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• Multiple sendto() using UDP socket

  - by ereOn

  Hi, I have a network software which uses UDP to communicate with other instances of the same program. For different reasons, I must use UDP here. I recently had problems sending huge ammounts of data over UDP and had to implement a fragmentation system to split my messages into small data chunks. So far, it worked well but I now encounter an issue when I have to send a lot of data chunks. I have the following algorithm: Split message into small data chunks (around 1500 bytes) Iterate over the data chunks list and for each, send it using sendto() However, when I send a lot of data chunks, the receiver only gets the first 6 messages. Sometimes it misses the sixth and receives the seventh. It depends. Anyway, sendto() always indicates success. This always happen when I test my software over a loopback interface (127.0.0.1) but never over my LAN network. If I add something like std::cout << "test" << std::endl; between the sendto() then every frame is received. I am aware that UDP allows packet loss and that my frames might be loss for a lot of reasons and I suppose it has to do with the rate I am sending the data chunks at. What would be the right approach here ? Implementing some acknowledgement mechanism (just like TCP) seems overkill. Adding some arbitrary waiting time between the sendto() is ugly and will probably decrease performance. Increasing (if possible) the receiver UDP internal buffer ? I don't even know if this is possible. Something else ? I really need your advices here. Thank very much.

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• move_uploaded_file() error

  - by James R.

  I have a website on free hosting - 000webhost.com and it allows you to upload images. However, when I try to upload an image, I get these errors: Warning: move_uploaded_file(images/SmallSmileyFace.jpg) [function.move-uploaded-file]: failed to open stream: Permission denied in /home/a6621074/public_html/m/write.php on line 76 Warning: move_uploaded_file() [function.move-uploaded-file]: Unable to move '/tmp/phpcmW3mo' to 'images/SmallSmileyFace.jpg' in /home/a6621074/public_html/m/write.php on line 76 This is the code: if (!empty($_FILES['fileImage']['name'])) { // check image type and size if ((($imagetype == 'image/gif') || ($imagetype == 'image/jpeg') || ($imagetype == 'image/pjpeg') || ($imagetype == 'image/png')) && ($imagesize > 0) && ($imagesize <= 32768)) { if ($_FILES['fileImage']['error'] == 0) { //move file $target = 'images/' . $image; if (move_uploaded_file($_FILES['fileImage']['tmp_name'], $target)) { $query = "INSERT INTO reviews (post_date, food_name, location, cafeteria, review, image, rating, user_id) VALUES (NOW(), '$foodname', '$location', '$cafeteria', '$review', '$image', $rate, $id)"; mysqli_query($dbc, $query); //confirm success echo '<p>Thank you for your submission!</p>'; } else { echo '<p class="errmsg">There was a problem uploading your image.</p>'; } } @unlink($_FILES['fileImage']['tmp_name']); } else { echo '<p class="errmsg">The screen shot must be a GIF, JPEG, or PNG image file no greater than 32KB in size.</p>'; } } Any ideas?

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• WPF performance on scaling a large scene

  - by Mark

  I have a full screen app that I want to be able to zoom in on certain areas. I have the code working fine, but I notice that when I get closer in, the zoom in animation (which animates the ScaleTransform.ScaleX and ScaleTransform.ScaleY properties on a Parent canvas) starts to jerk down a little and the frame rate suffers. Im not using any BitmapEffects or anything, and ideally I would like my scene to get more complicated than it currently already is. The scene is quite large, 1980x1024, this is a requirement and cannot be changed. The current layout is like this: <Canvas x:name="LayoutRoot"> <Canvas x:Name="ContainerCanvas"> <local:MyControl x:Name="c1" /> <!-- numerous or ther controls and elements that compose the scene --> </Canvas> </Canvas> The code that zooms in just animates the RenderTransform of the ContainerCanvas, which in tern, scales its children which gives the desired effect. However, Im wondering if I need to swap out the ContainerCanvas for a ViewBox or something like that? Ive never really worked with ViewBox/Viewport controls before in WPF can they even help me out here? Smooth zooming is a huge requirement of the client and I must get this resolved. All ideas are welcome Thanks a lot Mark

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• Record/Playback with AudioQueue on iPhone

