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• Patterns for wrapping a command line tool in another language

  - by Tom Duckering

  I'm currently writing some Java to wrap around an extensive command line tool. It feels like I'm writing a lot of similar code. I'm wondering if there are any established patterns for wrapping command line tools - passing arguments and handling output and so on. Specific examples in Java would obviously be great, but any general suggestions or pointers are welcome too.

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• Quick create C# properties from variables

  - by user204588

  Hello, For C#, I hate writing out the variables and then writing out all the properties. Isn't there a way to select all variables, right click and create all the properties.

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• How do you combine "Revision Control" with "WorkFlow" for R?

  - by Tal Galili

  Hello all, I remember coming across R users writing that they use "Revision control" (e.g: "Source control"), and I am curious to know: How do you combine "Revision control" with your statistical analysis WorkFlow? Two (very) interesting discussions talk about how to deal with the WorkFlow. But neither of them refer to the revision control element: http://stackoverflow.com/questions/1266279/how-to-organize-large-r-programs http://stackoverflow.com/questions/1429907/workflow-for-statistical-analysis-and-report-writing A Long Update To The Question: Following some of the people's answers, and Dirk's question in the comment, I would like to direct my question a bit more. After reading the Wiki article about "revision control" (which I was previously not familiar with), it was clear to me that when using revision control, what one does is to build a development structure of his code. This structure either leads to a "final product" or to several branches. When building something like, let's say, a website. There is usually one end product you work towards (the website), with some prototypes along the way. But when doing a statistical analysis, the work (to my view) is different. Sometimes you know where you want to get to. But more often, you explore. Explore cleaning the dataset. Explore different methods for statistical analysis, and ask various questions of your data (and I am writing this, knowing how Frank Harrell, and other experience statisticians feels about Data dredging). That is way the WorkFlow question with statistical programming is (in my view) a serious and deep question, raising many issues, The simpler ones are technical: Which revision control software do you use (and why) ? Which IDE do you use(and why) ? The more interesting question are about work process: How do you structure your files? What do you keep as a separate file and what as a revision? or asking in a different way - What should be a "branch" and what should be a "sub project" in your code? For example: When starting to explore your data, should a plot be creating and then erased because it didn't lead any where (but kept as a revision) or should there be a backup file of that path? How you solve this tension was my initial curiosity. The second question is "what might I be missing?". What rules (of thumb) should one follow so to avoid common pitfalls doing statistical programming with version control? In my intuition, I feel that statistical programming is inherently different then software development (I am writing this without being a real expert in statistical programming, and even less so in software development). That's way I am unsure which of the lessons I have read here about version control would be applicable. Thanks a lot, Tal

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• How do I make a docstring in VB.NET?

  - by Wayne Werner

  Hi, I'm writing a .dll in Visual Basic. When writing code in Visual Studio if I do something like Console.WriteLine( it will pop up a tooltip with a bit of documentation for the function. Is it possible to write something in my function/sub that would provide that information to Visual Studio? Thanks

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• Can anyone write a XSL-fo for this XML File with SVG tags?

  - by atrueguy

  Hi all this XML file is very unique with SVG tags, I am stuck in writing an XSL-fo for this xml file, can one help me out in writing a XSL FO, if not the exact answer, atleast give me a idea of how to write, please see the xml file in the below link. http://kzekaa.bay.livefilestore.com/y1pDRDfrEn98IkEO7MQ9MEkC-RQE4QxwsrgVV57WrGWK_AEsqzpwJWkydbnE3NVwrMNT2l9mIG7rErd_NPO94Fmrhrm2Z_zleID/Cleaned_file_source.xml

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• Why doesn't Oracle SQL allow us to use column aliases in GROUP BY clauses?

  - by Mehper C. Palavuzlar

  This is a situation I'm generally facing while writing SQL queries. I think that writing the whole column (e.g. long case expressions, sum functions with long parameters) instead of aliases in GROUP BY expressions makes the query longer and less readable. Why doesn't Oracle SQL allow us to use the column aliases in GROUP BY clause? There must be an important reason behind it.

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• Can anyone write a XSL-fo for the XML File with SVG tags?

  - by atrueguy

  Hi all this XML file is very unique with SVG tags, I am stuck in writing an XSL-fo for this xml file, can one help me out in writing a XSL FO, if not the exact answer, atleast give me a idea of how to write, please see the xml file in the below link.

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• c++ volatile multithreading variables

  - by anon

  I'm writing a C++ app. I have a class variable that more than one thread is writing to. In C++, anything that can be modified without the compiler "realizing" that it's being changed needs to be marked volatile right? So if my code is multi threaded, and one thread may write to a var while another reads from it, do I need to mark the var volaltile? [I don't have a race condition since I'm relying on writes to ints being atomic] Thanks!

