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• C# cross thread dialogue co-operation

  - by John Attridge

  K I am looking at a primarily single thread windows forms application in 3.0. Recently my boss had a progress dialogue added on a separate thread so the user would see some activity when the main thread went away and did some heavy duty work and locked out the GUI. The above works fine unless the user switches applications or minimizes as the progress form sits top most and will not disappear with the main application. This is not so bad if there are lots of little operations as the event structure of the main form catches up with its events when it gets time so minimized and active flags can be checked and thus the dialog thread can hide or show itself accordingly. But if a long running sql operation kicks off then no events fire. I have tried intercepting the WndProc command but this also appears queued when a long running sql operation is executing. I have also tried picking up the processes, finding the current app and checking various memory values isiconic and the like inside the progress thread but until the sql operation finishes none of these get updated. Removing the topmost causes the dialog to disappear when another app activates but if the main app is then brought back it does not appear again. So I need a way to find out if the other thread is minimized or no longer active that does not involve querying the actual thread as that locks until the sql operation finishes. Now I know that this is not the best way to write this and it would be better to have all the heavy processing on separate threads leaving the GUI free but as this is a huge ancient legacy app the time to re-write in that fashion will not be provided so I have to work with what I have got. Any help is appreciated

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• How can I speed up a 1800-line PHP include? It's slowing my pageload down to 10sec/view

  - by somerandomguy

  I designed my code to put all important functions in a single PHP file that's now 1800 lines long. I call it in other PHP files--AJAX processors, for example--with a simple "require_once("codeBank.php")". I'm discovering that it takes about 10 seconds to load up all those functions, even though I have nothing more than a few global arrays and a bunch of other functions involved. The main AJAX processor code, for example, is taking 8 seconds just to do a simple syntax verification (whose operational function is stored in codeBank.php). When I comment out the require_once, my AJAX response time speeds up from 10sec to 40ms, so it's pretty clear that PHP's trying to do something with those 1800 lines of functions. That's even with APC installed, which is surprising. What should I do to get my code speed back to the sub-100ms level? Am I failing to get the cache's benefit somehow? Do I need to cut that single function bank file into different pieces? Are there other subtle things that I could be doing to screw up my response time? Or barring all that, what are some tools to dig further into which PHP operations are hitting speed bumps?

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• Tree iterator, can you optimize this any further?

  - by Ron

  As a follow up to my original question about a small piece of this code I decided to ask a follow up to see if you can do better then what we came up with so far. The code below iterates over a binary tree (left/right = child/next ). I do believe there is room for one less conditional in here (the down boolean). The fastest answer wins! The cnt statement can be multiple statements so lets make sure this appears only once The child() and next() member functions are about 30x as slow as the hasChild() and hasNext() operations. Keep it iterative <-- dropped this requirement as the recursive solution presented was faster. This is C++ code visit order of the nodes must stay as they are in the example below. ( hit parents first then the children then the 'next' nodes). BaseNodePtr is a boost::shared_ptr as thus assignments are slow, avoid any temporary BaseNodePtr variables. Currently this code takes 5897ms to visit 62200000 nodes in a test tree, calling this function 200,000 times. void processTree (BaseNodePtr current, unsigned int & cnt ) { bool down = true; while ( true ) { if ( down ) { while (true) { cnt++; // this can/will be multiple statesments if (!current->hasChild()) break; current = current->child(); } } if ( current->hasNext() ) { down = true; current = current->next(); } else { down = false; current = current->parent(); if (!current) return; // done. } } }

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• localhost + staging + production environments?

  - by Kentor

  Hello, I have a website say www.livesite.com which is currently running. I have been developing a new version of the website on my local machine with http://localhost and then committing my changes with svn to www.testsite.com where I would test the site on the livesite.com server but under another domain (its the same environment as the live site but under a different domain). Now I am ready to release the new version to livesite.com. Doing it the first time is easy, I could just copy & paste everything from testsite.com to livesite.com (not sure its the best way to do it). I want to keep testsite.com as a testing site where I would push updates, test them and once satisfied move to livesite.com but I am not sure how to do that after the new site is launched.. I don't think copy pasting the whole directory is the right way of doing it and it will break the operations of current users on the livesite.com. I also want to keep my svn history on testsite.com. What is the correct way of doing this with SVN ? Thank you so much!

