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  • Java @Contented annotation to help reduce false sharing

    - by Dave
    See this posting by Aleksey Shipilev for details -- @Contended is something we've wanted for a long time. The JVM provides automatic layout and placement of fields. Usually it'll (a) sort fields by descending size to improve footprint, and (b) pack reference fields so the garbage collector can process a contiguous run of reference fields when tracing. @Contended gives the program a way to provide more explicit guidance with respect to concurrency and false sharing. Using this facility we can sequester hot frequently written shared fields away from other mostly read-only or cold fields. The simple rule is that read-sharing is cheap, and write-sharing is very expensive. We can also pack fields together that tend to be written together by the same thread at about the same time. More generally, we're trying to influence relative field placement to minimize coherency misses. Fields that are accessed closely together in time should be placed proximally in space to promote cache locality. That is, temporal locality should condition spatial locality. Fields accessed together in time should be nearby in space. That having been said, we have to be careful to avoid false sharing and excessive invalidation from coherence traffic. As such, we try to cluster or otherwise sequester fields that tend to written at approximately the same time by the same thread onto the same cache line. Note that there's a tension at play: if we try too hard to minimize single-threaded capacity misses then we can end up with excessive coherency misses running in a parallel environment. Theres no single optimal layout for both single-thread and multithreaded environments. And the ideal layout problem itself is NP-hard. Ideally, a JVM would employ hardware monitoring facilities to detect sharing behavior and change the layout on the fly. That's a bit difficult as we don't yet have the right plumbing to provide efficient and expedient information to the JVM. Hint: we need to disintermediate the OS and hypervisor. Another challenge is that raw field offsets are used in the unsafe facility, so we'd need to address that issue, possibly with an extra level of indirection. Finally, I'd like to be able to pack final fields together as well, as those are known to be read-only.

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  • Is it good to use same keyword for multiple pages in one domain?

    - by Phanen
    Hi, I want to know after Google recent updates, will it be good opt to use same keywords for multiple pages? Say- my keyword is "driver update" and I have a folder "HP" in website. Hp has lots of models like HP Elitebook, HP Envy, HP Mini, HP Pavilion and much more. HP Elitebook has many versions like HP Elitebook 2530p, HP Elitebook 2730p, HP Elitebook 8530w. Now should I create pages like "Driver update in HP Elitebook 2530p" , "Driver update in HP Elitebook 2730p", "Driver update in P Elitebook 8530w" or a single page "Driver update in HP Elitebook"? Which one will be the best option for better SE ranking- " single page or multiple pages using same keyword for different model versions" ?

