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• Reversible pseudo-random sequence generator

  - by user350651

  I would like some sort of method to create a fairly long sequence of random numbers that I can flip through backwards and forwards. Like a machine with "next" and "previous" buttons, that will give you random numbers. Something like 10-bit resolution (i.e. positive integers in a range from 0 to 1023) is enough, and a sequence of 100k numbers. It's for a simple game-type app, I don't need encryption-strength randomness or anything, but I want it to feel fairly random. I have a limited amount of memory available though, so I can't just generate a chunk of random data and go through it. I need to get the numbers in "interactive time" - I can easily spend a few ms thinking about the next number, but not comfortably much more than that. Eventually it will run on some sort of microcontroller, probably just an Arduino. I could do it with a simple linear congruential generator (LCG). Going forwards is simple, to go backwards I'd have to cache the most recent numbers and store some points at intervals so I can recreate the sequence from there. But maybe there IS some pseudo-random generator that allows you to go both forwards and forwards? It should be possible to hook up two linear feedback shift registers (LFSRs) to roll in different directions, no? Or maybe I can just get by with garbling the index number using a hash function of some sort? I'm going to try that first. Any other ideas?

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• Reducing Time Complexity in Java

  - by Koeneuze

  Right, this is from an older exam which i'm using to prepare my own exam in january. We are given the following method: public static void Oorspronkelijk() { String bs = "Dit is een boodschap aan de wereld"; int max = -1; char let = '*'; for (int i=0;i<bs.length();i++) { int tel = 1; for (int j=i+1;j<bs.length();j++) { if (bs.charAt(j) == bs.charAt(i)) tel++; } if (tel > max) { max = tel; let = bs.charAt(i); } } System.out.println(max + " keer " + let); } The questions are: what is the output? - Since the code is just an algorithm to determine the most occuring character, the output is "6 keer " (6 times space) What is the time complexity of this code? Fairly sure it's O(n²), unless someone thinks otherwise? Can you reduce the time complexity, and if so, how? Well, you can. I've received some help already and managed to get the following code: public static void Nieuw() { String bs = "Dit is een boodschap aan de wereld"; HashMap<Character, Integer> letters = new HashMap<Character, Integer>(); char max = bs.charAt(0); for (int i=0;i<bs.length();i++) { char let = bs.charAt(i); if(!letters.containsKey(let)) { letters.put(let,0); } int tel = letters.get(let)+1; letters.put(let,tel); if(letters.get(max)<tel) { max = let; } } System.out.println(letters.get(max) + " keer " + max); } However, I'm uncertain of the time complexity of this new code: Is it O(n) because you only use one for-loop, or does the fact we require the use of the HashMap's get methods make it O(n log n) ? And if someone knows an even better way of reducing the time complexity, please do tell! :)

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• Python - wxPython custom button -> unbound method __init__()? what?

  - by Wallter

  After looking at questions like this it doesn't make sense that my __init__(self, parrent, id) would be throwing a unbound error? help? main.py import wx from customButton import customButton from wxPython.wx import * class MyFrame(wx.Frame): def __init__(self, parent, ID, title): wxFrame.__init__(self, parent, ID, title, wxDefaultPosition, wxSize(400, 400)) # Non-important code here... # This is the first declaration of the Button1 # This is also where the ERROR is thrown. # Omitting this line causes the window to execute # flawlessly. self.Button1 = customButton.__init__(self, parent, -1) # ... finishes in a basic wx.program style... customButton.py # I've included all of the code in the file # because have no idea where the bug/error happens import wx from wxPython.wx import * class Custom_Button(wx.PyControl): # The BMP's Over_bmp = None #wxEmptyBitmap(1,1,1) # When the mouse is over Norm_bmp = None #wxEmptyBitmap(1,1,1) # The normal BMP Push_bmp = None #wxEmptyBitmap(1,1,1) # The down BMP def __init__(self, parent, id, **kwargs): wx.PyControl.__init__(self,parent, id, **kwargs) # Set the BMP's to the ones given in the constructor #self.Over_bmp = wx.Bitmap(wx.Image(MOUSE_OVER_BMP, wx.BITMAP_TYPE_ANY).ConvertToBitmap()) #self.Norm_bmp = wx.Bitmap(wx.Image(NORM_BMP, wx.BITMAP_TYPE_ANY).ConvertToBitmap()) #self.Push_bmp = wx.Bitmap(wx.Image(PUSH_BMP, wx.BITMAP_TYPE_ANY).ConvertToBitmap()) #self.Pos_bmp = self.pos self.Bind(wx.EVT_LEFT_DOWN, self._onMouseDown) self.Bind(wx.EVT_LEFT_UP, self._onMouseUp) self.Bind(wx.EVT_LEAVE_WINDOW, self._onMouseLeave) self.Bind(wx.EVT_ENTER_WINDOW, self._onMouseEnter) self.Bind(wx.EVT_ERASE_BACKGROUND,self._onEraseBackground) self.Bind(wx.EVT_PAINT,self._onPaint) self._mouseIn = self._mouseDown = False def _onMouseEnter(self, event): self._mouseIn = True def _onMouseLeave(self, event): self._mouseIn = False def _onMouseDown(self, event): self._mouseDown = True def _onMouseUp(self, event): self._mouseDown = False self.sendButtonEvent() def sendButtonEvent(self): event = wx.CommandEvent(wx.wxEVT_COMMAND_BUTTON_CLICKED, self.GetId()) event.SetInt(0) event.SetEventObject(self) self.GetEventHandler().ProcessEvent(event) def _onEraseBackground(self,event): # reduce flicker pass def _onPaint(self, event): dc = wx.BufferedPaintDC(self) dc.SetFont(self.GetFont()) dc.SetBackground(wx.Brush(self.GetBackgroundColour())) dc.Clear() dc.DrawBitmap(self.Norm_bmp) # draw whatever you want to draw # draw glossy bitmaps e.g. dc.DrawBitmap if self._mouseIn: # If the Mouse is over the button dc.DrawBitmap(self, self.Mouse_over_bmp, self.Pos_bmp, useMask=False) if self._mouseDown: # If the Mouse clicks the button dc.DrawBitmap(self, self.Push_bmp, self.Pos_bmp, useMask=False)

