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• Throttling CPU/Memory usage of a Thread in Java?

  - by Nalandial

  I'm writing an application that will have multiple threads running, and want to throttle the CPU/memory usage of those threads. There is a similar question for C++, but I want to try and avoid using C++ and JNI if possible. I realize this might not be possible using a higher level language, but I'm curious to see if anyone has any ideas. EDIT: Added a bounty; I'd like some really good, well thought out ideas on this. EDIT 2: The situation I need this for is executing other people's code on my server. Basically it is completely arbitrary code, with the only guarantee being that there will be a main method on the class file. Currently, multiple completely disparate classes, which are loaded in at runtime, are executing concurrently as separate threads. I inherited this code (the original author is gone). The way it's written, it would be a pain to refactor to create separate processes for each class that gets executed. If that's the only good way to limit memory usage via the VM arguments, then so be it. But I'd like to know if there's a way to do it with threads. Even as a separate process, I'd like to be able to somehow limit its CPU usage, since as I mentioned earlier, several of these will be executing at once. I don't want an infinite loop to hog up all the resources. EDIT 3: An easy way to approximate object size is with java's Instrumentation classes; specifically, the getObjectSize method. Note that there is some special setup needed to use this tool.

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• Mac CoreLocation Services does not ask for permissions

  - by Ryan Nichols

  I'm writing a Mac App that needs to use CoreLocation services. The code and location works fine, as long as I manually authenticate the service inside the security preference pane. However the framework is not automatically popping up with a permission dialog. The documentation states: Important The user has the option of denying an application’s access to the location service data. During its initial uses by an application, the Core Location framework prompts the user to confirm that using the location service is acceptable. If the user denies the request, the CLLocationManager object reports an appropriate error to its delegate during future requests. I do get an error to my delegate, and the value of +locationServicesEnabled is correct on CLLocationManager. The only part missing is the prompt to the user about permissions. This occurs on my development MPB and a friends MBP. Neither of us can figure out whats wrong. Has anyone run into this? Relevant code: _locationManager = [CLLocationManager new]; [_locationManager setDelegate:self]; [_locationManager setDesiredAccuracy:kCLLocationAccuracyKilometer]; ... [_locationManager startUpdatingLocation]; UPDATE: Answer It seems there is a problem with Sandboxing in which the CoreLocation framework is not allowed to talk to com.apple.CoreLocation.agent. I suspect this agent is responsible for prompting the user for permissions. If you add the Location Services Entitlement (com.apple.security.personal-information.location) it only gives your app the ability to use the CL framework. However you also need access to the CoreLocation agent to ask the user for permissions. You can give your app access by adding the entitlement 'com.apple.security.temporary-exception.mach-lookup.global-name' with a value of 'com.apple.CoreLocation.agent'. Users will be prompted for access automatically like you would expect. I've filed a bug to apple on this already.

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• Storing multiple inputs with the same name in a CodeIgniter session

  - by Joshua Cody

  I've posted this in the CodeIgniter forum and exhausted the forum search engine as well, so apologies if cross-posting is frowned upon. Essentially, I've got a single input, set up as <input type="text" name="goal">. At a user's request, they may add another goal, which throws a duplicate to the DOM. What I need to do is grab these values in my CodeIgniter controller and store them in a session variable. My controller is currently constructed thusly: function goalsAdd(){ $meeting_title = $this->input->post('topic'); $meeting_hours = $this->input->post('hours'); $meeting_minutes = $this->input->post('minutes'); $meeting_goals = $this->input->post('goal'); $meeting_time = $meeting_hours . ":" . $meeting_minutes; $sessionData = array( 'totaltime' => $meeting_time, 'title' => $meeting_title, 'goals' => $meeting_goals ); $this->session->set_userdata($sessionData); $this->load->view('test', $sessionData); } Currently, obviously, my controller gets the value of each input, writing over previous values in its wake, leaving only a string of the final value. I need to store these, however, so I can print them on a subsequent page. What I imagine I'd love to do is extend the input class to be able to call $this-input-posts('goal'). Eventually I will need to store other arrays to session values. But I'm totally open to implementation suggestion. Thanks so much for any help you can give.

