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• Segmentation fault when creating a Phonon MediaObject

  - by Luke Hansford

  I have music playing program made using PySide which uses Phonon to playback audio. I updated to MacOS X Mavericks a few days ago, which meant I needed to reinstall PySide. I'm not sure which of these actions has caused this, but now whenever I try to create a Phonon MediaObject I get a Segmentation Fault: 11 from Python. It's not just in my program, it happens when trying to create a MediaObject in Python without any other actions. I'm getting the following error message from my Mac whenever it crashes: Process: Python [13711] Path: /usr/local/Cellar/python/2.7.5/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python Identifier: org.python.python Version: 2.7.5 (2.7.5) Code Type: X86-64 (Native) Parent Process: bash [13707] Responsible: Terminal [13704] User ID: 501 Date/Time: 2013-11-01 19:47:53.164 +1000 OS Version: Mac OS X 10.9 (13A603) Report Version: 11 Anonymous UUID: C2686854-18CA-9D37-26E9-60050E3C4DA6 Sleep/Wake UUID: BB983BF6-CCE2-44D1-82A0-1C73382DFFE4 Crashed Thread: 0 Dispatch queue: com.apple.main-thread Exception Type: EXC_BAD_ACCESS (SIGSEGV) Exception Codes: KERN_INVALID_ADDRESS at 0x0000000000000008 VM Regions Near 0x8: --> __TEXT 00000001082e8000-00000001082e9000 [ 4K] r-x/rwx SM=COW /usr/local/Cellar/python/2.7.5/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python Thread 0 Crashed:: Dispatch queue: com.apple.main-thread 0 QtCore 0x000000010a1b34cb QObject::moveToThread(QThread*) + 17 1 QtDBus 0x000000010d55f98b QDBusDefaultConnection::QDBusDefaultConnection(QDBusConnection::BusType, char const*) + 171 2 QtDBus 0x000000010d55ebdf QDBusConnection::sessionBus() + 71 3 phonon 0x000000010d50228d Phonon::FactoryPrivate::FactoryPrivate() + 189 4 phonon 0x000000010d5024d5 Phonon::$_249::operator->() + 99 5 phonon 0x000000010d502991 Phonon::Factory::registerFrontendObject(Phonon::MediaNodePrivate*) + 17 6 phonon 0x000000010d50b27e Phonon::MediaNodePrivate::MediaNodePrivate(Phonon::MediaNodePrivate::CastId) + 80 7 phonon 0x000000010d50f570 Phonon::MediaObjectPrivate::MediaObjectPrivate() + 24 8 phonon 0x000000010d50be9d Phonon::MediaObject::MediaObject(QObject*) + 45 9 phonon.so 0x000000010d42f24a Sbk_Phonon_MediaObject_Init + 458 10 org.python.python 0x0000000108338707 type_call + 189 11 org.python.python 0x00000001082f74fd PyObject_Call + 101 12 org.python.python 0x00000001083714f0 PyEval_EvalFrameEx + 15525 13 org.python.python 0x0000000108373aaf fast_function + 182 14 org.python.python 0x0000000108370919 PyEval_EvalFrameEx + 12494 15 org.python.python 0x000000010836d721 PyEval_EvalCodeEx + 1638 16 org.python.python 0x000000010836d0b5 PyEval_EvalCode + 54 17 org.python.python 0x000000010838beb8 run_mod + 53 18 org.python.python 0x000000010838bf5f PyRun_FileExFlags + 137 19 org.python.python 0x000000010838baad PyRun_SimpleFileExFlags + 718 20 org.python.python 0x000000010839c58b Py_Main + 3039 21 libdyld.dylib 0x00007fff8e4fb5fd start + 1 Thread 1:: Dispatch queue: com.apple.libdispatch-manager 0 libsystem_kernel.dylib 0x00007fff8c938662 kevent64 + 10 1 libdispatch.dylib 0x00007fff923e743d _dispatch_mgr_invoke + 239 2 libdispatch.dylib 0x00007fff923e7152 _dispatch_mgr_thread + 52 Thread 2: 0 libsystem_kernel.dylib 0x00007fff8c937e6a __workq_kernreturn + 10 1 libsystem_pthread.dylib 0x00007fff90bd8f08 _pthread_wqthread + 330 2 libsystem_pthread.dylib 0x00007fff90bdbfb9 start_wqthread + 13 Thread 3: 0 libsystem_kernel.dylib 0x00007fff8c937e6a __workq_kernreturn + 10 1 libsystem_pthread.dylib 0x00007fff90bd8f08 _pthread_wqthread + 330 2 libsystem_pthread.dylib 0x00007fff90bdbfb9 start_wqthread + 13 Thread 4: 0 libsystem_kernel.dylib 0x00007fff8c937e6a __workq_kernreturn + 10 1 libsystem_pthread.dylib 0x00007fff90bd8f08 _pthread_wqthread + 330 2 libsystem_pthread.dylib 0x00007fff90bdbfb9 start_wqthread + 13 Thread 0 crashed with X86 Thread State (64-bit): rax: 0x00007feba0d19700 rbx: 0x000000010d5b7098 rcx: 0x00000000002f4180 rdx: 0x000000000012c040 rdi: 0x0000000000000000 rsi: 0x00007feba0d19700 rbp: 0x00007fff57917210 rsp: 0x00007fff579171d0 r8: 0x00007feba0fd5d10 r9: 0x00007feba0ff5310 r10: 0x0000000019c04cbe r11: 0x0000000070769b38 r12: 0x00007fff57917220 r13: 0x00007feba0c07190 r14: 0x0000000000000000 r15: 0x00007feba0fe1430 rip: 0x000000010a1b34cb rfl: 0x0000000000010202 cr2: 0x0000000000000008 Logical CPU: 0 Error Code: 0x00000004 Trap Number: 14 Anyone have any ideas about what is happening?