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• Accessing and manipulating lwpf listbox datatemplate elements

  - by black sensei

  Hello good people , i'm trying to achieve a functionality but i'm don't know how to start it. I'm using vs 2008 sp1 and i'm consuming a webservice which returns a collection (is contactInfo[]) that i bind to a ListBox with little datatemplate on it. <ListBox Margin="-146,-124,-143,-118.808" Name="contactListBox" MaxHeight="240" MaxWidth="300" MinHeight="240" MinWidth="300"> <ListBox.ItemTemplate> <DataTemplate> <TextBlock> <CheckBox Name="contactsCheck" Uid="{Binding fullName}" Checked="contacts_Checked" /><Label Content="{Binding fullName}" FontSize="15" FontWeight="Bold"/> <LineBreak/> <Label Content="{Binding mobile}" FontSize="10" FontStyle="Italic" Foreground="DimGray" /> <Label Content="{Binding email}" FontStyle="Italic" FontSize="10" Foreground="DimGray"/> </TextBlock> </DataTemplate> </ListBox.ItemTemplate> </ListBox> Every works fine so far. so When a checkbox is checked i'll like to access the information of the labels (either the) belonging to the same row or attached to it and append the information to a global variable for example (for each checkbox checked). My problem right now is that i don't know how to do that. Can any one shed some light on how to do that? if you notice Checked="contacts_Checked" that's where i planned to perform the operations. thanks for reading and helping out

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• Better way to compare neighboring cells in matrix

  - by HyperCube

  Suppose I have a matrix of size 100x100 and I would like to compare each pixel to its direct neighbor (left, upper, right, lower) and then do some operations on the current matrix or a new one of the same size. A sample code in Python/Numpy could look like the following: (the comparison 0.5 has no meaning, I just want to give a working example for some operation while comparing the neighbors) import numpy as np my_matrix = np.random.rand(100,100) new_matrix = np.array((100,100)) my_range = np.arange(1,99) for i in my_range: for j in my_range: if my_matrix[i,j+1] > 0.5: new_matrix[i,j+1] = 1 if my_matrix[i,j-1] > 0.5: new_matrix[i,j-1] = 1 if my_matrix[i+1,j] > 0.5: new_matrix[i+1,j] = 1 if my_matrix[i-1,j] > 0.5: new_matrix[i-1,j] = 1 if my_matrix[i+1,j+1] > 0.5: new_matrix[i+1,j+1] = 1 if my_matrix[i+1,j-1] > 0.5: new_matrix[i+1,j-1] = 1 if my_matrix[i-1,j+1] > 0.5: new_matrix[i-1,j+1] = 1 This can get really nasty if I want to step into one neighboring cell and start from it to do a similar task... Do you have some suggestions how this can be done in a more efficient manner? Is this even possible?

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• Is it possible to cache all the data in a SQL Server CE database using LinqToSql?

  - by DanM

  I'm using LinqToSql to query a small, simple SQL Server CE database. I've noticed that any operations involving sub-properties are disappointingly slow. For example, if I have a Customer table that is referenced by an Order table, LinqToSql will automatically create an EntitySet<Order> property. This is a nice convenience, allowing me to do things like Customer.Order.Where(o => o.ProductName = "Stopwatch"), but for some reason, SQL Server CE hangs up pretty bad when I try to do stuff like this. One of my queries, which isn't really that complicated takes 3-4 seconds to complete. I can get the speed up to acceptable, even fast, if I just grab the two tables individually and convert them to List<Customer> and List<Order>, then join then manually with my own query, but this is throwing out a lot of what makes LinqToSql so appealing. So, I'm wondering if I can somehow get the whole database into RAM and just query that way, then occasionally save it. Is this possible? How? If not, is there anything else I can do to boost the performance besides resorting to doing all the joins manually? Note: My database in its initial state is about 250K and I don't expect it to grow to more than 1-2Mb. So, loading the data into RAM certainly wouldn't be a problem from a memory point of view. Update Here are the table definitions for the example I used in my question: create table Order ( Id int identity(1, 1) primary key, ProductName ntext null ) create table Customer ( Id int identity(1, 1) primary key, OrderId int null references Order (Id) )