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• Optimizing processing and management of large Java data arrays

  - by mikera

  I'm writing some pretty CPU-intensive, concurrent numerical code that will process large amounts of data stored in Java arrays (e.g. lots of double[100000]s). Some of the algorithms might run millions of times over several days so getting maximum steady-state performance is a high priority. In essence, each algorithm is a Java object that has an method API something like: public double[] runMyAlgorithm(double[] inputData); or alternatively a reference could be passed to the array to store the output data: public runMyAlgorithm(double[] inputData, double[] outputData); Given this requirement, I'm trying to determine the optimal strategy for allocating / managing array space. Frequently the algorithms will need large amounts of temporary storage space. They will also take large arrays as input and create large arrays as output. Among the options I am considering are: Always allocate new arrays as local variables whenever they are needed (e.g. new double[100000]). Probably the simplest approach, but will produce a lot of garbage. Pre-allocate temporary arrays and store them as final fields in the algorithm object - big downside would be that this would mean that only one thread could run the algorithm at any one time. Keep pre-allocated temporary arrays in ThreadLocal storage, so that a thread can use a fixed amount of temporary array space whenever it needs it. ThreadLocal would be required since multiple threads will be running the same algorithm simultaneously. Pass around lots of arrays as parameters (including the temporary arrays for the algorithm to use). Not good since it will make the algorithm API extremely ugly if the caller has to be responsible for providing temporary array space.... Allocate extremely large arrays (e.g. double[10000000]) but also provide the algorithm with offsets into the array so that different threads will use a different area of the array independently. Will obviously require some code to manage the offsets and allocation of the array ranges. Any thoughts on which approach would be best (and why)?

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• Powershell - Splitting string into seperate components

  - by TheD

  I am writing a script which will basically do the following: Read from a text file some arguements: DriveLetter ThreeLetterCode ServerName VolumeLetter Integer Eg. W MSS SERVER01 C 1 These values happen to form a folder destination W:\MSS\, and a filename which works in the following naming convention: SERVERNAME_VOLUMELETTER_VOL-b00X-iYYY.spi - Where The X is the Integer above The value Y I need to work out later, as this happens to be the value of the incremental image (backups) and I need to work out the latest incremental. So at the moment -- Count lines in file, and loop for this many lines. $lines = Get-Content -Path PostBackupCheck-Textfile.txt | Measure-Object -Line for ($i=0; $i -le $lines.Lines; $i++) Within this loop I need to do a Get-Content to read off the line I am currently looking at i.e. line 0, line 1, line 2, as there will be multiple lines in the format I wrote at the beginning and split the line into an array, whereby each part of the file, as seen above naming convention, is in a[0], a[1], a[2]. etc The reason for this is because, I need to then sort the folder that contains these, find the latest file, by date, and take the _iXXX.spi part and place this into the array value a[X] so I then have a complete filename to mount. This value will replace iYYY.spi It's a little complex because I also have to make sure when I do a Get-ChildItem with -Include before I sort it all by date, I am only including the filename that matches the arguements fed to it from the text file : So, SERVER01_C_VOL-b001-iYYY.spi and not anything else. i.e. not SERVER01_D_VOL-b001-iYYY.spi Then take the iYYY value from the sort on the Get-ChildItem -Include and place that into the appropriate array item. I've literally no idea where to start, so any ideas are appreciated! Hopefully I've explained in enough detail. I have also placed the code on Pastebin: http://pastebin.com/vtFifTW6 Thanks!

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• Accessing objects on one nib file from another nib file

  - by ASN

  I have two nib files Main.nib and Preferernces.nib I have a class CalendarView.m that inherits from NSView .It has a method for drawing calendar - (void)drawCalendar; In Main.nib window I have NSWindow(My Main window) which has an NSView item on it for displaying calendar.Main window has an NSPopUp button that shows a menu when application runs. Menu has a 'Preferences' menu item which on clicking show a preferences panel(NSPanel) that panel is in Preferences.nib file.Panel has a colorwell item .When application is executed clcking on colorwell show a color panel to choose color .But I am unable to apply that color to my calendar. I have another class PreferencesWindowController.m that shows preferences panel . It has a method changeColor that takes selected color from colors panel and make changes to user defaults . I have IBOutlet CalendarView *calView as a member in PreferencesWindowController.h class. In changeColor mehod I am writing - calView = [[CalendarView alloc] init]; [calView drawCalendar]; On debugging call goes to drawCalendar method of CalendarView but skips some part of it and goes to end of function without redrawing. On restarting the application color is applied but I want it to happen while application is executing, so that there is no need to rerun the application to view changes.

