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  • DBD::CSV: Problem with file-name-extensions

    - by sid_com
    In this script I have problems with file-name-extensions: if I use /home/mm/test_x it works, with file named /home/mm/test_x.csv it doesn't: #!/usr/bin/env perl use warnings; use strict; use 5.012; use DBI; my $table_1 = '/home/mm/test_1.csv'; my $table_2 = '/home/mm/test_2.csv'; #$table_1 = '/home/mm/test_1'; #$table_2 = '/home/mm/test_2'; my $dbh = DBI->connect( "DBI:CSV:" ); $dbh->{RaiseError} = 1; $table_1 = $dbh->quote_identifier( $table_1 ); $table_2 = $dbh->quote_identifier( $table_2 ); my $sth = $dbh->prepare( "SELECT a.id, a.name, b.city FROM $table_1 AS a NATURAL JOIN $table_2 AS b" ); $sth->execute; $sth->dump_results; $dbh->disconnect; Output with file-name-extention: DBD::CSV::st execute failed: Execution ERROR: No such column '"/home/mm/test_1.csv".id' called from /usr/local/lib/perl5/site_perl/5.12.0/x86_64-linux/DBD/File.pm at 570. Output without file-name-extension: '1', 'Brown', 'Laramie' '2', 'Smith', 'Watertown' 2 rows Is this a bug?

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  • Multhreading in Java

    - by Vijay Selvaraj
    I'm working with core java and IBM Websphere MQ 6.0. We have a standalone module say DBcomponent that hits the database and fetches a resultset based on the runtime query. The query is passed to the application via MQ messaging medium. We have a trigger configured for the queue which invokes the DBComponent whenever a message is available in the queue. The DBComponent consumes the message, constructs the query and returns the resultset to another queue. In this overall process we use log4j to log statements on a log file for auditing. The connection is pooled to the database using Apache pool. I am trying to check whether the log messages are logged correctly using a sample program. The program places the input message to the queue and checks for the logs in the log file. Its expected for the trigger method invocation to complete before i try to check for the message in log file, but every time my program to check for log message gets executed first leading my check to failure. Even if i introduce a Thread.sleep(time) doesn't solves the case. How can i make it to keep my method execution waiting until the trigger operation completes? Any suggestion will be helpful.

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  • Dragging an UIView inside UIScrollView

    - by Sergey Mikhanov
    Hello community! I am trying to solve a basic problem with drag and drop on iPhone. Here's my setup: I have a UIScrollView which has one large content subview (I'm able to scroll and zoom it) Content subview has several small tiles as subviews that should be dragged around inside it. My UIScrollView subclass has this method: - (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event { UIView *tile = [contentView pointInsideTiles:[self convertPoint:point toView:contentView] withEvent:event]; if (tile) { return tile; } else { return [super hitTest:point withEvent:event]; } } Content subview has this method: - (UIView *)pointInsideTiles:(CGPoint)point withEvent:(UIEvent *)event { for (TileView *tile in tiles) { if ([tile pointInside:[self convertPoint:point toView:tile] withEvent:event]) return tile; } return nil; } And tile view has this method: - (void)touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event { UITouch *touch = [touches anyObject]; CGPoint location = [touch locationInView:self.superview]; self.center = location; } This works, but not fully correct: the tile sometimes "falls down" during the drag process. More precisely, it stops receiving touchesMoved: invocations, and scroll view starts scrolling instead. I noticed that this depends on the drag speed: the faster I drag, the quicker the tile "falls". Any ideas on how to keep the tile glued to the dragging finger? Thanks in advance!

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  • How to access C arrays from assembler for Windows x64?