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• How do you fix an SVN 409 Conflict Error

  - by NerdStarGamer

  I used to use SVN 1.4 on OS X Leopard and everything was fine. A couple of weeks ago I installed a fresh copy of OS X 10.6. The version of SVN that comes with Snow Leopard is 1.6.5. I went ahead and built my own copy with 1.6.6. I'm using the built in apache server and just hosting repositories locally. Everything appeared to work fine until I actually tried to commit something. Everytime I try to commit a change, I get the following message: Transmitting file data .svn: Commit failed (details follow): svn: MERGE of '/svn/svn2': 409 Conflict (http://localhost) This happens with my old repositories, so I created a couple of new ones. Same deal. I also tried using the 1.6.5 version that comes with the system...same. Finally, I tried upgrading to the latest stable SVN (1.6.9) and still got the same problem. The Apache error logs the following for each failed commit: [Mon Mar 29 19:53:10 2010] [error] [client ::1] Could not MERGE resource "/svn/svn2/!svn/act/d399326f-c20f-424f-bb68-3bb40503b5b1" into "/svn/svn2". [409, #0] [Mon Mar 29 19:53:10 2010] [error] [client ::1] An error occurred while committing the transaction. [409, #2] [Mon Mar 29 19:53:10 2010] [error] [client ::1] Can't open directory '/usr/local/svn/svn2/db/transactions/5-6.txn/\xeb\xa9\x0f\x1f': No such file or directory [409, #2] [Mon Mar 29 19:53:11 2010] [error] [client ::1] Could not DELETE /svn/svn2/!svn/act/d399326f-c20f-424f-bb68-3bb40503b5b1. [500, #0] [Mon Mar 29 19:53:11 2010] [error] [client ::1] could not open transaction. [500, #2] [Mon Mar 29 19:53:11 2010] [error] [client ::1] Can't open file '/usr/local/svn/svn2/db/transactions/5-6.txn/props': No such file or directory [500, #2] And from the access log: ::1 - - [30/Mar/2010:13:02:20 -0400] "OPTIONS /svn/svn2 HTTP/1.1" 401 401 ::1 - user [30/Mar/2010:13:02:20 -0400] "OPTIONS /svn/svn2 HTTP/1.1" 200 188 ::1 - user [30/Mar/2010:13:02:20 -0400] "PROPFIND /svn/svn2 HTTP/1.1" 207 647 ::1 - user [30/Mar/2010:13:02:20 -0400] "PROPFIND /svn/svn2 HTTP/1.1" 207 647 ::1 - user [30/Mar/2010:13:02:20 -0400] "PROPFIND /svn/svn2/!svn/vcc/default HTTP/1.1" 207 398 ::1 - user [30/Mar/2010:13:02:20 -0400] "PROPFIND /svn/svn2/!svn/bln/6 HTTP/1.1" 207 449 ::1 - user [30/Mar/2010:13:02:20 -0400] "REPORT /svn/svn2/!svn/vcc/default HTTP/1.1" 200 1172 Curiously, the commit does actually commit the changes, but the working copy doesn't see that and everything gets screwy. I've tried to Google every variation I can think of for this problem, but the search results are pretty much useless. I'm not using TortoiseSVN or anything special and commits fail on a new repository, so I know it's not a problem with my old repos. Any help would be greatly appreciated.

