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  • Proper Usage of Arrays and Functions [closed]

    - by Ssegawa Victor
    Can some one help me write a C code that solves the following problem. PROBLEM Consider the faculty registrar who has to process results for 1st year 1st semester students. Students offer five courses CSC 1100, CSK 1101, CSC 1104, CSC 1105 and CSC 1106. The courses have credit units 4,4,4,3 and 3 respectively. Lecturers provide course work and exam marks. For each course, course work constitutes 40% of the final mark while the exam constitutes 60% of the final mark. The role of the registrar is to Compute the final mark for each student for each course. The final mark must be a whole number Compute the grade and grade point of the students for each course they offered. According to senate regulations, grades and grade points are awarded to final marks according to the following criteria Range Grade Grade Point 90 – 100 A+ 5.0 80 – 89 A 5.0 75 – 79 B+ 4.5 70 – 74 B 4.0 65 – 69 C+ 3.5 60 – 64 C 3.0 55 – 59 D+ 2.5 50 – 54 D 2.0 45 – 49 E 1.5 40 – 44 E- 1.0 0 – 39 F 0.0 Put a comment ‘Retake’ to a student for every course where the Grade Point is less than 2.0 Compute the cumulative grade point average CGPA for each student. The senate formula for CGPA is GGPA =(?_(i=1)^(i=N)¦?CU _i×GP _i ?)/(?_(i=1)^(i=N)¦CU i) Put a comment “Progress” for any student whose GGPA is greater than 2 and “Stay Put” on a student whose CGPA is less than 2 You are required to create a c program that considers a class of 25 students and: 1.Initializes an array ‘student’ which stores student names 2.Initializes arrays for course work and exam for each course. ‘cw_csc_1100’ and ‘ex_csc_1100’ store course work and exam marks (respectively) for CSC 1100. The same approach is considered for all other courses 3.Initializes the coursework and exam marks arrays with marks between 0 and 99 4.Write appropriate functions that will generate the final marks, generate grades, generate grade points, generate cumulative grade points, generate comments for students and comments for courses per student 5.Create appropriate arrays for final marks and insert the data there using the appropriate functions 6.Without having to create any extra arrays, use the functions created to generate a report per student that looks like the one bellow. Student Name: Ngubiri Course Unit Final mark Grade Grade Point Course Comment CSC 1100 43 E- 1.0 Retake CSK 1101 50 D 2.0 CSC 1104 59 D+ 2.5 CSC 1105 70 B 4.0 CSC 1106 65 C+ 3.5 CGPA 2.47 Overall Comment Progress NB It is advisable that the indices are used to identify the owners. Eg if student[x] is John, then cs_csc_100[x] should be a mark for John since the index is the same

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  • Announcing a new Free Windows Azure Platform Trial offer

    - by Eric Nelson
    We now have a  truly useful Windows Azure Platform trial. Which makes me very happy as I was a vocal critic of the original trial offer. Simply put, the small number of compute hours it included made it useless for many potential early adopters. This is now fixed. The new Introductory Special now includes a generous 750 hours of compute – enough to run a web role 24/7. Enjoy! Related Links Full announcement If you are an ISV then there is a better offer for you via Microsoft Platform Ready and Cloud Essentials and keep an eye on our events for ISVs as we will be doing Windows Azure Platform technical briefings starting March 31st.

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  • Google Cloud Platform : nouvelles fonctionnalités, augmentation des capacités des centres de données et réduction des prix

    Google Cloud Platform : nouvelles fonctionnalités réduction des prix et augmentation des capacités des centres de données en Europe Google a apporté une mise à jour importante à son offre Google Cloud Platform. Google Cloud Platform est une suite de solution Cloud computing (SaaS et IaaS) pour les développeurs, les entreprises et biens plus. L'offre comprend les plateformes : App Engine, Cloud Storage, BigQuery, Compute Engine, Cloud SQL, etc. Compute Engine, l'offre IaaS (Infrastructure as a Service) de l'éditeur dévoilée en juin dernier avec quatre types d'instances, s'enrichit de 36 nouveaux types d'instances, avec à la clé une réduction générale des prix. De...