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• A specific data structure

  - by user550413

  Well, this question is a bit specific but I think there is some general idea in it that I can't get it. Lets say I got K servers (which is a constant that I know its size). I have a program that get requests and every request has an id and server id that will handle it. I have n requests - unknown size and can be any number. I need a data structure to support the next operations within the given complexity: GetServer - the function gets the request ID and returns the server id that is supposed to handle this request at the current situation and not necessarily the original server (see below). Complexity: O(log K) at average. KillServer - the function gets as input a server id that should be removed and another server id that all the requests of the removed server should be passed to. Complexity: O(1) at the worst case. -- Place complexity for all the structure is O(K+n) -- The KillServer function made me think using a Union-Find as I can do the union in O(1) as requested but my problem is the first operation. Why it's LogK? Actually, no matter how I "save" the requests if I want to access to any request (lets say it's an AVL tree) so the complexity will be O(log n) at the worst case and said that I can't assume Kn (and probably K Tried thinking about it a couple of hours but I can't find any solution. Known structures that can be used are: B+ tree, AVL tree, skip list, hash table, Union-Find, rank tree and of course all the basics like arrays and such.

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• Use jQuery's dataTable plugin with a nested Ajax call

  - by mrr0ng

  I am trying to use a nested ajax call to populate a table, and once the table is built, use jQuery's dataTable plugin to pretty it up. The problem I am running into is an order of operations question. When do I call the dataTable function so that I can be assured that the table is built AFTER the values are populated? When I try the following code, the dataTable is created before the rows are built. <script type="text/javascript"> $(document).ready(function() { $.ajax({ url:"http://totalrockregistration.com/feeds/bands.php", dataType:"jsonp", success: function(jsonData){ $.each(jsonData.bands, function(i,bands){ if (bands.barID == "<?php echo $_GET["barID"]; ?>"){ var songIdFromBandJson = bands.song; var bandNameFromJson = bands.name; var bandScoreFromJson = bands.score; $.ajax({ url:"http://totalrockregistration.com/feeds/songs.php", dataType:"jsonp", success: function(songsJsonData){ $.each(songsJsonData.songs, function(i,songs){ if (songIdFromBandJson == songs.id){ var songName=(songs.name); $("#leaderBoardTable tbody").append("<tr><td>"+bandNameFromJson+"</td><td>"+bandScoreFromJson+"</td><td>"+songName+"</td></tr>"); } }); } }); } }); makeLeaderTable(); }, }); function makeLeaderTable(){ $('#leaderBoardTable').dataTable({ "aaSorting": [[ 1, "desc" ]], "iDisplayLength": 50 }); } }); </script>

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• WCF consumed as WebService adds a boolean parameter?