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• Is ther anyone familiar with Erica Sadun's APIKit(app private api scanner)?

  - by user262325

  Hello everyone I'm trying to use APIKit to scan my codes to detect if there is private API. apiscanner should run as ./apiscanner ~/Desktop/MyPath/myapp.app I used command 'cd' go to the directory where apiscanner is. But if I call ./apiscanner ~/Desktop/MyPath/MyApp.app on terminal it reports Last login: Sun Jun 13 07:22:07 on ttys002 unknown required load command 0x80000022 Trace/BPT trap logout Even if I copy the files apiscanner and doit to MyPath, then execute, I get the same problem. I think there is something wrong when I run apiscanner under Mac OS X. Welcome any comment Thanks

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• Copy from a password field in form

  - by Ali

  I was designing a form which asks the user to type in a password and then to verify again in the next field. I noticed however, that if I copy and paste from the first password field to the other, the values are not same. It seems my Firefox running on Mac OS X, copies the asterisk graphic instead, which has the value '\x95' Is it possible to copy the underlying text from the password field? Thanks

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• Best Cross Platform Networking Framework For iPhone Dev

  - by Carmen

  I am looking to write a client/server application that will run on both iPhone, OS X and Windows. What are the best solutions for networking that will work on all 3 platforms? I have looked into Qt and it doesn't look like it has support for iPhone. I have also looked at boost, and that looks like it can be compiled for the iPhone. However I was hoping for a somewhat higher level framework like what Qt has to offer.

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• MonoTouch & C# VS Objective C for iphone app

  - by Eyla

  Greeting, I'm a C# programmer guy. I'm planning to start developing app for iphone but I'm not sure if I should use C# under MonoTouch or just use the native language for iphone OS Objective C. Is there a different to program for iphone app using C# or Objective C? Is there limitation using C# to program app for iphone or it can do as much as Objective C can do to develop iphone app?

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• Linux scp command issue

  - by George2

  Hello everyone, I am using scp command to copy file from a MacBook Pro OS X 10.5 to another Linux box (Red Hat Linux Enterprise 5). I am using the following command on Mac, sudo scp ~/.ssh/mykey.rsa [email protected], there is no output from Mac command line. I am not sure whether the scp is success or not. Where is the location the file mykey.rsa on remote computer 10.10.100.101? thanks in advance, George

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• Reflection to access advanced telephony features

