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  • Are there well-known examples of web products that were killed by slow service?

    - by Jeremy Wadhams
    It's a basic tenet of UX design that users prefer fast pages. http://www.useit.com/alertbox/response-times.html http://www.nytimes.com/2012/03/01/technology/impatient-web-users-flee-slow-loading-sites.html?pagewanted=all It's supposedly even baked into Google's ranking algorithm now: fast sites rank higher, all else being equal. But are there well known examples of web services where the popular narrative is "it was great, but it was so slow people took their money elsewhere"? I can pretty easily think of example problems with scale (Twitter's fail whale) or reliability (Netflix and Pinterest outages caused by a single datacenter in a storm). But can (lack of) speed really kill?

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  • Which game logic should run when doing prediction for PNP state updates

    - by spaceOwl
    We are writing a multiplayer game, where each game client (player) is responsible for sending state updates regarding its "owned" objects to other players. Each message that arrives to other (remote) clients is processed as such: Figure out when the message was sent. Create a diff between NOW and that time. Run game specific logic to bring the received state to "current" time. I am wondering which sort of logic should execute as part of step #3 ? Our game is composed of a physical update (position, speed, acceleration, etc) and many other components that can update an object's state and occur regularly (locally). There's a trade off here - Getting the new state quickly or remaining "faithful" to the true state representation and executing the whole thing to predict the "true" state when receiving state updates from remote clients. Which one is recommended to be used? and why?

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  • Is Java much harder to "tweak" for performance compared with C/C++?

    - by user997112
    Does the "magic" of the JVM hinder the influence a programmer has over micro-optimisations in Java? I recently read in C++ sometimes the ordering of the data members can provide optimizations (granted, in the microsecond environment) and I presumed a programmer's hands are tied when it comes to squeezing performance from Java? I appreciate a decent algorithm provides greater speed-gains, but once you have the correct algorithm is Java harder to tweak due to the JVM control? If not, could people give examples of what tricks you can use in Java (besides simple compiler flags).

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  • Diagnosing packet loss / high latency in Ubuntu