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• StreamWriter appends random data

  - by void

  Hi I'm seeing odd behaviour using the StreamWriter class writing extra data to a file using this code: public void WriteToCSV(string filename) { StreamWriter streamWriter = null; try { streamWriter = new StreamWriter(filename); Log.Info("Writing CSV report header information ... "); streamWriter.WriteLine("\"{0}\",\"{1}\",\"{2}\",\"{3}\"", ((int)CSVRecordType.Header).ToString("D2", CultureInfo.CurrentCulture), m_InputFilename, m_LoadStartDate, m_LoadEndDate); int recordCount = 0; if (SummarySection) { Log.Info("Writing CSV report summary section ... "); foreach (KeyValuePair<KeyValuePair<LoadStatus, string>, CategoryResult> categoryResult in m_DataLoadResult.DataLoadResults) { streamWriter.WriteLine("\"{0}\",\"{1}\",\"{2}\",\"{3}\"", ((int)CSVRecordType.Summary).ToString("D2", CultureInfo.CurrentCulture), categoryResult.Value.StatusString, categoryResult.Value.Count.ToString(CultureInfo.CurrentCulture), categoryResult.Value.Category); recordCount++; } } Log.Info("Writing CSV report cases section ... "); foreach (KeyValuePair<KeyValuePair<LoadStatus, string>, CategoryResult> categoryResult in m_DataLoadResult.DataLoadResults) { foreach (CaseLoadResult result in categoryResult.Value.CaseLoadResults) { if ((LoadStatus.Success == result.Status && SuccessCases) || (LoadStatus.Warnings == result.Status && WarningCases) || (LoadStatus.Failure == result.Status && FailureCases) || (LoadStatus.NotProcessed == result.Status && NotProcessedCases)) { streamWriter.Write("\"{0}\",\"{1}\",\"{2}\",\"{3}\",\"{4}\"", ((int)CSVRecordType.Result).ToString("D2", CultureInfo.CurrentCulture), result.Status, result.UniqueId, result.Category, result.ClassicReference); if (RawResponse) { streamWriter.Write(",\"{0}\"", result.ResponseXml); } streamWriter.WriteLine(); recordCount++; } } } streamWriter.WriteLine("\"{0}\",\"{1}\"", ((int)CSVRecordType.Count).ToString("D2", CultureInfo.CurrentCulture), recordCount); Log.Info("CSV report written to '{0}'", fileName); } catch (IOException execption) { string errorMessage = string.Format(CultureInfo.CurrentCulture, "Unable to write XML report to '{0}'", fileName); Log.Error(errorMessage); Log.Error(exception.Message); throw new MyException(errorMessage, exception); } finally { if (null != streamWriter) { streamWriter.Close(); } } } The file produced contains a set of records on each line 0 to N, for example: [Record Zero] [Record One] ... [Record N] However the file produced either contains nulls or incomplete records from further up the file appended to the end. For example: [Record Zero] [Record One] ... [Record N] [Lots of nulls] or [Record Zero] [Record One] ... [Record N] [Half complete records] This also happens in separate pieces of code that also use the StreamWriter class. Furthermore, the files produced all have sizes that are multiples of 1024. I've been unable to reproduce this behaviour on any other machine and have tried recreating the environment. Previous versions of the application didn't exhibite this behaviour despite having the same code for the methods in question. EDIT: Added extra code.

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• Thread safety in C# arrays

  - by Betamoo

  Does having 2 different threads : one reading from a C# array (e.g from first location), and another one writing to the same C# array but to a different location(e.g to the last location) is thread safe or not? (And I mean here without locking reading nor writing)

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• Facebook "like" button for blogger

  - by Veraa

  Hi, i have been looking for a javascript code which is like the facebook "like" widget to put in my blogger site. The examples of the buttons are like in the following website, http://textsfromlastnight.com/ Where people are able to flag the "Good Nights" or "Bad Nights". I have no experienced in writing scripts neither do i have any script writing programs, so was wondering if any people can help with the scripts, or maybe tutorials would be of great help! Thanks!

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• Hibernate Distributed Cache

  - by DD

  Hi, I'm looking to setup Hibernate with distributed cache where I have one application writing to the DB and another one reading from the DB. Is there an easy way to notify the reading application when the writing one has written through Hibernate? The distributed cache will invalidate the cache but I need the reading application to know a change has been made to refresh its data immediately. Thanks, D

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• TabControl without the tabs (QStackWidget in c#)

  - by elcuco

  I am writing an application who's GUI changes depending on several conditions. I implemented this in Qt4 and internally used QStackWidget (basically, it's a series of controls, which only one can be visible each time). I am currently using a TabControl - what are my alternatives in C#? EDIT: I wrote a Qt4 application which was using QStackWidget. Now I am re-writing the same application in C#. No code is shared, this is a different application.

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• Java writes bad wave files

  - by Cliff

  I'm writing out wave files in Java using AudioInputStream output = new AudioInputStream(new ByteArrayInputStream(rawPCMSamples), new AudioFormat(22000,16,1,true,false), rawPCMSamples.length) AudioSystem.write(output, AudioFileFormat.Type.WAVE, new FileOutputStream('somefile.wav')) And I get what appears to be corrupt wave files on OSX. They won't play from Finder however using the same code behind a servlet writing directly to the response stream and setting the Content-Type to audio/wave seems to play fine in quicktime. What gives?

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• Metaprogramming on web server

  - by bobobobo

  From time to time, I find myself writing server code that produces JavaScript code as the output result. I can point out why it is really bad: Inextricable tie between server code and client code. Can render client code un-reusable. But sometimes, it just seems to make sense. And isn't it kinda sorta interesting? I guess the question is, is writing server code that produces JavaScript code a really bad practice, or "does everyone do it"?