  - by Biranchi

  Hi, I am currently using Audio Queues on the iPhone to record and playback audio. What I would like to be able to do is to record some audio, allow the user to pause the record queue, and to seek back and forward through the audio to select a position from where they can start recording from again. I have got over the seeking issue by making the playback AudioQueueBuffer sizes small enough so that the play audio queue callback happens at a rate that allows the user to use a slider control to hear the audio as they adjust the slider back and forth. I think I can achieve the recording at a new position by setting the inStartingPacket parameter of the AudioFileWritePackets function that I call from the Audio Recording Queue callback. The trouble is this only inserts audio over the previously recorded audio. The file length obviously doesn't change so if the user were to go backwards and record less audio than before, the old audio still remains after the end of the newly recorded audio. Is there a way I can get the AudioFile to truncate at the point the user starts to insert the new audio, is there some other way I can remove the old audio starting at the insert position or is there a better way about going about this task? Thanks

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• jquery access sibling TD in table

  - by Rob

  I have the following HTML Code. What I'm try to do is to have the div named javaRatingDiv to be displayed once the checkbox with the name java is checked. I can't seem to figure out how to navigate to the next TD in a table via jquery. <div id="languages"> <table style="width:inherit"> <tr style="height:50px; vertical-align:top"> <td>Select the languages that you are familiar with and rate your knowledge:</td> </tr> <tr> <table style="width:75%;" align="center"> <tr id="tableRow"> <td id="firstTD"><input type="checkbox" name="java" value="java" />&nbsp;Java</td> <td id="secondTD" style="width:200px;"> <div id="javaRatingDiv" style="display:none"> <input name="javaRating" type="radio" value="1" class="star"/> <input name="javaRating" type="radio" value="2" class="star"/> </div> </td> </tr> </table> </tr> </table> </div>

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• Filtering documents against a dictionary key in MongoDB

  - by Thomas

  I have a collection of articles in MongoDB that has the following structure: { 'category': 'Legislature', 'updated': datetime.datetime(2010, 3, 19, 15, 32, 22, 107000), 'byline': None, 'tags': { 'party': ['Peter Hoekstra', 'Virg Bernero', 'Alma Smith', 'Mike Bouchard', 'Tom George', 'Rick Snyder'], 'geography': ['Michigan', 'United States', 'North America'] }, 'headline': '2 Mich. gubernatorial candidates speak to students', 'text': [ 'BEVERLY HILLS, Mich. (AP) \u2014 Two Democratic and Republican gubernatorial candidates found common ground while speaking to private school students in suburban Detroit', "Democratic House Speaker state Rep. Andy Dillon and Republican U.S. Rep. Pete Hoekstra said Friday a more business-friendly government can help reduce Michigan's nation-leading unemployment rate.", "The candidates were invited to Detroit Country Day Upper School in Beverly Hills to offer ideas for Michigan's future.", 'Besides Dillon, the Democratic field includes Lansing Mayor Virg Bernero and state Rep. Alma Wheeler Smith. Other Republicans running are Oakland County Sheriff Mike Bouchard, Attorney General Mike Cox, state Sen. Tom George and Ann Arbor business leader Rick Snyder.', 'Former Republican U.S. Rep. Joe Schwarz is considering running as an independent.' ], 'dateline': 'BEVERLY HILLS, Mich.', 'published': datetime.datetime(2010, 3, 19, 8, 0, 31), 'keywords': "Governor's Race", '_id': ObjectId('4ba39721e0e16cb25fadbb40'), 'article_id': 'urn:publicid:ap.org:0611e36fb084458aa620c0187999db7e', 'slug': "BC-MI--Governor's Race,2nd Ld-Writethr" } If I wanted to write a query that looked for all articles that had at least 1 geography tag, how would I do that? I have tried writing db.articles.find( {'tags': 'geography'} ), but that doesn't appear to work. I've also thought about changing the search parameter to 'tags.geography', but am having a devil of a time figuring out what the search predicate would be.