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• Putting BigDecimal data into HSQLDB test database using DbUnit

  - by Denise

  Hi everyone, I'm using Hibernate JPA in my backend. I am writing a unit test using JUnit and DBUnit to insert a set of data into an in-memory HSQL database. My dataset contains: <order_line order_line_id="1" quantity="2" discount_price="0.3"/> Which maps to an OrderLine Java object where the discount_price column is defined as: @Column(name = "discount_price", precision = 12, scale = 2) private BigDecimal discountPrice; However, when I run my test case and assert that the discount price returned equals 0.3, the assertion fails and says that the stored value is 0. If I change the discount_price in the dataset to be 0.9, it rounds up to 1. I've checked to make sure HSQLDB isn't doing the rounding and it definitely isn't because I can insert an order line object using Java code with a value like 5.3 and it works fine. To me, it seems like DBUtils is for some reason rounding the number I've defined. Is there a way I can force this to not happen? Can anyone explain why it might be doing this? Thanks!

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• ASP.net file operations delay

  - by mtranda

  Ok, so here's the problem: I'm reading the stream from a FileUpload control, reading in chunks of n bytes and writing the array in a loop until I reach the stream's end. Now the reason I do this is because I need to check several things while the upload is still going on (rather than doing a Save(); which does the whole thing in one go). Here's the problem: when doing this from the local machine, I can see the file just fine as it's uploading and its size increases (had to add a Sleep(); clause in the loop to actually get to see the file being written). However, when I upload the file from a remote machine, I don't get to see it until the the file has completed uploading. Also, I've added another call to write the progress to a text file as the progress is going on, and I get the same thing. Local: the file updates as the upload goes on, remote: the token file only appears after the upload's done (which is somewhat useless since I need it while the upload's still happening). Is there some sort of security setting in (or ASP.net) that maybe saves files in a temporary location for remote machines as opposed to the local machine and then moves them to the specified destination? I would liken this with ASP.net displaying error messages when browsing from the local machine (even on the public hostname) as opposed to the generic compilation error page/generic exception page that is shown when browsing from a remote machine (and customErrors are not off) Any clues on this? Thanks in advance.

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• How can I write System preferences with Java? Can I invoke UAC?

  - by Jonas

  How can I write system preferences with Java, using Preferences.systemRoot()? I tried with: Preferences preferences = Preferences.systemRoot(); preferences.put("/myapplication/databasepath", pathToDatabase); But I got this error message: 2010-maj-29 19:02:50 java.util.prefs.WindowsPreferences openKey VARNING: Could not open windows registry node Software\JavaSoft\Prefs at root 0x80000002. Windows RegOpenKey(...) returned error code 5. Exception in thread "AWT-EventQueue-0" java.lang.SecurityException: Could not open windows registry node Software\JavaSoft\Prefs at root 0x80000002: Access denied at java.util.prefs.WindowsPreferences.openKey(Unknown Source) at java.util.prefs.WindowsPreferences.openKey(Unknown Source) at java.util.prefs.WindowsPreferences.openKey(Unknown Source) at java.util.prefs.WindowsPreferences.putSpi(Unknown Source) at java.util.prefs.AbstractPreferences.put(Unknown Source) at biz.accountia.pos.install.Setup$2.actionPerformed(Setup.java:43) I would like to do this, because I want to install an embedded JavaDB database, and let multiple users on the computer to use the same database with the application. How to solve this? Can I invoke UAC and do this as Administrator from Java? And if I log in as Administrator when writing, can I read the values with my Java application if I'm logged in as a User?

