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  • Reflection: Is using reflection still "bad" or "slow"? What has changed with reflection since 2002?

    - by blesh
    I've noticed when dealing with Expressions or Expression Trees I'm using reflection a lot to set and get values in properties and what have you. It has occurred to me that the use of reflection seems to be getting more and more common. Things like DataAnotations for validation, Attribute heavy ORMs, etc. Have me wondering: What has changed since the days years and years ago when I used to be told to avoid reflection if at all possible? So what, if anything has changed? Is it just the speed of the machines? Have there been changes to the framework to speed up reflection? Or has nothing really changed? Is it still "bad" or "slow" to use reflection? EDIT: To clarify my question a little.

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  • Play PlayStation Games on a Rooted Nook Simple Touch

    - by Jason Fitzpatrick
    Just when you feel like you’ve seen it all, some guy comes along and shows you how he can play original PlayStation games on his ebook reader. Check out the video to see the surprisingly full-speed–albeit black and white–graphics in action. The secret sauce in Sean’s cool setup? He’s rooted the device and installed Free PlayStation Emulator (FPSE) on it–along with the NoRefresh hack–to enjoy touch-screen controls and PS emulation. The whole thing is shockingly smooth; once you get past the choppy intro videos, the games run at full speed. [via Hack A Day] HTG Explains: Why Do Hard Drives Show the Wrong Capacity in Windows? Java is Insecure and Awful, It’s Time to Disable It, and Here’s How What Are the Windows A: and B: Drives Used For?

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  • Oracle Open World starts on Sunday, Sept 30

    - by Mike Dietrich
    Oracle Open World 2012 starts on Sunday this week - and we are really looking forward to see you in one of our presentations, especially theDatabase Upgrade on SteriodsReal Speed, Real Customers, Real Secretson Monday, Oct 1, 12:15pm in Moscone South 307(just skip the lunch - the boxed food is not healthy at all): Monday, Oct 1, 12:15 PM - 1:15 PM - Moscone South - 307 Database Upgrade on Steroids:Real Speed, Real Customers, Real Secrets Mike Dietrich - Consulting Member Technical Staff, Oracle Georg Winkens - Technical Manager, Amadeus Data Processing Carol Tagliaferri - Senior Development Manager, Oracle  Looking to improve the performance of your database upgrade and learn about other ways to reduce upgrade time? Isn’t everyone? In this session, you will learn directly from Oracle’s Upgrade Development team about what you can do to speed things up. Find out about ways to reduce upgrade downtime such as using a transient logical standby database and/or Oracle GoldenGate, and get other hints and tips. Learn about new features that improve upgrade performance and reduce downtime. Hear Georg Winkens, DB Services technical manager from Amadeus, speak about his upgrade experience, and get real-life performance measurements and advice for a successful upgrade. . And don't forget: we already start on Sunday so if you'd like to learn about the SAP database upgrades at Deutsche Messe: Sunday, Sep 30, 11:15 AM - 12:00 PM - Moscone West - 2001Oracle Database Upgrade to 11g Release 2 with SAP Applications Andreas Ellerhoff - DBA, Deutsche Messe AG Mike Dietrich - Consulting Member Technical Staff, Oracle Jan Klokkers - Sr.Director SAP Development, Oracle Deutsche Messe began to use Oracle6 Database at the end of the 1980s and has been using Oracle Database technology together with SAP applications successfully since 2002. At the end of 2010, it took the first steps of an upgrade to Oracle Database 11g Release 2 (11.2), and since mid-2011, all SAP production systems there run successfully with Oracle Database 11g. This presentation explains why Deutsche Messe uses Oracle Database together with SAP applications, discusses the many reasons for the upgrade to Release 11g, and focuses on the operational top aspects from a DBA perspective. . And unfortunately the Hands-On-Lab is sold out already ... We would like to apologize but we have absolutely ZERO influence on either the number of runs or the number of available seats.  Tuesday, Oct 2, 10:15 AM - 12:45 PM - Marriott Marquis - Salon 12/13 Hands On Lab:Upgrading an Oracle Database Instance, Using Best Practices Roy Swonger - Senior Director, Software Development, Oracle Carol Tagliaferri - Senior Development Manager, Oracle Mike Dietrich - Consulting Member Technical Staff, Oracle Cindy Lim - PMTS, Oracle Carol Palmer - Principal Product Manager, Oracle This hands-on lab gives participants the opportunity to work through a database upgrade from an older release of Oracle Database to the very latest Oracle Database release available. Participants will learn how the improved automation of the upgrade process and the generation of fix-up scripts can quickly help fix database issues prior to upgrading. The lab also uses the new parallel upgrade feature to improve performance of the upgrade, resulting in less downtime. Come get inside information about database upgrades from the Database Upgrade development team. . See you soon

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  • Improving performance of fuzzy string matching against a dictionary [closed]

    - by Nathan Harmston
    Hi, So I'm currently working for with using SecondString for fuzzy string matching, where I have a large dictionary to compare to (with each entry in the dictionary has an associated non-unique identifier). I am currently using a hashMap to store this dictionary. When I want to do fuzzy string matching, I first check to see if the string is in the hashMap and then I iterate through all of the other potential keys, calculating the string similarity and storing the k,v pair/s with the highest similarity. Depending on which dictionary I am using this can take a long time ( 12330 - 1800035 entries ). Is there any way to speed this up or make it faster? I am currently writing a memoization function/table as a way of speeding this up, but can anyone else think of a better way to improve the speed of this? Maybe a different structure or something else I'm missing. Many thanks in advance, Nathan

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  • Very very slow transfer speeds between Windows 7 and samba server running on Ubuntu 11.10/12.04 minimal