  - by Martín Marconcini

  I've created the default WCF Service in VS2008. It's called "Service1" public class Service1 : IService1 { public string GetData( int value ) { return string.Format("You entered: {0}", value); } public CompositeType GetDataUsingDataContract( CompositeType composite ) { if ( composite.BoolValue ) { composite.StringValue += "Suffix"; } return composite; } } It works fine, the interface is IService1: [ServiceContract] public interface IService1 { [OperationContract] string GetData( int value ); [OperationContract] CompositeType GetDataUsingDataContract( CompositeType composite ); // TODO: Add your service operations here } This is all by default; Visual Studio 2008 created all this. I then created a simple Winforms app to "test" this. I added the Service Reference to my the above mentioned service and it all works. I can instanciate and call myservice1.GetData(100); and I get the result. But I was told that this service will have to be consumed by a Winforms .NET 2.0 app via Web Services, so I proceeded to add the reference to a new Winforms .NET 2.0 application created from scratch (only one winform called form1). This time, when adding the "web reference", it added the typical "localhost" one belonging to webservices; the wizard saw the WCF Service (running on background) and added it. When I tried to consume this, I found out that the GetData(int) method, was now GetData(int, bool). Here's the code private void button1_Click( object sender, EventArgs e ) { localhost.Service1 s1 = new WindowsFormsApplication2.localhost.Service1(); Console.WriteLine(s1.GetData(100, false)); } Notice the false in the GetData call? I don't know what that parameter is or where did that come from, it is called "bool valueSpecified". Does anybody know where this is coming from? Anything else I should do to consume a WCF Service as a WebService from .NET 2.0? (winforms).

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• Need help debugging a huge chunk of JSON data...

  - by meder

  I have a huge chunk, so large that I can't manually edit the file and need to read it in and do regex operations to see what's wrong. Basically - my server is PHP 5.1.6 and I can't update it. This features an older json_decode which is less featured than the 5.2/5.3 versions. json_decode returns NULL and json_last_error is being invoked but the function doesn't exist except in PHP 5.3 so I'm manually trying to see what's wrong. $regex = '#[^0-9"$a-zA-Z{:}().]#'; $json = preg_replace( $regex, '', $json ); $tree = json_decode ( $json, true ); var_dump($tree); // NULL A snippet of the JSON.. somewhere in the middle {"109":0,"103":1,"102":59,"101":70,"100":4299,"94":0,"50":51,"46":0,"45":0,"44":0,"43":0,"42":0,"23":0,"22":0,"18":0,"17":1,"16":1,"13":160,"8":4298}},"2":{"d":{"109":0,"103":92,"102":54,"101":53,"100":4301,"94":0,"50":4278,"49":328,"46":1,"45":0,"44":1,"43":0,"42":0,"26":0,"23":0,"22":0,"18":0,"17":1,"16":1,"8":4300},"m":{"94":1,"100":1,"26":1,"50":1,"8":1,"49":1,"18":1,"43":1,"42":1,"109":1},"c":{"\/":{"d":{"109":0,"100":4301,"94":0,"50":4278,"49":328,"43":0,"42":0,"26":0,"18":0,"8":4300}},"G":{"d":{"109":1,"100":4303,"94":1,"68":17,"50":64,"49":53,"43":1,"42":1,"34":0,"18":1,"13":2216,"11":0,"8":4302}}}},"3": The }}}} is suspicious but this probably just closes 4 nested object literals. Would appreciate any insight.

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• The sign of zero with float2

  - by JackOLantern

  Consider the following code performing operations on complex numbers with C/C++'s float: float real_part = log(3.f); float imag_part = 0.f; float real_part2 = (imag_part)*(imag_part)-(real_part*real_part); float imag_part2 = (imag_part)*(real_part)+(real_part*imag_part); The result will be real_part2= -1.20695 imag_part2= 0 angle= 3.14159 where angle is the phase of the complex number and, in this case, is pi. Now consider the following code: float real_part = log(3.f); float imag_part = 0.f; float real_part2 = (-imag_part)*(-imag_part)-(real_part)*(real_part); float imag_part2 = (-imag_part)*(real_part)+(real_part)*(-imag_part); The result will be real_part2= -1.20695 imag_part2= 0 angle= -3.14159 The imaginary part of the result is -0 which makes the phase of the result be -pi. Although still accomplishing with the principal argument of a complex number and with the signed property of floating point's 0, this changes is a problem when one is defining functions of complex numbers. For example, if one is defining sqrt of a complex number by the de Moivre formula, this will change the sign of the imaginary part of the result to a wrong value. How to deal with this effect?