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• Has the recent version of subversion dealt with "Access Denied" errors from windows services that mo

  - by Eric LaForce

  Does anyone know if this subversion "bug" has been dealt with? https://svn.apache.org/repos/asf/subversion/tags/1.6.9/www/faq.html#windows-access-denied I'm getting occasional "Access Denied" errors on Windows. They seem to happen at random. Why? These appear to be due to the various Windows services that monitor the filesystem for changes (anti-virus software, indexing services, the COM+ Event Notification Service). This is not really a bug in Subversion, which makes it difficult for us to fix. A summary of the current state of the investigation is available here. A workaround that should reduce the incidence rate for most people was implemented in revision 7598; if you have an earlier version, please update to the latest release. Currently I am experiencing this same behavior in version 1.5.6 when I try and do a SVN switch (I have suspected McAfee as the culprit for a while and when I saw this I feel it validates my suspicions). I read through the link given but it seems pretty old, so I didn't know if this FAQ was just outdated and the issue has actually be resolved. Thanks for any help. Configuration: SVN 1.5.6 TortoiseSVN 1.5.9 Build 15518 Windows XP SP3 32-bit

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• Bubble Breaker Game Solver better than greedy?

  - by Gregory

  For a mental exercise I decided to try and solve the bubble breaker game found on many cell phones as well as an example here:Bubble Break Game The random (N,M,C) board consists N rows x M columns with C colors The goal is to get the highest score by picking the sequence of bubble groups that ultimately leads to the highest score A bubble group is 2 or more bubbles of the same color that are adjacent to each other in either x or y direction. Diagonals do not count When a group is picked, the bubbles disappear, any holes are filled with bubbles from above first, ie shift down, then any holes are filled by shifting right A bubble group score = n * (n - 1) where n is the number of bubbles in the bubble group The first algorithm is a simple exhaustive recursive algorithm which explores going through the board row by row and column by column picking bubble groups. Once the bubble group is picked, we create a new board and try to solve that board, recursively descending down Some of the ideas I am using include normalized memoization. Once a board is solved we store the board and the best score in a memoization table. I create a prototype in python which shows a (2,15,5) board takes 8859 boards to solve in about 3 seconds. A (3,15,5) board takes 12,384,726 boards in 50 minutes on a server. The solver rate is ~3k-4k boards/sec and gradually decreases as the memoization search takes longer. Memoization table grows to 5,692,482 boards, and hits 6,713,566 times. What other approaches could yield high scores besides the exhaustive search? I don't seen any obvious way to divide and conquer. But trending towards larger and larger bubbles groups seems to be one approach Thanks to David Locke for posting the paper link which talks above a window solver which uses a constant-depth lookahead heuristic.

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• Flash video slooow in AIR 2 HTMLLoader component

  - by shane

  I am working on a full screen kiosk application in Flex 4/Air 2 using Flash Builder 4. We have a company training website which staff can access via the kiosk, and the main content is interactive flash training videos. Our target machines are by no means 'beefy', they are Atom n270s @ 1.6Ghz with 1Gb RAM. As it stands the videos are all but unusable when used from within the Air application, the application becomes completely unresponsive (100% cpu usage, click events take approx 5-10 seconds to register). So far I have tried: increasing the default frame rate from 24fps to 60. No improvement. nativeWindow.stage.frameRate = 60; running the videos in a stripped down version of my app, just a full screen HTMLLoader component pointed at the training website. No better than before. disabled hyper threading. The Atom CPU is split into two virtual cores, and the AIR app was only able to use one thread so maxed out at 50% CPU usage. Since the kiosk will only run the AIR app I am happy to loose hyper threading to increase the performance of the Air app. Marginal Improvement. The same website with the same videos is responsive if viewed in ie7 on the same machine, although Internet Explorer takes advantage of the CPU’s hyper threading. The flash videos are built with Adobe Captivate and from what I understand employee JavaScript to relay results back to the server. I will add more information about the video content asap as the training guru is back in the office later this week.

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• video streaming infrastructure

  - by alchemical

  We would like to set-up a live video-chat web site and are looking for basic architectural advice and/or a recomendation for a particular framework to use. Here are the basic features of the site: Most streams will be broadcast live from a single person with a web cam, etc., and viewed by typically 1-10 people, although there could be up to 100+ viewers on the high side. Audio and video do not have to be super-high quality, but do need to be "good enough". The main point is to convey the basic info in the video (and audio). If occasionally the frame-rate drops low and then goes back to normal fairly soon, we could live with that. Budget is an issue, so we are in general looking for a lower cost solution that will give us most of what we need in temers of performance and quality. We are looking at Peer1 for co-lo. The rest of our web site will be .Net / Windows platform. We are open to looking at any platform for the best streaming solution, although our technical expertise is currently more on the Windows side.