    - by kuzyt
    As mentioned in the title I tried transferring files between Windows 7 and the samba server running on both Ubuntu 11.10 and 12.04 but both showed very slow transfer speeds. Can someone please guide me in the right direction to debug this problem ? wget --output-document=/dev/null http://tokyo1.linode.com/100MB-tokyo.bin --2012-08-21 22:02:17-- http://tokyo1.linode.com/100MB-tokyo.bin Resolving tokyo1.linode.com (tokyo1.linode.com)... 106.187.33.12 Connecting to tokyo1.linode.com (tokyo1.linode.com)|106.187.33.12|:80... connected. HTTP request sent, awaiting response... 200 OK Length: 104857600 (100M) [application/octet-stream] Saving to: `/dev/null' 8% [=============> ] 8,923,980 64.8K/s eta 15m 0s wlan0 IEEE 802.11abgn ESSID:"TNET" Mode:Managed Frequency:2.462 GHz Access Point: 58:6D:8F:26:20:7A Bit Rate=117 Mb/s Tx-Power=20 dBm Retry long limit:7 RTS thr:off Fragment thr:off Power Management:off Link Quality=57/70 Signal level=-53 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:101 Invalid misc:2448 Missed beacon:0 03:00.0 Network controller: Atheros Communications Inc. AR9300 Wireless LAN adaptor (rev 01) Subsystem: Atheros Communications Inc. Device 3112 Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx- Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx+ Latency: 0, Cache Line Size: 64 bytes Interrupt: pin A routed to IRQ 16 Region 0: Memory at fea00000 (64-bit, non-prefetchable) [size=128K] Expansion ROM at fea20000 [disabled] [size=64K] Capabilities: [40] Power Management version 3 Flags: PMEClk- DSI- D1+ D2- AuxCurrent=375mA PME(D0+,D1+,D2-,D3hot+,D3cold-) Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME- Capabilities: [50] MSI: Enable- Count=1/4 Maskable+ 64bit+ Address: 0000000000000000 Data: 0000 Masking: 00000000 Pending: 00000000 Capabilities: [70] Express (v2) Endpoint, MSI 00 DevCap: MaxPayload 128 bytes, PhantFunc 0, Latency L0s <1us, L1 <8us ExtTag- AttnBtn- AttnInd- PwrInd- RBE+ FLReset- DevCtl: Report errors: Correctable- Non-Fatal- Fatal- Unsupported- RlxdOrd- ExtTag- PhantFunc- AuxPwr- NoSnoop- MaxPayload 128 bytes, MaxReadReq 512 bytes DevSta: CorrErr- UncorrErr- FatalErr- UnsuppReq- AuxPwr- TransPend- LnkCap: Port #0, Speed 2.5GT/s, Width x1, ASPM L0s L1, Latency L0 <2us, L1 <64us ClockPM- Surprise- LLActRep- BwNot- LnkCtl: ASPM Disabled; RCB 64 bytes Disabled- Retrain- CommClk+ ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt- LnkSta: Speed 2.5GT/s, Width x1, TrErr- Train- SlotClk+ DLActive- BWMgmt- ABWMgmt- DevCap2: Completion Timeout: Not Supported, TimeoutDis+ DevCtl2: Completion Timeout: 50us to 50ms, TimeoutDis- LnkCtl2: Target Link Speed: 2.5GT/s, EnterCompliance- SpeedDis-, Selectable De-emphasis: -6dB Transmit Margin: Normal Operating Range, EnterModifiedCompliance- ComplianceSOS- Compliance De-emphasis: -6dB LnkSta2: Current De-emphasis Level: -6dB Capabilities: [100 v1] Advanced Error Reporting UESta: DLP- SDES- TLP- FCP- CmpltTO- CmpltAbrt- UnxCmplt- RxOF- MalfTLP- ECRC- UnsupReq- ACSViol- UEMsk: DLP- SDES- TLP- FCP- CmpltTO- CmpltAbrt- UnxCmplt- RxOF- MalfTLP- ECRC- UnsupReq- ACSViol- UESvrt: DLP+ SDES+ TLP- FCP+ CmpltTO- CmpltAbrt- UnxCmplt- RxOF+ MalfTLP+ ECRC- UnsupReq- ACSViol- CESta: RxErr- BadTLP- BadDLLP- Rollover- Timeout- NonFatalErr- CEMsk: RxErr- BadTLP- BadDLLP- Rollover- Timeout- NonFatalErr+ AERCap: First Error Pointer: 00, GenCap- CGenEn- ChkCap- ChkEn- Capabilities: [140 v1] Virtual Channel Caps: LPEVC=0 RefClk=100ns PATEntryBits=1 Arb: Fixed- WRR32- WRR64- WRR128- Ctrl: ArbSelect=Fixed Status: InProgress- VC0: Caps: PATOffset=00 MaxTimeSlots=1 RejSnoopTrans- Arb: Fixed- WRR32- WRR64- WRR128- TWRR128- WRR256- Ctrl: Enable+ ID=0 ArbSelect=Fixed TC/VC=01 Status: NegoPending- InProgress- Capabilities: [300 v1] Device Serial Number 00-00-00-00-00-00-00-00 Kernel driver in use: ath9k Kernel modules: ath9k

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  • Which techniques to study?

    - by Djentleman
    Just to give you some background info, I'm studying a programming major at a tertiary level and am in my third year, so I'm not a newbie off the street. However, I am still quite new to game programming as a subset of programming. One of my personal projects for next semester is to design and create a 2D platformer game with emphasis on procedural generation and "neato" effects (think metroidvania). I've written up a list of some techniques to help me improve my personal skills (using XNA for the time being). The list is as follows: QuadTrees: Build a basic program in XNA that moves basic 2D sprites (circles and squares) around a set path and speed and changes their colour when they collide. Add functionality to add and delete objects of different sizes (select a direction and speed when adding and just drag and drop them in). Particles: Build a basic program in XNA in which you can select different colours and create particle effects of those colours on screen by clicking and dragging the mouse around (simple particles emerging from where the mouse is clicked). Add functionality where you can change the amount of particles to be drawn and the speed at which they travel and when they expire. Possibly implement gravity and wind after part 3 is complete. Physics: Build a basic program in XNA where you have a ball in a set 2D environment, a wind slider, and a gravity slider (can go to negative for reverse gravity). You can click to drag the ball around and release to throw it and, depending on what you do, the ball interacts with the environment. Implement other shapes afterwards. Random 2D terrain generation: Build a basic program in XNA that randomly generates terrain (including hills, caves, etc) created from 2D tiles. Add functionality that draws the tiles from a tileset and places different tiles depending on where they lie on the y-axis (dirt on top, then rock, then lava, etc). Randomised objects: Build a basic program in XNA that, when a button is clicked, displays a randomised item sprite based on parameters (type, colour, etc) with the images pulled from tilesets. Add the ability to save the item as an object, which stores it in a side-pane where it can be selected for viewing. Movement: Build a basic program in XNA where you can move an object around in an environment (tile-based) with a camera that pans with it. No gravity. Implement gravity and wind, allow the character to jump and fall with some basic platforms. So my question is this: Are there any other commonly used techniques that I should research, and can I get some suggestions as to the effectiveness of the techniques I've chosen to work on (e.g., don't do QuadTree stuff because [insert reason here], or, do [insert technique here] before you start working on particles because [insert reason here])? I hope this is clear enough and please let me know if I can further clarify anything!

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  • Java or Python for internet application?

    - by jpartogi
    In choosing a technology for internet applications where the number of users may scale over time, which one should we consider: Java or Python? What are the considerations in choosing one and not the other? If speed and scalability is our main criteria, which one should we use? We have looked around and it seems that there are more websites that use Python [i.e : Quora, digg, reddit, bitbucket and disqus] than Java. Based on that, can we say that Python is more suitable for internet applications where speed and scalability is the main criteria? However we have browsed around and found some comments saying that Java is actually faster than Python. Thank you for your insights.

