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  • How do I speed up and cache mmap file access over NFS on Linux?

    - by Zan Lynx
    The server and client are both 64-bit Ubuntu 10.04 LTS. The application in question is a custom app that uses mmap() for fast random file access. Its ideal state is when the entire file is cached in RAM. The network connections are really fast 10Gb Ethernet. It is a virtual server blade setup. It isn't the network connections slowing things down because everything performs superbly when using a virtual disk (iSCSI to the SAN). But when we run the application on a NFS home directory mount, performance goes to the dogs. It appears that the Linux kernel isn't caching anything. So it is reading every single disk block needed by mmap() accesses over and over and over again. The NFS mount is done through autofs, which has only default settings. /proc/mounts shows the NFS mount is done with the following options: rw,relatime,vers=3,rsize=131072,wsize=131072,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=192.168.11.52,mountvers=3,mountproto=tcp,addr=192.168.11.52 How can I make Ubuntu 10.04 cache the file instead of reloading it all the time?

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  • How can I speed up my macro in Excel 2003?

    - by user144872
    I have a macro that copies data from one cell to another and uses a VLOOKUP formula, among other things. My spreadsheet contains nearly 2000 rows. When I run it in Excel 2003, Excel starts to slow down as the macro processes rows 500 and above. It gets even worse when it reaches the 1000th row. It takes more than 5 hours to complete. In Excel 2007, however, the macro runs for only half an hour. Can anyone help me find a good solution?

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  • how can I estimate the conversion speed (fps) of a video based on CPU power? [closed]

    - by Ahoura Ghotbi
    Atm I am running a video sharing website and I am converting alot of videos. the queue is getting a bit too long (400 videos). I am planning on purchasing a new server and I was wondering if there anyway I can estimate the fps while converting 10 videos at the same time? Regards EXTRA INFO I am using MP4Box (which uses ffmpeg) to handle the encoding etc. Its encoding at 23 CRF, audio bitrate of 96 and audio sampling rate of 44100. The server will have the following processor : Dual Opteron 6272 (2 x 16 cores, 32 cores total) + 128GB RAM.

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  • mdadm lvm and ext4 slowness - How can I speed it up?

    - by beatbreaker
    I can't figure out why I'm getting such terrible times out of my mdadm and in particular the lvm partitions in it. I made the raid: mdadm --create --verbose /dev/md0 --level=5 --chunk=1024 --raid-devices=4 /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1 # cat /proc/mdstat Personalities : [raid6] [raid5] [raid4] md0 : active raid5 sda1[0] sdd1[3] sdc1[2] sdb1[1] 2930279424 blocks level 5, 1024k chunk, algorithm 2 [4/4] [UUUU] I then created the physical volume, volume group, and logical volumes, I then formatted the logical volumes to ext4 using the following commands I got from here: http://busybox.net/~aldot/mkfs_stride.html mkfs.ext3 -b 4096 -E stride=256,stripe-width=768 /dev/datavg/blah Now I'm confused, I had these lvs running real quick before in mdadm but now that I've 'optimized' everything it's slower, eg, before: /dev/datavg/lv_audio: Timing buffered disk reads: 598 MB in 3.01 seconds = 198.85 MB/sec but now after: /dev/datavg/audio: Timing buffered disk reads: 198 MB in 3.00 seconds = 65.96 MB/sec That's pitiful! What's happened here? Did I not follow the instructions correctly? Can i reshape the ext4 partitons to default back to what they were? (I used defaults before and they were fine!)

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  • Does a 300mbps 802.11n wireless connection have any noticeable speed improvement over 54mbps g?

    - by j j
    300mbps sounds wonderful, but not with my horrible Comcast internet connection. I doubt there's an internet connection in America that even hits 54mbps. So I'm guessing that the only reason someone would be inclined to upgrade is for faster data transfer within the local network. With my internet connection where download rates are rarely ever above a few hundred kilobytes a second, would I even see any improvement in switching from 802.11g to 802.11n?