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• How expensive is synchronization?

  - by someguy

  I am writing a networking application using the java.nio api. My plan is to perform I/O on one thread, and handle events on another. To do this though, I need to synchronize reading/writing so that a race condition is never met. Bearing in mind that I need to handle thousands of connections concurrently, is synchronization worth it, or should I use a single thread for I/O and event handling?

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• Interrupt mechanism in C,C++

  - by mawia

  Hey I was writing a udp client server in which a client waits for packets from server.But I want to limit this wait for certain time.After client don't get response for a certain moment in raise an alarm,basically it comes out and start taking remedy steps.So what are the possible solution for it.I think writing a wrapper around recv will work but how exactly this has to be done,I mean how will make recv raise alarm for you after that time limit. Any Help in this regard will be appreciated. Thanks!

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• How do i pass null into stdin like this perl code?

  - by acidzombie24

  This is my question and apparently this is the answer. I found you can stdout to null by writing NUL in command prompt so i tried writing < NUL at the end of my argument. No luck. How do i pass in null or do something with the IO locks like that perl code does so i can get my ffmpeg script not locking up after 15 or so seconds?

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• ImgBurn fails to burn data CD-R disk due to "Layouts do not match" error

  - by 0xAether

  I have a reoccurring problem with the program ImgBurn. Whenever I try and burn anything to a CD-R using ImgBurn it burns just fine, except for when I go and verify the disk. It tells me that the "Layouts do not match". Windows 7 shows the disk as completely blank. Although, I see on the bottom of the disk it has been written to. I can burn ISO files to DVD-R's just fine. This only seems to happen with CD-R's. The CD-R's I'm using are Memorex Cool Colors 52x CD-R's. I have looked on Google, and it seems like I'm not the only one this happens to. Unfortunately, no one is able to provide an explanation. I have included the log file from the last CD I just burnt. If you need anything else to better diagnose this problem, I will gladly provide it. ; //****************************************\\ ; ImgBurn Version 2.5.7.0 - Log ; Monday, 19 November 2012, 16:11:57 ; \\****************************************// ; ; I 16:04:55 ImgBurn Version 2.5.7.0 started! I 16:04:55 Microsoft Windows 7 Ultimate x64 Edition (6.1, Build 7601 : Service Pack 1) I 16:04:55 Total Physical Memory: 4,156,380 KB - Available: 3,317,144 KB I 16:04:55 Initialising SPTI... I 16:04:55 Searching for SCSI / ATAPI devices... I 16:04:56 -> Drive 1 - Info: Optiarc DVD RW AD-7560S SH03 (D:) (SATA) I 16:04:56 Found 1 DVD±RW/RAM! I 16:05:37 Operation Started! I 16:05:37 Source File: C:\Users\Aaron\Desktop\VMware Workstation 9.iso I 16:05:37 Source File Sectors: 223,057 (MODE1/2048) I 16:05:37 Source File Size: 456,820,736 bytes I 16:05:37 Source File Volume Identifier: VMwareWorksta9 I 16:05:37 Source File Volume Set Identifier: 20121119_2102 I 16:05:37 Source File File System(s): ISO9660, Joliet I 16:05:37 Destination Device: [1:0:0] Optiarc DVD RW AD-7560S SH03 (D:) (SATA) I 16:05:37 Destination Media Type: CD-R (Disc ID: 97m17s06f, Moser Baer India) I 16:05:37 Destination Media Supported Write Speeds: 10x, 16x, 20x, 24x I 16:05:37 Destination Media Sectors: 359,847 I 16:05:37 Write Mode: CD I 16:05:37 Write Type: SAO I 16:05:37 Write Speed: 6x I 16:05:37 Lock Volume: Yes I 16:05:37 Test Mode: No I 16:05:37 OPC: No I 16:05:37 BURN-Proof: Enabled W 16:05:37 Write Speed Miscompare! - MODE SENSE: 1,764 KB/s (10x), GET PERFORMANCE: 11,080 KB/s (63x) W 16:05:37 Write Speed Miscompare! - MODE SENSE: 1,764 KB/s (10x), GET PERFORMANCE: 11,080 KB/s (63x) W 16:05:37 Write Speed Miscompare! - MODE SENSE: 1,764 KB/s (10x), GET PERFORMANCE: 11,080 KB/s (63x) W 16:05:37 Write Speed Miscompare! - MODE SENSE: 1,764 KB/s (10x), GET PERFORMANCE: 11,080 KB/s (63x) W 16:05:37 Write Speed Miscompare! - MODE SENSE: 1,764 KB/s (10x), GET PERFORMANCE: 11,080 KB/s (63x) W 16:05:37 Write Speed Miscompare! - Wanted: 1,058 KB/s (6x), Got: 1,764 KB/s (10x) / 11,080 KB/s (63x) W 16:05:37 The drive only supports writing these discs at 10x, 16x, 20x, 24x. I 16:05:38 Filling Buffer... (80 MB) I 16:05:40 Writing LeadIn... I 16:06:07 Writing Session 1 of 1... (1 Track, LBA: 0 - 223056) I 16:06:07 Writing Track 1 of 1... (MODE1/2048, LBA: 0 - 223056) I 16:11:00 Synchronising Cache... I 16:11:18 Exporting Graph Data... I 16:11:18 Graph Data File: C:\Users\Aaron\AppData\Roaming\ImgBurn\Graph Data Files\Optiarc_DVD_RW_AD-7560S_SH03_MONDAY-NOVEMBER-19-2012_4-05_PM_97m17s06f_6x.ibg I 16:11:18 Export Successfully Completed! I 16:11:18 Operation Successfully Completed! - Duration: 00:05:41 I 16:11:18 Average Write Rate: 1,522 KB/s (10.1x) - Maximum Write Rate: 1,544 KB/s (10.3x) I 16:11:18 Cycling Tray before Verify... W 16:11:23 Waiting for device to become ready... I 16:11:47 Device Ready! E 16:11:47 CompareImageFileLayouts Failed! - Session Count Not Equal (1/0) E 16:11:47 Verify Failed! - Reason: Layouts do not match. I 16:11:57 Close Request Acknowledged I 16:11:57 Closing Down... I 16:11:57 Shutting down SPTI... I 16:11:57 ImgBurn closed!