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• Custom Calculations in a Matrix - Reporting Services 2005

  - by bfrancis

  I am writing a report to show gas usage (in gallons) used by each department. The request is to view each month and the gallons used by each department. A column is required to display what each departments target goal is, based on the gallons of gas they have used in a past time frame. Each departments target goal is x percent less than the total gallons used for said time frame. I currently have a matrix in Reporting Services with departments making up rows, months making up columns, and gallons filling the details. The matrix is being filled by dataset1. I have the data grouping as is requested for each month by each department. My problem is calculating the target goal. My thought was to create a second dataset (dataset2) that returns the gallons used based on the time frame requested. I grouped this data by department. I was hoping I could use the department field in each dataset to make sure the appropriate numbers were used. I added a new column which shows up next to the gallons field. As I attempted to build the Expression I found out that I could only grab the gallons used from dataset2 if I was summing the gallons field. This gives me the total gallons used by every department combined. I have tried to find resources with similar examples of what I am trying to accomplish but I cannot seem to come across one. I am trying to keep this as detailed as possible without making it too wordy. I would be more than happy to clarify or explain into further detail what I have written above if it is needed. If anyone has links, comments, or suggestions they would be greatly appreciated. A very simple visual or what I am hoping to accomplish is below. The months and departments would expand based on the data returned. months ------------------------------ departments| gallons/month | target goal

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• Correct initialization sequence for Linux serial port

  - by whitequark

  I wrote an application that must use serial ports on Linux, especially ttyUSB ones. Reading and writing operations are performed with standard select()/read() loop and write(), and there is probably nothing wrong in them, but initialization code (or absence of some part of it) damages something in the tty subsystem. Here it is: vuxboot(string filename, unsigned baud = B115200) : _debug(false) { _fd = open(filename.c_str(), O_RDWR | O_NOCTTY); if(!_fd) throw new io_error("cannot open port"); // Serial initialization was written with FTDI USB-to-serial converters // in mind. Anyway, who wants to use non-8n1 protocol? tcgetattr(_fd, &_termios); termios tio = {0}; tio.c_iflag = IGNPAR; tio.c_oflag = 0; tio.c_cflag = baud | CLOCAL | CREAD | CS8; tio.c_lflag = 0; tcflush(_fd, TCIFLUSH); tcsetattr(_fd, TCSANOW, &tio); } Another tcsetattr(_fd, TCSANOW, &_termios) sits in the destructor, but it is irrelevant. With or without this termios initialization, strange things happen in system after the application exits. Sometimes plain cat (or hd) exits immediately printing nothing or same stuff each time, sometimes it is waiting and not displaying any of the data that is surely sent onto the port; and close() (read() too, but not every time) emits a strange WARNING to dmesg referring to usb-serial.c. I checked the hardware and firmware tens of times (even on different machines) and I am sure it is working as intended; moreover, I stripped the firmware to just print same message over and over. How can I use serial port without destroying anything? Thanks.

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• mysql subselect alternative

  - by Arnold

  Hi, Lets say I am analyzing how high school sports records affect school attendance. So I have a table in which each row corresponds to a high school basketball game. Each game has an away team id and a home team id (FK to another "team table") and a home score and an away score and a date. I am writing a query that matches attendance with this seasons basketball games. My sample output will be (#_students_missed_class, day_of_game, home_team, away_team, home_team_wins_this_season, away_team_wins_this_season) I now want to add how each team did the previous season to my analysis. Well, I have their previous season stored in the game table but i should be able to accomplish that with a subselect. So in my main select statement I add the subselect: SELECT COUNT(*) FROM game_table WHERE game_table.date BETWEEN 'start of previous season' AND 'end of previous season' AND ( (game_table.home_team = team_table.id AND game_table.home_score > game_table.away_score) OR (game_table.away_team = team_table.id AND game_table.away_score > game_table.home_score)) In this case team-table.id refers to the id of the home_team so I now have all their wins calculated from the previous year. This method of calculation is neither time nor resource intensive. The Explain SQL shows that I have ALL in the Type field and I am not using a Key and the query times out. I'm not sure how I can accomplish a more efficient query with a subselect. It seems proposterously inefficient to have to write 4 of these queries (for home wins, home losses, away wins, away losses). I am sure this could be more lucid. I'll absolutely add color tomorrow if anyone has questions