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  • Drag camera/view in a 3D world

    - by Dono
    I'm trying to make a Draggable view in a 3D world. Currently, I've made it using mouse position on the screen, but, when I move the distance traveled by my mouse is not equal to the distance traveled in the 3D world. So, I've tried to do that : Compute a ray from mouse position to 3D world. Calculate intersection with the ground. Check intersection difference old position <- new position. Translate camera with the difference. I've got a problem with this method: The ray is computed with the current camera's position I move the camera I compute the new ray with new camera position. The difference between old ray and new ray is now invalid. So, graphically my camera don't stop to move to previous/new position everytime. How can I do a draggable camera with another solution ? Thanks!

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  • Is an extra collision-mesh for level-data worth the hassle?

    - by Serthy
    What is the optimal approach for collision-detection with the environment in an 3D engine (with triangle mesh based geometry, no bsp)? A) Use the render mesh [+] no need for additional work for artists to fiddle with collision detection [-] high detail is harder for physics calculation [+/-] maybe use collidable flags for materials [+/-] compute the collision-mesh from the render-mesh B) Use an additional collision mesh [+] faster/more optimal collision-detection [-] additional work (either by the artist or by the programmer who has to develop an algorithm to compute it from the render-mesh) [-] more memory useage How do AAA title handle this? And what are the indie dev's approaches?

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  • Postfix unable to create lock file, permission denied

    - by John Bowlinger
    I thought I had my postfix configuration all set up on my Amazon Ubuntu server but I guess not. I'm trying to set up an admin email account for 3 virtually hosted Apache websites. Here's my postfix main.cf file: myhostname = ip-XX-XXX-XX-XXX.us-west-2.compute.internal alias_maps = hash:/etc/aliases alias_database = hash:/etc/aliases myorigin = /etc/mailname mydestination = ip-XX-XXX-XX-XXX.us-west-2.compute.internal, localhost.us-west-2.compute.internal, , localhost relayhost = mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 mailbox_size_limit = 0 recipient_delimiter = + inet_interfaces = all virtual_mailbox_domains = example1.com, example2.com, example3.com virtual_mailbox_base = /var/mail/vhosts virtual_mailbox_maps = hash:/etc/postfix/vmailbox virtual_minimum_uid = 100 virtual_uid_maps = static:115 virtual_gid_maps = static:115 virtual_alias_maps = hash:/etc/postfix/virtual Here's my vmailbox file: [email protected] example1.com/admin [email protected] example2.com/admin [email protected] example3.com/admin @example1.com example1.com/catchall @example2.com example2.com/catchall @example3.com example3.com/catchall And finally my virtual file: [email protected] postmaster [email protected] postmaster [email protected] postmaster When I try to send an email to through netcat to my one of my domains, I get: unable to create lock file /var/mail/vhosts/example1.com/admin.lock: Permission denied This is despite the fact that I set example1.com group to postfix and also my virtual_uid_maps and virtual_gid_maps are both set to Postfix group id of 115.

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  • Amazon AWS Ec2 instance, Elastic IP, Domain name from external domainseller, and Google Apps for Email

    - by Sid
    We are hosting our site on an Ec2 instance. Our Elastic IP is w.x.y.z and Public DNS is: ec2-w-x-y-z.compute-1.amazonaws.com. We've bought a domain name domainname.com from a lesser known domain-name-seller. We added an A-record pointing domainname.com to w.x.y.z. Will this work or do we need a CNAME record to point to the same too? We wanted to use Google apps for emailing so adjusted the TXT/MX records according to the Google Apps instructions to be able to send/recv email using @domainname.com email addresses. Have we got it right, more important, we came across queries relating to email sent from ec2-w-x-y-z.compute-1.amazonaws.com (our users can send email from their onsite accounts) going to spam (rDNS not pointing to domainname.com but to ec2-w-x-y-z.compute-1.amazonaws.com). How can we fix this? We came across SPF records, do they provide a complete solution? We aren't sure as to how to use them. Can you help pls? Thank you, Sid

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  • Allow incoming connections on Windows Server 2008 R2