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  • E160 ubuntu 12.04 can't detect the modem

    - by Matt
    i've got problem with e160 on ubuntu 12.04. I'cant configure network manager and connect because NM can't see the e160. I;ve tried lot of solutions with no result. ateusz@mateusz-Aspire-5738:~$ sudo usb_modeswitch -v 0x12d1 -p 0x1003 -H [sudo] password for mateusz: aLooking for default devices ... found matching product ID adding device Found device in default mode, class or configuration (1) Accessing device 002 on bus 001 ... Getting the current device configuration ... OK, got current device configuration (1) Using first interface: 0x00 Using endpoints 0x01 (out) and 0x82 (in) Not a storage device, skipping SCSI inquiry USB description data (for identification) ------------------------- Manufacturer: HUAWEI Technology Product: HUAWEI Mobile Serial No.: not provided ------------------------- Sending Huawei control message ... OK, Huawei control message sent - Run lsusb to note any changes. Bye. Dmesg [ 521.480062] usb 1-4: reset high-speed USB device number 4 using ehci_hcd [ 521.617792] option 1-4:1.1: GSM modem (1-port) converter detected [ 521.617945] usb 1-4: GSM modem (1-port) converter now attached to ttyUSB0 [ 521.618062] option 1-4:1.0: GSM modem (1-port) converter detected [ 521.618232] usb 1-4: GSM modem (1-port) converter now attached to ttyUSB1 [ 530.840276] option: option_instat_callback: error -108 [ 530.840455] option1 ttyUSB1: GSM modem (1-port) converter now disconnected from ttyUSB1 [ 530.840484] option 1-4:1.0: device disconnected [ 537.680378] option1 ttyUSB0: GSM modem (1-port) converter now disconnected from ttyUSB0 [ 537.680398] option 1-4:1.1: device disconnected [ 537.792088] usb 1-4: reset high-speed USB device number 4 using ehci_hcd [ 537.929549] option 1-4:1.1: GSM modem (1-port) converter detected [ 537.929702] usb 1-4: GSM modem (1-port) converter now attached to ttyUSB0 [ 537.929818] option 1-4:1.0: GSM modem (1-port) converter detected [ 537.929993] usb 1-4: GSM modem (1-port) converter now attached to ttyUSB1 [ 547.224294] option: option_instat_callback: error -108 [ 547.224470] option1 ttyUSB1: GSM modem (1-port) converter now disconnected from ttyUSB1 [ 547.224511] option 1-4:1.0: device disconnected [ 556.988066] tty_ldisc_hangup: waiting (usb-storage) for ttyUSB0 took too long, but we keep waiting... [ 558.990663] option1 ttyUSB0: GSM modem (1-port) converter now disconnected from ttyUSB0 [ 558.990698] option 1-4:1.1: device disconnected [ 559.100068] usb 1-4: reset high-speed USB device number 4 using ehci_hcd [ 559.241293] option 1-4:1.1: GSM modem (1-port) converter detected [ 559.241446] usb 1-4: GSM modem (1-port) converter now attached to ttyUSB0 [ 559.241565] option 1-4:1.0: GSM modem (1-port) converter detected [ 559.241739] usb 1-4: GSM modem (1-port) converter now attached to ttyUSB1 [ 568.728283] option: option_instat_callback: error -108 [ 568.728466] option1 ttyUSB1: GSM modem (1-port) converter now disconnected from ttyUSB1 [ 568.728496] option 1-4:1.0: device disconnected lsusb Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 008 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 002 Device 003: ID 064e:a103 Suyin Corp. Acer/HP Integrated Webcam [CN0314] Bus 005 Device 002: ID 09da:c20a A4 Tech Co., Ltd Bus 001 Device 002: ID 12d1:1003 Huawei Technologies Co., Ltd. E220 HSDPA Modem / E230/E270/E870 HSDPA/HSUPA Modem

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  • Impulsioned jumping

    - by Mutoh
    There's one thing that has been puzzling me, and that is how to implement a 'faux-impulsed' jump in a platformer. If you don't know what I'm talking about, then think of the jumps of Mario, Kirby, and Quote from Cave Story. What do they have in common? Well, the height of your jump is determined by how long you keep the jump button pressed. Knowing that these character's 'impulses' are built not before their jump, as in actual physics, but rather while in mid-air - that is, you can very well lift your finger midway of the max height and it will stop, even if with desacceleration between it and the full stop; which is why you can simply tap for a hop and hold it for a long jump -, I am mesmerized by how they keep their trajetories as arcs. My current implementation works as following: While the jump button is pressed, gravity is turned off and the avatar's Y coordenate is decremented by the constant value of the gravity. For example, if things fall at Z units per tick, it will rise Z units per tick. Once the button is released or the limit is reached, the avatar desaccelerates in an amount that would make it cover X units until its speed reaches 0; once it does, it accelerates up until its speed matches gravity - sticking to the example, I could say it accelerates from 0 to Z units/tick while still covering X units. This implementation, however, makes jumps too diagonal, and unless the avatar's speed is faster than the gravity, which would make it way too fast in my current project (it moves at about 4 pixels per tick and gravity is 10 pixels per tick, at a framerate of 40FPS), it also makes it more vertical than horizontal. Those familiar with platformers would notice that the character's arc'd jump almost always allows them to jump further even if they aren't as fast as the game's gravity, and when it doesn't, if not played right, would prove itself to be very counter-intuitive. I know this because I could attest that my implementation is very annoying. Has anyone ever attempted at similar mechanics, and maybe even succeeded? I'd like to know what's behind this kind of platformer jumping. If you haven't ever had any experience with this beforehand and want to give it a go, then please, don't try to correct or enhance my explained implementation, unless I was on the right way - try to make up your solution from scratch. I don't care if you use gravity, physics or whatnot, as long as it shows how these pseudo-impulses work, it does the job. Also, I'd like its presentation to avoid a language-specific coding; like, sharing us a C++ example, or Delphi... As much as I'm using the XNA framework for my project and wouldn't mind C# stuff, I don't have much patience to read other's code, and I'm certain game developers of other languages would be interested in what we achieve here, so don't mind sticking to pseudo-code. Thank you beforehand.

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  • Did I lost my RAID again?

    - by BarsMonster
    Hi! A little history: 2 years ago I was really excited to find out that mdadm is so powerful so it even can reshape arrays so you can start with a smaller array and the grow it as you need. I've bought 3x1Tb drives and made RAID-5. It was fine for a year. Then I bought 2x more, and tried to reshape to RAID-6 out of 5 drives, and due to some mess with superblock versions, lost all content. Had to rebuild it from scratch, but 2Tb of data were gone. Yesterday I bought 2 more drives, and this time I had everything: properly built array, UPS. I've disabled write intent map, added 2 new drives as a spare and run a command to grow array to 7-disk. It started working, but speed was ridiculously slow, ~100kb/sec. AFter processing first 37Mb at such an amasing speed, one of old HDDs fails. I properly shutdown PC and disconnected failed drive. After bootup it appeared it recreated intent map as it was still in mdadm config, so I removed it from config and rebooted again. Now all I see is that all mdadm processes deadlocks, and don't do anything. PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1937 root 20 0 12992 608 444 D 0 0.1 0:00.00 mdadm 2283 root 20 0 12992 852 704 D 0 0.1 0:00.01 mdadm 2287 root 20 0 0 0 0 D 0 0.0 0:00.01 md0_reshape 2288 root 18 -2 12992 820 676 D 0 0.1 0:00.01 mdadm And all I see in mdstat is: $ cat /proc/mdstat Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md0 : active raid6 sdb1[1] sdg1[4] sdf1[7] sde1[6] sdd1[0] sdc1[5] 2929683456 blocks super 1.2 level 6, 1024k chunk, algorithm 2 [7/6] [UU_UUUU] [>....................] reshape = 0.0% (37888/976561152) finish=567604147.2min speed=0K/sec I've already tried mdadm 2.6.7, 3.1.4 and 3.2 - nothing helps. Did I lost my data again? Any suggestions how can I make it work? OS is Ubuntu Server 10.04.2... PS. Needless to say that data is unaccessible - I cannot mount /dev/md0 as save the most valuable data. You can see my disappointment - the very specific thing I was excited about failed twice taking 5Tb of my data with it.