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  • How can I minimize the amount my router slows down my Internet connection speed?

    - by Lord Torgamus
    Background I'm working with what I assume is a pretty common Internet setup: a cable modem, a wireless router and a few Internet-connected devices. Lately, I've started being more demanding on my Internet connection, and noticed that using my router slows down my download speeds considerably. I just kind of dealt with it until Zune Marketplace on the Xbox 360 told me that a movie was going to take well over ten hours to download, and I just didn't want to wait that long. Good little scientist that I am, I tried to reduce the problem down to one variable. The test As a control, I turned off all the devices in the house that use wireless Internet, and unplugged all the wired devices except for the Xbox. I also power-cycled both the modem and the router. I then tried to download the movie again, and was told that it would still take over ten hours. Next, I unplugged the router, and connected the Xbox directly to the modem. The movie downloaded in just over one hour. As far as I can tell, this means that my ISP, other cable users near me, the remote servers, anything wireless-related and my machines' disk speeds can't be at fault. A similar experiment that replaced the Xbox with a wired laptop produced similar results. To me, this says "the router is responsible for things taking around ten times longer to download." My question I'd still prefer to use the router for a few reasons: it's a pain to connect and disconnect everything every time there's a big file to download direct connection to the modem isn't good for security only one machine can be connected directly to the modem at a time What can I do to have fast connection speeds while still using the router? I don't mind turning other machines off, as long as I don't have to mess with power and ethernet cables. EDIT : After asking this followup question and then this one, I installed dd-wrt on my router, and I seem to be getting higher and more consistent speeds. Perhaps more importantly, my memory use is fairly constant. I know this isn't an answer — which is why I'm not posting it as an answer — but it is how I resolved the situation, and hopefully it'll be helpful for someone.

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  • How does braking assist of car racing games work?

    - by Ayush Khemka
    There are a lot of PC car racing games around which have this unique driving assist which helps brake your car so that you can safely turn it. While in some games it just an 'assist', it will just help your car brake but won't ensure a safe turn. While in others, the braking assist will help you get a safe turn. I was wondering on what could be the algorithm that is followed to achieve it. A very basic algorithm I could think of was, Pre-determine the braking distance of an ideal car for every turn of the track, depending on the radius of the turn, and then start braking the car accordingly. For example, for a turn of less than 90o, the car would start braking automatically at 50m distance from the start of the turn. A more advanced algorithm, which would ensure a safe turn, could be Pre-determine the speed of the car at the start of each turn, individually for each track, turn and car. Also, pre-determine the deceleration rate of each car individually, which varies because of the car's performance. The braking assist would keep recording the speed of the car at a certain instant of time. Start braking the car appropriately so that the car gets to the exact speed needed at the start of the turn. For example, let the speed of a particular car at the start of a turn 43m in radius, be 120km/h. Let the deceleration rate of the car be 200km/h2. If, at some instant of time, the speed of the car is 200km/h, then the car would automatically start braking at 400m from the start of the turn.

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  • How to use gps receiver bu-353

    - by Parimal
    Hi I have a gps receiver bu-353 with usb interface i want to know how can i use it under ubuntu I ran the following command gpsd -n -N -D 2 /dev/ttyUSB0 I got the output as: gpsd: launching (Version 2.94) gpsd: listening on port gpsd gpsd: running with effective group ID 1000 gpsd: running with effective user ID 1000 gpsd: opening GPS data source type 3 at '/dev/ttyUSB0' gpsd: speed 38400, 8N1 gpsd: Garmin: garmin_gps Linux USB module not active. gpsd: speed 9600, 8O1 gpsd: speed 38400, 8N1 gpsd: gpsd_activate(): opened GPS (fd 6) gpsd: speed 4800, 8N1 gpsd: NTPD ntpd_link_activate: 0 gpsd: /dev/ttyUSB0 identified as type SiRF binary (2.687608 sec @ 4800bps) gpsd: detaching 127.0.0.1 (sub 1, fd 8) in detach_client gpsd: detaching 127.0.0.1 (sub 1, fd 8) in detach_client after this i started tangoGPS, which said no gps and no gpsd found