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  • Exiting a reboot loop

    - by user12617035
    If you're in a situation where the system is panic'ing during boot, you can use # boot net -s to regain control of your system. In my case, I'd added some diagnostic code to a (PCI) driver (that is used to boot the root filesystem). There was a bug in the driver, and each time during boot, the bug occurred, and so caused the system to panic: ... 000000000180b950 genunix:vfs_mountroot+60 (800, 200, 0, 185d400, 1883000, 18aec00) %l0-3: 0000000000001770 0000000000000640 0000000001814000 00000000000008fc %l4-7: 0000000001833c00 00000000018b1000 0000000000000600 0000000000000200 000000000180ba10 genunix:main+98 (18141a0, 1013800, 18362c0, 18ab800, 180e000, 1814000) %l0-3: 0000000070002000 0000000000000001 000000000180c000 000000000180e000 %l4-7: 0000000000000001 0000000001074800 0000000000000060 0000000000000000 skipping system dump - no dump device configured rebooting... If you're logged in via the console, you can send a BREAK sequence in order to gain control of the firmware's (OBP's) prompt. Enter Ctrl-Shift-[ in order to get the TELNET prompt. Once telnet has control, enter this: telnet> send brk You'll be presented with OBP's prompt: ok You then enter the following in order to boot into single-user mode via the network: ok boot net -s Note that booting from the network under Solaris will implicitly cause the system to be INSTALLED with whatever software had last been configured to be installed. However, we are using boot net -s as a "handle" with which to get at the Solaris prompt. Once at that prompt, we can perform actions as root that will let us back out our buggy driver (ok... MY buggy driver :-)) ...and replace it with the original, non-buggy driver. Entering the boot command caused the following output, as well as left us at the Solaris prompt (in single-user-mode): Sun Blade 1500, No Keyboard Copyright 1998-2004 Sun Microsystems, Inc. All rights reserved. OpenBoot 4.16.4, 1024 MB memory installed, Serial #53463393. Ethernet address 0:3:ba:2f:c9:61, Host ID: 832fc961. Rebooting with command: boot net -s Boot device: /pci@1f,700000/network@2 File and args: -s 1000 Mbps FDX Link up Timeout waiting for ARP/RARP packet Timeout waiting for ARP/RARP packet 4000 1000 Mbps FDX Link up Requesting Internet address for 0:3:ba:2f:c9:61 SunOS Release 5.10 Version Generic_118833-17 64-bit Copyright 1983-2005 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Booting to milestone "milestone/single-user:default". Configuring devices. Using RPC Bootparams for network configuration information. Attempting to configure interface bge0... Configured interface bge0 Requesting System Maintenance Mode SINGLE USER MODE # Our goal is to now move to the directory containing the buggy driver and replace it with the original driver (that we had saved away before ever loading our buggy driver! :-) However, since we booted from the network, the root filesystem ("/") is NOT mounted on one of our local disks. It is mounted on an NFS filesystem exported by our install server. To verify this, enter the following command: # mount | head -1 / on my-server:/export/install/media/s10u2/solarisdvd.s10s_u2dvd/latest/Solaris_10/Tools/Boot remote/read/write/setuid/devices/dev=4ac0001 on Wed Dec 31 16:00:00 1969 As a result, we have to create a temporary mount point and then mount the local disk onto that mount point: # mkdir /tmp/mnt # mount /dev/dsk/c0t0d0s0 /tmp/mnt Note that your system will not necessarily have had its root filesystem on "c0t0d0s0". This is something that you should also have recorded before you ever loaded your.. er... "my" buggy driver! :-) One can find the local disk mounted under the root filesystem by entering: # df -k / Filesystem kbytes used avail capacity Mounted on /dev/dsk/c0t0d0s0 76703839 4035535 71901266 6% / To continue with our example, we can now move to the directory of buggy-driver in order to replace it with the original driver. Note that /tmp/mnt is prefixed to the path of where we'd "normally" find the driver: # cd /tmp/mnt/platform/sun4u/kernel/drv/sparcv9 # ls -l pci\* -rw-r--r-- 1 root root 288504 Dec 6 15:38 pcisch -rw-r--r-- 1 root root 288504 Dec 6 15:38 pcisch.aar -rwxr-xr-x 1 root sys 211616 Jun 8 2006 pcisch.orig # cp -p pcisch.orig pcisch We can now synchronize any in-memory filesystem data structures with those on disk... and then reboot. The system will then boot correctly... as expected: # sync;sync # reboot syncing file systems... done Sun Blade 1500, No Keyboard Copyright 1998-2004 Sun Microsystems, Inc. All rights reserved. OpenBoot 4.16.4, 1024 MB memory installed, Serial #xxxxxxxx. Ethernet address 0:3:ba:2f:c9:61, Host ID: yyyyyyyy. Rebooting with command: boot Boot device: /pci@1e,600000/ide@d/disk@0,0:a File and args: SunOS Release 5.10 Version Generic_118833-17 64-bit Copyright 1983-2005 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Hostname: my-host NIS domain name is my-campus.Central.Sun.COM my-host console login: ...so that's how it's done! Of course, the easier way is to never write a buggy-driver... but.. then.. we all "have an eraser on the end of each of our pencils"... don't we ? :-) "...thank you... and good night..."

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  • READ_ME_FIRST: What Do I Do All of Those SPARC Threads?

    - by user12608550
    New Oracle Technical White Paper: READ_ME_FIRST: What Do I Do All of Those SPARC Threads? Executive Overview With an amazing 1,536 threads in an Oracle M5-32 system, the number of threads in a single system has never been so high. This offers a tremendous processing capacity, but one may wonder how to make optimal use of all these resources. In this technical white paper, we explain how the heavily threaded Oracle T5 and M5 servers can be deployed to efficiently consolidate and manage workloads using virtualization through Oracle Solaris Zones, Oracle VM Server for SPARC, and Oracle Enterprise Manager Ops Center, as well as how to improve the performance of a single application through multi-threading. READ_ME_FIRST: What Do I Do All of Those SPARC Threads?

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  • What is the standard way of delivering HTML5 games to portals and such?

    - by Bane
    Let me explain what I mean by "standard way of delivering"... Think about Flash games sites. Flash games can be delivered as a single file, either hosted by the site, or, I guess, provided by someone else. HTML5 games, on the other hand, don't have something so standard. Usually, they have their own page, and portals just link to that page. I think that it greatly hinders the purpose of that portal, because, well, you want people to stay on your site and look for other games. Now, I think that a some kind of iframe way of delivering games would help solve this problem greatly. I saw some games doing that, and they were often included on tutorial sites to show a live example, which is obviously a great thing. So, is there a standard at all? Any suggestions? Can you create a game that just preloads itself in an iframe (I heard something about a "single document" or something)?