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• JavaCard monitoring folder

  - by GxG

  I want to write a two way application: applet for javacard and an application in C#. I've got the C# covered but i want to know if with JavaCard i can monitor a folder on the memory and how would i go about doing that. I have a shared folder let's call it temp in which i want to store buffer information between the simulated smartcard and the C# application. The C# application will only read from that folder and display the information, but also it will write requests towards the smartcard. For example i simulate entering the PIN for the card. The applet will write a file containing available options and the C# application will read that file and display those options; from the C# app i will chose and option and write a request file in the same folder. This is when the smartcard which is monitoring that folder will read the request and issue a response. Can i make the smartcard monitor that folder? I was thinking of using encrypted XML files for the request/response operations. But simple .txt files are good to. I am limited to using JavaCard v2.2.1, and every operation has to be encrypted/decrypted. (with the ciphering i have no problem)

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• Low Throughput on Windows Named Pipe Over WAN

  - by MichaelB76

  I'm having problems with low performance using a Windows named pipe. The throughput drops off rapidly as the network latency increases. There is a roughly linear relationship between messages sent per second and round trip time. It seems that the client must ack each message before the server will send the next one. This leads to very poor performance, I can only send 5 (~100 byte) messages per second over a link with an RTT of 200 ms. The pipe is asynchronous, using multiple overlapped write operations (and multiple overlapped reads at the client end), but this is not improving throughput. Is it possible to send messages in parallel over a named pipe? The pipe is created using PIPE_TYPE_MESSAGE, would PIPE_READMODE_BYTE work better? Is there any other way I can improve performance? This is a deployed solution, so I can't simply replace the pipe with a socket connection (I've read that Windows named pipe aren't recommended for use over a WAN, and I'm wondering if this is why). I'd be grateful for any help with this matter.

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• localhost yes but phpmyadmin blank

  - by Giskin Leow

  WAMP people having problem with both localhost and phpmyadmin loads blank which usually the port problem. Mine is only phpmyadmin blank. sqlbuddy and phpinfo no problem. tried uninstall reinstalled wamp. tried xampp, same problem, all works well, not phpmyadmin. mysql log: 120905 8:03:08 [Note] Plugin 'FEDERATED' is disabled. 120905 8:03:08 InnoDB: The InnoDB memory heap is disabled 120905 8:03:08 InnoDB: Mutexes and rw_locks use Windows interlocked functions 120905 8:03:08 InnoDB: Compressed tables use zlib 1.2.3 120905 8:03:09 InnoDB: Initializing buffer pool, size = 128.0M 120905 8:03:09 InnoDB: Completed initialization of buffer pool 120905 8:03:09 InnoDB: highest supported file format is Barracuda. 120905 8:03:09 InnoDB: Waiting for the background threads to start 120905 8:03:10 InnoDB: 1.1.8 started; log sequence number 1595675 120905 8:03:11 [Note] Server hostname (bind-address): '(null)'; port: 3306 120905 8:03:11 [Note] - '(null)' resolves to '::'; 120905 8:03:11 [Note] - '(null)' resolves to '0.0.0.0'; 120905 8:03:11 [Note] Server socket created on IP: '0.0.0.0'. 120905 8:03:13 [Note] Event Scheduler: Loaded 0 events 120905 8:03:13 [Note] wampmysqld: ready for connections. apache log [Wed Sep 05 08:03:09 2012] [notice] Apache/2.2.22 (Win32) PHP/5.4.3 configured -- resuming normal operations [Wed Sep 05 08:03:09 2012] [notice] Server built: May 13 2012 13:32:42 [Wed Sep 05 08:03:09 2012] [notice] Parent: Created child process 3812 [Wed Sep 05 08:03:09 2012] [notice] Child 3812: Child process is running [Wed Sep 05 08:03:09 2012] [notice] Child 3812: Acquired the start mutex. [Wed Sep 05 08:03:09 2012] [notice] Child 3812: Starting 64 worker threads. [Wed Sep 05 08:03:09 2012] [notice] Child 3812: Starting thread to listen on port 80. [Wed Sep 05 08:03:09 2012] [notice] Child 3812: Starting thread to listen on port 80. [Wed Sep 05 08:04:14 2012] [error] [client 127.0.0.1] File does not exist: C:/wamp/www/favicon.ico [Wed Sep 05 08:09:50 2012] [error] [client 127.0.0.1] File does not exist: C:/wamp/www/favicon.ico [Wed Sep 05 08:41:03 2012] [error] [client 127.0.0.1] File does not exist: C:/wamp/www/phpMyAdmin