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  • how to use gps receiver bu-353 in ubuntu 10.10

    - by Parimal
    Hi I have a gps receiver bu-353 with usb interface i want to know how can i use it under ubuntu I ran the following command gpsd -n -N -D 2 /dev/ttyUSB0 i got the output as: gpsd: launching (Version 2.94) gpsd: listening on port gpsd gpsd: running with effective group ID 1000 gpsd: running with effective user ID 1000 gpsd: opening GPS data source type 3 at '/dev/ttyUSB0' gpsd: speed 38400, 8N1 gpsd: Garmin: garmin_gps Linux USB module not active. gpsd: speed 9600, 8O1 gpsd: speed 38400, 8N1 gpsd: gpsd_activate(): opened GPS (fd 6) gpsd: speed 4800, 8N1 gpsd: NTPD ntpd_link_activate: 0 gpsd: /dev/ttyUSB0 identified as type SiRF binary (2.687608 sec @ 4800bps) gpsd: detaching 127.0.0.1 (sub 1, fd 8) in detach_client gpsd: detaching 127.0.0.1 (sub 1, fd 8) in detach_client after this i started tangoGPS, which said no gps and no gpsd found

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  • Vehicle: Boat accelerating and turning in Unity

    - by Emilios S.
    I'm trying to make a player-controllable boat in Unity and I'm running into problems with my code. 1) I want to make the boat to accelerate and decelerate steadily instead of simply moving the speed I'm telling it to right away. 2) I want to make the player unable to steer the boat unless it is moving. 3) If possible, I want to simulate the vertical floating of a boat during its movement (it going up and down) My current code (C#) is this: using UnityEngine; using System.Collections; public class VehicleScript : MonoBehaviour { public float speed=10; public float rotationspeed=50; // Use this for initialization // Update is called once per frame void Update () { // Forward movement if(Input.GetKey(KeyCode.I)) speed = transform.Translate (Vector3.left*speed*Time.deltaTime); // Backward movement if(Input.GetKey(KeyCode.K)) transform.Translate (Vector3.right*speed*Time.deltaTime); // Left movement if(Input.GetKey(KeyCode.J)) transform.Rotate (Vector3.down*rotationspeed*Time.deltaTime); // Right movement if(Input.GetKey(KeyCode.L)) transform.Rotate (Vector3.up*rotationspeed*Time.deltaTime); } } In the current state of my code, when I press the specified keys, the boat simply moves 10 units/sec instantly, and also stops instantly. I'm not really sure how to make the things stated above, so any help would be appreciated. Just to clarify, I don't necessarily need the full code to implement those features, I just want to know what functions to use in order to achieve the desired effects. Thank you very much.

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  • Huawei E3276 LTE uplink slow in the routing Ubuntu, but not with other devices in the LAN

    - by Mytomi
    I have a Huawei E3276 LTE dongle (12d1:14fe - 12d1:1506) and a problem with the upstream speed. The problem is not only present with Ubuntu 14.04 LTS (64 bit workstation, kernel 3.16), but also with Raspbian Jessie for Raspberry PI (kernel 3.14). Upstream seems to be always limited to 5 Mbit/s whenever I check the speed from the Linux computer that I use as a LTE router. The other computers in the LAN always get about 10-15 Mbit/s upstream, even though the traffic is routed through the same Linux computer suffering from seemingly capped uplink. Downstream speed is always fine, 25 Mbit/s. I even installed Windows 7 in the same computer as Ubuntu and the speeds are 25 Mbit/s down, 15 Mbit/s up. So the problem is not with E3276 device itself or in the mobile subscription, but in the Huawei E3276 Linux compatibility. Maybe something in the kernel? I have made sure that the matter is not with iptables rules: the speed does not noticeably increase when iptables is disabled. Turning off IPv4 forwarding does not improve speed either. I'm not sure what settings and logs do help in debugging the situation. Please ask for more details, if you have a clue what might be wrong. Thanks, Mytomi