  - by Tyler

  I am trying to use reflection to access some advanced features of the telephony api not published. Currently I am having trouble instantiating a serviceManager object that is needed to get the "phone" service as a binder which I can then use to instantiate a telephony object which is needed to make a call, end call, etc... currently when I make the call serviceManagerObject = tempInterfaceMethod.invoke(null, new Object[] { new Binder() }); it returns a nullPointerException. I believe this has to due with creating a new Binder instead of sending the appropriate binder (which I am unsure of which one is appropriate) public void placeReflectedCall() throws ClassNotFoundException, SecurityException, NoSuchMethodException, IllegalArgumentException, IllegalAccessException, InvocationTargetException, InstantiationException { String serviceManagerName = "android.os.IServiceManager"; String serviceManagerNativeName = "android.os.ServiceManagerNative"; String telephonyName = "com.android.internal.telephony.ITelephony"; Class telephonyClass; Class telephonyStubClass; Class serviceManagerClass; Class serviceManagerStubClass; Class serviceManagerNativeClass; Class serviceManagerNativeStubClass; Method telephonyCall; Method telephonyEndCall; Method telephonyAnswerCall; Method getDefault; Method[] temps; Constructor[] serviceManagerConstructor; // Method getService; Object telephonyObject; Object serviceManagerObject; String number = "1111111111"; telephonyClass = Class.forName(telephonyName); telephonyStubClass = telephonyClass.getClasses()[0]; serviceManagerClass = Class.forName(serviceManagerName); serviceManagerNativeClass = Class.forName(serviceManagerNativeName); Method getService = // getDefaults[29]; serviceManagerClass.getMethod("getService", String.class); Method tempInterfaceMethod = serviceManagerNativeClass.getMethod( "asInterface", IBinder.class); // this does not work serviceManagerObject = tempInterfaceMethod.invoke(null, new Object[] { new Binder() }); IBinder retbinder = (IBinder) getService.invoke(serviceManagerObject, "phone"); Method serviceMethod = telephonyStubClass.getMethod("asInterface", IBinder.class); telephonyObject = serviceMethod .invoke(null, new Object[] { retbinder }); telephonyCall = telephonyClass.getMethod("call", String.class); telephonyEndCall = telephonyClass.getMethod("endCall"); telephonyAnswerCall = telephonyClass.getMethod("answerRingingCall"); telephonyCall.invoke(telephonyObject, number); } Thanks in advance for any answers.

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• Python ttk.Button -command, runs without button being pressed

  - by Markus Kothe

  I'm making a small script in python with ttk and I have a problem where a function runs where it shouldn't. The button code looks as follows: btReload = ttk.Button(treeBottomUI, text="Reload", width=17, command=loadModelTree(treeModel)) btReload.pack(side="left") and the function is as this: def loadModelTree(tree): print ("Loading models...") allModels = os.listdir(confModPath) for chunk in allModels: ... For some reason, the function runs without the button being pressed. Why?

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• IntelliJ: how to open files in an existing IntelliJ from the command line

  - by Alessandro Vernet

  I always have an IntelliJ running. Sometimes I want to open a file from outside IntelliJ. I can drag and drop a file to IntelliJ if am in the Finder, but if I am on the command line on OS X, how can I instruct IntelliJ to open a certain file? I am looking for something similar to the mate command provided by TextMate.

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• msi to exe conversion

  - by Arman

  How to convert msi file to exe in window OS, without using software. Kindly guide me how I can do it.

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• Problem with bootstrap loader and kernel