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  • Why is Java the lingua franca at so many institutions?

    - by Billy ONeal
    EDIT: This question at first seems to be bashing Java, and I guess at this point it is a bit. However, the bigger point I am trying to make is why any one single language is chosen as the one end all be all solution to all problems. Java happens to be the one that's used so that's the one I had to beat on here, but I'm not intentionality ripping Java a new one :) I don't like Java in most academic settings. I'm not saying the language itself is bad -- it has several extremely desirable aspects, most importantly the ability to run without recompilation on most any platform. Nothing wrong with using the language for Your Next App ^TM. (Not something I would personally do, but that's more because I have less experience with it, rather than it's design being poor) I think it is a waste that high level CS courses are taught using Java as a language. Too many of my co-students cannot program worth a damn, because they don't know how to work in a non-garbage-collected world. They don't fundamentally understand the machines they are programming for. When someone can work outside of a garbage collected world, they can work inside of one, but not vice versa. GC is a tool, not a crutch. But the way it is used to teach computer science students is a as a crutch. Computer science should not teach an entire suite of courses tailored to a single language. Students leave with the idea that all good design is idiomatic Java design, and that Object Oriented Design is the ONE TRUE WAY THAT IS THE ONLY WAY THINGS CAN BE DONE. Other languages, at least one of them not being a garbage collected language, should be used in teaching, in order to give the graduate a better understanding of the machines. It is an embarrassment that somebody with a PHD in CS from a respected institution cannot program their way out of a paper bag. What's worse, is that when I talk to those CS professors who actually do understand how things operate, they share feelings like this, that we're doing a disservice to our students by doing everything in Java. (Note that the above would be the same if I replaced it with any other language, generally using a single language is the problem, not Java itself) In total, I feel I can no longer respect any kind of degree at all -- when I can't see those around me able to program their way out of fizzbuzz problems. Why/how did it get to be this way?

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  • Does it really takes 5-10 years (or more) to be really good in programming?

    - by Ygam
    I don't get it. Why is there such a notion that it takes this long to be really proficient in a single language? I somehow think that this statement meant that it takes such a long time to master your language, and use it in a lot of context (web programming, desktop applications, mobile applications, etc.). Adding to that, sometimes you get stuck on a single language in your job and doing repetitive things and don't have much time to study other languages, thus for a certain amount of time, you don't really do much learning at all, and that adds to the amount of time. What do you think?

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  • Using packages (gems, eggs, etc.) to create decoupled architectures

    - by Juan Carlos Coto
    The main issue Seeing the good support most modern programming platforms have for package management (think gem, npm, pip, etc), does it make sense to design an application or system be composed of internally developed packages, so as to promote and create a loosely coupled architecture? Example An example of this would be to create packages for database access, as well as for authentication and other components of the system. These, of course, use external packages as well. Then, your system imports and uses these packages - instead of including their code within its own code base. Considerations To me, it seems that this would promote code decoupling and help maintainability, almost in a Web-based-vs.-desktop-application kind of way (updates are applied almost automatically, single code base for single functionality, etc.). Does this seem like a rational and sane design concept? Is this actually used as a standard way of structuring applications today? Thanks very much!

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  • SPARC T5-4 Engineering Simulation Solution

    - by Mike Mulkey-Oracle
    A recent Oracle internal performance evaluation for computer-based product design demonstrated that Oracle's SPARC T5-4 server running MSC's SimManager simulation software with Oracle Database 12c consolidates the work of multiple x86 servers while delivering better overall performance.   Engineering simulation solutions have taken the center stage in helping companies design and develop innovative products while reducing physical prototyping costs, and exploring a larger design space, resulting in more design possibilities. For this solution, a single SPARC T5-4 server running Oracle Solaris 11 was deployed to consolidate the MSC SimManager server, the Oracle Database 12c server, and the web application server onto a single platform. An automotive design workload was deployed to demonstrate how the SPARC T5-4 server can be used to consolidate the work of multiple x86 servers and deliver better overall performance while reducing complexity and achieving optimal product designs.  A joint Oracle/MSC Software solution brief describes this in more detail:  A Simplified Solution for Product Lifecycle Management —MSC SimManager on a SPARC T5-4 Server

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  • Where should I put a method that returns a list of active entries of a table?