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• collectd does not work

  - by bery

  I have installed collectd-5.0.0 on Fedora12 server and would like to run its service for receiving data from clients. I have enabled network plugin and rddtool plugin as commented: collectd.conf in server: BaseDir "/opt/collectd/var/lib/collectd" LoadPlugin "logfile" LoadPlugin network LoadPlugin rrdtool <Plugin network> Listen "192.168.8.37" "25826" </Plugin> collectd.conf in client: LoadPlugin logfile LoadPlugin cpu LoadPlugin network LoadPlugin memory <Plugin network> Server"192.168.8.37" "25826" </Plugin> collectd.log in server: [2011-08-03 02:36:04] Exiting normally. [2011-08-03 02:36:04] rrdtool plugin: Shutting down the queue thread. [2011-08-03 02:36:04] network plugin: Stopping receive thread. [2011-08-03 02:36:04] network plugin: Stopping dispatch thread. [2011-08-03 02:37:11] Initialization complete, entering read-loop. collectd.log in client: [2011-08-02 17:31:44] Initialization complete, entering read-loop. results thst execute netstat on server: netstat -ulpn | grep 25826 udp 0 0 192.168.8.37:25826 0.0.0.0:* 4744/collectd problem: but there is noting in "/opt/collectd/var/lib/collectd/" on ser yes,I move the port number of "25826" as your propose(But I think this is the default port for coolectd).there is no rdd files recived on server. collectd.log in client collectd [2011-08-03 10:01:36] plugin_read_thread: Handling memory'. [2011-08-03 10:01:36] plugin_read_thread: Handlingcpu'. [2011-08-03 10:01:36] plugin_dispatch_values: time = 1312380096.431; interval = 10.000; host = uml; plugin = memory; plugin_instance = ; type = memory; type_instance = used; [2011-08-03 10:01:36] plugin_dispatch_values: time = 1312380096.431; interval = 10.000; host = uml; plugin = cpu; plugin_instance = 0; type = cpu; type_instance = user; [2011-08-03 10:01:36] uc_update: uml/memory/memory-used: ds[0] = 280412160.000000 [2011-08-03 10:01:36] plugin: plugin_write: Writing values via network. [2011-08-03 10:01:36] uc_update: uml/cpu-0/cpu-user: ds[0] = 0.100008 [2011-08-03 10:01:36] plugin: plugin_write: Writing values via network. [2011-08-03 10:01:36] plugin_dispatch_values: time = 1312380096.431; interval = 10.000; host = uml; plugin = memory; plugin_instance = ; type = memory; type_instance = buffered; [2011-08-03 10:01:36] plugin_dispatch_values: time = 1312380096.431; interval = 10.000; host = uml; plugin = cpu; plugin_instance = 0; type = cpu; type_instance = nice; [2011-08-03 10:01:36] uc_update: uml/memory/memory-buffered: ds[0] = 344182784.000000 [2011-08-03 10:01:36] plugin: plugin_write: Writing values via network. [2011-08-03 10:01:36] uc_update: uml/cpu-0/cpu-nice: ds[0] = 0.000000 [2011-08-03 10:01:36] plugin: plugin_write: Writing values via network. [2011-08-03 10:01:36] network plugin: flush_buffer: send_buffer_fill = 1340 [2011-08-03 10:01:36] network plugin: network_send_buffer: buffer_len = 1340 ... [2011-08-03 10:01:36] plugin_read_thread: Next read of the cpu plugin at 1312380106.429064774. collectd.log in server collectd: [2011-08-03 20:18:08] type = network [2011-08-03 20:18:08] type = rrdtool [2011-08-03 20:18:08] network plugin: sockent_open: node = 192.168.8.37; service = 25826; [2011-08-03 20:18:08] fd = 3; calling bind' [2011-08-03 20:18:08] Done parsing/opt/collectd//share/collectd/types.db' [2011-08-03 20:18:08] interval_g = 10; [2011-08-03 20:18:08] timeout_g = 2; [2011-08-03 20:18:08] hostname_g = localhost.localdomain; [2011-08-03 20:18:08] Initialization complete, entering read-loop. It looks like, data is sending but doesn't be recived. Where is the mistake?