    - by Richard-MX
    Good day people. First, im new to Windows Server. I've always used Linux/Apache combo, but, my client has and AWS EC2 Windows Server 2008 R2 instance and he wants everything in there. Im working with IIS and PHP enabled as Fast-CGI and everything is working, but, i cant see the websites stored in it from internet. The public DNS that AWS gave us for that instance is: http://ec2-XX-XXX-XXX-121.us-west-2.compute.amazonaws.com/ But, if i copy paste that address, i get nothing, no IIS logo or something like that. My common sense tells me that maybe the firewall could be blocking the access. Can anyone help me and tell where to enable some rules to get this thing working? I don't wanna start enabling rules at random and make the system insecure. If you need any additional info, you can ask me and i will provide it. Thanks in advance. UPDATE: Amazon EC2 display this: Public DNS: ec2-XX-XXX-XXX-121.us-west-2.compute.amazonaws.com Private DNS: ip-XX-XXX-XX-252.us-west-2.compute.internal Private IPs: XX.XXX.XX.25 In my test microinstance, i just to use the Public DNS address (the one that starts with "ec2") and it works like a charm (of course, the micro instance have its own Public DNS im not assuming same address for both instances...) However, for the large instance, i tried to do the same. Set up everything as in the micro instance but if i use the Public DNS, it doesnt load anything. Im suspicious about the Windows Firewall, but, the HTTP related stuff is enabled. What should i do to get access to the large instance? I don't want to set up the domain yet, i want access from an amazon url. 2ND EDIT: all fixed. Charles pointed that maybe Security Groups was not properly set up for the instance. He was right. Just added HTTP service to the rules and all works good.

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  • Creating Active Directory on an EC2 box

    - by Chiggins
    So I have Active Directory set up on a Windows Server 2008 Amazon EC2 server. Its set up correctly I think, I never got any errors with it. Just to test that I got it all set up correctly, I have a Windows 7 Professional virtual machine set up on my network to join to AD. I set the VM to use the Active Directory box as its DNS server. I type in my domain to join it, but I get the following error: DNS was successfully queried for the service location (SRV) resource record used to locate a domain controller for domain "ad.win.chigs.me": The query was for the SRV record for _ldap._tcp.dc._msdcs.ad.win.chigs.me The following domain controllers were identified by the query: ip-0af92ac4.ad.win.chigs.me However no domain controllers could be contacted. Common causes of this error include: - Host (A) or (AAAA) records that map the names of the domain controllers to their IP addresses are missing or contain incorrect addresses. - Domain controllers registered in DNS are not connected to the network or are not running. It seems that I can talk to Active Directory, but when I'm trying to contact the Domain Controller, its giving a private IP to connect to, at least thats what I can make out of it. Here are some nslookup results. > win.chigs.me Server: ec2-184-73-35-150.compute-1.amazonaws.com Address: 184.73.35.150 Non-authoritative answer: Name: ec2-184-73-35-150.compute-1.amazonaws.com Address: 10.249.42.196 Aliases: win.chigs.me > ad.win.chigs.me Server: ec2-184-73-35-150.compute-1.amazonaws.com Address: 184.73.35.150 Name: ad.win.chigs.me Address: 10.249.42.196 win.chigs.me and ad.win.chigs.me are CNAME's pointing to my EC2 box. Any idea what I need to do so that I can join my virtual machine to the EC2 Active Directory set up I have? Thanks!

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  • Which is the fastest way to move 1Petabyte from one storage to a new one?

