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• Availability Best Practices on Oracle VM Server for SPARC

  - by jsavit

  This is the first of a series of blog posts on configuring Oracle VM Server for SPARC (also called Logical Domains) for availability. This series will show how to how to plan for availability, improve serviceability, avoid single points of failure, and provide resiliency against hardware and software failures. Availability is a broad topic that has filled entire books, so these posts will focus on aspects specifically related to Oracle VM Server for SPARC. The goal is to improve Reliability, Availability and Serviceability (RAS): An article defining RAS can be found here. Oracle VM Server for SPARC Principles for Availability Let's state some guiding principles for availability that apply to Oracle VM Server for SPARC: Avoid Single Points Of Failure (SPOFs). Systems should be configured so a component failure does not result in a loss of application service. The general method to avoid SPOFs is to provide redundancy so service can continue without interruption if a component fails. For a critical application there may be multiple levels of redundancy so multiple failures can be tolerated. Oracle VM Server for SPARC makes it possible to configure systems that avoid SPOFs. Configure for availability at a level of resource and effort consistent with business needs. Effort and resource should be consistent with business requirements. Production has different availability requirements than test/development, so it's worth expending resources to provide higher availability. Even within the category of production there may be different levels of criticality, outage tolerances, recovery and repair time requirements. Keep in mind that a simple design may be more understandable and effective than a complex design that attempts to "do everything". Design for availability at the appropriate tier or level of the platform stack. Availability can be provided in the application, in the database, or in the virtualization, hardware and network layers they depend on - or using a combination of all of them. It may not be necessary to engineer resilient virtualization for stateless web applications applications where availability is provided by a network load balancer, or for enterprise applications like Oracle Real Application Clusters (RAC) and WebLogic that provide their own resiliency. It's (often) the same architecture whether virtual or not: For example, providing resiliency against a lost device path or failing disk media is done for the same reasons and may use the same design whether in a domain or not. It's (often) the same technique whether using domains or not: Many configuration steps are the same. For example, configuring IPMP or creating a redundant ZFS pool is pretty much the same within the guest whether you're in a guest domain or not. There are configuration steps and choices for provisioning the guest with the virtual network and disk devices, which we will discuss. Sometimes it is different using domains: There are new resources to configure. Most notable is the use of alternate service domains, which provides resiliency in case of a domain failure, and also permits improved serviceability via "rolling upgrades". This is an important differentiator between Oracle VM Server for SPARC and traditional virtual machine environments where all virtual I/O is provided by a monolithic infrastructure that itself is a SPOF. Alternate service domains are widely used to provide resiliency in production logical domains environments. Some things are done via logical domains commands, and some are done in the guest: For example, with Oracle VM Server for SPARC we provide multiple network connections to the guest, and then configure network resiliency in the guest via IP Multi Pathing (IPMP) - essentially the same as for non-virtual systems. On the other hand, we configure virtual disk availability in the virtualization layer, and the guest sees an already-resilient disk without being aware of the details. These blogs will discuss configuration details like this. Live migration is not "high availability" in the sense of "continuous availability": If the server is down, then you don't live migrate from it! (A cluster or VM restart elsewhere would be used). However, live migration can be part of the RAS (Reliability, Availability, Serviceability) picture by improving Serviceability - you can move running domains off of a box before planned service or maintenance. The blog Best Practices - Live Migration on Oracle VM Server for SPARC discusses this. Topics Here are some of the topics that will be covered: Network availability using IP Multipathing and aggregates Disk path availability using virtual disks defined with multipath groups ("mpgroup") Disk media resiliency configuring for redundant disks that can tolerate media loss Multiple service domains - this is probably the most significant item and the one most specific to Oracle VM Server for SPARC. It is very widely deployed in production environments as the means to provide network and disk availability, but it can be confusing. Subsequent articles will describe why and how to configure multiple service domains. Note, for the sake of precision: an I/O domain is any domain that has a physical I/O resource (such as a PCIe bus root complex). A service domain is a domain providing virtual device services to other domains; it is almost always an I/O domain too (so it can have something to serve). Resources Here are some important links; we'll be drawing on their content in the next several articles: Oracle VM Server for SPARC Documentation Maximizing Application Reliability and Availability with SPARC T5 Servers whitepaper by Gary Combs Maximizing Application Reliability and Availability with the SPARC M5-32 Server whitepaper by Gary Combs Summary Oracle VM Server for SPARC offers features that can be used to provide highly-available environments. This and the following blog entries will describe how to plan and deploy them.