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• Clarification On Write-Caching Policy, Its Underlying Options And How It Applies To Hard Drives And Solid-State Drives

  - by Boris_yo

  In last week after doing more research on subject matter, I have been wondering about what I have been neglecting all those years to understand write-caching policy, always leaving it on default setting. Write-caching policy improves writing performance and consists of write-back caching and write-cache buffer flushing. This is how I understand all the above, but correct me if I erred somewhere: Write-through cache / Write-through caching itself is not a part of write caching policy per se and it's when data is written to both cache and storage device so if Windows will need that data later again, it is retrieved from cache and not from storage device which means only improved read performance as there is no need for waiting for storage device to read required data again. Since data is still written to storage device, write performance isn't improved and represents no risk of data loss or corruption in case of power failure or system crash while only data in cache gets lost. This option seems to be enabled by default and is recommended for removable devices with no need to use function of "Safely Remove Hardware" on user's part. Write-back caching is similar to above but without writing data to storage device, periodically releasing data from cache and writing to storage device when it is idle. In my opinion this option improves both read and write performance but represents risk if power failure or system crash occurs with the outcome of not only losing data eventually to be written to storage device, but causing file inconsistencies or corrupted file system. Write-back caching cannot be enabled together with write-through caching and it is not recommended to be enabled if no backup power supply is availabe. Write-cache buffer flushing I reckon is similar to write-back caching but enables immediate release and writing of data from cache to storage device right before power outage occurs but I don't know if it applies also to occasional system crash. This option seem to be complementary to write-back cache reducing or potentially eliminating risk of data loss or corruption of file system. I have questions about relevance of last 2 options to today's modern SSDs in order to get best performance and with less wear on SSDs: I know that traditional hard drives come with onboard cache (I wonder what type of cache that is), but do SSDs also come with cache? Assuming they do, is this cache faster than their NAND flash and system RAM and worth taking the risk of utilizing it by enabling write-back cache? I read somewhere that generally storage device's cache is faster than RAM, but I want to be sure. Additionally I read that write-caching should be enabled since current data that is to be written later to NAND flash is kept for a while in cache and provided there is data that gets modified a lot before finally being written, holding of this data and its periodic release reduces its write times to SSD thereby reducing its wearing. Now regarding to write-cache buffer flushing, I heard that SSD controllers are so fast by themselves that enabling this option is not required, because they manage flushing. However, once again, I don't know if SSDs have their own onboard cache and whether or not it is faster than their NAND flash and system RAM because if it is, keeping this option enabled would make sense. Recently I have posted question about issue with my Intel 330 SSD 120GB which was main reason to do deeper research having suspicion of write-caching policy being the culprit of SSD's freezing issue assuming data being released is what causes freezes. Currently I have write-cache enabled and write-cache buffer flushing disabled because I believe SSD controller's management of write-cache flushing and Windows write-cache buffer flushing are conflicting with each other: Since I want to troubleshoot in small steps to finally determine the source of issue, I have decided to start with write-caching policy and the move to drivers, switching to AHCI later on and finally disabling DIPM (device initiated power management) through registry modification thanks to @TomWijsman

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• LightDM will not start after stopping it