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  • Bad FPS for smaller size (OpenGL ES with SDL)

    - by ber4444
    If you saw my other question, well, there is still a little problem: Click here to watch on youtube Basically, the frame rate is very bad on the actual device, where for some reason the animation is scaled (it looks like the left side on the video). It is quite fast on the simulator where it is not scaled (right side). For a test, I submitted this new changeset that hard-codes the smaller size (plus increases the point size for HII regions to make the dust clouds more visible), and as you see in the video, now it is slow even in the simulator (left side shows the small size, right side shows the original size -- otherwise the code is the same). I'm clueless why it's soooo slow with a smaller galaxy, in fact it should be FASTER. As for general speed optimization (which is not strictly part of my question but is closely related to it, esp. if we need a workaround to speed things up), some initial ideas: reducing the number of items drawn may affect the appearance negatively but screen resolution could be reduced there are too many glBegin(GL_POINTS)/glEnd() blocks, we could draw more than just a single star at once

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  • Voxel Engine in Multiplayer?

    - by Oliver Schöning
    This is a question more out of Interest for now, because I am not even near to the point that I could create this project at the moment. I really like the progress on the Atomontage Engine. A Voxel engine that is WIP at the moment. I would like to create a Voxel SERVER eventually. First in JavaScript (That's what I am learning right now) later perhaps in C++ for speed. Remember, I am perfectly aware that this is very hard! This is a brainstorm for the next 10 years as for now. What I would like to achieve one day is a Multiplayer Game in the Browser where the voxels positions are updated by XYZ input from the server. The Browser Does only 3 things: sending player input to the server, updating Voxel positions send from the server and rendering the world. I imagine using something like the Three.js libary on the client side. So that would be my programming dream right there... Now to something simpler for the near future. Right now I am learning javascript. And I am making games with Construct2. (A really cool JavaScript "game maker") The plan is to create a 2D Voxel enviorment (Block Voxels) on the Socket.IO Server* and send the position of the Voxels and Players to the Client side which then positions the Voxel Blocks to the Server Output coordinates. I think that is a bit more manageable then the other bigger idea. And also there should be no worries about speed with this type of project in JavaScript (I hope). Extra Info: *I am using nodejs (Without really knowing what it does besides making Socket.IO work) So now some questions: Is the "dream project" doable in JavaScript? Or is C++ just the best option because it does not take as long to be interpreted at run time like JavaScript? What are the limitations? I can think of some: Need of a Powerful server depending on how much information the server has to process. Internet Speed; Sending the data of the Voxel positions to every player could add up being very high! The browser FPS might go down quickly if rendering to many objects. One way of fixing reducing the packages Could be to let the browser calculate some of the Voxel positions from Several Values. But that would slow down the Client side too. What about the more achievable project? I am almost 100% convinced that this is possible in JavaScript, and that there are several ways of doing this. This is just XY position Updating for now.. Hope this did make some sense. Please comment if you got something to say :D

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  • Coolbits not working

    - by usk
    I want to use coolbits to increase fan speed of my Fermi GPU. 280.13 driver installed. Ubuntu 11.10 I edited /etc/X11/xorg.conf as follows, by pressing Alt+F2 and gksu gedit /etc/X11/xorg.conf I get Section "Device" Identifier "Device0" Driver "nvidia" VendorName "NVIDIA Corporation" BoardName "GeForce GTX 470" Option "NoLogo" "True" Option "Coolbits" "4" EndSection Started getting these messages, Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap" So I did this, sudo aptitude install gtk2-engines-pixbuf terminal, a@z:~$ nvidia-settings -a [gpu:0]/GPUFanControlState=1 a@z:~$ nvidia-settings -q fans 1 Fan on z:0 [0] z:0[fan:0] (Fan 0) a@z:~$ nvidia-settings -a [fan:0]/GPUCurrentFanSpeed=80 ERROR: Error assigning value 80 to attribute 'GPUCurrentFanSpeed' (z:0[fan:0]) as specified in assignment '[fan:0]/GPUCurrentFanSpeed=80' (Unknown Error). So, it's not working; I can't enter the fan speed percentage. Also from NVidia X Server, there are no fan controls. http://en.gentoo-wiki.com/wiki/Nvidia#Manual_Fan_Control_for_nVIDIA_Settings

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  • Downloading large files hangs system

    - by Igor
    When Im trying to download large files, i.e. 1gb or more under FireFox, first of all it starts with very big download speed and in few seconds in almost get up to max (~11 MBps). It is downloading very fast, but when downloaded size becomes near 700-800mb and more, my system almost completely hangs, so I can do nothing - I just have to wait until it finishes downloading. Also when it hangs, I can't see the download progress - it looks like it completely hangs. Sometimes, however, if the file size is near 1gb, the system comes back from hang, finishing download, but sometimes I just cant wait before system comes back and have to kill FF from top (it takes me 2 minutes to do this, because of very slow system performance). I use Firefox as primary browser. If I use wget with direct link to file - everything is fine. Speed at max, no performance decrease. So what can I do?

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  • How to do a cacheable redirection?

    - by John Doe
    When users enter my website example.com, their "preferred" language is detected and they are redirected (using a 301 Moved Permanently redirection) to example.com/en/ (for english), example.com/it/ (for italian), etc. It works perfectly, but when I analized my website with the Google Page Speed tool it gave me the following advice. Many pages, especially mobile pages, redirect users to a different URL, for instance from www.example.com to m.example.com. Making this redirect cacheable by the user's browser can speed up page load times for repeat visitors to a site. And later it says We recommend using a 302 redirect with a cache lifetime of one day. The redirect should include a Vary: User-Agent header as well as a Cache-Control: private header. So my questions are, how can I do a "cacheable" redirection in PHP? Would the following be enough? header("HTTP/1.0 302 Moved Temporarily"); header("Location: example.com/whatever"); exit;

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  • Is there an algorithm for a pool game?

    - by Dmitri
    Hello! I am looking for algorithm to calculate direction and speed of balls in a pool game. I am sure there has to be some type of open source code for this since pool games are some of the oldest computer games I can remember. I mean, when one ball hits another, I need a algorithm to calculate direction of both of them. It will depend of exact angle of where they hit each other and on speed. I want to practice Java coding, so I am looking for java code or package that has this type of code.