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• Better drivers for SiS 650/740 integrated video?

  - by Bart van Heukelom

  I installed Xubuntu 10.10 on an old box today and the graphical performance is horrid. According to lspci, the video card is this: 01:00.0 VGA compatible controller: Silicon Integrated Systems [SiS] 65x/M650/740 PCI/AGP VGA Display Adapter (prog-if 00 [VGA controller]) Subsystem: ASUSTeK Computer Inc. Device 8081 Flags: 66MHz, medium devsel, IRQ 11 BIST result: 00 Memory at f0000000 (32-bit, prefetchable) [size=128M] Memory at e7800000 (32-bit, non-prefetchable) [size=128K] I/O ports at d800 [size=128] Expansion ROM at <unassigned> [disabled] Capabilities: <access denied> Kernel modules: sisfb Is there a way to make it faster? Alternative drivers? The additional drivers tool shows nothing. I'm specifically interested in improving Java's Java2D rendering speed, because I'll be running a "stat screen" written in that language on it.

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• How to list missing partitions?

  - by celebrimbor

  I have installed Ubuntu on one of my partition and Crunchbang on the other partition. As I wanted to make some continuous space, I moved Crunchbang partition and then checked fdisk output which looks like this Disk /dev/sda: 320.1 GB, 320072933376 bytes 255 heads, 63 sectors/track, 38913 cylinders, total 625142448 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xc7996dfa Device Boot Start End Blocks Id System /dev/sda1 * 63 80324 40131 de Dell Utility /dev/sda4 81918 625139711 312528897 f W95 Ext'd (LBA) /dev/sda5 81920 211816447 105867264 83 Linux /dev/sda6 299100160 341043199 20971520 83 Linux /dev/sda7 341045248 625139711 142047232 7 HPFS/NTFS/exFAT I cannot see sda2 and sda3 partition. How to find them?

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• How can I switch memory modules to 1600 Mhz?

  - by Salvador

  Some months ago I bought 4 Memory modules of 4GB DDR3 1600 KINGSTON HYPERX. The official Kingston manual says: *This module has been tested to run at DDR3-1600 at a low latency timing of 9-9-9-27 at 1.65V.The SPD is programmed to JEDEC standard latency DDR3-1333 timing of 9-9-9. I cannot find which is the real speed of my memory modules. I normally get from several tools that the real speed is 1333 Mhz srs@ubuntu:~$ sudo dmidecode -t memory # dmidecode 2.9 SMBIOS 2.6 present. Handle 0x005D, DMI type 16, 15 bytes Physical Memory Array Location: System Board Or Motherboard Use: System Memory Error Correction Type: None Maximum Capacity: 32 GB Error Information Handle: 0x005F Number Of Devices: 4 Handle 0x005C, DMI type 17, 28 bytes Memory Device Array Handle: 0x005D Error Information Handle: 0x0060 Total Width: 64 bits Data Width: 64 bits Size: 4096 MB Form Factor: DIMM Set: None Locator: ChannelA-DIMM0 Bank Locator: BANK 0 Type: <OUT OF SPEC> Type Detail: Synchronous Speed: 1333 MHz (0.8 ns) Manufacturer: Kingston Serial Number: 07288F23 Asset Tag: 9876543210 Part Number: 9905403-439.A00LF How can I switch memory modules to 1600 Mhz?

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• apt-get update bzip2 errors

  - by Tejas Kale

  I installed Ubuntu 11.10 today on my Lenovo w500. After that when i tried running sudo apt-get update This is the error i am getting. Get:117 http://ftp.jaist.ac.jp oneiric-security/universe TranslationIndex [73 B] 99% [48 Sources bzip2 0 B] [22 Sources bzip2 5,294 kB] 1,983 kB/s 0s bzip2: Compressed file ends unexpectedly; perhaps it is corrupted? *Possible* reason follows. bzip2: Inappropriate ioctl for device Input file = (stdin), output file = (stdout) It is possible that the compressed file(s) have become corrupted. You can use the -tvv option to test integrity of such files. You can use the `bzip2recover' program to attempt to recover data from undamaged sections of corrupted files. I found the following similar question : Errors while updating Ubuntu 11.10 , But the solutions mentioned ( changing the download server, running apt-get clean, apt-get autoclean) and have also tried removing the /var/cache/apt/archives/lists direcotry. As a result of this, I am unable to install any new packages.