    - by Sam Gammon
    We have a Linux box (Ubuntu 12.04) running Nginx (1.5.2), which acts as a reverse proxy/load balancer to some Tornado and Apache hosts. The upstream servers are physically and logically close (same DC, sometimes same-rack) and show sub-millisecond latency between them: PING appserver (10.xx.xx.112) 56(84) bytes of data. 64 bytes from appserver (10.xx.xx.112): icmp_req=1 ttl=64 time=0.180 ms 64 bytes from appserver (10.xx.xx.112): icmp_req=2 ttl=64 time=0.165 ms 64 bytes from appserver (10.xx.xx.112): icmp_req=3 ttl=64 time=0.153 ms We receive a sustained load of about 500 requests per second, and are currently seeing regular packet loss / latency spikes from the Internet, even from basic pings: sam@AM-KEEN ~> ping -c 1000 loadbalancer PING 50.xx.xx.16 (50.xx.xx.16): 56 data bytes 64 bytes from loadbalancer: icmp_seq=0 ttl=56 time=11.624 ms 64 bytes from loadbalancer: icmp_seq=1 ttl=56 time=10.494 ms ... many packets later ... Request timeout for icmp_seq 2 64 bytes from loadbalancer: icmp_seq=2 ttl=56 time=1536.516 ms 64 bytes from loadbalancer: icmp_seq=3 ttl=56 time=536.907 ms 64 bytes from loadbalancer: icmp_seq=4 ttl=56 time=9.389 ms ... many packets later ... Request timeout for icmp_seq 919 64 bytes from loadbalancer: icmp_seq=918 ttl=56 time=2932.571 ms 64 bytes from loadbalancer: icmp_seq=919 ttl=56 time=1932.174 ms 64 bytes from loadbalancer: icmp_seq=920 ttl=56 time=932.018 ms 64 bytes from loadbalancer: icmp_seq=921 ttl=56 time=6.157 ms --- 50.xx.xx.16 ping statistics --- 1000 packets transmitted, 997 packets received, 0.3% packet loss round-trip min/avg/max/stddev = 5.119/52.712/2932.571/224.629 ms The pattern is always the same: things operate fine for a while (<20ms), then a ping drops completely, then three or four high-latency pings (1000ms), then it settles down again. Traffic comes in through a bonded public interface (we will call it bond0) configured as such: bond0 Link encap:Ethernet HWaddr 00:xx:xx:xx:xx:5d inet addr:50.xx.xx.16 Bcast:50.xx.xx.31 Mask:255.255.255.224 inet6 addr: <ipv6 address> Scope:Global inet6 addr: <ipv6 address> Scope:Link UP BROADCAST RUNNING MASTER MULTICAST MTU:1500 Metric:1 RX packets:527181270 errors:1 dropped:4 overruns:0 frame:1 TX packets:413335045 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:240016223540 (240.0 GB) TX bytes:104301759647 (104.3 GB) Requests are then submitted via HTTP to upstream servers on the private network (we can call it bond1), which is configured like so: bond1 Link encap:Ethernet HWaddr 00:xx:xx:xx:xx:5c inet addr:10.xx.xx.70 Bcast:10.xx.xx.127 Mask:255.255.255.192 inet6 addr: <ipv6 address> Scope:Link UP BROADCAST RUNNING MASTER MULTICAST MTU:1500 Metric:1 RX packets:430293342 errors:1 dropped:2 overruns:0 frame:1 TX packets:466983986 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:77714410892 (77.7 GB) TX bytes:227349392334 (227.3 GB) Output of uname -a: Linux <hostname> 3.5.0-42-generic #65~precise1-Ubuntu SMP Wed Oct 2 20:57:18 UTC 2013 x86_64 GNU/Linux We have customized sysctl.conf in an attempt to fix the problem, with no success. Output of /etc/sysctl.conf (with irrelevant configs omitted): # net: core net.core.netdev_max_backlog = 10000 # net: ipv4 stack net.ipv4.tcp_ecn = 2 net.ipv4.tcp_sack = 1 net.ipv4.tcp_fack = 1 net.ipv4.tcp_tw_reuse = 1 net.ipv4.tcp_tw_recycle = 0 net.ipv4.tcp_timestamps = 1 net.ipv4.tcp_window_scaling = 1 net.ipv4.tcp_no_metrics_save = 1 net.ipv4.tcp_max_syn_backlog = 10000 net.ipv4.tcp_congestion_control = cubic net.ipv4.ip_local_port_range = 8000 65535 net.ipv4.tcp_syncookies = 1 net.ipv4.tcp_synack_retries = 2 net.ipv4.tcp_thin_dupack = 1 net.ipv4.tcp_thin_linear_timeouts = 1 net.netfilter.nf_conntrack_max = 99999999 net.netfilter.nf_conntrack_tcp_timeout_established = 300 Output of dmesg -d, with non-ICMP UFW messages suppressed: [508315.349295 < 19.852453>] [UFW BLOCK] IN=bond1 OUT= MAC=<mac addresses> SRC=118.xx.xx.143 DST=50.xx.xx.16 LEN=68 TOS=0x00 PREC=0x00 TTL=51 ID=43221 PROTO=ICMP TYPE=3 CODE=1 [SRC=50.xx.xx.16 DST=118.xx.xx.143 LEN=40 TOS=0x00 PREC=0x00 TTL=249 ID=10220 DF PROTO=TCP SPT=80 DPT=53817 WINDOW=8190 RES=0x00 ACK FIN URGP=0 ] [517787.732242 < 0.443127>] Peer 190.xx.xx.131:59705/80 unexpectedly shrunk window 1155488866:1155489425 (repaired) How can I go about diagnosing the cause of this problem, on a Debian-family Linux box?

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  • Switching from Java/Java EE career path to C POS path?