    - by marc.riera
    First of all, thanks for reading, and sorry for asking something related to my job. I understand that this is something that I should solve by myself but as you will see its something a bit difficult. A small description: Now Storage = 1PB using DDN S2A9900 storage for the OSTs, 4 OSS , 10 GigE network. (lustre 1.6) 100 compute nodes with 2x Infiniband 1 infiniband switch with 36 ports After Storage = Previous storage + another 1PB using DDN S2A 990 or LSI E5400 (still to decide) (lustre 2.0) 8 OSS , 10GigE network 100 compute nodes with 2x Infiniband Previous experience: transfered 120 TB in less than 3 days using following command: tar -C /old --record-size 2048 -b 2048 -cf - dir | tar -C /new --record-size 2048 -b 2048 -xvf - 2>&1 | tee /tmp/dir.log So , big problem here, using big mathematical equations I conclude that we are going to need 1 month to transfer the data from one side to the new one. During this time the researchers will need to step back, and I'm personally not happy with this. I'm telling you that we have infiniband connections because I think that may be there is a chance to use it to transfer the data using 18 compute nodes (18 * 2 IB = 36 ports) to transfer the data from one storage to the other. I'm trying to figure out if the IB switch will handle all the traffic but in case it just burn up will go faster than using 10GigE. Also, having lustre 1.6 and 2.0 agents on same server works quite well, with this there is no need to go by 1.8 to upgrade the metadata servers with two steps. Any ideas? Many thanks Note 1: Zoredache, we can divide it in two blocks (A)600Tb and (B)400Tb. The idea is to move (A) to new storage which is lustre2.0 formated, then format where (A) was with lustre2.0 and move (B) to this lustre2.0 block and extend with the space where (B) was. This way we will end with (A) and (B) on separate filesystems, with 1PB each.

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  • Home Server: storage virtualisation, what to choose?

    - by Huygens
    I'm looking for virtualisation solutions for storage and OS for a home server. A sort of private cloud where I manage the storage space independently of the VM one. This question focus on storage management. (I have another question related to the VM/compute instance management). Here my environement and wishes. Server: HP Proliant MicroServer with 8 GB RAM (AMD Turion dual core with AMD-V technology) with 1 250GB system disk and up to 4 HDD (2 TB) for "data" OS types: only Linux (perhaps a *BSD VM in the future) Linux distributions do not matter, I'm familiar with RHEL, Fedora, Suse, Ubuntu, but any other recommandation will be fine The 4 HDD is going to be a software RAID array, probably RAID 5. storage should be "virtualised/cloudified": easy to extend: if I add a NAS on the network, I can include the NAS space capacity within this storage space as one virtual disk. This can be a NAS, an external HDD or another server. cluster FS or S3 style space or OpenStack block storage? Whatever is easier to manage/maintain and easy to integrate/plug to VM/compute instance. I would prefer free (libre, as in a free speach) and open source tools. But it does not have to be free as in a free beer. Note: the VMs I intend to run on top of this server are one dedicated to backup, one for a "owncloud/dropbox"-like service and perhaps one for media server (hosting video and photos). I'm not sure if traditional VMs or compute instance are the most suitable for this.

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  • I want to create adjacency matrix using python

    - by A A
    I have very large data set it is almost 450000 lines and two rows, i want to compute adjacency matrix using python, because previously i have tried to do it in matlab, and it shows memory error because of large data values. my data values also start from 100 and goes upto 450000, Anyone can help me in this issue, as i am new to python. I have to first import the file into python using excel sheet or notepad and then compute the adjacency matrix

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  • Webservice with .NET

    - by mouthpiec
    Hi, I have an application that when run as a windows application takes around 4 secs to compute, but when run as a webservice, it takes a long time to compute (until a timeout). Do you have any idea what the problem might be? I am assuming that since the code is exactly the same, there are no problems such as infinite loops ..... it seems that it just takes longer. Do you have an idea what might the problem be? thanks

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  • How to avoid overflow in expr. A * B - C * D

    - by Ir0nm
    I need to compute an expression which looks like: A*B - C*D, where their types are: signed long long int A, B, C, D; Each number can be really big (not overflowing its type). While A*B could cause overflow, at same time expression A*B - C*D can be really small. How can I compute it correctly? For example: MAX * MAX - (MAX - 1) * (MAX + 1) == 1, where MAX = LLONG_MAX - n and n - some natural number.

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  • Communicate between separate MPI-Programs

    - by Fyg
    I have the following problem: Program 1 has a huge amount of data, say 10GB. The data in question consists of large integer- and double-arrays. Program 2 has 1..n MPI processes that use tiles of this data to compute results. How can I send the data from program 1 to the MPI Processes? Using File I/O is out of question. The compute node has sufficient RAM.

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  • Parsing timestamp with retarded Python

    - by jellybean
    I want to parse a timestamp from a log file that has been written via datetime.datetime.now().strftime('%Y%m%d%H%M%S') and then compute the number of seconds that have passed since this timestamp. I know I could do it with datetime.datetime.strptime to get back a datetime object and then compute a timedelta. Problem is, the strptime function has been introduced with Python 2.5 and I'm using Python2.4.4 (an upgrade is not possible in my context). Any easy way to do this?