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• How to speed up marching cubes?

  - by Dan Vinton

  I'm using this marching cube algorithm to draw 3D isosurfaces (ported into C#, outputting MeshGeomtry3Ds, but otherwise the same). The resulting surfaces look great, but are taking a long time to calculate. Are there any ways to speed up marching cubes? The most obvious one is to simply reduce the spatial sampling rate, but this reduces the quality of the resulting mesh. I'd like to avoid this. I'm considering a two-pass system, where the first pass samples space much more coarsely, eliminating volumes where the field strength is well below my isolevel. Is this wise? What are the pitfalls? Edit: the code has been profiled, and the bulk of CPU time is split between the marching cubes routine itself and the field strength calculation for each grid cell corner. The field calculations are beyond my control, so speeding up the cubes routine is my only option... I'm still drawn to the idea of trying to eliminate dead space, since this would reduce the number of calls to both systems considerably.

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• Optimizing mathematics on arrays of floats in Ada 95 with GNATC

  - by mat_geek

  Consider the bellow code. This code is supposed to be processing data at a fixed rate, in one second batches, It is part of an overal system and can't take up too much time. When running over 100 lots of 1 seconds worth of data the program takes 35 seconds; or 35%. How do I improce the code to get the processing time down to a minimum? The code will be running on an Intel Pentium-M which is a P3 with SSE2. package FF is new Ada.Numerics.Generic_Elementary_Functions(Float); N : constant Integer := 820; type A is array(1 .. N) of Float; type A3 is array(1 .. 3) of A; procedure F(state : in out A3; result : out A3; l : in A; r : in A) is s : Float; t : Float; begin for i in 1 .. N loop t := l(i) + r(i); t := t / 2.0; state(1)(i) := t; state(2)(i) := t * 0.25 + state(2)(i) * 0.75; state(3)(i) := t * 1.0 /64.0 + state(2)(i) * 63.0 /64.0; for r in 1 .. 3 loop s := state(r)(i); t := FF."**"(s, 6.0) + 14.0; if t > MAX then t := MAX; elsif t < MIN then t := MIN; end if; result(r)(i) := FF.Log(t, 2.0); end loop; end loop; end;

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• Thread implemented as a Singleton

  - by rocknroll

  Hi all, I have a commercial application made with C,C++/Qt on Linux platform. The app collects data from different sensors and displays them on GUI. Each of the protocol for interfacing with sensors is implemented using singleton pattern and threads from Qt QThreads class. All the protocols except one work fine. Each protocol's run function for thread has following structure: void <ProtocolClassName>::run() { while(!mStop) //check whether screen is closed or not { mutex.lock() while(!waitcondition.wait(&mutex,5)) { if(mStop) return; } //Code for receiving and processing incoming data mutex.unlock(); } //end while } Hierarchy of GUI. 1.Login screen. 2. Screen of action. When a user logs in from login screen, we enter the action screen where all data is displayed and all the thread's for different sensors start. They wait on mStop variable in idle time and when data arrives they jump to receiving and processing data. Incoming data for the problem protocol is 117 bytes. In the main GUI threads there are timers which when timeout, grab the running instance of protocol using <ProtocolName>::instance() function Check the update variable of singleton class if its true and display the data. When the data display is done they reset the update variable in singleton class to false. The problematic protocol has the update time of 1 sec, which is also the frame rate of protocol. When I comment out the display function it runs fine. But when display is activated the application hangs consistently after 6-7 hours. I have asked this question on many forums but haven't received any worthwhile suggestions. I Hope that here I will get some help. Also, I have read a lot of literature on Singleton, multithreading, and found that people always discourage the use of singletons especially in C++. But in my application I can think of no other design for implementation. Thanks in advance A Hapless programmer

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• Frameworks to manage dates (effective date and expiry dates)

  - by user214626

  Hello, We have an object that can has an effective date and expiry date.(Ex. i want to maintain the price of a commodity for a time period) Business Rules - Effective date is always a valid date (a datestamp) but, expiry date can be null to indicate that the object is active throughout. Also, both effective and expiry date can be set to some valid dates. Are there any frameworks that manage objects such that the objects are consistent,i.e there are no overlaps of the validity periods ? Ex. class XBOX { double price; Date effectiveDate; Date expiryDate; } XBOX x1 = new XBOX(400$, '2007-01-01','2008-12-31' ); XBOX x2 = new XBOX(200$, '2009-01-01',null ); Assume that we get a new rate from '2010-01-01' and a new XBOX object has to be created (to persist). Is there a framework/pattern that can do the following, so that the XBOX is consistent. x2.setExpiryDate('2009-12-31') XBOX x3 = new XBOX(150$, '2010-01-01',null ); Thanks in advance.