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• How to bind "rest" variables to list of values in macro in Scheme

  - by Slartibartfast

  I want to make a helper macro for writing match-extensions. I have something like this: (define-match-expander my-expander (? (stx) (let* ([dat (cdr (syntax-e stx))] [var1 (car dat))] [var2 (cadr dat)]) ;transformer goes here ))) So I wanted a macro that will do this let binding. I've started with something like this: (define-syntax-rule (define-my-expander (id vars ...) body) (define-match-expander id (? (stx) (match-let ([(vars ...) (cdr (syntax-e stx))]) body)))) but match-let isn't defined in transformation time. First question would be is there any other way of doing this (making this expanders, I mean)? Maybe there is already something similar in plt-scheme that I'm not aware of, or I'm doing it wrong in some way. Regardless of answer on the first question, if I ever want to bound list of variables to list of values inside of a macro, how should I do it? EDIT: In combination with Eli's answer macro now looks like this: (define-syntax-rule (define-my-expander (id vars ...) body) (define-match-expander id (? (stx) (syntax-case stx () [(_ vars ...) body]))))

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• JavaScript: Achieving precise animation end values?

  - by bobthabuilda

  I'm currently trying to write my own JavaScript library. I'm in the middle of writing an animation callback, but I'm having trouble getting precise end values, especially when animation duration times are smaller. Right now, I'm only targeting positional animation (left, top, right, bottom). When my animations complete, they end up having an error margin of 5px~ on faster animations, and 0.5px~ on animations 1000+ ms or greater. Here's the bulk of the callback, with notes following. var current = parseFloat( this[0].style[prop] || 0 ) // If our target value is greater than the current , gt = !!( value > current ) , delta = ( Math.abs(current - value) / (duration / 13) ) * (gt ? 1 : -1) , elem = this[0] , anim = setInterval( function(){ elem.style[prop] = ( current + delta ) + 'px'; current = parseFloat( elem.style[prop] ); if ( gt && current >= value || !gt && current <= value ) clearInterval( anim ); }, 13 ); this[0] and elem both reference the target DOM element. prop references the property to animate, left, top, bottom, right, etc. current is the current value of the DOM element's property. value is the desired value to animate to. duration is the specified duration (in ms) that the animation should last. 13 is the setInterval delay (which should roughly be the absolute minimal for all browsers). gt is a var that is true if value exceeds the initial current, else it is false. How can I resolve the error margin?

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• Automated UAT/functional tests on Swing applications without source code

  - by jas

  Our team is now working on a big Swing application. Our job basically focuses on writing extensions to the existing framework. A typical job would be adding a new panel/ or adding a new tab with some extra functionalities that suit our need. It seems FEST can help a lot in terms of unit-test our code. I am going to try it out this week. But the question here is if there is a way to do automated functional testing on the whole application. In another word, we do not only need to test our code but also the framework. After all, UAT is the most important part. I am currently considering decompiling the jar files we got into source code then we can identify the components and then use FEST. So, before I get started to give this approach a shot, I think I just ask for ideas and inspirations here. There must be people who have done similar things before. Would be nice if I could learn from the veterans who fought against this before . Thanks,

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• How do I browse a Websphere MQ message without removing it?

  - by jmgant

  I'm writing a .NET Windows Forms application that will post a message to a Websphere MQ queue and then poll a different queue for a response. If a response is returned, the application will partially process the response in real time. But the response needs to stay in the queue so that a daily batch job, which also reads from the response queue, can do the rest of the processing. I've gotten as far as reading the message. What I haven't been able to figure out is how to read it without removing it. Here's what I've got so far. I'm an MQ newbie, so any suggestions will be appreciated. And feel free to respond in C#. Public Function GetMessage(ByVal msgID As String) As MQMessage Dim q = ConnectToResponseQueue() Dim msg As New MQMessage() Dim getOpts As New MQGetMessageOptions() Dim runThru = Now.AddMilliseconds(CInt(ConfigurationManager.AppSettings("responseTimeoutMS"))) System.Threading.Thread.Sleep(1000) 'Wait for one second before checking for the first response' While True Try q.Get(msg, getOpts) Return msg Catch ex As MQException When ex.Reason = MQC.MQRC_NO_MSG_AVAILABLE If Now > runThru Then Throw ex System.Threading.Thread.Sleep(3000) Finally q.Close() End Try End While Return Nothing 'Should never reach here' End Function NOTE: I haven't verified that my code actually removes the message. But that's how I understand MQ to work, and that appears to be what's happening. Please correct me if that's not the default behavior.