    - by 0xdword32
    I've written an assembler function to speed up a few things for image processing (images are created with CreateDIBSection). For Win32 the assembler code works without problems, but for Win64 I get a crash as soon as I try to access my array data. I put the relevant info in a struct and my assembler function gets a pointer to this struct. The struct pointer is put into ebx/rbx and with indexing I read the data from the struct. Any idea what I am doing wrong? I use nasm together with Visual Studio 2008 and for Win64 I set "default rel". C++ code: struct myData { tUInt32 ulParam1; void* pData; }; CallMyAssemblerFunction(&myData); Assembler Code: Win32: ... push ebp; mov ebp,esp mov ebx, [ebp + 8]; pointer to our struct mov eax, [ebx]; ulParam1 mov esi, [ebx + 4]; pData, 4 byte pointer movd xmm0, [esi]; ... Win64: ... mov rbx, rcx; pointer to our struct mov eax, [rbx]; ulParam1 mov rsi, [rbx + 4]; pData, 8 byte pointer movd xmm0, [rsi]; CRASH! ...

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  • Conditional macro expansion

    - by Dave DeLong
    Heads up: This is a weird question. I've got some really useful macros that I like to use to simplify some logging. For example I can do Log(@"My message with arguments: %@, %@, %@", @"arg1", @"arg2", @"arg3"), and that will get expanded into a more complex method invocation that includes things like self, _cmd, __FILE__, __LINE__, etc, so that I can easily track where things are getting logged. This works great. Now I'd like to expand my macros to not only work with Objective-C methods, but general C functions. The problem is the self and _cmd portions that are in the macro expansion. These two parameters don't exist in C functions. Ideally, I'd like to be able to use this same set of macros within C functions, but I'm running into problems. When I use (for example) my Log() macro, I get compiler warnings about self and _cmd being undeclared (which makes total sense). My first thought was to do something like the following (in my macro): if (thisFunctionIsACFunction) { DoLogging(nil, nil, format, ##__VA_ARGS__); } else { DoLogging(self, _cmd, format, ##__VA_ARGS__); } This still produces compiler warnings, since the entire if() statement is substituted in place of the macro, resulting in errors with the self and _cmd keywords (even though they will never be executed during function execution). My next thought was to do something like this (in my macro): if (thisFunctionIsACFunction) { #define SELF nil #define CMD nil } else { #define SELF self #define CMD _cmd } DoLogging(SELF, CMD, format, ##__VA_ARGS__); That doesn't work, unfortunately. I get "error: '#' is not followed by a macro parameter" on my first #define. My other thought was to create a second set of macros, specifically for use in C functions. This reeks of a bad code smell, and I really don't want to do this. Is there some way I can use the same set of macros from within both Objective-C methods and C functions, and only reference self and _cmd if the macro is in an Objective-C method?

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  • How to call Twiter's Streaming/Filter Feed with urllib2/httplib?

    - by Simon
    Update: I switched this back from answered as I tried the solution posed in cogent Nick's answer and switched to Google's urlfetch: logging.debug("starting urlfetch for http://%s%s" % (self.host, self.url)) result = urlfetch.fetch("http://%s%s" % (self.host, self.url), payload=self.body, method="POST", headers=self.headers, allow_truncated=True, deadline=5) logging.debug("finished urlfetch") but unfortunately finished urlfetch is never printed - I see the timeout happen in the logs (it returns 200 after 5 seconds), but execution doesn't seem tor return. Hi All- I'm attempting to play around with Twitter's Streaming (aka firehose) API with Google App Engine (I'm aware this probably isn't a great long term play as you can't keep the connection perpetually open with GAE), but so far I haven't had any luck getting my program to actually parse the results returned by Twitter. Some code: logging.debug("firing up urllib2") req = urllib2.Request(url="http://%s%s" % (self.host, self.url), data=self.body, headers=self.headers) logging.debug("called urlopen for %s %s, about to call urlopen" % (self.host, self.url)) fobj = urllib2.urlopen(req) logging.debug("called urlopen") When this executes, unfortunately, my debug output never shows the called urlopen line printed. I suspect what's happening is that Twitter keeps the connection open and urllib2 doesn't return because the server doesn't terminate the connection. Wireshark shows the request being sent properly and a response returned with results. I tried adding Connection: close to my request header, but that didn't yield a successful result. Any ideas on how to get this to work? thanks -Simon