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  • Brightness Crash and Fan issues in 12.04.1

    - by S.A. McIntosh
    I would just like to state beforehand that I am a total novice in using Ubuntu when it comes to the more complex issues. So I thought it would be best to finally come here and ask for help before being re-directed or closed out for a solution. I have already looked high and low on this board for one but nothing came up for my particular case, so I might as well take a shot asking for the first time here. This is what I have at the moment: -Dell Insprion 1764 w/ 64-bit Intel i5 Core -Dual Boot: Windows 7/Ubuntu 12.04.1 32-bit (from 12.04 install) -Unity shell -Linux kernel: 3.2.0-32 generic-pae ...and this is my fglrxinfo: OpenGL vendor string: Advanced Micro Devices, Inc. OpenGL renderer string: ATI Mobility Radeon HD 5000 Series OpenGL version string: 4.2.11627 Compatibility Profile Context The one issue I have with using Ubuntu is brightness. With the driver in every time I use the slider in the brightness and lock settings or use the keyboard function, it freezes, goes black and comes up with a scrambled colors page like this in the video. So I have looked all over this board and the web for answers looking for a solution that might have an answer. This is what I have done so far to fix this: -First Solution: Looking around, I found this small fix using terminal: sudo gedit /etc/rc.local followed by adding this into "rc.local" echo # > /sys/class/backlight/acpi_video0/brightness This works rarely with the graphics driver still in and I often get lucky say during restart but reboot would only snap back the brightness at max. -Second Solution Simply remove the graphics driver while leaving the solution of first behind. This solves the issue but results in having the monitor flicker and flash at startup which in itself is not a problem to me but maybe not so good for monitor health. Also it causes the fan to speed up throughout the session and render any program that needs the driver useless. -Third Solution This is the most obvious. Just simply use the brightness on AMD Catalyst Control Center software that came with the driver, and I can say that it's form of brightness is HORRIBLE compared to the actual settings. Which leads up to where I am now, back to the driver to stop the fan speed-up and seems that the only solution to the brightness crash is to use the keyboard-controlled brightness at the login screen NOT the desktop if I want the issued effect but will just snap at max bright again if I restart. Fan speed problem is dealt with but now run the risk of crashing my computer if I so much touch the brightness settings. Speaking of which I found this on launchpad and it seems that the issue has been going far since June of 2012. Any help, redirect link or reference would be greatly appreciated. Thank you.

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  • The Faces in the Crowdsourcing

    - by Applications User Experience
    By Jeff Sauro, Principal Usability Engineer, Oracle Imagine having access to a global workforce of hundreds of thousands of people who can perform tasks or provide feedback on a design quickly and almost immediately. Distributing simple tasks not easily done by computers to the masses is called "crowdsourcing" and until recently was an interesting concept, but due to practical constraints wasn't used often. Enter Amazon.com. For five years, Amazon has hosted a service called Mechanical Turk, which provides an easy interface to the crowds. The service has almost half a million registered, global users performing a quarter of a million human intelligence tasks (HITs). HITs are submitted by individuals and companies in the U.S. and pay from $.01 for simple tasks (such as determining if a picture is offensive) to several dollars (for tasks like transcribing audio). What do we know about the people who toil away in this digital crowd? Can we rely on the work done in this anonymous marketplace? A rendering of the actual Mechanical Turk (from Wikipedia) Knowing who is behind Amazon's Mechanical Turk is fitting, considering the history of the actual Mechanical Turk. In the late 1800's, a mechanical chess-playing machine awed crowds as it beat master chess players in what was thought to be a mechanical miracle. It turned out that the creator, Wolfgang von Kempelen, had a small person (also a chess master) hiding inside the machine operating the arms to provide the illusion of automation. The field of human computer interaction (HCI) is quite familiar with gathering user input and incorporating it into all stages of the design process. It makes sense then that Mechanical Turk was a popular discussion topic at the recent Computer Human Interaction usability conference sponsored by the Association for Computing Machinery in Atlanta. It is already being used as a source for input on Web sites (for example, Feedbackarmy.com) and behavioral research studies. Two papers shed some light on the faces in this crowd. One paper tells us about the shifting demographics from mostly stay-at-home moms to young men in India. The second paper discusses the reliability and quality of work from the workers. Just who exactly would spend time doing tasks for pennies? In "Who are the crowdworkers?" University of California researchers Ross, Silberman, Zaldivar and Tomlinson conducted a survey of Mechanical Turk worker demographics and compared it to a similar survey done two years before. The initial survey reported workers consisting largely of young, well-educated women living in the U.S. with annual household incomes above $40,000. The more recent survey reveals a shift in demographics largely driven by an influx of workers from India. Indian workers went from 5% to over 30% of the crowd, and this block is largely male (two-thirds) with a higher average education than U.S. workers, and 64% report an annual income of less than $10,000 (keeping in mind $1 has a lot more purchasing power in India). This shifting demographic certainly has implications as language and culture can play critical roles in the outcome of HITs. Of course, the demographic data came from paying Turkers $.10 to fill out a survey, so there is some question about both a self-selection bias (characteristics which cause Turks to take this survey may be unrepresentative of the larger population), not to mention whether we can really trust the data we get from the crowd. Crowds can perform tasks or provide feedback on a design quickly and almost immediately for usability testing. (Photo attributed to victoriapeckham Flikr While having immediate access to a global workforce is nice, one major problem with Mechanical Turk is the incentive structure. Individuals and companies that deploy HITs want quality responses for a low price. Workers, on the other hand, want to complete the task and get paid as quickly as possible, so that they can get on to the next task. Since many HITs on Mechanical Turk are surveys, how valid and reliable are these results? How do we know whether workers are just rushing through the multiple-choice responses haphazardly answering? In "Are your participants gaming the system?" researchers at Carnegie Mellon (Downs, Holbrook, Sheng and Cranor) set up an experiment to find out what percentage of their workers were just in it for the money. The authors set up a 30-minute HIT (one of the more lengthy ones for Mechanical Turk) and offered a very high $4 to those who qualified and $.20 to those who did not. As part of the HIT, workers were asked to read an email and respond to two questions that determined whether workers were likely rushing through the HIT and not answering conscientiously. One question was simple and took little effort, while the second question required a bit more work to find the answer. Workers were led to believe other factors than these two questions were the qualifying aspect of the HIT. Of the 2000 participants, roughly 1200 (or 61%) answered both questions correctly. Eighty-eight percent answered the easy question correctly, and 64% answered the difficult question correctly. In other words, about 12% of the crowd were gaming the system, not paying enough attention to the question or making careless errors. Up to about 40% won't put in more than a modest effort to get paid for a HIT. Young men and those that considered themselves in the financial industry tended to be the most likely to try to game the system. There wasn't a breakdown by country, but given the demographic information from the first article, we could infer that many of these young men come from India, which makes language and other cultural differences a factor. These articles raise questions about the role of crowdsourcing as a means for getting quick user input at low cost. While compensating users for their time is nothing new, the incentive structure and anonymity of Mechanical Turk raises some interesting questions. How complex of a task can we ask of the crowd, and how much should these workers be paid? Can we rely on the information we get from these professional users, and if so, how can we best incorporate it into designing more usable products? Traditional usability testing will still play a central role in enterprise software. Crowdsourcing doesn't replace testing; instead, it makes certain parts of gathering user feedback easier. One can turn to the crowd for simple tasks that don't require specialized skills and get a lot of data fast. As more studies are conducted on Mechanical Turk, I suspect we will see crowdsourcing playing an increasing role in human computer interaction and enterprise computing. References: Downs, J. S., Holbrook, M. B., Sheng, S., and Cranor, L. F. 2010. Are your participants gaming the system?: screening mechanical turk workers. In Proceedings of the 28th international Conference on Human Factors in Computing Systems (Atlanta, Georgia, USA, April 10 - 15, 2010). CHI '10. ACM, New York, NY, 2399-2402. Link: http://doi.acm.org/10.1145/1753326.1753688 Ross, J., Irani, L., Silberman, M. S., Zaldivar, A., and Tomlinson, B. 2010. Who are the crowdworkers?: shifting demographics in mechanical turk. In Proceedings of the 28th of the international Conference Extended Abstracts on Human Factors in Computing Systems (Atlanta, Georgia, USA, April 10 - 15, 2010). CHI EA '10. ACM, New York, NY, 2863-2872. Link: http://doi.acm.org/10.1145/1753846.1753873