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• Graphical Email-client with Sent-emails -directory?

  - by hhh

  I asked this question here but without any answer. So I am now looking something to replace Evolution -email-client. So does there exist a graphical Email-client with Sent-directory? Or is it specified system-wide? P.s. I know Mutt has this feature but I cannot understand how graphical Email -clients work in this, perhaps I cannot just find this feature -- I don't know. Basically, I just want to see emails that I have sent. My email -client has many emails connected. Perhaps related I am also interested to have this kind of feature in Android -device, more here. Where do Sent -emails go in Evolution?

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• Question about wifi connection files/certificates

  - by I_am_that_man-with-hair

  Here is the output i get when i run my school's wifi .py file for secure login. I "python SecureW2_JoinNow.py" I've emailed them about it, but wanted to take a shot and post here, could be on my end. I can't make sense of this error, although the last line makes me think it's on my end. Fresh install, so maybe that is it... Traceback (most recent call last): File "SecureW2_JoinNow.py", line 252, in <module> main() File "SecureW2_JoinNow.py", line 248, in main nm.connect() File "SecureW2_JoinNow.py", line 196, in connect wireless_device = nm_iface.GetDeviceByIpIface('wlan0') File "/usr/lib/python2.7/dist-packages/dbus/proxies.py", line 70, in __call__ return self._proxy_method(*args, **keywords) File "/usr/lib/python2.7/dist-packages/dbus/proxies.py", line 145, in __call__ **keywords) File "/usr/lib/python2.7/dist-packages/dbus/connection.py", line 651, in call_blocking message, timeout) dbus.exceptions.DBusException: org.freedesktop.NetworkManager.UnknownDevice: No device found for the requested iface.

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• How to optimize collision detection

  - by Niklas

  I am developing a 2D Java Game with LibGDX. This is what it kinda looks like (simplified): The big black circle is the player, which you can move by tilting the smartphone. The red circles and blue rectangles are enemies, which will move from the right of the screen to the left. The player has to avoid crashing into them. Right now I am checking in the Game Loop every enemy against the player, whether they collide or not. This seems kinda inefficient to me, but I don't know how to improve it. I have tried the Quadtree approach, but it did not really work. The player could easily glitch through enemies and the collision was not detected. Unfortunately, I have destroyed the Quadtree implementation. I used this [tutorial/blog] as my Quadtree implementation(http://gamedevelopment.tutsplus.com/tutorials/quick-tip-use-quadtrees-to-detect-likely-collisions-in-2d-space--gamedev-374).

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• How can I best study a problem to determine whether recursion can/should be used?

  - by user10326

  In some cases, I fail to see that a problem could be solved by the divide and conquer method. To give a specific example, when studying the find max sub-array problem, my first approach is to brute force it by using a double loop to find the max subarray. When I saw the solution using the divide and conquer approach which is recursion-based, I understood it but ok. From my side, though, when I first read the problem statement, I did not think that recursion is applicable. When studying a problem, is there any technique or trick to see that a recursion based (i.e. divide and conquer) approach can be used or not?

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• Week in Geek: Rogue Antivirus Caught Using AVG Logo Edition

  - by Asian Angel

  This week we learned how to quickly cut a clip from a video file with Avidemux, “tile windows, remote control a desktop using an iOS device, taking advantage of Windows 7 libraries”, turn a home Ubuntu PC into a LAMP web server, enable desktop notifications for Gmail in Chrome, “what image channels are and what they mean”, and more Latest Features How-To Geek ETC How to Integrate Dropbox with Pages, Keynote, and Numbers on iPad RGB? CMYK? Alpha? What Are Image Channels and What Do They Mean? How to Recover that Photo, Picture or File You Deleted Accidentally How To Colorize Black and White Vintage Photographs in Photoshop How To Get SSH Command-Line Access to Windows 7 Using Cygwin The How-To Geek Video Guide to Using Windows 7 Speech Recognition Android Notifier Pushes Android Notices to Your Desktop Dead Space 2 Theme for Chrome and Iron Carl Sagan and Halo Reach Mashup – We Humans are Capable of Greatness [Video] Battle the Necromorphs Once Again on Your Desktop with the Dead Space 2 Theme for Windows 7 HTC Home Brings HTC’s Weather Widget to Your Windows Desktop Apps Uninstall Batch Removes Android Applications