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  • Best Practice - Removing item from generic collection in C#

    - by Matt Davis
    I'm using C# in Visual Studio 2008 with .NET 3.5. I have a generic dictionary that maps types of events to a generic list of subscribers. A subscriber can be subscribed to more than one event. private static Dictionary<EventType, List<ISubscriber>> _subscriptions; To remove a subscriber from the subscription list, I can use either of these two options. Option 1: ISubscriber subscriber; // defined elsewhere foreach (EventType event in _subscriptions.Keys) { if (_subscriptions[event].Contains(subscriber)) { _subscriptions[event].Remove(subscriber); } } Option 2: ISubscriber subscriber; // defined elsewhere foreach (EventType event in _subscriptions.Keys) { _subscriptions[event].Remove(subscriber); } I have two questions. First, notice that Option 1 checks for existence before removing the item, while Option 2 uses a brute force removal since Remove() does not throw an exception. Of these two, which is the preferred, "best-practice" way to do this? Second, is there another, "cleaner," more elegant way to do this, perhaps with a lambda expression or using a LINQ extension? I'm still getting acclimated to these two features. Thanks. EDIT Just to clarify, I realize that the choice between Options 1 and 2 is a choice of speed (Option 2) versus maintainability (Option 1). In this particular case, I'm not necessarily trying to optimize the code, although that is certainly a worthy consideration. What I'm trying to understand is if there is a generally well-established practice for doing this. If not, which option would you use in your own code?

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  • Which is the best jQuery-powered site?

    - by Reigel
    This "Top 10 JavaScript (jQuery) Powered Sites", posted about 2 years ago, was the one that invites me(after seeing the list) to use jQuery. All the sites in that list made me realize how cool it is to build sites powered by jQuery. And now more and more sites are being powered by jQuery. More and more developers are learning jQuery. Two years have past now but I still do a search to google for best sites and still got me to that link and which the link is not updated from the first time I have looked at it. Here at stackoverflow, there are lots of jQuery user. I was thinking if we can here show some of the sites that you know that is powered by jQuery which you think is best. If you can, please make it one site one answer, so that we can make a vote if it's really best jQuery powered site. We will take a look if it is really well implemented ( the way the codes are written, fast speed site, etc...) and deserves to be the best. Lot's of viewers will benefit from it. Like, we can view and have an idea of how we will make our next project cooler, faster, and powerful.

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  • Apache CXF REST Services w/ Spring AOP

    - by jconlin
    I'm trying to get Apache CXF JAX-RS services working with Spring AOP. I've created a simple logging class: public class AOPLogger{ public void logBefore(){ System.out.println("Logging Before!"); } } My Spring configuration (beans.xml): <aop:config> <aop:aspect id="aopLogger" ref="test.aop.AOPLogger"> <aop:before method="logBefore" pointcut="execution(* test.rest.RestService(..))"/> </aop:aspect> </aop:config> <bean id="aopLogger" class="test.aop.AOPLogger"/> I always get an NPE in RestService when a call is made to a Method getServletRequest(), which has: return messageContext.getHttpServletRequest(); If I remove the aop configuration or comment it out from my beans.xml, everything works fine. All of my actual Rest services extend test.rest.RestService (which is a class) and call getServletRequest(). I'm just trying to just get AOP up and running based off of the example in the CXF JAX-RS documentation. Does anyone have any idea what I'm doing wrong? Thanks!