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  • how to plot scatterplot and histogram using R [migrated]

    - by Wee Wang Wang
    I have a dataset about maximum wind speed(cm) as below: Year Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec 2011 4.5 5.6 5.0 5.4 5.0 5.0 5.2 5.3 4.8 5.4 5.4 3.8 2010 4.6 5.0 5.8 5.0 5.2 4.5 4.4 4.3 4.9 5.2 5.2 4.6 2009 4.5 5.3 4.3 3.9 4.7 5.0 4.8 4.7 4.9 5.6 4.9 4.1 2008 3.8 1.9 5.6 4.7 4.7 4.3 5.9 4.9 4.9 5.6 5.2 4.4 2007 4.6 4.6 4.6 5.6 4.2 3.6 2.5 2.5 2.5 3.3 5.6 1.5 2006 4.3 4.8 5.0 5.2 4.7 4.6 3.2 3.4 3.6 3.9 5.9 4.4 2005 2.7 4.3 5.7 4.7 4.6 5.0 5.6 5.0 4.9 5.9 5.6 1.8 How to create monthly max wind speed scatterplot (month in x-axis and wind speed in y-axis) and also the monthly max wind speed histogram by using R programming?

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  • Very slow write access to SSD disks on some Asus P8Z77 motherboards

    - by lenik
    I have Asus P8Z77-V LK motherboard, that ran Mint 13 (based on Ubuntu 12.04) just perfectly, but recently I've tried to install Mint 17 and noticed abysmal write performance. Write speed on SSD disk was about 1.5MB/sec, when it's supposed to be in 150-250MB/sec range. For write testing I've used dd if=/dev/zero of=/dev/sda bs=10M count=10 while booted up from LiveCD. I have also tested the read speed with hdparm -tT /dev/sda and got about 440MB/sec -- that's normal. I can tell, the read performance has not degraded at all and is not an issue here. Since I had a few different SSD disks and few motherboards, I've tested and tested and here are results: Asus P8H77 works fine with Mint13, has very slow write speed starting from Mint14. Asus P8Z77-V LK works with Mint13, has very slow write speed starting from Mint14. Asus P8Z77-V PRO works with Mint13, and works just fine with Mint14, 15, 16 and 17. The only difference between "PRO" version and others is that it has extra SATA controller onboard (in addition to the Z77 chipset SATA controller) providing extra 2 SATA ports. SSD disks work fine with "PRO" version when connected to the native SATA ports as well as to the ports provided by extra SATA controller, so this does not look like a hardware issue. As far as I can tell, there's something changed in the kernel while going from 3.2 to 3.5, that affects the detection of onboard SATA controller for Asus P8*77 motherboards, that screws up the write speed for SSD drives. Could anyone shed some light on how to fix this issue or, possibly, give a pointer to a more suitable place to ask this question?

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  • How do I calculate opposite of a vector, add some slack

    - by Jason94
    How can i calulate a valid range (RED) for my object's (BLACK) traveling direction (GREEN). The green is a Vector2 where x and y range is -1 to 1. What I'm trying to do here is to create rocket fuel burn effekt. So what i got is rocket speed (float) rocket direction (Vector2 x = [-1, 1], y = [-1, 1]) I may think that rocket speed does not matter as fuel burn effect (particle) is created on position with its own speed.