  - by Sweeters

  I am running Ubuntu 11.10 "Oneiric Ocelot", and in trying to install the nvidia CUDA developer drivers I switched to a virtual terminal (Ctrl-Alt-F5) and stopped lightdm (installation required that no X server instance be running) through sudo service lightdm stop. Re-starting lightdm with sudo service lightdm start did not work: A couple of * Starting [...] lines where displayed, but the process hanged. (I do not remember at which point, but I think it was * Starting System V runlevel compatibility. I manually rebooted my laptop, and ever since booting seems to hang, usually around the * Starting anac(h)ronistic cron [OK] log line (not consistently at that point, though). From that point on, I seem to be able to interact with my system only through a tty session (Ctrl-Alt-F1). I've tried purging and reinstalling both lightdm and gdm, as well as selecting both as the default display managers (through sudo dpkg-reconfigure [lightdm / gdm] or by manually editing /etc/X11/default-display-manager) through both apt-get and aptitude (that shouldn't make a difference anyway) after updating the packages, but the problem persists. Some of the responses I'm getting are the following: After running sudo dpkg-reconfigure lightdm (but not ... gdm) I get the following message: dpkg-maintscript-helper:warning: environment variable DPKG_MATINSCRIPT_NAME missing dpkg-maintscript-helper:warning: environment variable DPKG_MATINSCRIPT_PACKAGE missing After trying sudo service lightdm start or sudo start lightdm I get to see the boot loading screen again but nothing changes. If I go back to the tty shell I see lightdm start/running, process <num> but ps -e | grep lightdm gives no output. After trying sudo service gdm start or sudo starg gdm I get the gdm start/running, process <num> message, and gdm-binary is supposedly an active process, but all that happens is that the screen blinks a couple of times and nothing else. Other candidate solutions that I'd found on the web included running startx but when I try that I get an error output [...] Fatal server error: no screens found [...]. Moreover, I made sure that lightdm-gtk-greeter is installed but that did not help either. Please excuse my not including complete outputs/logs; I am writing this post from another computer and it's hard to manually copy the complete logs. Also, I've seen several posts that had to do with similar problems, but either there was no fix, or the one suggested did not work for me. In closing: Please help! I very much hope to avoid re-installing Ubuntu from scratch! :) Alex @mosi I did not manage to fix the NVIDIA kernel driver as per your instructions. I should perhaps mention that I'm on a Dell XPS15 laptop with an NVIDIA Optimus graphics card, and that I have bumblebee installed (which installs nvidia drivers during its installation, I believe). Issuing the mentioned commands I get the following: ~$uname -r 3.0.0-12-generic ~$lsmod | grep -i nvidia nvidia 11713772 0 ~$dmesg | grep -i nvidia [ 8.980041] nvidia: module license 'NVIDIA' taints kernel. [ 9.354860] nvidia 0000:01:00.0: power state changed by ACPI to D0 [ 9.354864] nvidia 0000:01:00.0: power state changed by ACPI to D0 [ 9.354868] nvidia 0000:01:00.0: enabling device (0006 -> 0007) [ 9.354873] nvidia 0000:01:00.0: PCI INT A -> GSI 16 (level, low) -> IRQ 16 [ 9.354879] nvidia 0000:01:00.0: setting latency timer to 64 [ 9.355052] NVRM: loading NVIDIA UNIX x86_64 Kernel Module 280.13 Wed Jul 27 16:53:56 PDT 2011 Also, running aptitude search nvidia gives me the following: p nvidia-173 - NVIDIA binary Xorg driver, kernel module a p nvidia-173-dev - NVIDIA binary Xorg driver development file p nvidia-173-updates - NVIDIA binary Xorg driver, kernel module a p nvidia-173-updates-dev - NVIDIA binary Xorg driver development file p nvidia-96 - NVIDIA binary Xorg driver, kernel module a p nvidia-96-dev - NVIDIA binary Xorg driver development file p nvidia-96-updates - NVIDIA binary Xorg driver, kernel module a p nvidia-96-updates-dev - NVIDIA binary Xorg driver development file p nvidia-cg-toolkit - Cg Toolkit - GPU Shader Authoring Language p nvidia-common - Find obsolete NVIDIA drivers i nvidia-current - NVIDIA binary Xorg driver, kernel module a p nvidia-current-dev - NVIDIA binary Xorg driver development file c nvidia-current-updates - NVIDIA binary Xorg driver, kernel module a p nvidia-current-updates-dev - NVIDIA binary Xorg driver development file i nvidia-settings - Tool of configuring the NVIDIA graphics dr p nvidia-settings-updates - Tool of configuring the NVIDIA graphics dr v nvidia-va-driver - v nvidia-va-driver - I've tried manually installing (sudo aptitude install <package>) packages nvidia-common and nvidia-settings-updates but to no avail. For example, sudo aptitude install nvidia-settings-updates returns the following log: Reading package lists... Building dependency tree... Reading state information... Reading extended state information... Initializing package states... Writing extended state information... No packages will be installed, upgraded, or removed. 0 packages upgraded, 0 newly installed, 0 to remove and 83 not upgraded. Need to get 0 B of archives. After unpacking 0 B will be used. Writing extended state information... Reading package lists... Building dependency tree... Reading state information... Reading extended state information... Initializing package states... Writing extended state information... The same happens with the Linux headers (i.e. I cannot seem to be able to install linux-headers-3.0.0-12-generic). The output of aptitude search linux-headers is as follows: v linux-headers - v linux-headers - v linux-headers-2.6 - i linux-headers-2.6.38-11 - Header files related to Linux kernel versi i linux-headers-2.6.38-11-generic - Linux kernel headers for version 2.6.38 on i A linux-headers-2.6.38-8 - Header files related to Linux kernel versi i A linux-headers-2.6.38-8-generic - Linux kernel headers for version 2.6.38 on v linux-headers-3 - v linux-headers-3.0 - v linux-headers-3.0 - i A linux-headers-3.0.0-12 - Header files related to Linux kernel versi p linux-headers-3.0.0-12-generic - Linux kernel headers for version 3.0.0 on p linux-headers-3.0.0-12-generic- - Linux kernel headers for version 3.0.0 on p linux-headers-3.0.0-12-server - Linux kernel headers for version 3.0.0 on p linux-headers-3.0.0-12-virtual - Linux kernel headers for version 3.0.0 on p linux-headers-generic - Generic Linux kernel headers p linux-headers-generic-pae - Generic Linux kernel headers v linux-headers-lbm - v linux-headers-lbm - v linux-headers-lbm-2.6 - v linux-headers-lbm-2.6 - p linux-headers-lbm-3.0.0-12-gene - Header files related to linux-backports-mo p linux-headers-lbm-3.0.0-12-gene - Header files related to linux-backports-mo p linux-headers-lbm-3.0.0-12-serv - Header files related to linux-backports-mo p linux-headers-server - Linux kernel headers on Server Equipment. p linux-headers-virtual - Linux kernel headers for virtual machines @heartsmagic I did try purging and reinstalling any nvidia driver packages, but it did not seem to make a difference, My xorg.conf file contains the following: # nvidia-xconfig: X configuration file generated by nvidia-xconfig # nvidia-xconfig: version 280.13 ([email protected]) Wed Jul 27 17:15:58 PDT 2011 Section "ServerLayout" Identifier "Layout0" Screen 0 "Screen0" 0 0 InputDevice "Keyboard0" "CoreKeyboard" InputDevice "Mouse0" "CorePointer" EndSection Section "Files" EndSection Section "InputDevice" # generated from default Identifier "Mouse0" Driver "mouse" Option "Protocol" "auto" Option "Device" "/dev/psaux" Option "Emulate3Buttons" "no" Option "ZAxisMapping" "4 5" EndSection Section "InputDevice" # generated from default Identifier "Keyboard0" Driver "kbd" EndSection Section "Monitor" Identifier "Monitor0" VendorName "Unknown" ModelName "Unknown" HorizSync 28.0 - 33.0 VertRefresh 43.0 - 72.0 Option "DPMS" EndSection Section "Device" Identifier "Device0" Driver "nvidia" VendorName "NVIDIA Corporation" EndSection Section "Screen" Identifier "Screen0" Device "Device0" Monitor "Monitor0" DefaultDepth 24 SubSection "Display" Depth 24 EndSubSection EndSection