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  • Haskell math performance

    - by Travis Brown
    I'm in the middle of porting David Blei's original C implementation of Latent Dirichlet Allocation to Haskell, and I'm trying to decide whether to leave some of the low-level stuff in C. The following function is one example—it's an approximation of the second derivative of lgamma: double trigamma(double x) { double p; int i; x=x+6; p=1/(x*x); p=(((((0.075757575757576*p-0.033333333333333)*p+0.0238095238095238) *p-0.033333333333333)*p+0.166666666666667)*p+1)/x+0.5*p; for (i=0; i<6 ;i++) { x=x-1; p=1/(x*x)+p; } return(p); } I've translated this into more or less idiomatic Haskell as follows: trigamma :: Double -> Double trigamma x = snd $ last $ take 7 $ iterate next (x' - 1, p') where x' = x + 6 p = 1 / x' ^ 2 p' = p / 2 + c / x' c = foldr1 (\a b -> (a + b * p)) [1, 1/6, -1/30, 1/42, -1/30, 5/66] next (x, p) = (x - 1, 1 / x ^ 2 + p) The problem is that when I run both through Criterion, my Haskell version is six or seven times slower (I'm compiling with -O2 on GHC 6.12.1). Some similar functions are even worse. I know practically nothing about Haskell performance, and I'm not terribly interested in digging through Core or anything like that, since I can always just call the handful of math-intensive C functions through FFI. But I'm curious about whether there's low-hanging fruit that I'm missing—some kind of extension or library or annotation that I could use to speed up this numeric stuff without making it too ugly.

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  • What is SSIS order of data transformation component method calls

    - by Ron Ruble
    I am working on a custom data transformation component. I'm using NUnit and NMock2 to test as I code. Testing and getting the custom UI and other features right is a huge pain, in part because I can't find any documentation about the order in which SSIS invokes methods on the component at design time as well as runtime. I can correct the issues readily enough, but it's tedious and time consuming to unregister the old version, register the new version, fire up the test ssis package, try to display the UI, get an obscure error message, backtrace it, modify the component and continue. One of the big issues involves the UI component needing access to the componentmetadata and buffermanager properties of the component at design time, and what I need to provide for to support properties that won't be initialized until after the user enters them in the UI. I can work through it; but if someone knows of some docs or tips that would speed me up, I'd greatly appreciate it. The samples I've found havn't been much use; they seem to be directed to showing off cool stuff (Twitter, weather.com) rather than actual work. Thanks in advance.

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  • DataTable won't DataBind with a DataTable.NewRow()

    - by David
    Is DataRow.NewRow() insufficient as the only row in a DataTable? I would expect this to work, but it doesn't. It's near the end of my Page_Load inside my If(!Postback) block. gridCPCP is GridView DataTable dt = new DataTable(); dt.Columns.Add("ID", int.MinValue.GetType()); dt.Columns.Add("Code", string.Empty.GetType()); dt.Columns.Add("Date", DateTime.MinValue.GetType()); dt.Columns.Add("Date2", DateTime.MinValue.GetType()); dt.Columns.Add("Filename", string.Empty.GetType()); //code to add rows if (dt.Rows.Count > 0) { gridCPCP.DataSource = dt; gridCPCP.DataBind(); } else { dt.Rows.Add(dt.NewRow()); gridCPCP.DataSource = dt; gridCPCP.DataBind(); //EXCEPTION int TotalColumns = gridCPCP.Rows[0].Cells.Count; gridCPCP.Rows[0].Cells.Clear(); gridCPCP.Rows[0].Cells.Add(new TableCell()); gridCPCP.Rows[0].Cells[0].ColumnSpan = TotalColumns; gridCPCP.Rows[0].Cells[0].Text = "No Record Found"; } The exception throws on gridCPCP.DataBind() and only when execution reaches the else block. If there were rows added above via dt.Rows.Add(new object[] { ... } binding works. System.ArgumentOutOfRangeException: Length cannot be less than zero. Parameter name: length

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  • Error Converting PIL B&W images to Numpy Arrays