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  • Moving in a diamond - enemy gets stuck

    - by Fibericon
    I have an enemy that I would like to move as follows: Start at (0, 200, 0) Move to (200, 0, 0) Move to (0, -200, 0) Move to (-200, 0, 0) Move to start point, repeat as long as it remains active. This is what I've done to achieve that: if (position.X < 200 && position.Y > 0) { Velocity = new Vector3(1, -1, 0) * speed; } else if (position.X >= 200 && position.Y <= 0 && position.Y > -200) { Velocity = new Vector3(-1, -1, 0) * speed; } else if (position.X <= 0 && position.Y <= -200) { Velocity = new Vector3(-1, 1, 0) * speed; } else { Velocity = new Vector3(1, 1, 0) * speed; } It moves to the second point, but then gets stuck and appears to vibrate in place. How should I be doing this?

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  • Move projectile in direction the gun is facing

    - by Manderin87
    I am attempting to have a projectile follow the direction a gun is facing. When using the following code I am unable to make the projectile go in the right direction. float speed = .5f; float dX = (float) -Math.cos(Math.toRadians(degree)) * speed; float dY = (float) Math.sin(Math.toRadians(degree)) * speed; Can anyone tell me what I am doing wrong? The degree is the direction the gun is facing in degree's.

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  • How can I judge the suitability of modern processors for systems with specific CPU requirements?

    - by Iszi
    Inspired by this question: How do I calculate clock speed in multi-core processors? The answers in the above question do a fair job of explaining why a lower-speed multi-core processor won't necessarily perform at the same level as a higher-speed single-core processor. Example: 4*2=8, but a quad-core 2 GHz processor isn't necessarily as fast as a single-core 8 GHz processor. However, I'm having a hard time putting the information in those answers to practical use in my mind. Particularly, I want to know how it should be used to judge whether a given CPU is appropriate for an application with specific requirements. Example scenarios: An application has a minimum CPU requirement of 2.4 GHz dual-core. Another application has a minimum CPU requirement of 1.8 GHz single-core. For either of the above scenarios: Would a higher-speed processor with fewer cores, or a lower-speed processor with more cores, be equally sufficient? If so, how can we determine the appropriate processor speeds required for a given number of cores?

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  • Floating point undesireable in highly critical code?

    - by Kirt Undercoffer
    Question 11 in the Software Quality section of "IEEE Computer Society Real-World Software Engineering Problems", Naveda, Seidman, lists fp computation as undesirable because "the accuracy of the computations cannot be guaranteed". This is in the context of computing acceleration for an emergency braking system for a high speed train. This thinking seems to be invoking possible errors in small differences between measurements of a moving object but small differences at slow speeds aren't a problem (or shouldn't be), small differences between two measurements at high speed are irrelevant - can there be a problem with small roundoff errors during deceleration for an emergency braking system? This problem has been observed with airplane braking systems resulting in hydroplaning but could this actually happen in the context of a high speed train? The concern about fp errors seems to not be well-founded in this context. Any insight? The fp is used for acceleration so perhaps the concern is inching over a speed limit? But fp should be just fine if they use a double in whatever implementation language. The actual problem in the text states: During the inspection of the code for the emergency braking system of a new high speed train (a highly critical, real-time application), the review team identifies several characteristics of the code. Which of these characteristics are generally viewed as undesirable? The code contains three recursive functions (well that one is obvious). The computation of acceleration uses floating point arithmetic. All other computations use integer arithmetic. The code contains one linked list that uses dynamic memory allocation (second obvious problem). All inputs are checked to determine that they are within expected bounds before they are used.

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  • Wireless internet works on W7 and on University Network but is extremely slow at home

    - by Rick
    I'm using ubuntu 12.04 with an Atheros wireless card. My internet speed in W7 is great. My internet speed in Ubuntu 12.04 at a university network is great. My internet speed in Ubuntu 12.04 at my home network is really slow. Some solutions I have tried but didn't work: Disabling IPv6 Running the following code: sudo ifconfig wlan0 down sudo rmmod -f iwlwifi sudo modprobe iwlwifi 11n_disable=1 sudo ifconfig wlan0 up Thanks for the help!

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