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• Is it legal to have different SOAP namespaces/versions between the request and response?

  - by Lord Torgamus

  THIRD EDIT: I now believe that this problem is due to a SOAP version mismatch (1.1 request, 1.2 response) masquerading as a namespace problem. Is it illegal to mix versions, or just bad style? Am I completely out of luck if I can't change my SOAP version or the service's? SECOND EDIT: Clarified error message, and tried to reduce "tl;dr"-ness. EDIT: [Link deleted, not related] Using soapUI, I'm sending a request that starts with: <soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" ... and getting a response that starts with: <soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" ... I know the service is getting the info, because processes down the line are working. However, my soapUI teststep fails. It has two active assertions: "SOAP Response" and "Not SOAP Fault." The failure marker is next to "SOAP Response," with the following message: line -1: Element Envelope@http://www.w3.org/2003/05/soap-envelope is not a valid Envelope@http://schemas.xmlsoap.org/soap/envelope/ document or a valid substitution. I have tried mixing and matching the namespace prefixes and schema URLs. Changing prefixes seems to have no effect; changing URLs causes a VersionMismatch error. I have also tried to use a substitution group, but that doesn't seem to be legal.

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• Java: Efficiency of the readLine method of the BufferedReader and possible alternatives

  - by Luhar

  We are working to reduce the latency and increase the performance of a process written in Java that consumes data (xml strings) from a socket via the readLine() method of the BufferedReader class. The data is delimited by the end of line separater (\n), and each line can be of a variable length (6KBits - 32KBits). Our code looks like: Socket sock = connection; InputStream in = sock.getInputStream(); BufferedReader inputReader = new BufferedReader(new InputStreamReader(in)); ... do { String input = inputReader.readLine(); // Executor call to parse the input thread in a seperate thread }while(true) So I have a couple of questions: Will the inputReader.readLine() method return as soon as it hits the \n character or will it wait till the buffer is full? Is there a faster of picking up data from the socket than using a BufferedReader? What happens when the size of the input string is smaller than the size of the Socket's receive buffer? What happens when the size of the input string is bigger than the size of the Socket's receive buffer? I am getting to grips (slowly) with Java's IO libraries, so any pointers are much appreciated. Thank you!

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• File Storage for Web Applications: Filesystem vs DB vs NoSQL engines

  - by El Yobo

  I have a web application that stores a lot of user generated files. Currently these are all stored on the server filesystem, which has several downsides for me. When we move "folders" (as defined by our application) we also have to move the files on disk (although this is more due to strange design decisions on the part of the original developers than a requirement of storing things on the filesystem). It's hard to write tests for file system actions; I have a mock filesystem class that logs actions like move, delete etc, without performing them, which more or less does the job, but I don't have 100% confidence in the tests. I will be adding some other jobs which need to access the files from other service to perform additional tasks (e.g. indexing in Solr, generating thumbnails, movie format conversion), so I need to get at the files remotely. Doing this over network shares seems dodgy... Dealing with permissions on the filesystem as sometimes given us problems in the past, although now that we've moved to a pure Linux environment this should be less of an issue. What are the downsides of storing files as BLOBs in MySQL? I guess that it would massively increase the database size and reduce the effectiveness of caches, but are there other problems? Do the same problems exist with NoSQL systems like Cassandra? Does anyone have any other suggestions that might be appropriate?

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• Is there a way to trace through only project source in Delphi?