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• Copy SQL Server data from one server to another on a schedule

  - by rwmnau

  I have a pair of SQL Servers at different webhosts, and I'm looking for a way to periodically update the one server using the other. Here's what I'm looking for: As automated as possible - ideally, without any involvement on my part once it's set up. Pushes a number of databases, in their entirely (including any schema changes) from one server to the other Freely allows changes on the source server without breaking my process. For this reason, I don't want to use replication, as I'd have to break it every time there's an update on the source, and then recreate the publication and subscription One database is about 4GB in size and contains binary data. I'm not sure if there's a way to export this to a script, but it would be a mammoth file if I did. Originally, I was thinking of writing something that takes a scheduled full backup of each database, FTPs the backups from one server to the other once they're done, and then the new server picks it up and restores it. The only downside I can see to this is that there's no way to know that the backups are done before starting to transfer them - can these backups be done synchronously? Also, the server being refreshes is our test server, so if there's some downtime involved in moving the data, that's fine. Does anybody out there have a better idea, or is what I'm currently considering the best non-replication way to go? Thanks for your help, everybody. UPDATE: I ended up designing a custom solution to get this done using BAT files, 7Zip,command line FTP, and OSQL, so it runs in a completely automatic way and aggregates the data from a dozen servers across the country. I've detailed the steps in a blog entry. Thanks for all your input!

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• Alternative to MS Project 2007 for production scheduling?

  - by john c

  OK... Im coming to grips with the fact that MS Project 2007 may not be the correct tool for my production scheduling. We serve 120 to 150 projects a year with durations from 6 weeks to 12 months. The task are simple (6 to 8 per project) and the resource pool is stable (15 to 20 people). It's really an assembly line product but with extremely varied durations. I need to be able to prioritize the projects for production and run projects concurrently to fully utilize my resources. What are the feelings of the stackoverflow community. Am I using the wrong program? I was really hoping to make this simple for non-programer types to input project data into a form and have the schedule software automated enough to make most of the decisions. Is there a better solution available commercially? I'd like to hold on writing a custom spreadsheet as a last resort but if that's the best route then so be it. Thank you so much for your input.

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• Turbogears 2.0 with Python 2.6

  - by AKSK

  I've tried to install TurboGears 2.0 with Python 2.6 on both Windows 7 and Windows XP, but both give the same error: File "D:\PythonProjects\tg2env\Scripts\paster-script.py", line 8, in <module> load_entry_point('pastescript==1.7.3', 'console_scripts', 'paster')() File "D:\PythonProjects\tg2env\lib\site-packages\pastescript-1.7.3-py2.6.egg\paste\script\command.py", line 73, in run commands = get_commands() File "D:\PythonProjects\tg2env\lib\site-packages\pastescript-1.7.3-py2.6.egg\paste\script\command.py", line 115, in get_ plugins = pluginlib.resolve_plugins(plugins) File "D:\PythonProjects\tg2env\lib\site-packages\pastescript-1.7.3-py2.6.egg\paste\script\pluginlib.py", line 81, in res pkg_resources.require(plugin) File "D:\PythonProjects\tg2env\lib\site-packages\setuptools-0.6c9-py2.6.egg\pkg_resources.py", line 626, in require File "D:\PythonProjects\tg2env\lib\site-packages\setuptools-0.6c9-py2.6.egg\pkg_resources.py", line 524, in resolve pkg_resources.DistributionNotFound: zope.sqlalchemy>=0.4: Not Found for: City_Guide (did you run python setup.py develop?) Now, according to the documentation on the main site, TurboGears 2.0 supports Python 2.6 in this page: TurboGears works with any version of python between 2.4 and 2.6. The most widely deployed version of python at the moment of this writing is version 2.5. Both python 2.4 and python 2.6 require additional steps which will be covered in the appropriate sections. But they never mention those steps in the documentation.