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  • Parsing timestamp with Python2.4

    - by jellybean
    I want to parse a timestamp from a log file that has been written via datetime.datetime.now().strftime('%Y%m%d%H%M%S') and then compute the number of seconds that have passed since this timestamp. I know I could do it with datetime.datetime.strptime to get back a datetime object and then compute a timedelta. Problem is, the strptime function has been introduced with Python 2.5 and I'm using Python2.4.4 (an upgrade is not possible in my context). Any easy way to do this?

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  • Stop running this script, IE7 using PHP

    - by Jomel Dicen
    I incorporate javascript in my PHP program: Try to check my codes. It loops depend on the number of records in database. for instance: $counter = 0; foreach($row_value as $data): echo $this->javascript($counter, $data->exrate, $data->tab); endforeach; private function javascript($counter=NULL, $exrate=NULL, $tab=NULL){ $js = " <script type='text/javascript'> $(function () { var textBox0 = $('input:text[id$=quantity{$counter}]').keyup(foo); var textBox1 = $('input:text[id$=mc{$counter}]').keyup(foo); var textBox2 = $('input:text[id$=lc{$counter}]').keyup(foo); function foo() { var value0 = textBox0.val(); var value1 = textBox1.val(); var value2 = textBox2.val(); var sum = add(value1, value2) * (value0 * {$exrate}); $('input:text[id$=result{$counter}]').val(parseFloat(sum).toFixed(2)); // Compute Total Quantity var qtotal = 0; $('.quantity{$tab}').each(function() { qtotal += Number($(this).val()); }); $('#tquantity{$tab}').text(qtotal); // Compute MC UNIT var mctotal = 0; $('.mc{$tab}').each(function() { mctotal += Number($(this).val()); }); $('#tmc{$tab}').text(mctotal); // Compute LC UNIT var lctotal = 0; $('.lc{$tab}').each(function() { lctotal += Number($(this).val()); }); $('#tlc{$tab}').text(lctotal); // Compute Result var result = 0; $('.result{$tab}').each(function() { result += Number($(this).val()); }); $('#tresult{$tab}').text(result); } function add() { var sum = 0; for (var i = 0, j = arguments.length; i < j; i++) { if (IsNumeric(arguments[i])) { sum += parseFloat(arguments[i]); } } return sum; } function IsNumeric(input) { return (input - 0) == input && input.length > 0; } }); </script> "; return $js; } When I running this on IE this message is always annoying me " Stop running this script? A script on this page is causing your web browser to run slowly. If it continues to run, your computer might become unresponsive." but in firefox it's functioning well.

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  • capistrano initial deployment

    - by Richard G
    I'm trying to set up Capistrano to deploy to an AWS box. This is the first time I've tried to set this up, so please bear with me. Could someone take a look at this and let me know if you can solve this error? The output below is the deploy.rb file, and it's output when it runs. set :application, "apparel1" set :repository, "git://github.com/rgilling/GroceryRun.git" set :scm, :git set :user, "ubuntu" set :scm_passphrase, "pre5ence" # Or: `accurev`, `bzr`, `cvs`, `darcs`, `git`, `mercurial`, `perforce`, `subversion` or `none` ssh_options[:keys] = ["/Users/rgilling/Documents/Projects/Apparel1/abesakey.pem"] ssh_options[:forward_agent] = true set :location, "ec2-107-22-27-42.compute-1.amazonaws.com" role :web, location # Your HTTP server, Apache/etc role :app, location # This may be the same as your `Web` server role :db, location, :primary => true # This is where Rails migrations will run set :deploy_to, "/var/www/#{application}" set :deploy_via, :remote_cache set :use_sudo, true # if you want to clean up old releases on each deploy uncomment this: # after "deploy:restart", "deploy:cleanup" # if you're still using the script/reaper helper you will need # these http://github.com/rails/irs_process_scripts # If you are using Passenger mod_rails uncomment this: namespace :deploy do task :start do ; end task :stop do ; end task :restart, :roles => :app, :except => { :no_release => true } do run "#{try_sudo} touch #{File.join(current_path,'tmp','restart.txt')}" end end Then the execution results in this permission error. I think I"ve set up the SSH etc. correctly... updating the cached checkout on all servers executing locally: "git ls-remote git://github.com/rgilling/GroceryRun.git HEAD" command finished in 1294ms * executing "if [ -d /var/www/apparel1/shared/cached-copy ]; then cd /var/www/apparel1/shared/cached-copy && git fetch -q origin && git fetch --tags -q origin && git reset -q --hard f35dc5868b52649eea86816d536d5db8c915856e && git clean -q -d -x -f; else git clone -q git://github.com/rgilling/GroceryRun.git /var/www/apparel1/shared/cached-copy && cd /var/www/apparel1/shared/cached-copy && git checkout -q -b deploy f35dc5868b52649eea86816d536d5db8c915856e; fi" servers: ["ec2-107-22-27-42.compute-1.amazonaws.com"] [ec2-107-22-27-42.compute-1.amazonaws.com] executing command ** **[ec2-107-22-27-42.compute-1.amazonaws.com :: err] error: cannot open .git/FETCH_HEAD: Permission denied**