    - by darga33
    I have a class named GuestbookEntry that maps to the properties that are in the database table named "guestbook". Very simple! Originally, I had a static method named getActiveEntries() that retrieved an array of all GuestbookEntry objects. Each row in the guestbook table was an object that was added to that array. Then while learning how to properly design PHP classes, I learned some things: Static methods are not desirable. Separation of Concerns Single Responsibility Principle If the GuestbookEntry class should only be responsible for managing single guestbook entries then where should this getActiveEntries() method most properly go? Update: I am looking for an answer that complies with the SOLID acronym principles and allows for test-ability. That's why I want to stay away from static calls/standard functions. DAO, repository, ...? Please explain as though your explanation will be part of "Where to Locate FOR DUMMIES"... :-)

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  • Most standard / Best way to keep the same top menu among different web pages?

    - by jsoldi
    What's the standard way to keep the same menu on top among different web pages without having to duplicate it on each page (I don't mean that it doesn't reload like when using frames and only loading the bottom part; I want the menu to scroll with the page when scrolling down, like this, this, this and pretty much every single web page that exists). I found this answer but the guy can't use Php and I can. Plus, I see several people giving different suggestions, but I assume there is a standard since pretty much every single web page in the whole web have a menu on top that stays the same among multiple pages . I'm just a newbie on web design (I can program Php and Html easily but I have no idea about standards and stuff like that since I'm self-taught guy ;)). What I would normally do is to include the menu with php but I'm not sure if this is the "standard".

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  • Variable names for Contact Information bits

    - by RustyTheBoyRobot
    I am in the middle of refactoring code and would like to get some ideas on variable naming so that my new names clearly represent the data they hold. I have a class called ContactMethod which makes sense to me; each instance is a different way to contact someone. My problem comes when naming the properties of ContactMethod. For example, one instance might be a Fax number of 555-555-5555 while another could be an Email address of [email protected]; I've got a property called contactMethodType to hold the values "fax" or "email", but I don't know what to call the "555-555-5555" or "[email protected]" part. Has anyone here created a good generic name for this piece of contact information? (PS - the old convention was to call it a "Phone" with fields "phoneType" holding the "fax"/"email" value and "phoneId" holding the number/address. Yuck.)

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  • Remote Desktop advice

    - by spoon16
    Coming from Windows, so that is what my expectations are based on. I have a Ubuntu desktop edition instance running as a virtual machine on a server. I would like to use it as my primary open source dev environment but the VNC tools I have used don't seem to be as rich as "Remote Desktop Connection" in Windows. The two things that are missing for me: connecting/logging into a non-console user sessions dynamically resizing the graphical resolution based on the size of the remote desktop window device sharing (USB devices plugged into client shared with remote) Is there an appropriate client that I can run on Windows to connect to my ubuntu dev instance that provides these capabilities?

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  • Game Design - When to separate out pieces into static libraries?

    - by Jason
    I am developing a game that has a lot of platform generic pieces. I am wanting to separate out various pieces into static libraries and I would like to know what other devs do. I am considering targeting other platforms and I want to maintain an much platform neutrality as I can. I have a lot of generic level data in C++ classes. THinking all of the level data could go into a single static library. I have a lot of generic OpenGL code that I think could also go into a single static library. I am already using CMAKE for some and XCode 4.5 for the Apple specific pieces. What do other devs do to stay platform neutral? Does anyone use Eclipse instead of XCode and Visual Studio on Windows?

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  • Is there a better way to handle data abstraction in this example?

    - by sigil
    I'm building an application that retrieves Sharepoint list data via a web service SPlists.Lists. To create an instance of the web service, I have the following class: class SharepointServiceCreator { public SPlists.Lists createService() { listsService.Url = "http://wss/sites/SPLists/_vti_bin/lists.asmx"; listsService.Credentials = System.Net.CredentialCache.DefaultCredentials; SPlists.Lists listsService=new SPlists.Lists(); } } I'm concerned that this isn't good OOP abstraction, though, because in order to create this service elsewhere in my application, I would need the following code: class someClass { public void someMethod() { SharepointServiceCreator s=new SharepointServiceCreator() SPlists.Lists listService=s.createService() } } Having to use declare the instance of listService in someMethod as type SPlists.Lists seems wrong, because it means that someClass needs to know about how SharepointServiceCreator is implemented. Or is this ok?