  - by Justin

  I'm using Delphi 2010 and I'm wondering if there's a way to trace through code which is in the project without tracing through calls to included VCLs. For example - you put in a breakpoint and then use Shift+F7 to trace through line-by-line. Now you run into a call to some lengthy procedure in a VCL - in my case it's often a Measurement Studio or other component that draws the doodads for a bunch of I/O, OPC, or other bits. At any rate, what happens is that the debugger hops out of the active source file, opens the component source, and traces through that line by line. Often this is hundreds or thousands of lines of code I don't care about - I just want to have it execute and return to the next source line in MY project. Obviously you can do this by setting breakpoints around every instance of an external call, but often there are too many to make this practical - I'd be spending an hour setting a hundred breakpoints every time I wanted to step through a section of code. Is there a setting or a tool somewhere that can do this? Allow one to trace through code within the project while silently executing code which is external to the project? Thanks in advance, Stack Overflow!

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• Wizard style navigation, dismissing a view and showing another one

  - by Robin Jamieson

  I'm making a set of screens similar to a wizard and I'd like to know how to make a view dismiss itself and its parent view and immediately show a 'DoneScreen' without worrying about resource leaks. My views look like the following: Base -> Level1 -> DoneScreen -> Level2 -> DoneScreen The Level1 controller is a navigation controller created with a view.xib and shown with [self presentModalViewController ...] by the Base controller. The Level1 controller is also responsible for creating the 'DoneScreen' which may be shown instead of the Level2 Screen based on a certain criteria. When the user taps a button on the screen, the Level1 controller instantiates the the Level2 controller and it displays it via [self.navigationController pushViewController ..] and Level2 controller's view has a 'Next' button. When the use hits the 'Next' button in the Level2 screen, I need to dismiss the current Level2's view as well as the Level1's view and display the 'DoneScreen', which would have been created and passed in to the Level2 controller from Level1. (partly to reduce code duplication, and partly to separate responsibilities among the controllers) In the Level2 controller, if I show the 'DoneScreen' first and dismiss itself with [self.navigationController popViewControllerAnimated:YES]; then the Level1 controller's modal view is still present above the 'Base' but under the Done screen. What's a good way to clear out all of these views except the Base and then show the 'DoneScreen'? Any good suggestions on how to get this done in a simple but elegant manner?

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• How to disable selective keys on the keyboard?

  - by Vilx-

  I'd like to write an application which disables certain keys on the keyboard while it's working. More specifically I'm interested in keys that might make the application loose focus (like ALT+TAB, WinKey, Ctrl+Shift+Esc, etc.) The need for this is has to do with babies/animals bashing wildly at the keyboard. :) My first idea was to use SetWindowsHookEx, however I ran into a problem. Since I need a global hook, the procedure would have to reside in a .DLL which would get injected in all active applications. But a .DLL can be either 64-bit or 32-bit, not both. And on a 64-bit system there are both types of applications. I guess then that I must write two copies of the hook .DLL - one for 32-bit and the other for 64-bit. And then I'd also have to launch two copies of the application as well, because the application first has to load the DLL itself before it can pass it on to SetWindowsHookEx(). Sounds pretty clumsy and awkward. Is there perhaps a better way? Or maybe I've misunderstood something?

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• Does Perl auto-vivify variables used as references in subroutine calls?

  - by FM

  I've declared 2010 to be the year of higher-order programming, so I'm learning Haskell. The introduction has a slick quick-sort demo, and I thought, "Hey, that's easy to do in Perl". It turned to be easier than I expected. Note that I don't have to worry about whether my partitions ($less and $more) are defined. Normally you can't use an undefined value as an array reference. use strict; use warnings; use List::MoreUtils qw(part); my @data = (5,6,7,4,2,9,10,9,5,1); my @sorted = qsort(@data); print "@sorted\n"; sub qsort { return unless @_; my $pivot = shift @_; my ($less, $more) = part { $_ < $pivot ? 0 : 1 } @_; # Works, even though $less and $more are sometimes undefined. return qsort(@$less), $pivot, qsort(@$more); } As best I can tell, Perl will auto-vivify a variable that you try to use as a reference -- but only if you are passing it to a subroutine. For example, my call to foo() works, but not the attempted print. use Data::Dumper qw(Dumper); sub foo { print "Running foo(@_)\n" } my ($x); print Dumper($x); # Fatal: Can't use an undefined value as an ARRAY reference. # print @$x, "\n"; # But this works. foo(@$x); # Auto-vivification: $x is now []. print Dumper($x); My questions: Am I understanding this behavior correctly? What is the explanation or reasoning behind why Perl does this? Is this behavior explained anywhere in the docs?