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• Creating circular generic references

  - by M. Jessup

  I am writing an application to do some distributed calculations in a peer to peer network. In defining the network I have two class the P2PNetwork and P2PClient. I want these to be generic and so have the definitions of: P2PNetwork<T extends P2PClient<? extends P2PNetwork<T>>> P2PClient<T extends P2PNetwork<? extends T>> with P2PClient defining a method of setNetwork(T network). What I am hoping to describe with this code is: A P2PNetwork is constituted of clients of a certain type A P2PClient may only belong to a network whose clients consist of the same type as this client (the circular-reference) This seems correct to me but if I try to create a non-generic version such as MyP2PClient<MyP2PNetwork<? extends MyP2PClient>> myClient; and other variants I receive numerous errors from the compiler. So my questions are as follows: Is a generic circular reference even possible (I have never seen anything explicitly forbidding it)? Is the above generic definition a correct definition of such a circular relationship? If it is valid, is it the "correct" way to describe such a relationship (i.e. is there another valid definition, which is stylistically preferred)? How would I properly define a non-generic instance of a Client and Server given the proper generic definition?

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• C# TcpClient, getting back the entire response from a telnet device

  - by Dan Bailiff

  I'm writing a configuration tool for a device that can communicate via telnet. The tool sends a command via TcpClient.GetStream().Write(...), and then checks for the device response via TcpClient.GetStream().ReadByte(). This works fine in unit tests or when I'm stepping through code slowly. If I run the config tool such that it performs multiple commands consecutively, then the behavior of the read is inconsistent. By inconsistent I mean sometimes the data is missing, incomplete or partially garbled. So even though the device performed the operation and responded, my code to check for the response was unreliable. I "fixed" this problem by adding a Thread.Sleep to make sure the read method waits long enough for the device to complete its job and send back the whole response (in this case 1.5 seconds was a safe amount). I feel like this is wrong, blocking everything for a fixed time, and I wonder if there is a better way to get the read method to wait only long enough to get the whole response from the device. private string Read() { if (!tcpClient.Connected) throw (new Exception("Read() failed: Telnet connection not available.")); StringBuilder sb = new StringBuilder(); do { ParseTelnet(ref sb); System.Threading.Thread.Sleep(1500); } while (tcpClient.Available > 0); return sb.ToString(); } private void ParseTelnet(ref StringBuilder sb) { while (tcpClient.Available > 0) { int input = tcpClient.GetStream().ReadByte(); switch (input) { // parse the input // ... do other things in special cases default: sb.Append((char)input); break; } } }

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• Python access an object byref / Need tagging

  - by Aaron C. de Bruyn

  I need to suck data from stdin and create a object. The incoming data is between 5 and 10 lines long. Each line has a process number and either an IP address or a hash. For example: pid=123 ip=192.168.0.1 - some data pid=123 hash=ABCDEF0123 - more data hash=ABCDEF123 - More data ip=192.168.0.1 - even more data I need to put this data into a class like: class MyData(): pid = None hash = None ip = None lines = [] I need to be able to look up the object by IP, HASH, or PID. The tough part is that there are multiple streams of data intermixed coming from stdin. (There could be hundreds or thousands of processes writing data at the same time.) I have regular expressions pulling out the PID, IP, and HASH that I need, but how can I access the object by any of those values? My thought was to do something like this: myarray = {} for each line in sys.stdin.readlines(): if pid and ip: #If we can get a PID out of the line myarray[pid] = MyData().pid = pid #Create a new MyData object, assign the PID, and stick it in myarray accessible by PID. myarray[pid].ip = ip #Add the IP address to the new object myarray[pid].lines.append(data) #Append the data myarray[ip] = myarray[pid] #Take the object by PID and create a key from the IP. <snip>do something similar for pid and hash, hash and ip, etc...</snip> This gives my an array with two keys (a PID and an IP) and they both point to the same object. But on the next iteration of the loop, if I find (for example) an IP and HASH and do: myarray[hash] = myarray[ip] The following is False: myarray[hash] == myarray[ip] Hopefully that was clear. I hate to admit that waaay back in the VB days, I remember being able handle objects byref instead of byval. Is there something similar in Python? Or am I just approaching this wrong?