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  • The Information Driven Value Chain - Part 1

    - by Paul Homchick
    One hundred years ago, there were places on Earth that no man had ever seen.  Today, a man standing in one of those places can instantaneously communicate with someone who may be strolling down the street on his way to lunch half way around the globe.  Our world is shrinking and becoming virtual. It is a world of incredible bounty and speed where we can get a product delivered to us anywhere on earth within a day or two. However, this world is also one of challenge where volatility, uncertainty, risk and chaos are our daily companions. To prosper amid the realities of this new world, the enterprise needs a business model. Globalization and instant communications demand greater operational flexibility than ever before. Extended supply chains have elevated the management of risk to a central concern, and regulatory demands from multiple governments place an increasing burden of compliance on companies. Finally, the speed of today's business requires continuous innovation to keep from falling behind the global competition.

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  • How to explain to non-technical person why the task will take much longer then they think?

    - by Mag20
    Almost every developer has to answer questions from business side like: Why is going to take 2 days to add this simple contact form? When developer estimates this task, they may divide it into steps: make some changes to Database optimize DB changes for speed add front end HTML write server side code add validation add client side javascript use unit tests make sure SEO is setup is working implement email confirmation refactor and optimize the code for speed ... These maybe hard to explain to non-technical person, who basically sees the whole task as just putting together some HTML and creating a table to store the data. To them it could be 2 hours MAX. So is there a better way to explain why the estimate is high to non-developer?

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  • Can you declare <canvas> methods within a template in javascript?

    - by Binarytales
    Not entirely sure I posed the question in the best way but here goes... I have been playing around with the HTML5 canvas API and have got as far as drawing a shape in the canvas and getting it to move around with the arrow keys. I then tried to move my various variables and functions to a template so I could spawn multiple shapes (that would eventually be controlled by different keys). This is what I have: function player(x, y, z, colour, speed){ this.lx = x; this.ly = y; this.speed = 10; this.playerSize = z; this.colour = colour; } playerOne = new player(100, 100, 10, "#F0F"); function persona(z, colour){ zone.fillStyle = colour; offset = 0 - (z / 2); zone.fillRect(offset, offset, z, z); } function move(x, y){ playerOne.lx = playerOne.lx + x; playerOne.ly = playerOne.ly + y; zone.clearRect(0, 0, 500, 500); zone.save(); zone.translate(playerOne.lx, playerOne.ly); persona(playerOne.playerSize, playerOne.colour); zone.restore(); } window.onkeydown = function() { var direction = this.event.keyCode; var s = playerOne.speed; // Arrow Keys if( direction == 38 && playerOne.ly >= 10){ // Up move(0,-s); } if( direction == 40 && playerOne.ly <= 490){ // Down move(0,s); } if( direction == 37 && playerOne.lx >= 10){ // Left move(-s,0); } if( direction == 39 && playerOne.lx <= 490){ // Right move(s,0); } }; window.onload = function() { zone = document.getElementById('canvas').getContext('2d'); zone.save(); zone.translate(playerOne.lx, playerOne.ly); persona(playerOne.playerSize, playerOne.colour); zone.restore(); }; So what I tried to do was move the persona function into the player template like this: function player(x, y, z, colour, speed){ this.lx = x; this.ly = y; this.speed = 10; function persona(){ zone.fillStyle = colour; var offset = 0 - (z / 2); zone.fillRect(offset, offset, z, z); } } And then where before it said persona(playerOne.playerSize, playerOne.colour); it now just says playerOne.persona(); But this is just totally flaking out and not working and I can't figure out why. I'm probably going about it all the wrong way and I think the problem is that I'm trying to manipulate the canvas.context (call zone in my script) from within a object/template. Perhaps its nothing to do with that at all and I an just not declaring my persona functions properly in the context of the template. Documentation for the canvas API is very thin on the ground and any hint in the right direction will be very much appreciated.

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  • Conways Game of Life C#

    - by Darren Young
    Hi, Not sure if this is the correct place for this question or SO - mods please move if necessary. I am going to have a go at creating GoL over the weekend as a little test project : http://en.wikipedia.org/wiki/Conway's_Game_of_Life I understand the algorithm, however I just wanted to check regarding the implementation, from maybe somebody that has tried it. Essentially, my first (basic) implementation, will be a static grid at a set speed. If I understand correctly, these are the steps I will need: Initial seed Create 2d array with initial set up Foreach iteration, create temporary array, calculating each cells new state based on the Game of Life algorithm Assign temp array to proper array. Redraw grid from proper array. My concerns are over speed. When I am populating the grid from the array, would it simply be a case of looping through the array, assigning on or off to each grid cell and then redraw the grid? Am I on the correct path?