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• Organization &amp; Architecture UNISA Studies &ndash; Chap 5

  - by MarkPearl

  Learning Outcomes Describe the operation of a memory cell Explain the difference between DRAM and SRAM Discuss the different types of ROM Explain the concepts of a hard failure and a soft error respectively Describe SDRAM organization Semiconductor Main Memory The two traditional forms of RAM used in computers are DRAM and SRAM DRAM (Dynamic RAM) Divided into two technologies… Dynamic Static Dynamic RAM is made with cells that store data as charge on capacitors. The presence or absence of charge in a capacitor is interpreted as a binary 1 or 0. Because capacitors have natural tendency to discharge, dynamic RAM requires periodic charge refreshing to maintain data storage. The term dynamic refers to the tendency of the stored charge to leak away, even with power continuously applied. Although the DRAM cell is used to store a single bit (0 or 1), it is essentially an analogue device. The capacitor can store any charge value within a range, a threshold value determines whether the charge is interpreted as a 1 or 0. SRAM (Static RAM) SRAM is a digital device that uses the same logic elements used in the processor. In SRAM, binary values are stored using traditional flip flop logic configurations. SRAM will hold its data as along as power is supplied to it. Unlike DRAM, no refresh is required to retain data. SRAM vs. DRAM DRAM is simpler and smaller than SRAM. Thus it is more dense and less expensive than SRAM. The cost of the refreshing circuitry for DRAM needs to be considered, but if the machine requires a large amount of memory, DRAM turns out to be cheaper than SRAM. SRAMS are somewhat faster than DRAM, thus SRAM is generally used for cache memory and DRAM is used for main memory. Types of ROM Read Only Memory (ROM) contains a permanent pattern of data that cannot be changed. ROM is non volatile meaning no power source is required to maintain the bit values in memory. While it is possible to read a ROM, it is not possible to write new data into it. An important application of ROM is microprogramming, other applications include library subroutines for frequently wanted functions, System programs, Function tables. A ROM is created like any other integrated circuit chip, with the data actually wired into the chip as part of the fabrication process. To reduce costs of fabrication, we have PROMS. PROMS are… Written only once Non-volatile Written after fabrication Another variation of ROM is the read-mostly memory, which is useful for applications in which read operations are far more frequent than write operations, but for which non volatile storage is required. There are three common forms of read-mostly memory, namely… EPROM EEPROM Flash memory Error Correction Semiconductor memory is subject to errors, which can be classed into two categories… Hard failure – Permanent physical defect so that the memory cell or cells cannot reliably store data Soft failure – Random error that alters the contents of one or more memory cells without damaging the memory (common cause includes power supply issues, etc.) Most modern main memory systems include logic for both detecting and correcting errors. Error detection works as follows… When data is to be read into memory, a calculation is performed on the data to produce a code Both the code and the data are stored When the previously stored word is read out, the code is used to detect and possibly correct errors The error checking provides one of 3 possible results… No errors are detected – the fetched data bits are sent out An error is detected, and it is possible to correct the error. The data bits plus error correction bits are fed into a corrector, which produces a corrected set of bits to be sent out An error is detected, but it is not possible to correct it. This condition is reported Hamming Code See wiki for detailed explanation. We will probably need to know how to do a hemming code – refer to the textbook (pg. 188 – 189) Advanced DRAM organization One of the most critical system bottlenecks when using high-performance processors is the interface to main memory. This interface is the most important pathway in the entire computer system. The basic building block of main memory remains the DRAM chip. In recent years a number of enhancements to the basic DRAM architecture have been explored, and some of these are now on the market including… SDRAM (Synchronous DRAM) DDR-DRAM RDRAM SDRAM (Synchronous DRAM) SDRAM exchanges data with the processor synchronized to an external clock signal and running at the full speed of the processor/memory bus without imposing wait states. SDRAM employs a burst mode to eliminate the address setup time and row and column line precharge time after the first access In burst mode a series of data bits can be clocked out rapidly after the first bit has been accessed SDRAM has a multiple bank internal architecture that improves opportunities for on chip parallelism SDRAM performs best when it is transferring large blocks of data serially There is now an enhanced version of SDRAM known as double data rate SDRAM or DDR-SDRAM that overcomes the once-per-cycle limitation of SDRAM