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  • msdxm.ocx and duration issues

    - by greendaale
    This is a VB6 question. How does Windows Media Player compute duration? Is it possible to detect corrupt media files and do not compute duration on these? I sometimes get duration = 0, why does that happen? Thanks :)

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  • Computing e^(-j) in C..

    - by Erkan H
    I need to compute imaginary exponential in C. As far as I know, there is no complex number library in C. It is possible to get e^x with exp(x) of math.h, but how can I compute the value of e^(-j), where j = sqrt(-1)?

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  • InfiniBand Enabled Diskless PXE Boot

    - by Neeraj Gupta
    When you want to bring up a compute server in your environment and need InfiniBand connectivity, usually you go through various installation steps. This could involve operating systems like Linux, followed by a compatible InfiniBand software distribution, associated dependencies and configurations. What if you just want to run some InfiniBand diagnostics or troubleshooting tools from a test machine ? What if something happened to your primary machine and while recovering in rescue mode, you also need access to your InfiniBand network ? Often times we use opensource community supported small Linux distributions but they don't come with required InfiniBand support and tools. In this weblog, I am going to provide instructions on how to add InfniBand support to a specific Linux image - Parted Magic.This is a free to use opensource Linux distro often used to recover or rescue machines. The distribution itself will not be changed at all. Yes, you heard it right ! I have built an InfiniBand Add-on package that will be passed to the default kernel and initrd to get this all working. Pr-requisites You will need to have have a PXE server ready on your ethernet based network. The compute server you are trying to PXE boot should have a compatible IB HCA and must be connected to an active IB network. Required Downloads Download the Parted Magic small distribution for PXE from Parted Magic website. Download InfiniBand PXE Add On package. Right Click and Download from here. Do not extract contents of this file. You need to use it as is. Prepare PXE Server Extract the contents of downloaded pmagic distribution into a temporary directory. Inside the directory structure, you will see pmagic directory containing two files - bzImage and initrd.img. Copy this directory in your TFTP server's root directory. This is usually /tftpboot unless you have a different setup. For Example: cp pmagic_pxe_2012_2_27_x86_64.zip /tmp cd /tmp unzip pmagic_pxe_2012_2_27_x86_64.zip cd pmagic_pxe_2012_2_27_x86_64 # ls -l total 12 drwxr-xr-x  3 root root 4096 Feb 27 15:48 boot drwxr-xr-x  2 root root 4096 Mar 17 22:19 pmagic cp -r pmagic /tftpboot As I mentioned earlier, we dont change anything to the default pmagic distro. Simply provide the add-on package via PXE append options. If you are using a menu based PXE server, then add an entry to your menu. For example /tftpboot/pxelinux.cfg/default can be appended with following section. LABEL Diskless Boot With InfiniBand Support MENU LABEL Diskless Boot With InfiniBand Support KERNEL pmagic/bzImage APPEND initrd=pmagic/initrd.img,pmagic/ib-pxe-addon.cgz edd=off load_ramdisk=1 prompt_ramdisk=0 rw vga=normal loglevel=9 max_loop=256 TEXT HELP * A Linux Image which can be used to PXE Boot w/ IB tools ENDTEXT Note: Keep the line starting with "APPEND" as a single line. If you use host specific files in pxelinux.cfg, then you can use that specific file to add the above mentioned entry. Boot Computer over PXE Now boot your desired compute machine over PXE. This does not have to be over InfiniBand. Just use your standard ethernet interface and network. If using menus, then pick the new entry that you created in previous section. Enable IPoIB After a few minutes, you will be booted into Parted Magic environment. Open a terminal session and see if InfiniBand is enabled. You can use commands like: ifconfig -a ibstat ibv_devices ibv_devinfo If you are connected to InfiniBand network with an active Subnet Manager, then your IB interfaces must have come online by now. You can proceed and assign IP address to them. This will enable you at IPoIB layer. Example InfiniBand Diagnostic Tools I have added several InfiniBand Diagnistic tools in this add-on. You can use from following list: ibstat, ibstatus, ibv_devinfo, ibv_devices perfquery, smpquery ibnetdiscover, iblinkinfo.pl ibhosts, ibswitches, ibnodes Wrap Up This concludes this weblog. Here we saw how to bring up a computer with IPoIB and InfiniBand diagnostic tools without installing anything on it. Its almost like running diskless !