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• Design advice for avoiding change in several classes

  - by Anders Svensson

  Hi, I'm trying to figure out how to design a small application more elegantly, and make it more resistant to change. Basically it is a sort of project price calculator, and the problem is that there are many parameters that can affect the pricing. I'm trying to avoid cluttering the code with a lot of if-clauses for each parameter, but still I have e.g. if-clauses in two places checking for the value of the size parameter. I have the Head First Design Patterns book, and have tried to find ideas there, but the closest I got was the decorator pattern, which has an example where starbuzz coffee sets prices depending first on condiments added, and then later in an exercise by adding a size parameter (Tall, Grande, Venti). But that didn't seem to help, because adding that parameter still seemed to add if-clause complexity in a lot of places (and this being an exercise they didn't explain that further). What I am trying to avoid is having to change several classes if a parameter were to change or a new parameter added, or at least change in as few places as possible (there's some fancy design principle word for this that I don't rememeber :-)). Here below is the code. Basically it calculates the price for a project that has the tasks "Writing" and "Analysis" with a size parameter and different pricing models. There will be other parameters coming in later too, like "How new is the product?" (New, 1-5 years old, 6-10 years old), etc. Any advice on the best design would be greatly appreciated, whether a "design pattern" or just good object oriented principles that would make it resistant to change (e.g. adding another size, or changing one of the size values, and only have to change in one place rather than in several if-clauses): public class Project { private readonly int _numberOfProducts; protected Size _size; public Task Analysis { get; set; } public Task Writing { get; set; } public Project(int numberOfProducts) { _numberOfProducts = numberOfProducts; _size = GetSize(); Analysis = new AnalysisTask(numberOfProducts, _size); Writing = new WritingTask(numberOfProducts, _size); } private Size GetSize() { if (_numberOfProducts <= 2) return Size.small; if (_numberOfProducts <= 8) return Size.medium; return Size.large; } public double GetPrice() { return Analysis.GetPrice() + Writing.GetPrice(); } } public abstract class Task { protected readonly int _numberOfProducts; protected Size _size; protected double _pricePerHour; protected Dictionary<Size, int> _hours; public abstract int TotalHours { get; } public double Price { get; set; } protected Task(int numberOfProducts, Size size) { _numberOfProducts = numberOfProducts; _size = size; } public double GetPrice() { return _pricePerHour * TotalHours; } } public class AnalysisTask : Task { public AnalysisTask(int numberOfProducts, Size size) : base(numberOfProducts, size) { _pricePerHour = 850; _hours = new Dictionary<Size, int>() { { Size.small, 56 }, { Size.medium, 104 }, { Size.large, 200 } }; } public override int TotalHours { get { return _hours[_size]; } } } public class WritingTask : Task { public WritingTask(int numberOfProducts, Size size) : base(numberOfProducts, size) { _pricePerHour = 650; _hours = new Dictionary<Size, int>() { { Size.small, 125 }, { Size.medium, 100 }, { Size.large, 60 } }; } public override int TotalHours { get { if (_size == Size.small) return _hours[_size] * _numberOfProducts; if (_size == Size.medium) return (_hours[Size.small] * 2) + (_hours[Size.medium] * (_numberOfProducts - 2)); return (_hours[Size.small] * 2) + (_hours[Size.medium] * (8 - 2)) + (_hours[Size.large] * (_numberOfProducts - 8)); } } } public enum Size { small, medium, large } public partial class Form1 : Form { public Form1() { InitializeComponent(); List<int> quantities = new List<int>(); for (int i = 0; i < 100; i++) { quantities.Add(i); } comboBoxNumberOfProducts.DataSource = quantities; } private void comboBoxNumberOfProducts_SelectedIndexChanged(object sender, EventArgs e) { Project project = new Project((int)comboBoxNumberOfProducts.SelectedItem); labelPrice.Text = project.GetPrice().ToString(); labelWriterHours.Text = project.Writing.TotalHours.ToString(); labelAnalysisHours.Text = project.Analysis.TotalHours.ToString(); } } At the end is a simple current calling code in the change event for a combobox that set size... (BTW, I don't like the fact that I have to use several dots to get to the TotalHours at the end here either, as far as I can recall, that violates the "principle of least knowledge" or "the law of demeter", so input on that would be appreciated too, but it's not the main point of the question) Regards, Anders