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• OpenGL behaving strangely

  - by Mk12

  OpenGL is acting very strangely for some reason. In my subclass of NSOpenGLView, I have the following code in -prepareOpenGL: - (void)prepareOpenGL { GLfloat lightAmbient[] = { 0.5f, 0.5f, 0.5f, 1.0f }; GLfloat lightDiffuse[] = { 1.0f, 1.0f, 1.0f, 1.0f }; GLfloat lightPosition[] = { 0.0f, 0.0f, 2.0f }; quality = 0; zCoord = -6; [self loadTextures]; glEnable(GL_LIGHTING); glEnable(GL_TEXTURE_2D); glShadeModel(GL_SMOOTH); glClearColor(0.2f, 0.2f, 0.2f, 0.0f); glClearDepth(1.0f); glEnable(GL_DEPTH_TEST); glDepthFunc(GL_LEQUAL); glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST); glLightfv(GL_LIGHT1, GL_AMBIENT, lightAmbient); glLightfv(GL_LIGHT1, GL_DIFFUSE, lightDiffuse); glLightfv(GL_LIGHT1, GL_POSITION, lightPosition); glEnable(GL_LIGHT1); gameState = kGameStateRunning; int i = 0; // HERE ******** [NSTimer scheduledTimerWithTimeInterval:0.03f target:self selector:@selector(processKeys) userInfo:nil repeats:YES]; // Synchronize buffer swaps with vertical refresh rate GLint swapInt = 1; [[self openGLContext] setValues:&swapInt forParameter:NSOpenGLCPSwapInterval]; // Setup and start displayLink [self setupDisplayLink]; } I wanted to assign the timer that processes key input to an ivar so that I could invalidate it when the game is paused (and reinstantiate it on resume), however when I did that (as apposed to leaving it at [NSTimer scheduledTimer…), OpenGL doesn't display the cube I draw. When I take it away, it's fine. So i tried just adding a harmless statement, int i = 0; (maked // HERE *******), and that makes the lighting not work! When I take it away, everything is fine, but when I put it back, everything is dark. Can someone come up with a rational explanation for this? Thanks.

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• Neural Network settings for fast training

  - by danpalmer

  I am creating a tool for predicting the time and cost of software projects based on past data. The tool uses a neural network to do this and so far, the results are promising, but I think I can do a lot more optimisation just by changing the properties of the network. There don't seem to be any rules or even many best-practices when it comes to these settings so if anyone with experience could help me I would greatly appreciate it. The input data is made up of a series of integers that could go up as high as the user wants to go, but most will be under 100,000 I would have thought. Some will be as low as 1. They are details like number of people on a project and the cost of a project, as well as details about database entities and use cases. There are 10 inputs in total and 2 outputs (the time and cost). I am using Resilient Propagation to train the network. Currently it has: 10 input nodes, 1 hidden layer with 5 nodes and 2 output nodes. I am training to get under a 5% error rate. The algorithm must run on a webserver so I have put in a measure to stop training when it looks like it isn't going anywhere. This is set to 10,000 training iterations. Currently, when I try to train it with some data that is a bit varied, but well within the limits of what we expect users to put into it, it takes a long time to train, hitting the 10,000 iteration limit over and over again. This is the first time I have used a neural network and I don't really know what to expect. If you could give me some hints on what sort of settings I should be using for the network and for the iteration limit I would greatly appreciate it. Thank you!