  - by dboarman-FissureStudios

  We are working on a project to learn how to write a kernel and learn the ins and outs. We have a bootstrap loader written and it appears to work. However we are having a problem with the kernel loading. I'll start with the first part: bootloader.asm: [BITS 16] [ORG 0x0000] ; ; all the stuff in between ; ; the bottom of the bootstrap loader datasector dw 0x0000 cluster dw 0x0000 ImageName db "KERNEL SYS" msgLoading db 0x0D, 0x0A, "Loading Kernel Shell", 0x0D, 0x0A, 0x00 msgCRLF db 0x0D, 0x0A, 0x00 msgProgress db ".", 0x00 msgFailure db 0x0D, 0x0A, "ERROR : Press key to reboot", 0x00 TIMES 510-($-$$) DB 0 DW 0xAA55 ;************************************************************************* The bootloader.asm is too long for the editor without causing it to chug and choke. In addition, the bootloader and kernel do work within bochs as we do get the message "Welcome to our OS". Anyway, the following is what we have for a kernel at this point. kernel.asm: [BITS 16] [ORG 0x0000] [SEGMENT .text] ; code segment mov ax, 0x0100 ; location where kernel is loaded mov ds, ax mov es, ax cli mov ss, ax ; stack segment mov sp, 0xFFFF ; stack pointer at 64k limit sti mov si, strWelcomeMsg ; load message call _disp_str mov ah, 0x00 int 0x16 ; interrupt: await keypress int 0x19 ; interrupt: reboot _disp_str: lodsb ; load next character or al, al ; test for NUL character jz .DONE mov ah, 0x0E ; BIOS teletype mov bh, 0x00 ; display page 0 mov bl, 0x07 ; text attribute int 0x10 ; interrupt: invoke BIOS jmp _disp_str .DONE: ret [SEGMENT .data] ; initialized data segment strWelcomeMsg db "Welcome to our OS", 0x00 [SEGMENT .bss] ; uninitialized data segment Using nasm 2.06rc2 I compile as such: nasm bootloader.asm -o bootloader.bin -f bin nasm kernel.asm -o kernel.sys -f bin We write bootloader.bin to the floppy as such: dd if=bootloader.bin bs=512 count=1 of/dev/fd0 We write kernel.sys to the floppy as such: cp kernel.sys /dev/fd0 As I stated, this works in bochs. But booting from the floppy we get output like so: Loading Kernel Shell ........... ERROR : Press key to reboot Other specifics: OpenSUSE 11.2, GNOME desktop, AMD x64 Any other information I may have missed, feel free to ask. I tried to get everything in here that would be needed. If I need to, I can find a way to get the entire bootloader.asm posted somewhere. We are not really interested in using GRUB either for several reasons. This could change, but we want to see this boot successful before we really consider GRUB.

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• Web Safe Area (optimal resolution) for web app design

  - by M.A.X

  I'm in the process of designing a new web app and I'm wondering for what 'web safe area' should I optimize the app layout and design. I did some investigation and thinking on my own but wanted to share this to see what the general opinion is. Here is what I found: Optimal Display Resolution: w3schools web stats seems to be the most referenced source (however they state that these are results from their site and is biased towards tech savvy users) http://www.w3counter.com/globalstats.php (aggregate data from something like 15,000 different sites that use their tracking services) StatCounter Global Stats Display Resolution (Stats are based on aggregate data collected by StatCounter on a sample exceeding 15 billion pageviews per month collected from across the StatCounter network of more than 3 million websites) NetMarketShare Screen Resolutions (marketshare.hitslink.com) (a web analytics consulting firm, they get data from browsers of site visitors to their on-demand network of live stats customers. The data is compiled from approximately 160 million visitors per month) Display Resolution Summary: There is a bit of variation between the above sources but in general as of Jan 2011 looks like 1024x768 is about 20%, while ~85% have a higher resolution of at least 1280x768 (1280x800 is the most common of these with 15-20% of total web, depending on the source; 1280x1024 and 1366x768 follow behind with 9-14% of the share). My guess would be that the higher resolution values will be even more common if we filter on North America, and even higher if we filter on N.American corporate users (unfortunately I couldn't find any free geographically filtered statistics). Another point to note is that the 1024x768 desktop user population is likely lower than the aforementioned 20%, seeing as the iPad (1024x768 native display) is likely propping up those number. My recommendation would be to optimize around the 1280x768 constraint (*note: 1280x768 is actually a relatively rare resolution, but I think it's a valid constraint range considering that 1366x768 is relatively common and 1280 is the most common horizontal resolution). Browser + OS Constraints: To further add to the constraints we have to subtract the space taken up by the browser (assuming IE, which is the most space consuming) and the OS (assuming WinXP-Win7): Win7 has the biggest taskbar footprint at a height of 40px (XP's and Vista's is 30px) The default IE8 view uses up 25px at the bottom of the screen with the status bar and a further 120px at the top of the screen with the windows title bar and the browser UI (assuming the default 'favorites' toolbar is present, it would instead be 91px without the favorites toolbar). Assuming no scrollbar, we also loose a total of 4px horizontally for the window outline. This means that we are left with 583px of vertical space and 1276px of horizontal. In other words, a Web Safe Area of 1276 x 583 Is this a correct line of thinking? I tried to Google some design best practices but most still talk about designing around 1024x768 which seems to be quickly disappearing. Any help on this would be greatly appreciated! Thanks.