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• Opening a Unicode file with Perl

  - by Jaco Pretorius

  I'm using osql to run several sql scripts against a database and then I need to look at the results file to check if any errors occurred. The problem is that perl doesn't seem to like the fact that the results files are unicode. I wrote a little test script to test it and the output comes out all warbled. $file = shift; open OUTPUT, $file or die "Can't open $file: $!\n"; while (<OUTPUT>) { print $_; if (/Invalid|invalid|Cannot|cannot/) { push(@invalids, $file); print "invalid file - $inputfile - schedule for retry\n"; last; } } Any ideas? I've tried decoding using decode_utf8 but it makes no difference. I've also tried to set the encoding when opening the file. I think the problem might be that osql puts the result file in UTF-16 format, but I'm not sure. When I open the file in textpad it just tells me 'Unicode'. Edit: Using perl v5.8.8

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• Reducing the opacity on a div without reducing the opacity of the contents

  - by user352744

  Want to reduce the opacity of page contents container background without reducing the opacity of the contents. <div id="container"> <div id="page contents"> page contents goes here, like amazing articles and all that. </div> </div> Needs to be able to expand with the content, thus can't have a fixed height. Absolute positioning it underneath the content will mean there will be no relationship between the two divs and it wont expand with the contents, so I think this is a dead end, feel free to say otherwise. Can't use Jquery as could be too laggy and not instant. Other options preferred please. May have to use 'png' background images but were hoping not to as it is a template and needs to be able to change colour based on colour schemes. Could generate images on demand but not ideal. Oh and to top it off cant use CSS3 as wont work in IE! of course! Any suggestions?

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• How to configure Eclipse XML formatting?

  - by tputkonen

  I would like to change the way Eclipse formats XML files. For example, if I have in pom.xml file a section as follows: <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>3.8.1</version> <scope>test</scope> </dependency> After ctrl+shift+f it will look like: <dependency> <groupId> junit </groupId> <artifactId> junit </artifactId> <version> 3.8.1 </version> <scope> test </scope> </dependency> I prefer the first version, so how to configure Eclipse to format XML files to look like that?

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• Is it wise to use temporary tables?

  - by Industrial

  Hi guys, We have a mySQL database table for products. We are utilizing a cache layer to reduce database load, but we think that it's a good idea to minimize the actual data needed to be stored in the cache layer to speed up the application further. All the products in the database, that is visible to visitors have a price attached to them: The prices are stored in a different table, called prices . There are multiple price categories depending on which discount level each visitor (customer) applies to. From time to time, there are campaigns which means that a special price for each product is available. The special prices are stored in a table called specials. Is it a bad to make a temp table that binds the tables together? It would only have the neccessary information and would ofcourse be cached. -------------|-------------|------------ | productId | hasPrice | hasSpecial -------------|-------------|------------ 1 | 1 | 0 2 | 1 | 1 By doing such, it would be super easy to know if the specific product really has a price, without having to iterate through the complete prices or specials table each time a product should be listed or presented. Are temp tables a common thing for web applications or is it just bad design?

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• HDFS some datanodes of cluster are suddenly disconnected while reducers are running