    - by Muhammad
    I am a Java/Java EE Developer with about 3 years in this field. I like low-level programming so much... I favor back-end code over front-end. I've a knowledge in C and know little about C++. I got an offer to work with C in Point-of-Sale Payment terminals. I don't know much about how POS works (IDE/toolsets, etc). although I have a payment experience (ISO8583, etc...) I need you own opinion from Switching from the Java's High-level world to POS low-level world Although I love low-level world, but I am afraid from not being found what I seek.. I know programmers are not measured by the tools they use (including prog. langs.) but with their minds. I need your opinions of: Is programming POS terminals in C is an interesting thing, or I'll find myself doing usual code-writing job? (especially I am about to switch my whole career path). I find myself writing an elegant code in Java (like: Sobat http://code.google.com/p/sobat/) a code where I find myself in... So do I'll find the same thing in POS C? or It will all about Libraries that I'll call to finish my work?! Lastly, does this thing worse adventure with my current career (stability, conference, etc.. )? (as I currently don't think to move to a new job) Thanks.

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  • Low graphics performance with Intel HD graphics

    - by neil
    hey, my laptop should be capable of running some games fine but doesn't. Examples are egoboo and tome. http://www.ebuyer.com/product/237739 this is my laptop. I tried the gears test and i only get 60 FPS, on IRC they said thats a big issue and should try the forums. I am using Ubuntu 11.04 and was told I should have the newest drivers. neil@neil-K52F:~$ /usr/lib/nux/unity_support_test --print OpenGL vendor string: Tungsten Graphics, Inc OpenGL renderer string: Mesa DRI Intel(R) Ironlake Mobile GEM 20100330 DEVELOPMENT OpenGL version string: 2.1 Mesa 7.10.2 Not software rendered: yes Not blacklisted: yes GLX fbconfig: yes GLX texture from pixmap: yes GL npot or rect textures: yes GL vertex program: yes GL fragment program: yes GL vertex buffer object: yes GL framebuffer object: yes GL version is 1.4+: yes Unity supported: yes

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  • Low level Linux graphics

    - by math4tots
    For educational purposes, I'd like to write an application on a Linux environment that can process keyboard events and draw graphics without huge dependencies like X or SDL. I presume that this must be possible, because X and SDL are just programs themselves, so they must rely on other methods inherent to the environment. Is this understanding correct? If so, where might I learn to write such a program? My limited experience tells me that it would involve making calls to the kernel, and/or writing to special files; however, I haven't been able to find any tutorials on the matter (I am not even sure what to Google). Also, in case it is relevant, I am running Debian Squeeze on Virtualbox. I have used a netinst cd without networking, so there isn't much installed on it currently. I will install gcc, but I am hoping I can get by with nothing more.

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  • Ubuntu stuck in low resolution after UNinstalling / disabling NVidia drivers

    - by Han Cnx
    Tried the Nvidia driver, installed using the Additional Drivers panel. Didn't like it much; the CPU seemed to overheat more and the brightness controls stopped working. Also selecting a second display is a pain using that horrible NVidia settings thing. So wanted to disabled it again.. problem is, UBuntu is then stuck in either 640x480 or 800x600 (second time I tried to install it back and then remove again). How can I get this back the way it was? The original Ubuntu drivers worked just fine, allowing me to run Unity and games properly. I tried a xserver-xorg reconfigure but this didn't do anything. (No xorg.conf file either). This is on a Lenovo Thinkpad T410i

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  • Low coupling and tight cohesion

    - by hidayat
    Of course it depends on the situation. But when a lower lever object or system communicate with an higher level system, should callbacks or events be preferred to keeping a pointer to higher level object? For example, we have a world class that has a member variable vector<monster> monsters. When the monster class is going to communicate with the world class, should I prefer using a callback function then or should I have a pointer to the world class inside the monster class?