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• GUI for touchscreen panel

  - by Surjya Narayana Padhi

  Hi Geeks, I am planning to design an embedded device which will have atom processor platform and linux OS in it. It will have an 7" touchscreen panel. In stead of going for KDE and GNOME desktops I want to design my small desktop environment for the device. Can anyone please suggest which GUI tool I should use to design a desktop from scratch?

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• My Access KeyChain certificate [Xcode]

  - by Momeks

  Hi , i create a provision and developer identity.certificate with apple provision assistant and i have huge problem , everything done , but when i add my certificate into KeyChain , the certificate add , but doesn't show on the Keys and my Certificate :( and xcode Organizer says a valid signing identity matching this profile could not be found in your keychain and compiler : Code Sign error: The identity 'iPhone Developer' doesn't match any valid certificate/private key pair in the default keychain i didn't have this problem on the leopard with sdk 3.1 my current os is 10.6.2 SDK 3.1.3 what's the problem ?

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• Reading Alias files

  - by Girish Kolari

  I want to read alias in Mac OS X programatically. When I tried it always read original file. Any idea how it can be done? thanks for your all suggestions.

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• How to find the type of shopping cart used to implement in website

  - by harigm

  Is there way to identify which shopping cart open source technology has been used to implemente for any given website? For example: if you are looking at shopping.yahoo.com,shopping.rediff.com can we tell which Shopping cart tool they have used for Example : zen cart, os commerce , magento etc.... I am trying to idenify the website which has zen cart implementation or magento implementation?

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• optimizing operating systems to provide maximum informix performance.

  - by Frank Developer

  Are there any Informix-specific guides for optimizing any operating system where an ifx engine is running? For example, in Linux, strip-down to a bare minimum all unecessary binaries, daemons, utilities, tune kernel parameters, optimize raw and cooked devices (hdparm). Someday, maybe, informix can create its own proprietary PICK-like O/S. The general idea is for the OS where ifx sits on have the smallest footprint, lowest overhead impact on ifx and provide optimized ifx performance.

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• iPhone Javascript execution time

  - by Rudiger

  Hi guys, In the Apple docs it says that JavaScript execution time is limited to 10 seconds for each top-level entry point. If your script executes for more than 10 seconds, Safari on iPhone OS stops executing the script at a random place I plan to have some Javascript run every 10 seconds or so that will do an AJAX query to the server and rewrite just the section of the page necessary. Will this be possible with these restrictions on the device?

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• Go - How to read/write to file?

  - by Seth Hoenig

  I've been trying to learn Go / Golang on my own, but I've been stumped on trying read and write to ordinary files. I can get as far as: inFile,_ := os.Open(INFILE,0,0); but actually getting the content of the file doesn't make sense, since the read function takes a []byte as a parameter?? func (file *File) Read(b []byte) (n int, err Error)

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• Access COM DLL using VS 2008 on Windows 7 64 bit

  - by Nitin

  I am using Windows 7 64 bit OS and VS 2008 SP1 as development environment. One of the console application uses a COM component. When I try to create an instance of a class from the COM component, I got following error: Creating an instance of the COM component with CLSID {CE92C3B9-9A93-40E1-85AB-6A49170AEF7F} from the IClassFactory failed due to the following error: 80010105.

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• Is ther any DLL or DLL like concept in Android?

  - by Prashant

  Hello, We know that we can use a concept "Java Package" but I just wanted to know that whether Android has provided a DLL or DLL like concept where we can write a most of the functionality. Or can we use Activity for serving a purpose of DLL. Can any one tell me is there any concept like DLL on Android OS? Can we develop a DLL for better modularization and other benefits on Android? Thanks and Regards, Prashant.

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• What is the fastest cyclic synchronization in Java (ExecutorService vs. CyclicBarrier vs. X)?