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• Clean Code: A Handbook of Agile Software Craftsmanship – book review

  - by DigiMortal

     Writing code that is easy read and test is not something that is easy to achieve. Unfortunately there are still way too much programming students who write awful spaghetti after graduating. But there is one really good book that helps you raise your code to new level – your code will be also communication tool for you and your fellow programmers. “Clean Code: A Handbook of Agile Software Craftsmanship” by Robert C. Martin is excellent book that helps you start writing the easily readable code. Of course, you are the one who has to learn and practice but using this book you have very good guide that keeps you going to right direction. You can start writing better code while you read this book and you can do it right in your current projects – you don’t have to create new guestbook or some other simple application to start practicing. Take the project you are working on and start making it better! My special thanks to Robert C. Martin I want to say my special thanks to Robert C. Martin for this book. There are many books that teach you different stuff and usually you have markable learning curve to go before you start getting results. There are many books that show you the direction to go and then leave you alone figuring out how to achieve all that stuff you just read about. Clean Code gives you a lot more – the mental tools to use so you can go your way to clean code being sure you will be soon there. I am reading books as much as I have time for it. Clean Code is top-level book for developers who have to write working code. Before anything else take Clean Code and read it. You will never regret your decision. I promise. Fragment of editorial review “Even bad code can function. But if code isn’t clean, it can bring a development organization to its knees. Every year, countless hours and significant resources are lost because of poorly written code. But it doesn’t have to be that way. What kind of work will you be doing? You’ll be reading code—lots of code. And you will be challenged to think about what’s right about that code, and what’s wrong with it. More importantly, you will be challenged to reassess your professional values and your commitment to your craft. Readers will come away from this book understanding How to tell the difference between good and bad code How to write good code and how to transform bad code into good code How to create good names, good functions, good objects, and good classes How to format code for maximum readability How to implement complete error handling without obscuring code logic How to unit test and practice test-driven development This book is a must for any developer, software engineer, project manager, team lead, or systems analyst with an interest in producing better code.” Table of contents Clean code Meaningful names Functions Comments Formatting Objects and data structures Error handling Boundaries Unit tests Classes Systems Emergence Concurrency Successive refinement JUnit internals Refactoring SerialDate Smells and heuristics A Concurrency II org.jfree.date.SerialDate Cross references of heuristics Epilogue Index

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• Low level programming - what's in it for me?

  - by back2dos

  For years I have considered digging into what I consider "low level" languages. For me this means C and assembly. However I had no time for this yet, nor has it EVER been neccessary. Now because I don't see any neccessity arising, I feel like I should either just schedule some point in time when I will study the subject or drop the plan forever. My Position For the past 4 years I have focused on "web technologies", which may change, and I am an application developer, which is unlikely to change. In application development, I think usability is the most important thing. You write applications to be "consumed" by users. The more usable those applications are, the more value you have produced. In order to achieve good usability, I believe the following things are viable Good design: Well-thought-out features accessible through a well-thought-out user interface. Correctness: The best design isn't worth anything, if not implemented correctly. Flexibility: An application A should constantly evolve, so that its users need not switch to a different application B, that has new features, that A could implement. Applications addressing the same problem should not differ in features but in philosophy. Performance: Performance contributes to a good user experience. An application is ideally always responsive and performs its tasks reasonably fast (based on their frequency). The value of performance optimization beyond the point where it is noticeable by the user is questionable. I think low level programming is not going to help me with that, except for performance. But writing a whole app in a low level language for the sake of performance is premature optimization to me. My Question What could low level programming teach me, what other languages wouldn't teach me? Am I missing something, or is it just a skill, that is of very little use for application development? Please understand, that I am not questioning the value of C and assembly. It's just that in my everyday life, I am quite happy that all the intricacies of that world are abstracted away and managed for me (mostly by layers written in C/C++ and assembly themselves). I just don't see any concepts, that could be new to me, only details I would have to stuff my head with. So what's in it for me? My Conclusion Thanks to everyone for their answers. I must say, nobody really surprised me, but at least now I am quite sure I will drop this area of interest until any need for it arises. To my understanding, writing assembly these days for processors as they are in use in today's CPUs is not only unneccesarily complicated, but risks to result in poorer runtime performance than a C counterpart. Optimizing by hand is nearly impossible due to OOE, while you do not get all kinds of optimizations a compiler can do automatically. Also, the code is either portable, because it uses a small subset of available commands, or it is optimized, but then it probably works on one architecture only. Writing C is not nearly as neccessary anymore, as it was in the past. If I were to write an application in C, I would just as much use tested and established libraries and frameworks, that would spare me implementing string copy routines, sorting algorithms and other kind of stuff serving as exercise at university. My own code would execute faster at the cost of type safety. I am neither keen on reeinventing the wheel in the course of normal app development, nor trying to debug by looking at core dumps :D I am currently experimenting with languages and interpreters, so if there is anything I would like to publish, I suppose I'd port a working concept to C, although C++ might just as well do the trick. Again, thanks to everyone for your answers and your insight.

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