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• Why is creating a ring buffer shared by different processes so hard (in C++), what I am doing wrong?

  - by recipriversexclusion

  I am being especially dense about this but it seems I'm missing an important, basic point or something, since what I want to do should be common: I need to create a fixed-size ring buffer object from a manager process (Process M). This object has write() and read() methods to write/read from the buffer. The read/write methods will be called by independent processes (Process R and W) I have implemented the buffer, SharedBuffer<T&>, it allocates buffer slots in SHM using boost::interprocess and works perfectly within a single process. I have read the answers to this question and that one on SO, as well as asked my own, but I'm still in the dark about how to have different processes access methods from a common object. The Boost doc has an example of creating a vector in SHM, which is very similar to what I want, but I want to instantiate my own class. My current options are: Use placement new, as suggested by Charles B. to my question; however, he cautions that it's not a good idea to put non-POD objects in SHM. But my class needs the read/write methods, how can I handle those? Add an allocator to my class definition, e.g. have SharedBuffer<T&, Alloc> and proceed similarly to the vector example given in boost. This sounds really complicated. Change SharedBuffer to a POD class, i.e. get rid of all the methods. But then how to synchronize reading and writing between processes? What am I missing? Fixed-length ring buffers are very common, so either this problem has a solution or else I'm doing something wrong.

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• Parse and read data frame in C?

  - by user253656

  I am writing a program that reads the data from the serial port on Linux. The data are sent by another device with the following frame format: |start | Command | Data | CRC | End | |0x02 | 0x41 | (0-127 octets) | | 0x03| ---------------------------------------------------- The Data field contains 127 octets as shown and octet 1,2 contains one type of data; octet 3,4 contains another data. I need to get these data I know how to write and read data to and from a serial port in Linux, but it is just to write and read a simple string (like "ABD") My issue is that I do not know how to parse the data frame formatted as above so that I can: get the data in octet 1,2 in the Data field get the data in octet 3,4 in the Data field get the value in CRC field to check the consistency of the data Here the sample snip code that read and write a simple string from and to a serial port in Linux: int writeport(int fd, char *chars) { int len = strlen(chars); chars[len] = 0x0d; // stick a <CR> after the command chars[len+1] = 0x00; // terminate the string properly int n = write(fd, chars, strlen(chars)); if (n < 0) { fputs("write failed!\n", stderr); return 0; } return 1; } int readport(int fd, char *result) { int iIn = read(fd, result, 254); result[iIn-1] = 0x00; if (iIn < 0) { if (errno == EAGAIN) { printf("SERIAL EAGAIN ERROR\n"); return 0; } else { printf("SERIAL read error %d %s\n", errno, strerror(errno)); return 0; } } return 1; } Does anyone please have some ideas? Thanks all.

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• Is the Windows dev environment worth the cost?

  - by MCS

  I recently made the move from Linux development to Windows development. And as much of a Linux enthusiast that I am, I have to say - C# is a beautiful language, Visual Studio is terrific, and now that I've bought myself a trackball my wrist has stopped hurting from using the mouse so much. But there's one thing I can't get past: the cost. Windows 7, Visual Studio, SQL Server, Expression Blend, ViEmu, Telerik, MSDN - we're talking thousands for each developer on the project! You're definitely getting something for your money - my question is, is it worth it? [Not every developer needs all the aforementioned tools - but have you ever heard of anyone writing C# code without Visual Studio? I've worked on pretty large software projects in Linux without having to pay for any development tool whatsoever.] Now obviously, if you're already a Windows shop, it doesn't pay to retrain all your developers. And if you're looking to develop a Windows desktop app, you just can't do that in Linux. But if you were starting a new web application project and could hire developers who are experts in whatever languages you want, would you still choose Windows as your development platform despite the high cost? And if yes, why?

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