    - by Elliot
    I am getting weird errors when I try to convert a black and white PIL image to a numpy array. An example of the code I am working with is below. if image.mode != '1': image = image.convert('1') #convert to B&W data = np.array(image) #convert data to a numpy array n_lines = data.shape[0] #number of raster passes line_range = range(data.shape[1]) for l in range(n_lines): # process one horizontal line of the image line = data[l] for n in line_range: if line[n] == 1: write_line_to(xl, z+scale*n, speed) #conversion to other program code elif line[n] == 0: run_to(xl, z+scale*n) #conversion to other program code I have tried this using both array and asarray for the conversion, and gotten different errors. If I use array, then the data I get out is nothing like what I put in. It looks like several very shrunken partial images side by side, with the remainder of the image space filled in in black. If I use asarray, then the entirety of python crashes during the raster step (on a random line). If I work with a greyscale image ('L'), then neither of these errors occurs for either array or asarray. Does anyone know what I am doing wrong? Is there something odd about the way PIL encodes B&W images, or something special I need to pass numpy to make it convert properly?

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  • Need help in tuning a sql-query

    - by Viper
    Hello, i need some help to boost this SQL-Statement. The execution time is around 125ms. During the runtime of my program this sql (better: equally structured sqls for different tables) will be called 300.000 times. The average row count in the tables lies around 10.000.000 rows and new rows (updates/inserts) will be added with a timestamp each day. Data which are interesting for this particular export-program lies in the last 1-3 days. Maybe this is helpful for an index to create. The data i need is the current valid row for a given id and the forerunner datarow to get the updates (if exists). We use a Oracle 11g database and Dot.Net Framework 3.5 SQL-Statement to boost: select ID_SOMETHING, -- Number(12) ID_CONTRIBUTOR, -- Char(4 Byte) DATE_VALID_FROM, -- DATE DATE_VALID_TO -- DATE from TBL_SOMETHING XID where ID_SOMETHING = :ID_INSTRUMENT and ID_CONTRIBUTOR = :ID_CONTRIBUTOR and DATE_VALID_FROM <= :EXPORT_DATE and DATE_VALID_TO >= :EXPORT_DATE order by DATE_VALID_FROM asc; Here i uploaded the current Explain-Plan for this query. I'm not a database expert so i don't know which index-type would fit best for this requirement. I have seen that there are many different possible index-types which could be applied. Maybe Oracle Optimizer Hints are helpful, too. Does anyone has a good idea for tuning this sql or can point me in a right direction?

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  • Function returning dictionary, not seen by calling function

    - by twiga
    Hi There, I have an interesting problem, which is a function that returns a Dictionary<String,HashSet<String>>. The function converts some primitive structs to a Dictionary Class. The function is called as follows: Dictionary<String, HashSet<String>> Myset = new Dictionary<String,HashSet<String>>(); Myset = CacheConverter.MakeDictionary(_myList); Upon execution of the two lines above, Myset is non-existent to the debugger. Adding a watch results in: "The name 'Myset' does not exist in the current context" public Dictionary<String, HashSet<String>> MakeDictionary(LightWeightFetchListCollection _FetchList) { Dictionary<String, HashSet<String>> _temp = new Dictionary<String, HashSet<String>>(); // populate the Dictionary // return return _temp; } The Dictionary _temp is correctly populated by the called function and _temp contains all the expected values. The problem seems to be with the dictionary not being returned at all. Examples I could find on the web of functions returning primitive Dictionary<string,string> work as expected.

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  • TypeError: Error #1009 - (Null reference error) With Flash.

    - by Wind Chimez
    I am not an expert in flash, but i do work with AS and tweak Flash projects , though not having deep expertise in it. Currently i need to revamp a flash website done by one another guy, and the code base given to me, upon execution is throwing the following error. "--- TypeError: Error #1009: Cannot access a property or method of a null object reference. at NewSite_fla::MainTimeline/__setProp_ContactOutP1_ContactOut_Contents_0() at NewSite_fla::MainTimeline/frame1() --" The structure of the project is like, it has the different sections split into different movie clips. There is no single main timeline, but click actions on different areas of seperate movie clips will take them between one another. All the AS logic of event handling are written inline in FLA , no seperate Document class exists. Preloader Movie clip is the first one getting loaded. As i understood the error is getting thrown initially itself, and it is not happening due to any Action script logic written inline, because it is throwing error even before hitting the first inline AS code. I am not able to figure Out what exactly it causing the problem, or where to resolve it. I really got stuck at this point. Any help will be great.I had not seen the particular solution i am looking for anywhere yet, though Error #1009 is common. I uploaded the fla, here ( http://tinyurl.com/249e95p ), for reference.It may not be working , since the included/refered video files and all are not there, but reviwing the action code/movie clips will be possible. Please let me know if somebody will be able to trace the issue exactly.