  - by user1429825

  I have 8 slave computers and 1 master computer for running Hadoop (ver 0.21) some datanodes of cluster are suddenly disconnected while I was running MapReduce code on 10GB data After all mappers finished and around 80% of reducers was processed, randomly one or more datanode disconned from network. and then the other datanodes start to disappear from network even if I killed the MapReduce job when I found some datanode was disconnected. I've tried to change dfs.datanode.max.xcievers to 4096, turned off fire-walls of all computing node, disabled selinux and increased the number of file open limit to 20000 but they didn't work at all... anyone have a idea to solve this problem? followings are error log from mapreduce 12/06/01 12:31:29 INFO mapreduce.Job: Task Id : attempt_201206011227_0001_r_000006_0, Status : FAILED java.io.IOException: Bad connect ack with firstBadLink as ***.***.***.148:20010 at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.createBlockOutputStream(DFSOutputStream.java:889) at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.nextBlockOutputStream(DFSOutputStream.java:820) at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.run(DFSOutputStream.java:427) and followings are logs from datanode 2012-06-01 13:01:01,118 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: Receiving block blk_-5549263231281364844_3453 src: /*.*.*.147:56205 dest: /*.*.*.142:20010 2012-06-01 13:01:01,136 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: DatanodeRegistration(*.*.*.142:20010, storageID=DS-1534489105-*.*.*.142-20010-1337757934836, infoPort=20075, ipcPort=20020) Starting thread to transfer block blk_-3849519151985279385_5906 to *.*.*.147:20010 2012-06-01 13:01:19,135 WARN org.apache.hadoop.hdfs.server.datanode.DataNode: DatanodeRegistration(*.*.*.142:20010, storageID=DS-1534489105-*.*.*.142-20010-1337757934836, infoPort=20075, ipcPort=20020):Failed to transfer blk_-5797481564121417802_3453 to *.*.*.146:20010 got java.net.ConnectException: > Connection timed out at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method) at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:701) at org.apache.hadoop.net.SocketIOWithTimeout.connect(SocketIOWithTimeout.java:206) at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:373) at org.apache.hadoop.hdfs.server.datanode.DataNode$DataTransfer.run(DataNode.java:1257) at java.lang.Thread.run(Thread.java:722) 2012-06-01 13:06:20,342 INFO org.apache.hadoop.hdfs.server.datanode.DataBlockScanner: Verification succeeded for blk_6674438989226364081_3453 2012-06-01 13:09:01,781 WARN org.apache.hadoop.hdfs.server.datanode.DataNode: DatanodeRegistration(*.*.*.142:20010, storageID=DS-1534489105-*.*.*.142-20010-1337757934836, infoPort=20075, ipcPort=20020):Failed to transfer blk_-3849519151985279385_5906 to *.*.*.147:20010 got java.net.SocketTimeoutException: 480000 millis timeout while waiting for channel to be ready for write. ch : java.nio.channels.SocketChannel[connected local=/*.*.*.142:60057 remote=/*.*.*.147:20010] at org.apache.hadoop.net.SocketIOWithTimeout.waitForIO(SocketIOWithTimeout.java:246) at org.apache.hadoop.net.SocketOutputStream.waitForWritable(SocketOutputStream.java:164) at org.apache.hadoop.net.SocketOutputStream.transferToFully(SocketOutputStream.java:203) at org.apache.hadoop.hdfs.server.datanode.BlockSender.sendChunks(BlockSender.java:388) at org.apache.hadoop.hdfs.server.datanode.BlockSender.sendBlock(BlockSender.java:476) at org.apache.hadoop.hdfs.server.datanode.DataNode$DataTransfer.run(DataNode.java:1284) at java.lang.Thread.run(Thread.java:722) hdfs-site.xml <configuration> <property> <name>dfs.name.dir</name> <value>/home/hadoop/data/name</value> </property> <property> <name>dfs.data.dir</name> <value>/home/hadoop/data/hdfs1,/home/hadoop/data/hdfs2,/home/hadoop/data/hdfs3,/home/hadoop/data/hdfs4,/home/hadoop/data/hdfs5</value> </property> <property> <name>dfs.replication</name> <value>3</value> </property> <property> <name>dfs.datanode.max.xcievers</name> <value>4096</value> </property> <property> <name>dfs.http.address</name> <value>0.0.0.0:20070</value> <description>50070 The address and the base port where the dfs namenode web ui will listen on. If the port is 0 then the server will start on a free port. </description> </property> <property> <name>dfs.datanode.http.address</name> <value>0.0.0.0:20075</value> <description>50075 The datanode http server address and port. If the port is 0 then the server will start on a free port. </description> </property> <property> <name>dfs.secondary.http.address</name> <value>0.0.0.0:20090</value> <description>50090 The secondary namenode http server address and port. If the port is 0 then the server will start on a free port. </description> </property> <property> <name>dfs.datanode.address</name> <value>0.0.0.0:20010</value> <description>50010 The address where the datanode server will listen to. If the port is 0 then the server will start on a free port. </description> <property> <name>dfs.datanode.ipc.address</name> <value>0.0.0.0:20020</value> <description>50020 The datanode ipc server address and port. If the port is 0 then the server will start on a free port. </description> </property> <property> <name>dfs.datanode.https.address</name> <value>0.0.0.0:20475</value> </property> <property> <name>dfs.https.address</name> <value>0.0.0.0:20470</value> </property> </configuration> mapred-site.xml <configuration> <property> <name>mapred.job.tracker</name> <value>masternode:29001</value> </property> <property> <name>mapred.system.dir</name> <value>/home/hadoop/data/mapreduce/system</value> </property> <property> <name>mapred.local.dir</name> <value>/home/hadoop/data/mapreduce/local</value> </property> <property> <name>mapred.map.tasks</name> <value>32</value> <description> default number of map tasks per job.</description> </property> <property> <name>mapred.tasktracker.map.tasks.maximum</name> <value>4</value> </property> <property> <name>mapred.reduce.tasks</name> <value>8</value> <description> default number of reduce tasks per job.</description> </property> <property> <name>mapred.map.child.java.opts</name> <value>-Xmx2048M</value> </property> <property> <name>io.sort.mb</name> <value>500</value> </property> <property> <name>mapred.task.timeout</name> <value>1800000</value> <!-- 30 minutes --> </property> <property> <name>mapred.job.tracker.http.address</name> <value>0.0.0.0:20030</value> <description> 50030 The job tracker http server address and port the server will listen on. If the port is 0 then the server will start on a free port. </description> </property> <property> <name>mapred.task.tracker.http.address</name> <value>0.0.0.0:20060</value> <description> 50060 </property> </configuration>

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• Optimization headers for UITableView?