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• Question about architecting asp.net mvc application ?

  - by Misnomer

  I have read little bit about architecture and also patterns in order to follow the best practices. So this is the architecture we have and I wanted to know what you think of it and any proposed changes or improvements to it - Presentation Layer - Contains all the views,controllers and any helper classes that the view requires also it containes the reference to Model Layer and Business Layer. Business Project - Contains all the business logic and validation and security helper classes that are being used by it. It contains a reference to DataAccess Layer and Model Layer. Data Access Layer - Contains the actual queries being made on the entity classes(CRUD) operations on the entity classes. It contains reference to Model Layer. Model Layer - Contains the entity framework model,DTOs,Enums.Does not really have a reference to any of the above layers. What are your thoughts on the above architecture ? The problem is that I am getting confused by reading about like say the repository pattern, domain driven design and other design patterns. The architecture we have although not that strict still is relatively alright I think and does not really muddle things but I maybe wrong. I would appreciate any help or suggestions here. Thanks !

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• What is common between environments within a shell terminal session?

  - by Matt1776

  I have a custom shell script that runs each time a user logs in or identity is assumed, its been placed in /etc/profile.d and performs some basic env variable operations. Recently I added some code so that if screen is running it will reattach it without needing me to type anything. There are some problems however. If I log-in as root, and su - to another user, the code runs a second time. Is there a variable I can set when the code runs the first time that will prevent a second run of the code? I thought to write something to the disk but then I dont want to prevent the code from running if I begin a new terminal session. Here is the code in question. It first attempts to reattach - if unsuccessful because its already attached (as it might be on an interruped session) it will 'take' the session back. screen -r if [ -z "$STY" ]; then exec screen -dR fi Ultimately this bug prevents me from substituting user to another user because as soon as I do so, it grabs the screen session and puts me right back where I started. Pretty frustrating

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• Add two hexBinarys with XPATH 1.0

  - by fielding

  Hi, my xml document looks somewhat like that (Values are both xsl:hexBinary): <Offsets> <Offset> <Name>ErrorOffset</Name> <Value>DD</Value> </Offset> <Offset> <Name>OtherOffset</Name> <Value>FF</Value> </Offset> </Offsets> <Value> <Name>Error1</Name> <Code>01</Code> </Value> <Value> <Name>Error2</Name> <Code>02</Code> <Offset>ErrorOffset</Offset> </Value> now i want to transform this to a new xml file: <Value> <Name>Error1</Name> <Code>01</Code> </Value> <Value> <Name>Error2</Name> <Code>DF</Code> </Value> All that should happen is adding <Offset> to the basic <Value>. But plain + returns NaN and sum() expects only one parameter. XSLT and XPATH are quite nice, but it goes on my nerves that easy operations like adding two hex values just dont work as easy as it should.