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  • Flash: Memory usage is low but framerate keeps dropping

    - by Cyborg771
    So I'm working on a puzzle game in flash. For all intents and purposes it's like Tetris. I spawn blocks, they move around the screen, then they get destroyed and disappear. I was having some trouble with the memory usage being too high over time so I read up on memory management and I think I have that figured out now. It's definitely climbing slower than it was before, but the framerate is still taking a huge dive after playing for a while. If it's not a memory leak what else could be causing this? Thanks in advance.

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  • Hosting multiple low traffic websites on ec2

    - by Niko Sams
    We have like 30 websites with almost no traffic (<~10 visits / day) which are currently hosted on a dedicated server. We are evaluating hosting on Amazon EC2 however I'm not sure how to do that properly. One (micro) instance per website is too expensive ~10 websites on one instance (using apache virtual hosts) make auto scaling impossible (or at least difficult) Or is cloud computing not suitable for such a usecase?

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  • Ubuntu LiveCD/USB image that boots directly to low graphics desktop

    - by user14146
    I use Ubuntu as a diagnostic tool sometimes, and it would be great to get a modification that lets you boot directly to the LiveCD desktop, preferably with the special effects dialed down. Is there such a tool? Unetbootin doesn't seem to let you do this, and Remastersys could probably do this, but I'd have to dig into the code quite a bit and figure out what to remove, which I can do, but I figured someone might have already done this and would save me the trouble.

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  • Styles of games that work at low-resolution

    - by Brendan Long
    I'm taking a class on compilers, and the goal is to write a compiler for Meggy Jr devices (Arduino). The goal is just to make a simple compilers with loops and variables and stuff. Obviously, that's lame, so the "real goal" is to make an impressive game on the device. The problem is that it only has 64 pixels to work with (technically 72, but the top 8 are single-color and not part of the main display, so they're really only useful for displaying things like money). My problem is thinking of something to do on a device that small. It doesn't really matter if it's original, but it can't be something that's already available. My first idea was "snake", but that comes with the SDK. Same with a side-scrolling shooter. Remaining ideas include a tower defense game (hard to write, hard to control), an RPG (same), tetris (lame).. The problem is that all of the games I like require a high-resolution screen because they have a lot of text. Even a really simple game like nethack would be hard because each creature would be a single color. tl;dr What styles of games require a. No text; and b. Few enough objects that representing them each with a single color is acceptable? EDIT: To clarify, the display is 8x8 for a total of 64 pixels, not 64x64.

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  • Fans are noisy and battery life is low

    - by Igor Ryzhov
    I worked on Windows 8 previosly and I never had problems: my laptop was quiet and battery life was about 5-6 hours without charge. Then I installed Ubuntu 12.10 and my problems started: now fans are always on and have very strong noise and battery life shortened to 1-1.5 hour! How can I solve this problem? UPD: Full specifications: http://www.onyougo.co.uk/samsung-700z5a-s01ru-notebooks-laptops-features_pi1492384e2

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  • Styles of games that work at low-resolution

    - by Brendan Long
    I'm taking a class on compilers, and the goal is to write a compiler for Meggy Jr devices (Arduino). The goal is just to make a simple compilers with loops and variables and stuff. Obviously, that's lame, so the "real goal" is to make an impressive game on the device. The problem is that it only has 64 pixels to work with (technically 72, but the top 8 are single-color and not part of the main display, so they're really only useful for displaying things like money). My problem is thinking of something to do on a device that small. It doesn't really matter if it's original, but it can't be something that's already available. My first idea was "snake", but that comes with the SDK. Same with a side-scrolling shooter. Remaining ideas include a tower defense game (hard to write, hard to control), an RPG (same), tetris (lame).. The problem is that all of the games I like require a high-resolution screen because they have a lot of text. Even a really simple game like nethack would be hard because each creature would be a single color. tl;dr What styles of games require a. No text; and b. Few enough objects that representing them each with a single color is acceptable?