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  • Applications: The mathematics of movement, Part 1

    - by TechTwaddle
    Before you continue reading this post, a suggestion; if you haven’t read “Programming Windows Phone 7 Series” by Charles Petzold, go read it. Now. If you find 150+ pages a little too long, at least go through Chapter 5, Principles of Movement, especially the section “A Brief Review of Vectors”. This post is largely inspired from this chapter. At this point I assume you know what vectors are, how they are represented using the pair (x, y), what a unit vector is, and given a vector how you would normalize the vector to get a unit vector. Our task in this post is simple, a marble is drawn at a point on the screen, the user clicks at a random point on the device, say (destX, destY), and our program makes the marble move towards that point and stop when it is reached. The tricky part of this task is the word “towards”, it adds a direction to our problem. Making a marble bounce around the screen is simple, all you have to do is keep incrementing the X and Y co-ordinates by a certain amount and handle the boundary conditions. Here, however, we need to find out exactly how to increment the X and Y values, so that the marble appears to move towards the point where the user clicked. And this is where vectors can be so helpful. The code I’ll show you here is not ideal, we’ll be working with C# on Windows Mobile 6.x, so there is no built-in vector class that I can use, though I could have written one and done all the math inside the class. I think it is trivial to the actual problem that we are trying to solve and can be done pretty easily once you know what’s going on behind the scenes. In other words, this is an excuse for me being lazy. The first approach, uses the function Atan2() to solve the “towards” part of the problem. Atan2() takes a point (x, y) as input, Atan2(y, x), note that y goes first, and then it returns an angle in radians. What angle you ask. Imagine a line from the origin (0, 0), to the point (x, y). The angle which Atan2 returns is the angle the positive X-axis makes with that line, measured clockwise. The figure below makes it clear, wiki has good details about Atan2(), give it a read. The pair (x, y) also denotes a vector. A vector whose magnitude is the length of that line, which is Sqrt(x*x + y*y), and a direction ?, as measured from positive X axis clockwise. If you’ve read that chapter from Charles Petzold’s book, this much should be clear. Now Sine and Cosine of the angle ? are special. Cosine(?) divides x by the vectors length (adjacent by hypotenuse), thus giving us a unit vector along the X direction. And Sine(?) divides y by the vectors length (opposite by hypotenuse), thus giving us a unit vector along the Y direction. Therefore the vector represented by the pair (cos(?), sin(?)), is the unit vector (or normalization) of the vector (x, y). This unit vector has a length of 1 (remember sin2(?) + cos2(?) = 1 ?), and a direction which is the same as vector (x, y). Now if I multiply this unit vector by some amount, then I will always get a point which is a certain distance away from the origin, but, more importantly, the point will always be on that line. For example, if I multiply the unit vector with the length of the line, I get the point (x, y). Thus, all we have to do to move the marble towards our destination point, is to multiply the unit vector by a certain amount each time and draw the marble, and the marble will magically move towards the click point. Now time for some code. The application, uses a timer based frame draw method to draw the marble on the screen. The timer is disabled initially and whenever the user clicks on the screen, the timer is enabled. The callback function for the timer follows the standard Update and Draw cycle. private double totLenToTravelSqrd = 0; private double startPosX = 0, startPosY = 0; private double destX = 0, destY = 0; private void Form1_MouseUp(object sender, MouseEventArgs e) {     destX = e.X;     destY = e.Y;     double x = marble1.x - destX;     double y = marble1.y - destY;     //calculate the total length to be travelled     totLenToTravelSqrd = x * x + y * y;     //store the start position of the marble     startPosX = marble1.x;     startPosY = marble1.y;     timer1.Enabled = true; } private void timer1_Tick(object sender, EventArgs e) {     UpdatePosition();     DrawMarble(); } Form1_MouseUp() method is called when ever the user touches and releases the screen. In this function we save the click point in destX and destY, this is the destination point for the marble and we also enable the timer. We store a few more values which we will use in the UpdatePosition() method to detect when the marble has reached the destination and stop the timer. So we store the start position of the marble and the square of the total length to be travelled. I’ll leave out the term ‘sqrd’ when speaking of lengths from now on. The time out interval of the timer is set to 40ms, thus giving us a frame rate of about ~25fps. In the timer callback, we update the marble position and draw the marble. We know what DrawMarble() does, so here, we’ll only look at how UpdatePosition() is implemented; private void UpdatePosition() {     //the vector (x, y)     double x = destX - marble1.x;     double y = destY - marble1.y;     double incrX=0, incrY=0;     double distanceSqrd=0;     double speed = 6;     //distance between destination and current position, before updating marble position     distanceSqrd = x * x + y * y;     double angle = Math.Atan2(y, x);     //Cos and Sin give us the unit vector, 6 is the value we use to magnify the unit vector along the same direction     incrX = speed * Math.Cos(angle);     incrY = speed * Math.Sin(angle);     marble1.x += incrX;     marble1.y += incrY;     //check for bounds     if ((int)marble1.x < MinX + marbleWidth / 2)     {         marble1.x = MinX + marbleWidth / 2;     }     else if ((int)marble1.x > (MaxX - marbleWidth / 2))     {         marble1.x = MaxX - marbleWidth / 2;     }     if ((int)marble1.y < MinY + marbleHeight / 2)     {         marble1.y = MinY + marbleHeight / 2;     }     else if ((int)marble1.y > (MaxY - marbleHeight / 2))     {         marble1.y = MaxY - marbleHeight / 2;     }     //distance between destination and current point, after updating marble position     x = destX - marble1.x;     y = destY - marble1.y;     double newDistanceSqrd = x * x + y * y;     //length from start point to current marble position     x = startPosX - (marble1.x);     y = startPosY - (marble1.y);     double lenTraveledSqrd = x * x + y * y;     //check for end conditions     if ((int)lenTraveledSqrd >= (int)totLenToTravelSqrd)     {         System.Console.WriteLine("Stopping because destination reached");         timer1.Enabled = false;     }     else if (Math.Abs((int)distanceSqrd - (int)newDistanceSqrd) < 4)     {         System.Console.WriteLine("Stopping because no change in Old and New position");         timer1.Enabled = false;     } } Ok, so in this function, first we subtract the current marble position from the destination point to give us a vector. The first three lines of the function construct this vector (x, y). The vector (x, y) has the same length as the line from (marble1.x, marble1.y) to (destX, destY) and is in the direction pointing from (marble1.x, marble1.y) to (destX, destY). Note that marble1.x and marble1.y denote the center point of the marble. Then we use Atan2() to get the angle which this vector makes with the positive X axis and use Cosine() and Sine() of that angle to get the unit vector along that same direction. We multiply this unit vector with 6, to get the values which the position of the marble should be incremented by. This variable, speed, can be experimented with and determines how fast the marble moves towards the destination. After this, we check for bounds to make sure that the marble stays within the screen limits and finally we check for the end condition and stop the timer. The end condition has two parts to it. The first case is the normal case, where the user clicks well inside the screen. Here, we stop when the total length travelled by the marble is greater than or equal to the total length to be travelled. Simple enough. The second case is when the user clicks on the very corners of the screen. Like I said before, the values marble1.x and marble1.y denote the center point of the marble. When the user clicks on the corner, the marble moves towards the point, and after some time tries to go outside of the screen, this is when the bounds checking comes into play and corrects the marble position so that the marble stays inside the screen. In this case the marble will never travel a distance of totLenToTravelSqrd, because of the correction is its position. So here we detect the end condition when there is not much change in marbles position. I use the value 4 in the second condition above. After experimenting with a few values, 4 seemed to work okay. There is a small thing missing in the code above. In the normal case, case 1, when the update method runs for the last time, marble position over shoots the destination point. This happens because the position is incremented in steps (which are not small enough), so in this case too, we should have corrected the marble position, so that the center point of the marble sits exactly on top of the destination point. I’ll add this later and update the post. This has been a pretty long post already, so I’ll leave you with a video of how this program looks while running. Notice in the video that the marble moves like a bot, without any grace what so ever. And that is because the speed of the marble is fixed at 6. In the next post we will see how to make the marble move a little more elegantly. And also, if Atan2(), Sine() and Cosine() are a little too much to digest, we’ll see how to achieve the same effect without using them, in the next to next post maybe. Ciao!