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• Installing Image_Graph and using with BASE

  - by PPowerHouseK

  Hello all, I have Windows 7 with the latest XAMPP installation. I configured BASE to work, for the most part. My problem is that in BASE, when I click on the graph alerts button, I get this error: Error loading the Graphing library: Check your Pear::Image_Graph installation! * Image_Graph can be found here:at http://pear.veggerby.dk/. Without this library no graphing operations can be performed. * Make sure PEAR libraries can be found by php at all: pear config-show | grep "PEAR directory" PEAR directory php_dir /usr/share/pear This path must be part of the include path of php (cf. /etc/php.ini): php -i | grep "include_path" include_path => .:/usr/share/pear:/usr/share/php => .:/usr/share/pear:/usr/share/php</code> I think it may have to do with the include path of the php.ini so here is what it currently says: ;;;;;;;;;;;;;;;;;;;;;;;;; ; Paths and Directories ; ;;;;;;;;;;;;;;;;;;;;;;;;; ; UNIX: "/path1:/path2" ;include_path = ".:/php/includes" ; ; Windows: "\path1;\path2" ;include_path = ".;c:\php\includes" ; ; PHP's default setting for include_path is ".;/path/to/php/pear" ; http://php.net/include-path include_path = ".;C:\xampp\php\PEAR" I am really at a loss as to how to resolve this. I searched for a while for some documentation but most referred to installing on ubuntu. I don't know any pear or php, so if you know how to fix this please explain thoroughly. I am willing to supply as much information as needed.

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• Is this use of PreparedStatements in a Thread in JAVA correct?

  - by Gormcito

  I'm still an undergrad just working part time and so I'm always trying to be aware of better ways to do things. Recently I had to write a program for work where the main thread of the program would spawn "task" threads (for each db "task" record) which would perform some operations and then update the record to say that it has finished. Therefore I needed a database connection object and PreparedStatement objects in or available to the ThreadedTask objects. This is roughly what I ended up writing, is creating a PreparedStatement object per thread a waste? I thought static PreparedStatments could create race conditions... Thread A stmt.setInt(); Thread B stmt.setInt(); Thread A stmt.execute(); Thread B stmt.execute(); A´s version never gets execed.. Is this thread safe? Is creating and destroying PreparedStatement objects that are always the same not a huge waste? public class ThreadedTask implements runnable { private final PreparedStatement taskCompleteStmt; public ThreadedTask() { //... taskCompleteStmt = Main.db.prepareStatement(...); } public run() { //... taskCompleteStmt.executeUpdate(); } } public class Main { public static final db = DriverManager.getConnection(...); }

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• How to parse mathematical expressions involving parentheses

  - by Rob P.

  Please forgive my title, I really don't know how to phrase it better. This isn't a school assignment or anything, but I realize it's a mostly academic question. But, what I've been struggling to do is parse 'math' text and come up with an answer. For Example - I can figure out how to parse '5 + 5' or '3 * 5' - but I fail when I try to correctly chain operations together. (5 + 5) * 3 It's mostly just bugging me that I can't figure it out. If anyone can point me in a direction, I'd really appreciate it. EDIT Thanks for all of the quick responses. I'm sorry I didn't do a better job of explaining. First - I'm not using regular expressions. I also know there are already libraries available that will take, as a string, a mathematical expression and return the correct value. So, I'm mostly looking at this because, sadly, I don't "get it". Second - What I've tried doing (is probably misguided) but I was counting '(' and ')' and evaluating the deepest items first. In simple examples, this worked; but my code is not pretty and more complicated stuff crashes. When I 'calculated' the lowest level, I was modifying the string. So... (5 + 5) * 3 Would turn into 10 * 3 Which would then evaluate to 30 But it just felt 'wrong'. I hope that helps clarify things. I'll certainly check out the links provided.

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• Android: Calculator on showing 0 immediately after the dot