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  • Images in database vs file system

    - by Jesse
    We have a project coming up where we will be building a whole backend CMS system that will power our entire extranet and intranet with one package. The question I have been trying to find an answer to is which is better: storing images in the database (SQL Server 2005) so we may have integrity, single replication plan, etc OR storing on the file system? One issue we have is that we have multiple servers load balanced that require to have the same data at all times. As of now we have SQL replication taking care of that but file replication seems to be a little tougher. Another concern we have is that we would like to have multiple resolutions of the same image, we are not sure if creating and storing each version on the file system would be best or maybe dynamically pulling and creating the resolution image we would like upon request. Our concerns are the with the following: Data integrity Data replication Multiple resolutions Speed of database vs file system Overhead load of database vs file system Data management and backup Does anyone have a similar situation or have any input on what would be recommended? Thanks in advance for the help!

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  • jQuery Cycle : Multiple Instances, detect end of each instance

    - by guylabbe.ca
    I am using multiple instances of Cycle for a portfolio; Only one is shown and the others are hidden. Each Cycle is a project with multiple images. The only thing I can't figure out is how to detect the end of the « current » Cycle instance. with after: function, it is triggered for all instances at once, impossible to get « local » events. Here is my code : $('.sldr_closeup').each(function() { var currId = $(this).attr('id'); window['num_'+currId] = 0; $(this).cycle({ timeout:0, speed:500, fx:'fade', next:'.nextimages', prev:'.previmages', fit:1, nowrap:1, autstop:0, after : function(c,n,o,f) { var currId = $(this).parent('div').attr('id'); (f) ? window['num_'+currId] ++ : window['num_'+currId] --; if ((o.slideCount == window['num_'+currId] )) { alert(currId); $('.nextimages').stop().fadeTo(400,0,function(){ if(currId != $('.projectList .projet').last().find('a').attr('rel')) $('.nextproject').stop().fadeTo(400,1); $(this).hide(); }); } } }).cycle('pause'); });

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  • Code bacteria: evolving mathematical behavior

    - by Stefano Borini
    It would not be my intention to put a link on my blog, but I don't have any other method to clarify what I really mean. The article is quite long, and it's in three parts (1,2,3), but if you are curious, it's worth the reading. A long time ago (5 years, at least) I programmed a python program which generated "mathematical bacteria". These bacteria are python objects with a simple opcode-based genetic code. You can feed them with a number and they return a number, according to the execution of their code. I generate their genetic codes at random, and apply an environmental selection to those objects producing a result similar to a predefined expected value. Then I let them duplicate, introduce mutations, and evolve them. The result is quite interesting, as their genetic code basically learns how to solve simple equations, even for values different for the training dataset. Now, this thing is just a toy. I had time to waste and I wanted to satisfy my curiosity. however, I assume that something, in terms of research, has been made... I am reinventing the wheel here, I hope. Are you aware of more serious attempts at creating in-silico bacteria like the one I programmed? Please note that this is not really "genetic algorithms". Genetic algorithms is when you use evolution/selection to improve a vector of parameters against a given scoring function. This is kind of different. I optimize the code, not the parameters, against a given scoring function.