  - by Alex Dunlop

  Which Java synchronization construct is likely to provide the best performance for a concurrent, iterative processing scenario with a fixed number of threads like the one outlined below? After experimenting on my own for a while (using ExecutorService and CyclicBarrier) and being somewhat surprised by the results, I would be grateful for some expert advice and maybe some new ideas. Existing questions here do not seem to focus primarily on performance, hence this new one. Thanks in advance! The core of the app is a simple iterative data processing algorithm, parallelized to the spread the computational load across 8 cores on a Mac Pro, running OS X 10.6 and Java 1.6.0_07. The data to be processed is split into 8 blocks and each block is fed to a Runnable to be executed by one of a fixed number of threads. Parallelizing the algorithm was fairly straightforward, and it functionally works as desired, but its performance is not yet what I think it could be. The app seems to spend a lot of time in system calls synchronizing, so after some profiling I wonder whether I selected the most appropriate synchronization mechanism(s). A key requirement of the algorithm is that it needs to proceed in stages, so the threads need to sync up at the end of each stage. The main thread prepares the work (very low overhead), passes it to the threads, lets them work on it, then proceeds when all threads are done, rearranges the work (again very low overhead) and repeats the cycle. The machine is dedicated to this task, Garbage Collection is minimized by using per-thread pools of pre-allocated items, and the number of threads can be fixed (no incoming requests or the like, just one thread per CPU core). V1 - ExecutorService My first implementation used an ExecutorService with 8 worker threads. The program creates 8 tasks holding the work and then lets them work on it, roughly like this: // create one thread per CPU executorService = Executors.newFixedThreadPool( 8 ); ... // now process data in cycles while( ...) { // package data into 8 work items ... // create one Callable task per work item ... // submit the Callables to the worker threads executorService.invokeAll( taskList ); } This works well functionally (it does what it should), and for very large work items indeed all 8 CPUs become highly loaded, as much as the processing algorithm would be expected to allow (some work items will finish faster than others, then idle). However, as the work items become smaller (and this is not really under the program's control), the user CPU load shrinks dramatically: blocksize | system | user | cycles/sec 256k 1.8% 85% 1.30 64k 2.5% 77% 5.6 16k 4% 64% 22.5 4096 8% 56% 86 1024 13% 38% 227 256 17% 19% 420 64 19% 17% 948 16 19% 13% 1626 Legend: - block size = size of the work item (= computational steps) - system = system load, as shown in OS X Activity Monitor (red bar) - user = user load, as shown in OS X Activity Monitor (green bar) - cycles/sec = iterations through the main while loop, more is better The primary area of concern here is the high percentage of time spent in the system, which appears to be driven by thread synchronization calls. As expected, for smaller work items, ExecutorService.invokeAll() will require relatively more effort to sync up the threads versus the amount of work being performed in each thread. But since ExecutorService is more generic than it would need to be for this use case (it can queue tasks for threads if there are more tasks than cores), I though maybe there would be a leaner synchronization construct. V2 - CyclicBarrier The next implementation used a CyclicBarrier to sync up the threads before receiving work and after completing it, roughly as follows: main() { // create the barrier barrier = new CyclicBarrier( 8 + 1 ); // create Runable for thread, tell it about the barrier Runnable task = new WorkerThreadRunnable( barrier ); // start the threads for( int i = 0; i < 8; i++ ) { // create one thread per core new Thread( task ).start(); } while( ... ) { // tell threads about the work ... // N threads + this will call await(), then system proceeds barrier.await(); // ... now worker threads work on the work... // wait for worker threads to finish barrier.await(); } } class WorkerThreadRunnable implements Runnable { CyclicBarrier barrier; WorkerThreadRunnable( CyclicBarrier barrier ) { this.barrier = barrier; } public void run() { while( true ) { // wait for work barrier.await(); // do the work ... // wait for everyone else to finish barrier.await(); } } } Again, this works well functionally (it does what it should), and for very large work items indeed all 8 CPUs become highly loaded, as before. However, as the work items become smaller, the load