  - by Pask

  I have an optimization problem for the headers of a table with plain style. If I use the standard view for the table (the classic gray with titles set by titleForHeaderInSection:) everything is ok and the scrolling is smooth and immediate. When, instead, use this code to set my personal view: - (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section { return [self headerPerTitolo:[titoliSezioni objectAtIndex:section]]; } - (UIImageView *)headerPerTitolo:(NSString *)titolo { UIImageView *headerView = [[[UIImageView alloc] initWithFrame:CGRectMake(10.0, 0.0, 320.0, 44.0)] autorelease]; headerView.image = [UIImage imageNamed:kNomeImmagineHeader]; headerView.alpha = kAlphaSezioniTablePlain; UILabel * headerLabel = [[[UILabel alloc] initWithFrame:CGRectZero] autorelease]; headerLabel.backgroundColor = [UIColor clearColor]; headerLabel.opaque = NO; headerLabel.textColor = [UIColor whiteColor]; headerLabel.font = [UIFont boldSystemFontOfSize:16]; headerLabel.frame = CGRectMake(10.0,-11.0, 320.0, 44.0); headerLabel.textAlignment = UITextAlignmentLeft; headerLabel.text = titolo; [headerView addSubview:headerLabel]; return headerView; } scrolling is jerky and not immediate (sliding the finger on the screen does not match an immediate shift of the table). I do not know what caused this problem, maybe the fact that every time the method viewForHeaderInSection: is called, the code runs to create a new UIImageView. I tried many ways to solve the problem, such as creating an array of all the necessary view: apart from more time spent loading at startup, there is a continuing problem of low reactivity of the table. 've Attempted by reducing the size of UIImageView positioned from about 66 KB to 4 KB: not only has a deterioration in quality of colors (which distorts a bit 'original graphics), but ... the problem persists! Perhaps you have suggestions about it, or know me obscure techniques that enable me to optimize this aspect of my application ... I apologize for my English, I used Google for translation.

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• Recommended approach to port to ASP.NET MVC

  - by tshao

  I think many of us used to face the same question, what's the best practices to port existing web forms App to MVC. The situation for me is that we'll support both web forms and MVC at the same time. It means, we create new features in MVC, while maintaining legacy pages in web forms, and they're all in a same project. The point is: we want to keep the DRY (do not repeat yourself) principle and reduce duplicate code as much as possible. The ASPX page is not a problem as we only create new features in MVC, but there're still some shared components we want to re-use the both new / legacy pages: Master page UserControl The question here is: Is that possible to create a common master page / usercontrol that could be used in both web forms and MVC? I know that ViewMasterPage inherits from MasterPage and ViewUserControl inherits from UserControl, so it's maybe OK to let both web forms and MVC ASPX page refer to the MVC version. I did some testing and found sometimes it generates errors during the rendering of usercontrols. Any idea / experience you can share with me? Very appreciate to it.

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• Caching Authentication Data

  - by PartlyCloudy

  Hi, I'm currently implementing a REST web service using CouchDB and RESTlet. The RESTlet layer is mainly for authentication and some minor filtering of the JSON data served by CouchDB: Clients <= HTTP = [ RESTlet <= HTTP = CouchDB ] I'm using CouchDB also to store user login data, because I don't want to add an additional database server for that purpose. Thus, each request to my service causes two CouchDB requests conducted by RESTlet (auth data + "real" request). In order to keep the service as efficent as possible, I want to reduce the number of requests, in this case redundant requests for login data. My idea now is to provide a cache (i.e.LRU-Cache via LinkedHashMap) within my RESTlet application that caches login data, because HTTP caching will probabily not be enough. But how do I invalidate the cache data, once a user changes the password, for instance. Thanks to REST, the application might run on several servers in parallel, and I don't want to create a central instance just to cache login data. Currently, I save requested auth data in the cache and try to auth new requests by using them. If a authentication fails or there is now entry available, I'll dispatch a GET request to my CouchDB storage in order to obtain the actual auth data. So in a worst case, users that have changed their data will perhaps still be able to login with their old credentials. How can I deal with that? Or what is a good strategy to keep the cache(s) up-to-date in general? Thanks in advance.