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• Need help choosing database server

  - by The Pretender

  Good day everyone. Recently I was given a task to develop an application to automate some aspects of stocks trading. While working on initial architecture, the database dilemma emerged. What I need is a fast database engine which can process huge amounts of data coming in very fast. I'm fairly experienced in general programming, but I never faced a task of developing a high-load database architecture. I developed a simple MSSQL database schema with several many-to-many relationships during one of my projects, but that's it. What I'm looking for is some advice on choosing the most suitable database engine and some pointers to various manuals or books which describe high-load database development. Specifics of the project are as follows: OS: Windows NT family (Server 2008 / 7) Primary platform: .NET with C# Database structure: one table to hold primary items and two or three tables with foreign keys to the first table to hold additional information. Database SELECT requirements: Need super-fast selection by foreign keys and by combination of foreign key and one of the columns (presumably DATETIME) Database INSERT requirements: The faster the better :) If there'll be significant performance gain, some parts can be written in C++ with managed interfaces to the rest of the system. So once again: given all that stuff I just typed, please give me some advice on what the best database for my project is. Links or references to some manuals and books on the subject are also greatly appreciated. EDIT: I'll need to insert 3-5 rows in 2 tables approximately once in 30-50 milliseconds and I'll need to do SELECT with 0-2 WHERE clauses queries with similar rate.

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• rs232 communication, general timing question

  - by Sunny Dee

  Hi, I have a piece of hardware which sends out a byte of data representing a voltage signal at a frequency of 100Hz over the serial port. I want to write a program that will read in the data so I can plot it. I know I need to open the serial port and open an inputstream. But this next part is confusing me and I'm having trouble understanding the process conceptually: I create a while loop that reads in the data from the inputstream 1 byte at a time. How do I get the while loop timing so that there is always a byte available to be read whenever it reaches the readbyte line? I'm guessing that I can't just put a sleep function inside the while loop to try and match it to the hardware sample rate. Is it just a matter of continuing reading the inputstream in the while loop, and if it's too fast then it won't do anything (since there's no new data), and if it's too slow then it will accumulate in the inputstream buffer? Like I said, i'm only trying to understand this conceptually so any guidance would be much appreciated! I'm guessing the idea is independent of which programming language I'm using, but if not, assume it is for use in Java. Thanks!

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• Does Firefox on OS X Lion make use of Full Page Zoom for the touchpad? How to customize behavior?

  - by Steven Lu

  I really like the smooth pinch-zoom of Safari using the touchpad, but the two-finger scroll on Firefox is so much better than the scrolling performance in Safari. So I really like to use Firefox, but then I miss out on two-finger-double-tap to zoom to paragraph width, and the smooth pinch gesture zoom. What I'm wondering is if it is possible to write a Firefox Extension to improve the update rate of the full-page zoom in Firefox that is already functioning via the touchpad pinch gesture. I feel like it is specifically programmed to zoom at certain zoom levels: 100%, 120%, 150% (these are guesses of mine) but I think it would be great if I can get some more control there to make it work more like the zoom functionality in Safari. Also the two-finger-double-tap on a paragraph or element to zoom to it would be really awesome as well. https://developer.mozilla.org/en/Full_page_zoom This seems to indicate (if "full page zoom" is what I think it is) that an extension has the ability to zoom to an arbitrary scale factor, but what remains is to find out if it is possible to obtain or hook the touchpad pinch gesture. Update: I have updated the toolkit.zoomManager.zoomValues option in about:config to include more zoom levels: .3,.5,.67,.8,.9,1,1.01,1.02,1.03,1.04,1.05,1.06,1.07,1.08,1.09,1.1,1.2,1.33,1.5,1.7,2,2.4,3 Notice how I inserted a bunch of entries between 1 and 1.1. But it isn't switching between them any faster (why would it?) so it's less usable than before because of waiting for it to respond fast enough. It's clear that re-rendering the page at a different zoom level requires time and in order for the zoom to be dynamic, some kind of screen capture and scale effect must be performed (which is what Safari does). I guess such a thing is probably doable but I don't think I could pull it off. :-/

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• MySQL - How do I inner join sorting the joined data