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  • Problem when getting pageContent of an unavailable URL in Java

    - by tiendv
    I have a code for get pagecontent from a URL: import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.net.URL; import java.net.URLConnection; public class GetPageFromURLAction extends Thread { public String stringPageContent; public String targerURL; public String getPageContent(String targetURL) throws IOException { String returnString=""; URL urlString = new URL(targetURL); URLConnection openConnection = urlString.openConnection(); String temp; BufferedReader in = new BufferedReader( newInputStreamReader(openConnection.getInputStream())); while ((temp = in.readLine()) != null) { returnString += temp + "\n"; } in.close(); // String nohtml = sb.toString().replaceAll("\\<.*?>",""); return returnString; } public String getStringPageContent() { return stringPageContent; } public void setStringPageContent(String stringPageContent) { this.stringPageContent = stringPageContent; } public String getTargerURL() { return targerURL; } public void setTargerURL(String targerURL) { this.targerURL = targerURL; } @Override public void run() { try { this.stringPageContent=this.getPageContent(targerURL); } catch (IOException e) { e.printStackTrace(); } } } Sometimes I receive an HTTP error of 405 or 403 and result string is null. I have tried checking permission to connect to the URL with: URLConnection openConnection = urlString.openConnection(); openConnection.getPermission() but it usualy returns null. Does mean that i don't have permission to access the link? I have tried stripping off the query portion of the URL with: String nohtml = sb.toString().replaceAll("\\<.*?>",""); where sb is a Stringbulder, but it doesn't seem to strip off the whole query substring. In an unrelated question, I'd like to use threads here because I must retrieve many URLs; how can I create a multi-thread client to improve the speed?

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  • Temporary storage for keeping data between program iterations?

    - by mr.b
    I am working on an application that works like this: It fetches data from many sources, resulting in pool of about 500,000-1,500,000 records (depends on time/day) Data is parsed Part of data is processed in a way to compare it to pre-existing data (read from database), calculations are made, and stored in database. Resulting dataset that has to be stored in database is, however, much smaller in size (compared to original data set), and ranges from 5,000-50,000 records. This process almost always updates existing data, perhaps adds few more records. Then, data from step 2 should be kept somehow, somewhere, so that next time data is fetched, there is a data set which can be used to perform calculations, without touching pre-existing data in database. I should point out that this data can be lost, it's not irreplaceable (key information can be read from database if needed), but it would speed up the process next time. Application components can (and will be) run off different computers (in the same network), so storage has to be reachable from multiple hosts. I have considered using memcached, but I'm not quite sure should I do so, because one record is usually no smaller than 200 bytes, and if I have 1,500,000 records, I guess that it would amount to over 300 MB of memcached cache... But that doesn't seem scalable to me - what if data was 5x that amount? If it were to consume 1-2 GB of cache only to keep data in between iterations (which could easily happen)? So, the question is: which temporary storage mechanism would be most suitable for this kind of processing? I haven't considered using mysql temporary tables, as I'm not sure if they can persist between sessions, and be used by other hosts in network... Any other suggestion? Something I should consider?

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  • Client-Side Dynamic Removal of <script> Tags in <head>

    - by merv
    Is it possible to remove script tags in the <head> of an HTML document client-side and prior to execution of those tags? On the server-side I am able to insert a <script> above all other <script> tags in the <head>, except one, and I would like to be able to remove all subsequent scripts. I do not have the ability to remove <script> tags from the server side. What I've tried: (function (c,h) { var i, s = h.getElementsByTagName('script'); c.log("Num scripts: " + s.length); i = s.length - 1; while(i > 1) { h.removeChild(s[i]); i -= 1; } })(console, document.head); However, the logged number of scripts comes out to only 1, since (as @ryan pointed out) the code is being executed prior to the DOM being ready. Although wrapping the code above in a document.ready event callback does enable proper calculation of the number of <script> tags in the <head>, waiting until the DOM is ready fails to prevent the scripts from loading. Is there a reliable means of manipulating the HTML prior to the DOM being ready? Background If you want more context, this is part of an attempt to consolidate scripts where no option for server-side aggregation is available. Many of the JS libraries being loaded are from a CMS with limited configuration options. The content is mostly static, so there is very little concern about manually aggregating the JavaScript and serving it from a different location. Any suggestions for alternative applicable aggregation techniques would also be welcome.