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• Extend the bootstrap-typeahead in order to take an object instead of a string

  - by Lorraine Bernard

  _.extend($.fn.typeahead.Constructor.prototype, { render: function (items) { var that = this; items = $(items).map(function (i, item) { i = $(that.options.item) .attr('data-value', item[that.options.display]) .attr('data-id', item.id); i.find('a').html(that.highlighter(item)); return i[0]; }); items.first().addClass('active'); this.$menu.html(items); return this; }, select: function () { var val = this.$menu.find('.active').attr('data-value'), id = this.$menu.find('.active').attr('data-id'); this.$element .val(this.updater(val, id)) .change(); return this.hide() } }); return function (element, options) { var getSource = function () { var users = app.userCollection.filter(function (model) { if (options && options.excludeCurrentUser) { return model.id !== app.currentUser.id; } }); return _.map(users, function (user) { return { id: user.get('id'), full_name: user.get('first_name') + ' ' + user.get('last_name') }; }); }; element.typeahead({ minLength: 3, source: getSource, display: 'full_name', sorter: function (items) { var beginswith = [], caseSensitive = [], caseInsensitive = [], item, itemDisplayed; while (item = items.shift()) { itemDisplayed = item[this.options.display]; if (!itemDisplayed.toLowerCase().indexOf(this.query.toLowerCase())) { beginswith.push(item); } else if (~itemDisplayed.indexOf(this.query)) { caseSensitive.push(item); } else { caseInsensitive.push(item); } } return beginswith.concat(caseSensitive, caseInsensitive); }, highlighter: function (item) { var query = this.query.replace(/[\-\[\]{}()*+?.,\\\^$|#\s]/g, '\\$&'); return item[this.options.display].replace(new RegExp('(' + query + ')', 'ig'), function ($1, match) { return '<strong>' + match + '</strong>'; }); }, matcher: function (item) { var value = item[this.options.display]; return { value: ~value.toLowerCase().indexOf(this.query.toLowerCase()), id: item.id }; }, updater: function (item, userId) { options.hiddenInputElement.val(userId); return item; } }); };

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• Trying to get django app to work with mod_wsgi on CentOS 5

  - by David

  I'm running CentOS 5, and am trying to get a django application working with mod_wsgi. I'm using .wsgi settings I got working on Ubuntu. Here is the error: [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] SystemError: dynamic module not initialized properly [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] mod_wsgi (pid=23630): Target WSGI script '/data/hosting/cubedev/apache/django.wsgi' cannot be loaded as Python module. [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] mod_wsgi (pid=23630): Exception occurred processing WSGI script '/data/hosting/cubedev/apache/django.wsgi'. [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] Traceback (most recent call last): [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] File "/data/hosting/cubedev/apache/django.wsgi", line 8, in [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] import django.core.handlers.wsgi [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] File "/opt/python2.6/lib/python2.6/site-packages/django/core/handlers/wsgi.py", line 1, in [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] from threading import Lock [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] File "/opt/python2.6/lib/python2.6/threading.py", line 13, in [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] from functools import wraps [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] File "/opt/python2.6/lib/python2.6/functools.py", line 10, in [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] from _functools import partial, reduce [Thu Mar 04 10:52:15 2010] [error] [client 10.1.0.251] SystemError: dynamic module not initialized properly And here is my .wsgi file import os import sys os.environ['PYTHON_EGG_CACHE'] = '/tmp/django/' os.environ['DJANGO_SETTINGS_MODULE'] = 'cube.settings' sys.path.append('/data/hosting/cubedev') import django.core.handlers.wsgi application = django.core.handlers.wsgi.WSGIHandler()

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• Speeding up inner-joins and subqueries while restricting row size and table membership

  - by hiffy

  I'm developing an rss feed reader that uses a bayesian filter to filter out boring blog posts. The Stream table is meant to act as a FIFO buffer from which the webapp will consume 'entries'. I use it to store the temporary relationship between entries, users and bayesian filter classifications. After a user marks an entry as read, it will be added to the metadata table (so that a user isn't presented with material they have already read), and deleted from the stream table. Every three minutes, a background process will repopulate the Stream table with new entries (i.e. whenever the daemon adds new entries after the checks the rss feeds for updates). Problem: The query I came up with is hella slow. More importantly, the Stream table only needs to hold one hundred unread entries at a time; it'll reduce duplication, make processing faster and give me some flexibility with how I display the entries. The query (takes about 9 seconds on 3600 items with no indexes): insert into stream(entry_id, user_id) select entries.id, subscriptions_users.user_id from entries inner join subscriptions_users on subscriptions_users.subscription_id = entries.subscription_id where subscriptions_users.user_id = 1 and entries.id not in (select entry_id from metadata where metadata.user_id = 1) and entries.id not in (select entry_id from stream where user_id = 1); The query explained: insert into stream all of the entries from a user's subscription list (subscriptions_users) that the user has not read (i.e. do not exist in metadata) and which do not already exist in the stream. Attempted solution: adding limit 100 to the end speeds up the query considerably, but upon repeated executions will keep on adding a different set of 100 entries that do not already exist in the table (with each successful query taking longer and longer). This is close but not quite what I wanted to do. Does anyone have any advice (nosql?) or know a more efficient way of composing the query?