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• metro style on windows and android

  - by MRM

  I want to develop a rather simple app using windows 8 metro style for GUI. But i need this app to have the same appearance, GUI, for both platforms, so that end users that uses it both on PC and a mobile device to have the same visual experience and a flawless navigation. So, does anyone have knowledge of a Java framework or library to satisfy these needs? Or maybe a method to create a web-based app using HTML, PHP, JScript etc. (maybe something using a local server, on the same machine, because a web server is out of discussion, at least for the moment)? Any idea, method, technology related to the subject is also helpful. And if what you are thinking at can be used for IOS too, the better.

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• Sprites as Actors

  - by Scán

  Hello, I'm not experienced in GameDev questions, but as a programmer. In the language Scala, you can have scalable multi-tasking with Actors, very stable, as I hear. You can even habe hundreds of thousands of them running at once without a problem. So I thought, maybe you can use these as a base class for 2D-Sprites, to break out of the game-loop thing that requires to go through all the sprites and move them. They'd basically move themselves, event-driven. Would that make sense for a game? Having it multitasked like that? After all, it will run on the JVM, though that should not be much of a problem nowadays.

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• Size limit while using UICollectionView as tiled map for iOS game?

  - by Alexander Winn

  I'm working on a turn-based strategy game for iOS, (picture Civilization 2 as a template example), and I'm considering using a UICollectionView as my game map. Each cell would be a tile, and I could use the "didSelectCell" method to handle player interaction with each tile. Here's my question: I know that UICollectionViewCells are dequeued and reused by the OS, so does that mean that the map could support an effectively infinitely-large map, so long as only a few cells are onscreen at a time? However many cells were onscreen would be held in memory, and obviously the data source would take up some memory, but would my offscreen map be limited to a certain size or could it be enormous so long as the number of cells visible at any one time wasn't too much for the device to handle? Basically, is there any memory weight to offscreen cells, or do only visible cells have any impact? Also, does a UICollectionView seem like a bad idea for a game map, in a way I haven't thought of yet? It seems like it work well, but I haven't tried it yet so any thoughts are welcome.

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• Mobile Internet Modem Olivetti Olicard 155 does not work in Ubuntu 12.10

  - by João Fracassi

  I have a problem, I bought a 3G mobile modem, but does not work in Ubuntu 12.10, also did not work on Ubuntu 12.04. I installed the USB Modeswitch and has the same flaw, does not recognize the modem within the connection manager, I connect the modem to the USB port and wait up to 20 minutes and does not recognize the modem. I ran the command recognizes the modem and lsusb as "Bus 001 Device 007: ID 0b3c: C004 Olivetti TechCenter." Does anyone have this modem, you can help me solve the problem, or does anyone have a solution? Because the manufacturer does not support Linux and according to some forums usbmodeswitch supports esste model. Olivetti Olicard modem 155.

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• Find vertices of a convex hull

  - by Jeff Bullard

  I am attempting to do this within CGAL. From a 3D point cloud, find the convex hull, then loop over the finite facets of the convex hull and print each facet's vertices. It seems like there should be a straightforward way to do this; I would have expected that 3D polyhedra would own a vector of facet objects, each of which in turn would own a vector of its edges, each of which in turn would own a vector of its vertices, and that their would be some access through this hierarchy using iterators. But so far I have been unable to find a simple way to navigate through this hierarchy (if it exists).

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• What is Atomicity?

  - by James Jeffery

  I'm really struggling to find a concrete, easy to grasp, explanation of Atomicity. My understanding thus far is that to ensure an operation is atomic you wrap the critical code in a locker. But that's about as much as I actually understand. Definitions such as the one below make no sense to me at all. An operation during which a processor can simultaneously read a location and write it in the same bus operation. This prevents any other processor or I/O device from writing or reading memory until the operation is complete. Atomic implies indivisibility and irreducibility, so an atomic operation must be performed entirely or not performed at all. What does the last sentence mean? Is the term indivisibility relating to mathematics or something else? Sometimes the jargon with these topics confuse more than they teach.