still shrinks dramatically: blocksize | system | user | cycles/sec 256k 1.9% 85% 1.30 64k 2.7% 78% 6.1 16k 5.5% 52% 25 4096 9% 29% 64 1024 11% 15% 117 256 12% 8% 169 64 12% 6.5% 285 16 12% 6% 377 For large work items, synchronization is negligible and the performance is identical to V1. But unexpectedly, the results of the (highly specialized) CyclicBarrier seem MUCH WORSE than those for the (generic) ExecutorService: throughput (cycles/sec) is only about 1/4th of V1. A preliminary conclusion would be that even though this seems to be the advertised ideal use case for CyclicBarrier, it performs much worse than the generic ExecutorService. V3 - Wait/Notify + CyclicBarrier It seemed worth a try to replace the first cyclic barrier await() with a simple wait/notify mechanism: main() { // create the barrier // create Runable for thread, tell it about the barrier // start the threads while( ... ) { // tell threads about the work // for each: workerThreadRunnable.setWorkItem( ... ); // ... now worker threads work on the work... // wait for worker threads to finish barrier.await(); } } class WorkerThreadRunnable implements Runnable { CyclicBarrier barrier; @NotNull volatile private Callable<Integer> workItem; WorkerThreadRunnable( CyclicBarrier barrier ) { this.barrier = barrier; this.workItem = NO_WORK; } final protected void setWorkItem( @NotNull final Callable<Integer> callable ) { synchronized( this ) { workItem = callable; notify(); } } public void run() { while( true ) { // wait for work while( true ) { synchronized( this ) { if( workItem != NO_WORK ) break; try { wait(); } catch( InterruptedException e ) { e.printStackTrace(); } } } // do the work ... // wait for everyone else to finish barrier.await(); } } } Again, this works well functionally (it does what it should). blocksize | system | user | cycles/sec 256k 1.9% 85% 1.30 64k 2.4% 80% 6.3 16k 4.6% 60% 30.1 4096 8.6% 41% 98.5 1024 12% 23% 202 256 14% 11.6% 299 64 14% 10.0% 518 16 14.8% 8.7% 679 The throughput for small work items is still much worse than that of the ExecutorService, but about 2x that of the CyclicBarrier. Eliminating one CyclicBarrier eliminates half of the gap. V4 - Busy wait instead of wait/notify Since this app is the primary one running on the system and the cores idle anyway if they're not busy with a work item, why not try a busy wait for work items in each thread, even if that spins the CPU needlessly. The worker thread code changes as follows: class WorkerThreadRunnable implements Runnable { // as before final protected void setWorkItem( @NotNull final Callable<Integer> callable ) { workItem = callable; } public void run() { while( true ) { // busy-wait for work while( true ) { if( workItem != NO_WORK ) break; } // do the work ... // wait for everyone else to finish barrier.await(); } } } Also works well functionally (it does what it should). blocksize | system | user | cycles/sec 256k 1.9% 85% 1.30 64k 2.2% 81% 6.3 16k 4.2% 62% 33 4096 7.5% 40% 107 1024 10.4% 23% 210 256 12.0% 12.0% 310 64 11.9% 10.2% 550 16 12.2% 8.6% 741 For small work items, this increases throughput by a further 10% over the CyclicBarrier + wait/notify variant, which is not insignificant. But it is still much lower-throughput than V1 with the ExecutorService. V5 - ? So what is the best synchronization mechanism for such a (presumably not uncommon) problem? I am weary of writing my own sync mechanism to completely replace ExecutorService (assuming that it is too generic and there has to be something that can still be taken out to make it more efficient). It is not my area of expertise and I'm concerned that I'd spend a lot of time debugging it (since I'm not even sure my wait/notify and busy wait variants are correct) for uncertain gain. Any advice would be greatly appreciated.

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• R/XLL: Interface to call XLL method in R

  - by Neerav

  I am trying to call the methods defined in the XLL addin(for Excel) from R. Something similar to this Python code: import os from win32com.client import Dispatch Path = 'myxll.xll' xlApp = Dispatch("Excel.Application") xlApp.RegisterXLL(Path) # function call from excel # =xllfunction("param1","param2",...) result = xlApp.run('xllfunction', "param1","param2",...) Is there any library in R that does the XLL interface? Thanks for your help.

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• How can I view a .evt file saved with the Event viewer of another computer?

  - by Adolfo G.U.

  I have a .evt file saved with the EventViewer of another computer. I think I can use my computer's EventViewer as long as I have the same version of the OS. Are there any other alternatives?

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