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• C++ Switch won't compile with externally defined variable used as case

  - by C Nielsen

  I'm writing C++ using the MinGW GNU compiler and the problem occurs when I try to use an externally defined integer variable as a case in a switch statement. I get the following compiler error: "case label does not reduce to an integer constant". Because I've defined the integer variable as extern I believe that it should compile, does anyone know what the problem may be? Below is an example: test.cpp #include <iostream> #include "x_def.h" int main() { std::cout << "Main Entered" << std::endl; switch(0) { case test_int: std::cout << "Case X" << std::endl; break; default: std::cout << "Case Default" << std::endl; break; } return 0; } x_def.h extern const int test_int; x_def.cpp const int test_int = 0; This code will compile correctly on Visual C++ 2008. Furthermore a Montanan friend of mine checked the ISO C++ standard and it appears that any const-integer expression should work. Is this possibly a compiler bug or have I missed something obvious? Here's my compiler version information: Reading specs from C:/MinGW/bin/../lib/gcc/mingw32/3.4.5/specs Configured with: ../gcc-3.4.5-20060117-3/configure --with-gcc --with-gnu-ld --with-gnu-as --host=mingw32 --target=mingw32 --prefix=/mingw --enable-threads --disable-nls --enable-languages=c,c++,f77,ada,objc,java --disable-win32-registry --disable-shared --enable-sjlj-exceptions --enable-libgcj --disable-java-awt --without-x --enable-java-gc=boehm --disable-libgcj-debug --enable-interpreter --enable-hash-synchronization --enable-libstdcxx-debug Thread model: win32 gcc version 3.4.5 (mingw-vista special r3)

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• Decoding a jpg in the background in WP7

  - by Shahar Prish

  I have a bunch of apps in the marketplace, and so far I have been able, by changing my functionality or going the extra mile, to work around the issue of being unable to decode a jpg in the background into a WriteableBitmap. I am finding a situation where I can't think of good ways to "work around" the issue. I need to decode the image I get from MediaLibrary, reduce it's resolution to something managable (800x800), rotate it potentially and save to local storage. By far, the thing that takes the most time (80%) is decoding the bitmap to 800x800 - it takes between 700ms to 1000 ms. A user may add 7-10 images when starting, which translates to ~10 seconds of waiting for the images being added. I tried doing this lazily, but at some point you need to pay the piper and the app essentially stutters for ~1000ms at that point and the experience is not great. Is there an alternative I am missing for loading the image in the background somehow? (Note on why CreateOptions.BackgroundCreation is no good for me: It loads the image into a BitmapImage which is great if you want to just use it, but not so great for what I need to do which is create a copy in Isolated Storage).

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• Condensing repeating JQuery code

  - by Craig Ward

  I have a page that has a large image on it with a number of thumbnails. When you mouse over a thumbnail the main image changes to the image you have just rolled your mouse over. The problem is the more thumbnails I have, the more repeated code I have. How could I reduce it? The Jquery code is as follows. <script type="text/javascript"> $('#thumb1') .mouseover(function(){ $('#big_img').fadeOut('slow', function(){ $('#big_img').attr('src', '0001.jpg'); $('#big_img').fadeIn('slow'); }); }); $('#thumb2') .mouseover(function(){ $('#big_img').fadeOut('slow', function(){ $('#big_img').attr('src', 'p_0002.jpg'); $('#big_img').fadeIn('slow'); }); }); $('#thumb3') .mouseover(function(){ $('#big_img').fadeOut('slow', function(){ $('#big_img').attr('src', '_img/p_0003.jpg'); $('#big_img').fadeIn('slow'); }); }); $('#thumb4') .mouseover(function(){ $('#big_img').fadeOut('slow', function(){ $('#big_img').attr('src', '0004.jpg'); $('#big_img').fadeIn('slow'); }); }); </script> #big_img = the ID of the full size image #thumb1, #thumb2, #thumb3, #thumb4 = The ID's of the thumbnails The main code for the page is PHP if that helps.

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• How to set ReceiveBufferSize for UDPClient? or Does it make sense to set? C#

  - by Jack

  Hello all. I am implementing a UDP data transfer thing. I have several questions about UDP buffer. I am using UDPClient to do the UDP send / receive. and my broadband bandwidth is 150KB/s (bytes/s, not bps). I send out a 500B datagram out to 27 hosts 27 hosts send back 10KB datagram back if they receive. So, I should receive 27 responses, right? however, I only get averagely 8 - 12 instead. I then tried to reduce the size of the response down to 500B, yes, I receive all. A thought of mine is that if all 27 hosts send back 10KB response at almost same time, the incoming traffic will be 270KB/s (likely), that exceeds my incoming bandwidth so loss happens. Am I right? But I think even if the incoming traffic exceeds the bandwidth, is the Windows supposed to put the datagram in the buffer and wait for receive? I then suspect that maybe the ReceiveBufferSize of my UdpClient is too small? by default, it is 8092B?? I don't know whether I am all right at these points. Please give me some help.

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