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• Raycasting mouse coordinates to rotated object?

  - by SPL

  I am trying to cast a ray from my mouse to a plane at a specified position with a known width and length and height. I know that you can use the NDC (Normalized Device Coordinates) to cast ray but I don't know how can I detect if the ray actually hit the plane and when it did. The plane is translated -100 on the Y and rotated 60 on the X then translated again -100. Can anyone please give me a good tutorial on this? For a complete noob! I am almost new to matrix and vector transformations.

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• Nicest way to map rgb colors from html to led

  - by back_ache

  I have attached an rgb led to a color picker on a webpage and have hit the obvious problem that though the led is 8-bit like html the color rendition is very different so with the more subtle shades the led values for the color are wildly different to the html values. The brute-force method would be for me to have a lookup-table on the webserver to map the two sets of values but would ideally like to do it more elegantly Before I start listing all my 101 ideas for doing this I wondered if anyone else had come across the issue, the end-game would be to be able to abstract the color-rendition of different leds and make it available as a webservice (html value and device id in, led value out)

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• Referring to hardware/software in first-person? [closed]

  - by JYelton

  At my company, there is a habit for the engineers to refer to their respective hardware/firmware/software in the first-person as if the device they are responsible for is a manifestation of themselves. I'll give you an example: Hardware Engineer: "I don't receive the first byte, so I stay off." Software Engineer: "I'm sending you the first byte after the ack flag, so I thought you were getting it." Hardware Engineer: "No, you're not turning me on." It was this very example I overheard today that nearly had me giggling in fits. "You're not turning me on." Well, I should hope not! So, is it common practice for engineers to do this, or simply unprofessional? Any suggestions for changing this apparently bad habit?

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• Ubuntu and VirtualBox

  - by Sinan

  I have the following configuration, A host running Windows 7; A guest running Ubuntu 14.04 LTS (VirtualBox); I am connecting a Cisco router directly to my PC running Windows 7 and testing the router for netflow packets in the virtualBox I am having a difficulty capturing the traffic of the netflow from the Cisco device in my virtualBox using port 2222. I tried to use the many different networking modes provided by virutalBox (i.e. NAT, Bridged Adapter, Host only adapter) but I am not successful in capturing the netflow traffic. Could you please advise me on the configuration setup that need to be done on the virtual box to allow capturing the traffic coming from the router. I successfully capture the netflow traffic on my PC (windows 7). Thank you

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• Polite busy-waiting with WRPAUSE on SPARC