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  • Best intro to C++ static metaprogramming?

    - by jwfearn
    Static metaprogramming (aka "template metaprogramming") is a great C++ technique that allows the execution of programs at compile-time. A light bulb went off in my head as soon as I read this canonical metaprogramming example: #include <iostream> using namespace std; template< int n > struct factorial { enum { ret = factorial< n - 1 >::ret * n }; }; template<> struct factorial< 0 > { enum { ret = 1 }; }; int main() { cout << "7! = " << factorial< 7 >::ret << endl; // 5040 return 0; } If one wants to learn more about C++ static metaprogramming, what are the best sources (books, websites, on-line courseware, whatever)?

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  • Can Haskell's Parsec library be used to implement a recursive descent parser with backup?

    - by Thor Thurn
    I've been considering using Haskell's Parsec parsing library to parse a subset of Java as a recursive descent parser as an alternative to more traditional parser-generator solutions like Happy. Parsec seems very easy to use, and parse speed is definitely not a factor for me. I'm wondering, though, if it's possible to implement "backup" with Parsec, a technique which finds the correct production to use by trying each one in turn. For a simple example, consider the very start of the JLS Java grammar: Literal: IntegerLiteral FloatingPointLiteral I'd like a way to not have to figure out how I should order these two rules to get the parse to succeed. As it stands, a naive implementation like this: literal = do { x <- try (do { v <- integer; return (IntLiteral v)}) <|> (do { v <- float; return (FPLiteral v)}); return(Literal x) } Will not work... inputs like "15.2" will cause the integer parser to succeed first, and then the whole thing will choke on the "." symbol. In this case, of course, it's obvious that you can solve the problem by re-ordering the two productions. In the general case, though, finding things like this is going to be a nightmare, and it's very likely that I'll miss some cases. Ideally, I'd like a way to have Parsec figure out stuff like this for me. Is this possible, or am I simply trying to do too much with the library? The Parsec documentation claims that it can "parse context-sensitive, infinite look-ahead grammars", so it seems like something like I should be able to do something here.

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  • Cache consistency & spawning a thread

    - by Dave Keck
    Background I've been reading through various books and articles to learn about processor caches, cache consistency, and memory barriers in the context of concurrent execution. So far though, I have been unable to determine whether a common coding practice of mine is safe in the strictest sense. Assumptions The following pseudo-code is executed on a two-processor machine: int sharedVar = 0; myThread() { print(sharedVar); } main() { sharedVar = 1; spawnThread(myThread); sleep(-1); } main() executes on processor 1 (P1), while myThread() executes on P2. Initially, sharedVar exists in the caches of both P1 and P2 with the initial value of 0 (due to some "warm-up code" that isn't shown above.) Question Strictly speaking – preferably without assuming any particular CPU – is myThread() guaranteed to print 1? With my newfound knowledge of processor caches, it seems entirely possible that at the time of the print() statement, P2 may not have received the invalidation request for sharedVar caused by P1's assignment in main(). Therefore, it seems possible that myThread() could print 0. References These are the related articles and books I've been reading. (It wouldn't allow me to format these as links because I'm a new user - sorry.) Shared Memory Consistency Models: A Tutorial hpl.hp.com/techreports/Compaq-DEC/WRL-95-7.pdf Memory Barriers: a Hardware View for Software Hackers rdrop.com/users/paulmck/scalability/paper/whymb.2009.04.05a.pdf Linux Kernel Memory Barriers kernel.org/doc/Documentation/memory-barriers.txt Computer Architecture: A Quantitative Approach amazon.com/Computer-Architecture-Quantitative-Approach-4th/dp/0123704901/ref=dp_ob_title_bk

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