  - by Gary

  I'm trying to write a report which will join a person, their work, and their hourly wage at the time of work. I cannot seem to figure out the best way to join the person's cost when the date is less than the date of the work. Let's say a person cost $30 per hour at the start of the year then got a $10 raise o Feb 5 and another on Mar 1. 01/01/2010 $30.00 (per hour) 02/05/2010 $40.00 03/01/2010 $45.00 The person put in hours several days which span the rasies. 01/05/2010 10 hours (should be at $30/hr) 01/27/2010 5 hours (again at $30) 02/10/2010 10 hours (at $40/hr) 03/03/2010 5 hours (at $45/hr) I'm trying to write one SQL statement which will pull the hours, the cost per hour, and the hours*cost. The cost is the hourly rate last entered into the system so the cost date is less than the work date, ordered by cost date limit 1. SELECT person.id, person.name, work.hours, person_costs.value, work.hours * person_costs.value AS value FROM person INNER JOIN work ON (person.id = work.person_id) INNER JOIN person_costs ON (person.id = person_costs.person_id AND person_costs.date < work.date) WHERE person.id = 1234 ORDER BY work.date ASC The problem I'm having, the person_costs isn't ordered by date in descending order. It's pulling out "any" value (naturally sorted by record position) which matches the condition. How do I select the first person_cost value which is older than the work date? Thanks!

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• Optimize GROUP BY&ORDER BY query

  - by Jan Hancic

  I have a web page where users upload&watch videos. Last week I asked what is the best way to track video views so that I could display the most viewed videos this week (videos from all dates). Now I need some help optimizing a query with which I get the videos from the database. The relevant tables are this: video (~239371 rows) VID(int), UID(int), title(varchar), status(enum), type(varchar), is_duplicate(enum), is_adult(enum), channel_id(tinyint) signup (~115440 rows) UID(int), username(varchar) videos_views (~359202 rows after 6 days of collecting data, so this table will grow rapidly) videos_id(int), views_date(date), num_of_views(int) The table video holds the videos, signup hodls users and videos_views holds data about video views (each video can have one row per day in that table). I have this query that does the trick, but takes ~10s to execute, and I imagine this will only get worse over time as the videos_views table grows in size. SELECT v.VID, v.title, v.vkey, v.duration, v.addtime, v.UID, v.viewnumber, v.com_num, v.rate, v.THB, s.username, SUM(vvt.num_of_views) AS tmp_num FROM video v LEFT JOIN videos_views vvt ON v.VID = vvt.videos_id LEFT JOIN signup s on v.UID = s.UID WHERE v.status = 'Converted' AND v.type = 'public' AND v.is_duplicate = '0' AND v.is_adult = '0' AND v.channel_id <> 10 AND vvt.views_date >= '2001-05-11' GROUP BY vvt.videos_id ORDER BY tmp_num DESC LIMIT 8 And here is a screenshot of the EXPLAIN result: So, how can I optimize this?

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• MySQL table data transformation -- how can I dis-aggregate MySQL time data?

  - by lighthouse65

  We are coding for a MySQL data warehousing application that stores descriptive data (User ID, Work ID, Machine ID, Start and End Time columns in the first table below) associated with time and production quantity data (Output and Time columns in the first table below) upon which aggregate (SUM, COUNT, AVG) functions are applied. We now wish to dis-aggregate time data for another type of analysis. Our current data table design: +---------+---------+------------+---------------------+---------------------+--------+------+ | User ID | Work ID | Machine ID | Event Start Time | Event End Time | Output | Time | +---------+---------+------------+---------------------+---------------------+--------+------+ | 080025 | ABC123 | M01 | 2008-01-24 16:19:15 | 2008-01-24 16:34:45 | 2120 | 930 | +---------+---------+------------+---------------------+---------------------+--------+------+ Reprocessing dis-aggregation that we would like to do would be to transform table content based on a granularity of minutes, rather than the current production event ("Event Start Time" and "Event End Time") granularity. The resulting reprocessing of existing table rows would look like: +---------+---------+------------+---------------------+--------+ | User ID | Work ID | Machine ID | Production Minute | Output | +---------+---------+------------+---------------------+--------+ | 080025 | ABC123 | M01 | 2010-01-24 16:19 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:20 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:21 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:22 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:23 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:24 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:25 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:26 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:27 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:28 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:29 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:30 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:31 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:22 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:33 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:34 | 133 | +---------+---------+------------+---------------------+--------+ So the reprocessing would take an existing row of data created at the granularity of production event and modify the granularity to minutes, eliminating redundant (Event End Time, Time) columns while doing so. It assumes a constant rate of production and divides output by the difference in minutes plus one to populate the new table's Output column. I know this can be done in code...but can it be done entirely in a MySQL insert statement (or otherwise entirely in MySQL)? I am thinking of a INSERT ... INTO construction but keep getting stuck. An additional complexity is that there are hundreds of machines to include in the operation so there will be multiple rows (one for each machine) for each minute of the day. Any ideas would be much appreciated. Thanks.

