what type of Visa/MC is used -- ie. they charge you more for cards with big rewards attached to them. Interchange plus billing means you only pay the processor what Visa/MC charges them, plus a flat fee. (Amex and Discover charge their own rates directly to merchants, so this doesn't apply to those cards. You'll find Amex rates to be in the 3% range and Discover could be as low as 1%. Visa/MC is in the 2% range). This service is supposed to do the negotiation for you (I haven't used it, this is not an ad, and I'm not affiliated with the website, but this service is greatly needed.) This blog post gives a complete rundown of handling credit cards (specifically for the UK).

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• Problem with load testing Web Service - VSTS 2008

  - by Carlos

  Hello, I have a webtest with makes a simple call to a WebService which looks like that: MyWebService webService = new MyWebService(); webService.Timeout = 180000; webService.myMethod(); I am not using ThinkTimes, also the Run Duration is set to 5 minutes. When I ran this test simulating only 1 user, I check the counters and I found something like that: Tests Total: 4500 Network Interface\Bytes sent (agent machine): 35,500 Then I ran the same tests, but this time simulating 2 users and I got something like that: Tests Total: 2225 Network Interface\Bytes sent (agent machine): 30,500 So when I increased the numbers of users the tests/sec was half than when I use only 1 user and the bytes sent by the agent was also lower. I think it is strange, because it doesn't seems I have a bottleneck in my agent machine since CPU is never higher than 30% and I have over 1.5GB of RAM free, also my network utilization is like 0.5% of its capacity. In order to troubleshot this I ran a test using Step Pattern, the simulated users went from 20 to 800 users. When I check the requests/sec it is practically constant through the whole test, so it is clear there is something in my test or my environment which is preventing the number of requests from gets higher. It would be a expected behavior if the "response time" was getting higher because it would tell me the requests wasn't been processed properly, but the strange thing is the response time is practically constant all the time and it is pretty low actually. I have no idea why my agent can't send more requests when I increase the numbers of users, any help/tip/guess would be really appreciate.

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