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  • Non use of persisted data

    - by Dave Ballantyne
    Working at a client site, that in itself is good to say, I ran into a set of circumstances that made me ponder, and appreciate, the optimizer engine a bit more. Working on optimizing a stored procedure, I found a piece of code similar to : select BillToAddressID, Rowguid, dbo.udfCleanGuid(rowguid) from sales.salesorderheaderwhere BillToAddressID = 985 A lovely scalar UDF was being used,  in actuality it was used as part of the WHERE clause but simplified here.  Normally I would use an inline table valued function here, but in this case it wasn't a good option. So this seemed like a pretty good case to use a persisted column to improve performance. The supporting index was already defined as create index idxBill on sales.salesorderheader(BillToAddressID) include (rowguid) and the function code is Create Function udfCleanGuid(@GUID uniqueidentifier)returns varchar(255)with schemabindingasbegin Declare @RetStr varchar(255) Select @RetStr=CAST(@Guid as varchar(255)) Select @RetStr=REPLACE(@Retstr,'-','') return @RetStrend Executing the Select statement produced a plan of : Nothing surprising, a seek to find the data and compute scalar to execute the UDF. Lets get optimizing and remove the UDF with a persisted column Alter table sales.salesorderheaderadd CleanedGuid as dbo.udfCleanGuid(rowguid)PERSISTED A subtle change to the SELECT statement… select BillToAddressID,CleanedGuid from sales.salesorderheaderwhere BillToAddressID = 985 and our new optimized plan looks like… Not a lot different from before!  We are using persisted data on our table, where is the lookup to fetch it ?  It didnt happen,  it was recalculated.  Looking at the properties of the relevant Compute Scalar would confirm this ,  but a more graphic example would be shown in the profiler SP:StatementCompleted event. Why did the lookup happen ? Remember the index definition,  it has included the original guid to avoid the lookup.  The optimizer knows this column will be passed into the UDF, run through its logic and decided that to recalculate is cheaper than the lookup.  That may or may not be the case in actuality,  the optimizer has no idea of the real cost of a scalar udf.  IMO the default cost of a scalar UDF should be seen as a lot higher than it is, since they are invariably higher. Knowing this, how do we avoid the function call?  Dropping the guid from the index is not an option, there may be other code reliant on it.   We are left with only one real option,  add the persisted column into the index. drop index Sales.SalesOrderHeader.idxBillgocreate index idxBill on sales.salesorderheader(BillToAddressID) include (rowguid,cleanedguid) Now if we repeat the statement select BillToAddressID,CleanedGuid from sales.salesorderheaderwhere BillToAddressID = 985 We still have a compute scalar operator, but this time it wasnt used to recalculate the persisted data.  This can be confirmed with profiler again. The takeaway here is,  just because you have persisted data dont automatically assumed that it is being used.

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