  - by pearmak

  I am now working on a calculator, and everything works fine except for decimal places. The calculator contains 2 displays actually, one is called fakedisplay for actual operations, and one is called Display, for presenting the desired format, ie adding commas. When pressing 12345.678, Display will follow fakedisplay and present as 12,345.678, but if i press 12345.009, the fakedisplay will work normally as 12345.009, but the Display stuck as 12,345 until 9 is pressed, and at that time it will show 12,345.009 normally. However, it is strange that when the user presses 0, there is no response, and until pressing 9, 009 will then immediately append. I know this arise from the parsing code, but based on this, how could I amend the following code? I really cannot think of any solution... Many thanks for all your advice! one.setOnClickListener(new View.OnClickListener() { if (str.length()<15) {Fakedisplay.append("1");} DecimalFormat myFormatter1 = new DecimalFormat("###,###,###,###.#################"); String str1=Fakedisplay.getText().toString(); String stripped1 = Double.valueOf(str1).toString(); stripped1 = myFormatter1.format(Double.valueOf(stripped1)); if (stripped1.endsWith(".0")) stripped1 = stripped1.substring(0, stripped1.length() - 2); Display.setText(stripped1);

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• Parallelize or vectorize all-against-all operation on a large number of matrices?

  - by reve_etrange

  I have approximately 5,000 matrices with the same number of rows and varying numbers of columns (20 x ~200). Each of these matrices must be compared against every other in a dynamic programming algorithm. In this question, I asked how to perform the comparison quickly and was given an excellent answer involving a 2D convolution. Serially, iteratively applying that method, like so list = who('data_matrix_prefix*') H = cell(numel(list),numel(list)); for i=1:numel(list) for j=1:numel(list) if i ~= j eval([ 'H{i,j} = compare(' char(list(i)) ',' char(list(j)) ');']); end end end is fast for small subsets of the data (e.g. for 9 matrices, 9*9 - 9 = 72 calls are made in ~1 s). However, operating on all the data requires almost 25 million calls. I have also tried using deal() to make a cell array composed entirely of the next element in data, so I could use cellfun() in a single loop: # who(), load() and struct2cell() calls place k data matrices in a 1D cell array called data. nextData = cell(k,1); for i=1:k [nextData{:}] = deal(data{i}); H{:,i} = cellfun(@compare,data,nextData,'UniformOutput',false); end Unfortunately, this is not really any faster, because all the time is in compare(). Both of these code examples seem ill-suited for parallelization. I'm having trouble figuring out how to make my variables sliced. compare() is totally vectorized; it uses matrix multiplication and conv2() exclusively (I am under the impression that all of these operations, including the cellfun(), should be multithreaded in MATLAB?). Does anyone see a (explicitly) parallelized solution or better vectorization of the problem?

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• Solving problems with near infinite potential solutions

  - by Zonda333

  Today I read the following problem: Use the digits 2, 0, 1, 1 and the operations +, -, x, ÷, sqrt, ^ , !, (), combinations, and permutations to write equations for the counting numbers 1 through 100. All four digits must be used in each expression. Only the digits 2, 0, 1, 1 may be used, and each must be used exactly once. Decimals may be used, as in .1, .02, etc. Digits may be combined; numbers such as 20 or 101 may be used. Example: 60 = 10*(2+1)!, 54 = ¹¹C2 - 0! Though I was able to quickly find around 50 solutions quite easily in my head, I thought programming it would be a far superior solution. However, I then realized I had no clue how to go about solving a problem like this. I am not asking for complete code for me to copy and paste, but for ideas about how I would solve this problems, and others like it that have nearly infinite potential solutions. As I will be writing it in python, where I have the most experience, I would prefer if the answers were more python based, but general ideas are great too.

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• C/C++ Bit Array or Bit Vector

  - by MovieYoda

  Hi, I am learning C/C++ programming & have encountered the usage of 'Bit arrays' or 'Bit Vectors'. Am not able to understand their purpose? here are my doubts - Are they used as boolean flags? Can one use int arrays instead? (more memory of course, but..) What's this concept of Bit-Masking? If bit-masking is simple bit operations to get an appropriate flag, how do one program for them? is it not difficult to do this operation in head to see what the flag would be, as apposed to decimal numbers? I am looking for applications, so that I can understand better. for Eg - Q. You are given a file containing integers in the range (1 to 1 million). There are some duplicates and hence some numbers are missing. Find the fastest way of finding missing numbers? For the above question, I have read solutions telling me to use bit arrays. How would one store each integer in a bit?

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