  - by Dave

  Unbounded busy-waiting is an poor idea for user-space code, so we typically use spin-then-block strategies when, say, waiting for a lock to be released or some other event. If we're going to spin, even briefly, then we'd prefer to do so in a manner that minimizes performance degradation for other sibling logical processors ("strands") that share compute resources. We want to spin politely and refrain from impeding the progress and performance of other threads — ostensibly doing useful work and making progress — that run on the same core. On a SPARC T4, for instance, 8 strands will share a core, and that core has its own L1 cache and 2 pipelines. On x86 we have the PAUSE instruction, which, naively, can be thought of as a hardware "yield" operator which temporarily surrenders compute resources to threads on sibling strands. Of course this helps avoid intra-core performance interference. On the SPARC T2 our preferred busy-waiting idiom was "RD %CCR,%G0" which is a high-latency no-nop. The T4 provides a dedicated and extremely useful WRPAUSE instruction. The processor architecture manuals are the authoritative source, but briefly, WRPAUSE writes a cycle count into the the PAUSE register, which is ASR27. Barring interrupts, the processor then delays for the requested period. There's no need for the operating system to save the PAUSE register over context switches as it always resets to 0 on traps. Digressing briefly, if you use unbounded spinning then ultimately the kernel will preempt and deschedule your thread if there are other ready threads than are starving. But by using a spin-then-block strategy we can allow other ready threads to run without resorting to involuntary time-slicing, which operates on a long-ish time scale. Generally, that makes your application more responsive. In addition, by blocking voluntarily we give the operating system far more latitude regarding power management. Finally, I should note that while we have OS-level facilities like sched_yield() at our disposal, yielding almost never does what you'd want or naively expect. Returning to WRPAUSE, it's natural to ask how well it works. To help answer that question I wrote a very simple C/pthreads benchmark that launches 8 concurrent threads and binds those threads to processors 0..7. The processors are numbered geographically on the T4, so those threads will all be running on just one core. Unlike the SPARC T2, where logical CPUs 0,1,2 and 3 were assigned to the first pipeline, and CPUs 4,5,6 and 7 were assigned to the 2nd, there's no fixed mapping between CPUs and pipelines in the T4. And in some circumstances when the other 7 logical processors are idling quietly, it's possible for the remaining logical processor to leverage both pipelines. Some number T of the threads will iterate in a tight loop advancing a simple Marsaglia xor-shift pseudo-random number generator. T is a command-line argument. The main thread loops, reporting the aggregate number of PRNG steps performed collectively by those T threads in the last 10 second measurement interval. The other threads (there are 8-T of these) run in a loop busy-waiting concurrently with the T threads. We vary T between 1 and 8 threads, and report on various busy-waiting idioms. The values in the table are the aggregate number of PRNG steps completed by the set of T threads. The unit is millions of iterations per 10 seconds. For the "PRNG step" busy-waiting mode, the busy-waiting threads execute exactly the same code as the T worker threads. We can easily compute the average rate of progress for individual worker threads by dividing the aggregate score by the number of worker threads T. I should note that the PRNG steps are extremely cycle-heavy and access almost no memory, so arguably this microbenchmark is not as representative of "normal" code as it could be. And for the purposes of comparison I included a row in the table that reflects a waiting policy where the waiting threads call poll(NULL,0,1000) and block in the kernel. Obviously this isn't busy-waiting, but the data is interesting for reference. _table { border:2px black dotted; margin: auto; width: auto; } _tr { border: 2px red dashed; } _td { border: 1px green solid; } _table { border:2px black dotted; margin: auto; width: auto; } _tr { border: 2px red dashed; } td { background-color : #E0E0E0 ; text-align : right ; } th { text-align : left ; } td { background-color : #E0E0E0 ; text-align : right ; } th { text-align : left ; } Aggregate progress T = #worker threads Wait Mechanism for 8-T threadsT=1T=2T=3T=4T=5T=6T=7T=8 Park thread in poll() 32653347334833483348334833483348 no-op 415 831 124316482060249729303349 RD %ccr,%g0 "pause" 14262429269228623013316232553349 PRNG step 412 829 124616702092251029303348 WRPause(8000) 32443361333133483349334833483348 WRPause(4000) 32153308331533223347334833473348 WRPause(1000) 30853199322432513310334833483348 WRPause(500) 29173070315032223270330933483348 WRPause(250) 26942864294930773205338833483348 WRPause(100) 21552469262227902911321433303348

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• How do I do JavaScript Array Animation