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  • Copying Properties between 2 Different Types&hellip;

    - by Shawn Cicoria
    I’m not sure where I had seen some of this base code, but this comes up time & time again on projects. Here’s a little method that copies all the R/W properties (public) between 2 distinct class definitions: It’s called as follows: private static void Test1() { MyClass obj1 = new MyClass() { Prop1 = "one", Prop2 = "two", Prop3 = 100 }; MyOtherClass obj2 = null; obj2 = CopyClass(obj1); Console.WriteLine(obj1); Console.WriteLine(obj2); } namespace Space1 { public class MyClass { public string Prop1 { get; set; } public string Prop2 { get; set; } public int Prop3 { get; set; } public override string ToString() { var rv = string.Format("MyClass: {0} Prop2: {1} Prop3 {2}", Prop1, Prop2, Prop3); return rv; } } } namespace Space2 { public class MyOtherClass { public string Prop1 { get; set; } public string Prop2 { get; set; } public int Prop3 { get; set; } public override string ToString() { var rv = string.Format("MyOtherClass: {0} Prop2: {1} Prop3 {2}", Prop1, Prop2, Prop3); return rv; } } Source of the method: /// /// Provides a Copy of Public fields between 2 distinct classes /// /// Source class name /// Target class name /// Instance of type Source /// An instance of type Target copying all public properties matching name from the Source. public static T CopyClass(S source) where T : new() { T target = default(T); BindingFlags flags = BindingFlags.Public | BindingFlags.Instance; if (source == null) { return (T)target; } if (target == null) target = new T(); PropertyInfo[] objProperties = target.GetType().GetProperties(flags); foreach (PropertyInfo pi in objProperties) { string name = pi.Name; PropertyInfo sourceProp = source.GetType().GetProperty(name, flags); if (sourceProp == null) { throw new ApplicationException(string.Format("CopyClass - object type {0} & {1} mismatch in property:{2}", source.GetType(), target.GetType(), name)); } if (pi.CanWrite && sourceProp.CanRead) { object sourceValue = sourceProp.GetValue(source, null); pi.SetValue(target, sourceValue, null); } else { throw new ApplicationException(string.Format("CopyClass - can't read/write a property object types {0} & {1} property:{2}", source.GetType(), target.GetType(), name)); } } return target; }

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  • SQL Live Monitor

    - by TiborKaraszi
    I just found this one out there and wanted to share it. It connects to an instance and show you a bunch of figures. Nothing you can't extract yourself with SQL queries, but sometimes it is just nice to have one tool which is very easy to use. Here's what it looks like when connecting to an instance with no load on it: As you can see, there are some hyperlinked pages as well, and there are also some interesting options (like logging to CSV or for PAL analysis) under the "Option" button. One more thing...(read more)

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  • Unable to connect FileZilla to ubuntu ec2

    - by user1775063
    I have a micro ubuntu instance on ec2. I have done a passwd to set it to simple password. I have installed vsftpd on the ec2 instance. And imported the ec2 pem file via FileZilla-Settings-SFTP, and configured vsftpd.conf with following listen=YES anonymous_enable=NO local_enable=YES write_enable=YES local_umask=022 dirmessage_enable=YES use_localtime=YES xferlog_enable=YES connect_from_port_20=YES secure_chroot_dir=/var/run/vsftpd/empty pam_service_name=vsftpd rsa_cert_file=/etc/ssl/private/vsftpd.pem local_root=/home/ubuntu pasv_enable=YES pasv_max_port=12100 pasv_min_port=12000 port_enable=YES I am using username ubuntu, password that_i_set, port 21. I get the following error Error: Critical error Error: Could not connect to server

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  • Where would a senior PHP developer locate the method getActiveEntries()?

    - by darga33
    I have a class named GuestbookEntry that maps to the properties that are in the database table named "guestbook". Very simple! Originally, I had a static method named getActiveEntries() that retrieved an array of all GuestbookEntry objects. Each row in the guestbook table was an object that was added to that array. Then while learning how to properly design PHP classes, I learned some things: Static methods are not desirable. Separation of Concerns Single Responsibility Principle If the GuestbookEntry class should only be responsible for managing single guestbook entries then where should this getActiveEntries() method most properly go? Update: I am looking for an answer that complies with the SOLID acronym principles and allows for test-ability. That's why I want to stay away from static calls/standard functions. DAO, repository, ...? Please explain as though your explanation will be part of "Where to Locate FOR DUMMIES"... :-)

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  • Does anyone know of a program like Elastics for Linux?

    - by coteyr
    On mac I would use Elastics (http://tundrabot.com/elastics) To kind of, monitor my EC2 instances. Most important to me was that it worked across several accounts and that it allowed me to connect to a running instance via ssh or RDP. This was the only real feature I care about. I can not always keep the IP address of the server that is running because ec2 is elastic, and it changes frequently. Is there any tool, like Elastics for linux/unity? Again it should support several accounts and be able to give me the IP addresses of the instance I select.

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