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• How do I label a group of radio boxes for WCAG / 508 Compliance? Is ASP.NET doing it wrong?

  - by Mark Brittingham

  I am trying to bring an existing web site into greater conformance with WCAG 2.0 Guidelines and am a bit confused over the output emitted by Microsoft (ASP.NET 4.0 although it was the same in 3.5). Suppose you have a question like: "How would you rate your health?" and a set of 5 answers created using an ASP.NET RadioButtonList. I place the question in an asp:Label with an "AssociatedControlID" that matches the ID of the RadioButtonList (e.g. "SelfRatingBox"). Seems pretty easy... Only the output that is generated has an html "label" with a "For" that is equal to the ID of a table that wraps up the RadioButtons. I assumed that this would work with page readers but our 508 compliance guy is saying that the reader isn't associating the label with the radio controls. The WCAG guidelines indicate that you have to use a fieldset around the entire group and a legend to capture the associated text (the question). So what gives? It would be ideal if MS could take my label and the radiobuttonlist and generate the appropriate fieldset and legend tags but it seems pretty clear that to achieve WCAG compliance, I'll have to roll my own. Is this correct or am I missing something?

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• How to improve performance of non-scalar aggregations on denormalized tables

  - by The Lazy DBA

  Suppose we have a denormalized table with about 80 columns, and grows at the rate of ~10 million rows (about 5GB) per month. We currently have 3 1/2 years of data (~400M rows, ~200GB). We create a clustered index to best suit retrieving data from the table on the following columns that serve as our primary key... [FileDate] ASC, [Region] ASC, [KeyValue1] ASC, [KeyValue2] ASC ... because when we query the table, we always have the entire primary key. So these queries always result in clustered index seeks and are therefore very fast, and fragmentation is kept to a minimum. However, we do have a situation where we want to get the most recent FileDate for every Region, typically for reports, i.e. SELECT [Region] , MAX([FileDate]) AS [FileDate] FROM HugeTable GROUP BY [Region] The "best" solution I can come up to this is to create a non-clustered index on Region. Although it means an additional insert on the table during loads, the hit isn't minimal (we load 4 times per day, so fewer than 100,000 additional index inserts per load). Since the table is also partitioned by FileDate, results to our query come back quickly enough (200ms or so), and that result set is cached until the next load. However I'm guessing that someone with more data warehousing experience might have a solution that's more optimal, as this, for some reason, doesn't "feel right".

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• Neural Network with softmax activation

  - by Cambium

  This is more or less a research project for a course, and my understanding of NN is very/fairly limited, so please be patient :) ============== I am currently in the process of building a neural network that attempts to examine an input dataset and output the probability/likelihood of each classification (there are 5 different classifications). Naturally, the sum of all output nodes should add up to 1. Currently, I have two layers, and I set the hidden layer to contain 10 nodes. I came up with two different types of implementations 1) Logistic sigmoid for hidden layer activation, softmax for output activation 2) Softmax for both hidden layer and output activation I am using gradient descent to find local maximums in order to adjust the hidden nodes' weights and the output nodes' weights. I am certain in that I have this correct for sigmoid. I am less certain with softmax (or whether I can use gradient descent at all), after a bit of researching, I couldn't find the answer and decided to compute the derivative myself and obtained softmax'(x) = softmax(x) - softmax(x)^2 (this returns an column vector of size n). I have also looked into the MATLAB NN toolkit, the derivative of softmax provided by the toolkit returned a square matrix of size nxn, where the diagonal coincides with the softmax'(x) that I calculated by hand; and I am not sure how to interpret the output matrix. I ran each implementation with a learning rate of 0.001 and 1000 iterations of back propagation. However, my NN returns 0.2 (an even distribution) for all five output nodes, for any subset of the input dataset. My conclusions: o I am fairly certain that my gradient of descent is incorrectly done, but I have no idea how to fix this. o Perhaps I am not using enough hidden nodes o Perhaps I should increase the number of layers Any help would be greatly appreciated! The dataset I am working with can be found here (processed Cleveland): http://archive.ics.uci.edu/ml/datasets/Heart+Disease

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