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  • MapRedux - PowerShell and Big Data

    - by Dittenhafer Solutions
    MapRedux – #PowerShell and #Big Data Have you been hearing about “big data”, “map reduce” and other large scale computing terms over the past couple of years and been curious to dig into more detail? Have you read some of the Apache Hadoop online documentation and unfortunately concluded that it wasn't feasible to setup a “test” hadoop environment on your machine? More recently, I have read about some of Microsoft’s work to enable Hadoop on the Azure cloud. Being a "Microsoft"-leaning technologist, I am more inclinded to be successful with experimentation when on the Windows platform. Of course, it is not that I am "religious" about one set of technologies other another, but rather more experienced. Anyway, within the past couple of weeks I have been thinking about PowerShell a bit more as the 2012 PowerShell Scripting Games approach and it occured to me that PowerShell's support for Windows Remote Management (WinRM), and some other inherent features of PowerShell might lend themselves particularly well to a simple implementation of the MapReduce framework. I fired up my PowerShell ISE and started writing just to see where it would take me. Quite simply, the ScriptBlock feature combined with the ability of Invoke-Command to create remote jobs on networked servers provides much of the plumbing of a distributed computing environment. There are some limiting factors of course. Microsoft provided some default settings which prevent PowerShell from taking over a network without administrative approval first. But even with just one adjustment, a given Windows-based machine can become a node in a MapReduce-style distributed computing environment. Ok, so enough introduction. Let's talk about the code. First, any machine that will participate as a remote "node" will need WinRM enabled for remote access, as shown below. This is not exactly practical for hundreds of intended nodes, but for one (or five) machines in a test environment it does just fine. C:> winrm quickconfig WinRM is not set up to receive requests on this machine. The following changes must be made: Set the WinRM service type to auto start. Start the WinRM service. Make these changes [y/n]? y Alternatively, you could take the approach described in the Remotely enable PSRemoting post from the TechNet forum and use PowerShell to create remote scheduled tasks that will call Enable-PSRemoting on each intended node. Invoke-MapRedux Moving on, now that you have one or more remote "nodes" enabled, you can consider the actual Map and Reduce algorithms. Consider the following snippet: $MyMrResults = Invoke-MapRedux -MapReduceItem $Mr -ComputerName $MyNodes -DataSet $dataset -Verbose Invoke-MapRedux takes an instance of a MapReduceItem which references the Map and Reduce scriptblocks, an array of computer names which are the remote nodes, and the initial data set to be processed. As simple as that, you can start working with concepts of big data and the MapReduce paradigm. Now, how did we get there? I have published the initial version of my PsMapRedux PowerShell Module on GitHub. The PsMapRedux module provides the Invoke-MapRedux function described above. Feel free to browse the underlying code and even contribute to the project! In a later post, I plan to show some of the inner workings of the module, but for now let's move on to how the Map and Reduce functions are defined. Map Both the Map and Reduce functions need to follow a prescribed prototype. The prototype for a Map function in the MapRedux module is as follows. A simple scriptblock that takes one PsObject parameter and returns a hashtable. It is important to note that the PsObject $dataset parameter is a MapRedux custom object that has a "Data" property which offers an array of data to be processed by the Map function. $aMap = { Param ( [PsObject] $dataset ) # Indicate the job is running on the remote node. Write-Host ($env:computername + "::Map"); # The hashtable to return $list = @{}; # ... Perform the mapping work and prepare the $list hashtable result with your custom PSObject... # ... The $dataset has a single 'Data' property which contains an array of data rows # which is a subset of the originally submitted data set. # Return the hashtable (Key, PSObject) Write-Output $list; } Reduce Likewise, with the Reduce function a simple prototype must be followed which takes a $key and a result $dataset from the MapRedux's partitioning function (which joins the Map results by key). Again, the $dataset is a MapRedux custom object that has a "Data" property as described in the Map section. $aReduce = { Param ( [object] $key, [PSObject] $dataset ) Write-Host ($env:computername + "::Reduce - Count: " + $dataset.Data.Count) # The hashtable to return $redux = @{}; # Return Write-Output $redux; } All Together Now When everything is put together in a short example script, you implement your Map and Reduce functions, query for some starting data, build the MapReduxItem via New-MapReduxItem and call Invoke-MapRedux to get the process started: # Import the MapRedux and SQL Server providers Import-Module "MapRedux" Import-Module “sqlps” -DisableNameChecking # Query the database for a dataset Set-Location SQLSERVER:\sql\dbserver1\default\databases\myDb $query = "SELECT MyKey, Date, Value1 FROM BigData ORDER BY MyKey"; Write-Host "Query: $query" $dataset = Invoke-SqlCmd -query $query # Build the Map function $MyMap = { Param ( [PsObject] $dataset ) Write-Host ($env:computername + "::Map"); $list = @{}; foreach($row in $dataset.Data) { # Write-Host ("Key: " + $row.MyKey.ToString()); if($list.ContainsKey($row.MyKey) -eq $true) { $s = $list.Item($row.MyKey); $s.Sum += $row.Value1; $s.Count++; } else { $s = New-Object PSObject; $s | Add-Member -Type NoteProperty -Name MyKey -Value $row.MyKey; $s | Add-Member -type NoteProperty -Name Sum -Value $row.Value1; $list.Add($row.MyKey, $s); } } Write-Output $list; } $MyReduce = { Param ( [object] $key, [PSObject] $dataset ) Write-Host ($env:computername + "::Reduce - Count: " + $dataset.Data.Count) $redux = @{}; $count = 0; foreach($s in $dataset.Data) { $sum += $s.Sum; $count += 1; } # Reduce $redux.Add($s.MyKey, $sum / $count); # Return Write-Output $redux; } # Create the item data $Mr = New-MapReduxItem "My Test MapReduce Job" $MyMap $MyReduce # Array of processing nodes... $MyNodes = ("node1", "node2", "node3", "node4", "localhost") # Run the Map Reduce routine... $MyMrResults = Invoke-MapRedux -MapReduceItem $Mr -ComputerName $MyNodes -DataSet $dataset -Verbose # Show the results Set-Location C:\ $MyMrResults | Out-GridView Conclusion I hope you have seen through this article that PowerShell has a significant infrastructure available for distributed computing. While it does take some code to expose a MapReduce-style framework, much of the work is already done and PowerShell could prove to be the the easiest platform to develop and run big data jobs in your corporate data center, potentially in the Azure cloud, or certainly as an academic excerise at home or school. Follow me on Twitter to stay up to date on the continuing progress of my Powershell MapRedux module, and thanks for reading! Daniel

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