  - by Henry

  I'm making a game but don't know how to do Array Animation with the png Array and game Surface that I made below. I'm trying to make it so that when the Right arrow key is pressed, the character animates as if it is walking to the right and when the Left arrow key is pressed it animates as if it is walking to the left (kind of like Mario). I put everything on a surface instead of the canvas. Everything is explained in the code below. I couldn't find help on this anywhere. I hope what I got below makes sense. I'm basically a beginner with JavaScript. I'll be back if more is needed: <!doctype html5> <html> <head></head> <script src="graphics.js"></script> <script src="object.js"></script> <body onkeydown ="keyDown(event)" onkeyup ="keyUp(event)" ></body> <script> //"Surface" is where I want to display my animation. It's like the HTML // canvas but it's not that. It's just the surface to where everything in the //game and the game itself will be displayed. var Surface = new Graphics(600, 400, "skyblue"); //here's the array that I want to use for animation var player = new Array("StandsRight.png", "WalksRight.png", "StandsLeft.png","WalksLeft.png" ); //Here is the X coordinate, Y coordinate, the beginning png for the animation, //and the object's name "player." I also turned the array into an object (but //I don't know if I was supposed to do that or not). var player = new Object(50, 100, 40, 115, "StandsRight.png","player"); //When doing animation I know that it requires a "loop", but I don't // know how to connect it so that it works with the arrays so that //it could animate. var loop = 0; //this actually puts "player" on screen. It makes player visible and //it is where I would like the animation to occur. Surface.drawObject(player); //this would be the key that makes "player" animation in the righward direction function keyDown(e) { if (e.keyCode == 39); } //this would be the key that makes "player" animation in the leftward direction function keyUp(e){ if (e.keyCode == 39); } //this is the Mainloop where the game will function MainLoop(); //the mainloop functionized function MainLoop(){ //this is how fast or slow I could want the entire game to go setTimeout(MainLoop, 10); } </script> </html> From here, are the "graphic.js" and the "object.js" files below. In this section is the graphics.js file. This graphics.js part below is linked to the: script src="graphics.js" html script section that I wrote above. Basically, below is a seperate file that I used for Graphics, and to run the code above, make this graphics.js code that I post below here, a separate filed called: graphics.js function Graphics(w,h,c) { document.body.innerHTML += "<table style='position:absolute;font- size:0;top:0;left:0;border-spacing:0;border- width:0;width:"+w+";height:"+h+";background-color:"+c+";' border=1><tr><td> </table>\n"; this.drawRectangle = function(x,y,w,h,c,n) { document.body.innerHTML += "<div style='position:absolute;font-size:0;left:" + x + ";top:" + y + ";width:" + w + ";height:" + h + ";background-color:" + c + ";' id='" + n + "'></div>\n"; } this.drawTexture = function(x,y,w,h,t,n) { document.body.innerHTML += "<img style='position:absolute;font-size:0;left:" + x + ";top:" + y + ";width:" + w + ";height:" + h + ";' id='" + n + "' src='" + t + "'> </img>\n"; } this.drawObject = function(o) { document.body.innerHTML += "<img style='position:absolute;font-size:0;left:" + o.X + ";top:" + o.Y + ";width:" + o.Width + ";height:" + o.Height + ";' id='" + o.Name + "' src='" + o.Sprite + "'></img>\n"; } this.moveGraphic = function(x,y,n) { document.getElementById(n).style.left = x; document.getElementById(n).style.top = y; } this.removeGraphic = function(n){ document.getElementById(n).parentNode.removeChild(document.getElementById(n)); } } Finally, is the object.js file linked to the script src="object.js"" in the html game file above the graphics.js part I just wrote. Basically, this is a separate file too, so thus, in order to run or test the html game code in the very first section I wrote, a person has to also make this code below a separate file called: object.js I hope this helps: function Object(x,y,w,h,t,n) { this.X = x; this.Y = y; this.Velocity_X = 0; this.Velocity_Y = 0; this.Previous_X = 0; this.Previous_Y = 0; this.Width = w; this.Height = h; this.Sprite = t; this.Name = n; this.Exists = true; } In all, this game is made based on a tutorial on youtube at: http://www.youtube.com/watch?v=t2kUzgFM4lY&feature=relmfu I'm just trying to learn how to add animations with it now. I hope the above helps. If not, let me know. Thanks

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• Bless doesn't fix white boot screen boot delay for single-boot Xubuntu 14.04 on Macbook 4,1

  - by elephant

  I still have a 30-second delay on the white boot-up screen before Xubuntu loads after trying various combinations of bless --device as recommended here: https://help.ubuntu.com/community/MactelSupportTeam/AppleIntelInstallation#Avoid_long_EFI_wait_before_GRUB I wonder if anyone has experienced this before, or can point me to some good steps for troubleshooting this issue? I have cycled my macbook dozens of times, it would be great to be able to boot quicker. I am single-booting Xubuntu 14.04 (no Mac OSX partitions or any other OS, just a GRUB partition at sda1, a main partition at sda2, and a swap at the end of the drive). Suggestions very appreciated.

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• Can a recursive function have iterations/loops?

  - by Omega

  I've been studying about recursive functions, and apparently, they're functions that call themselves, and don't use iterations/loops (otherwise it wouldn't be a recursive function). However, while surfing the web for examples (the 8-queens-recursive problem), I found this function: private boolean placeQueen(int rows, int queens, int n) { boolean result = false; if (row < n) { while ((queens[row] < n - 1) && !result) { queens[row]++; if (verify(row,queens,n)) { ok = placeQueen(row + 1,queens,n); } } if (!result) { queens[row] = -1; } }else{ result = true; } return result; } There is a while loop involved. ... so I'm a bit lost now. Can I use loops or not?

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