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  • Installed Ubuntu In a low Specs PC and it is too slow, even with LXDE

    - by Herudae
    I'm new with Linux and started with Ubuntu 11.10, I installed it in my PC (Core2Duo 2Ghz, 512Mb Ram DDR2, integrated video in Motherboard), I know the requirements for Unity are 1Gb Ram so I decided to download a Desktop environment more lightweight, so I Installed LXDE, it loads very fast, compared to the 3.5 min from login screen to open desktop in Unity, but it freezes every time I open a single program, I can't even navigate in Internet, it freezes, sometimes for a pair of minutes and the graph at bottom right is all green as if iyt were using 100% CPU, it happens with every program. As additional data it takes 3+ min to get from boot system selection screen to Login screen and 3.5 Min more to get into Ubuntu with Unity, with LXDE it turns to 30 secs aproximately. Is Ubuntu + LXDE Desktop Environment Package = Lubuntu? or should I download Lubuntu directly instead? I installed some other desktop environments, as Gnome but it doesn't log in, the screen just turns grey. Should I get an older Ubuntu version? I'm thinking about uninstalling Ubuntu but I'll try to deplete the options, thanks for your support.

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  • Low resolution Dektop intel i7 3770 and intel board DH67BL

    - by rtorres
    I installed Ubuntu 12.04.1 in a desktop with the following specs: CPU: Intel(R) Core(TM) i7-3770 CPU @ 3.40GHz Motherboard: Intel DH67B However the monitor is not identified (Monitor: Unknown) such that maximum resolution is 1024x768. This occurs with Samsung Syncmaster 2033 (resolution 1900x600), and is the same with ViewSonic VX2453mh-LED (resolution 1920x1080). I'd be very grateful if anyone could give me a suggestion as to how to fix the resolution.

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  • Circular motion on low powered hardware

    - by Akroy
    I was thinking about platforms and enemies moving in circles in old 2D games, and I was wondering how that was done. I understand parametric equations, and it's trivial to use sin and cos to do it, but could an NES or SNES make real time trig calls? I admit heavy ignorance, but I thought those were expensive operations. Is there some clever way to calculate that motion more cheaply? I've been working on deriving an algorithm from trig sum identities that would only use precalculated trig, but that seems convoluted.

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  • Screen resolution is too low with open source drivers on Ubuntu 12.10

    - by Chintan Parikh
    I'm on an AMD graphics card. When I use the open source xserver-xorg-video-radeon driver, Gnome shell works fine but my screen resolution can't be set higher than 1024x768. However, when I'm on the closed source fglrx drivers, the screen resolution works fine, but gnome shell doesn't (it goes to gnome classic for some reason). Does anyone know how I can either get gnome shell to work with fglrx, or how I can set my screen resolution with xserver-xorg-video-radeon?

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  • Medical Devices which supports Direct access through Bluetooth Low Energy [on hold]

    - by Suganthan
    I have went through this link and came to know that we can directly interact with BLE devices to read and write data, so I just want to know some medical device which supports direct access to third-party application (we can directly access the data from the medical device data). Is their any devices which supports direct access to the data Note: I already went through medical devices like Withings and Fitbit

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  • Monitor not detected - low resolution only

    - by Jens
    I just installed Ubuntu 11.1 on my desktop pc. It was a clean install, no upgrading. I have a Samsung Syncmaster BX2450 connected to the PC. My problem is that I cannot make Ubuntu recognize my monitor - which is capable of more than 1024. I ran a shut down of lightdm, and ran sudo X -configure, but it gave me a "configuration failed". Nothing seems to work - any ideas? VESA: GF119 Board - 13100000 xx@xxx:~$ lspci -nn |grep VGA 02:00.0 VGA compatible controller [0300]: nVidia Corporation GT520 [GeForce GT520] [10de:1040] (rev a1) xx@xxx:~$ xrandr -q xrandr: Failed to get size of gamma for output default Screen 0: minimum 640 x 480, current 1024 x 768, maximum 1024 x 768 default connected 1024x768+0+0 0mm x 0mm 1024x768 61.0* 800x600 61.0 640x480 60.0

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