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• Using 1920x1200 mode on SyncMaster T260HD in Linux

  - by dagorym

  I just got a Samsung SyncMaster T260HD monitor. It works straight out of the box with Windows but I can't seem to get it to work with Linux, which is my primary OS for day to day work. The computer boots up but when going into graphical mode on Linux the monitor gives me a "Mode not supported" error and doesn't display anything. I booted up windows and, using PowerStrip, grabbed the exact ModeLine that should be used to get the equivalent setting in Linux and added it to my xorg config file but it doesn't seem to help. the ModeLine is: ModeLine "1920x1200" 153.9 1920 1984 2016 2080 1200 1203 1209 1235 +hsync -vsync This is the modeline for the working display settings in windows but it doesn't seem to work in Linux My complete entry in the xorg.conf file for the monitor is Section "Monitor" Identifier "Monitor0" ModelName "SyncMaster" DisplaySize 518 324 HorizSync 30.0 - 81.0 VertRefresh 56.0 - 75.0 Option "dpms" ModeLine "1920x1200" 153.9 1920 1984 2016 2080 1200 1203 1209 1235 +hsync -vsync EndSection I'm running Scientific Linux 5.4 (clone of Redhat Enterprise Linux 5.4) but I've tried booting with a recent Linux Mint Distro as well as Ubuntu 9.04 and had the same problem. Any suggestions on other things I should try or might be missing? If anyone's gotten this to work I'd love to know. Thanks.

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• Querying a CSV file

  - by sheepsimulator

  Does anyone know of a simple tool that will open up a CSV file and let you do basic, SQLesque queries on it? Like a graphical tool of sorts, one that is easy to use. I know I could write a small script to do an import of the CSV into a SQLite database, but since I imagine someone else thought of this before me, I just wanted to inquire if one existed. What's prompting this question is I am getting frustrated with Excel's limited filtering capabilities. Perhaps some other data visualization manipulation tool would provide similar functionality. Free or OSS is preferred, but I'm open to any suggestions. EDIT: I really would prefer some clear tutorials on how to do the below instead of just "make your sheet an ODBC entry" or "write programs using ODBC files", or more ideas on apps to use. Note: I cannot use MS Access. Yet another EDIT: I'm still open for solutions using SQLite. My platform is a semi-ancient Win2k laptop, with a P4 on it. It's quite slow, so a resource-light solution is ideal and would likely get the win.

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• Is SHA-1 secure for password storage?

  - by Tgr

  Some people throw around remarks like "SHA-1 is broken" a lot, so I'm trying to understand what exactly that means. Let's assume I have a database of SHA-1 password hashes, and an attacker whith a state of the art SHA-1 breaking algorithm and a botnet with 100,000 machines gets access to it. (Having control over 100k home computers would mean they can do about 10^15 operations per second.) How much time would they need to find out the password of any one user? find out the password of a given user? find out the password of all users? find a way to log in as one of the users? find a way to log in as a specific user? How does that change if the passwords are salted? Does the method of salting (prefix, postfix, both, or something more complicated like xor-ing) matter? Here is my current understanding, after some googling. Please correct in the answers if I misunderstood something. If there is no salt, a rainbow attack will immediately find all passwords (except extremely long ones). If there is a sufficiently long random salt, the most effective way to find out the passwords is a brute force or dictionary attack. Neither collision nor preimage attacks are any help in finding out the actual password, so cryptographic attacks against SHA-1 are no help here. It doesn't even matter much what algorithm is used - one could even use MD5 or MD4 and the passwords would be just as safe (there is a slight difference because computing a SHA-1 hash is slower). To evaluate how safe "just as safe" is, let's assume that a single sha1 run takes 1000 operations and passwords contain uppercase, lowercase and digits (that is, 60 characters). That means the attacker can test 1015*60*60*24 / 1000 ~= 1017 potential password a day. For a brute force attack, that would mean testing all passwords up to 9 characters in 3 hours, up to 10 characters in a week, up to 11 characters in a year. (It takes 60 times as much for every additional character.) A dictionary attack is much, much faster (even an attacker with a single computer could pull it off in hours), but only finds weak passwords. To log in as a user, the attacker does not need to find out the exact password; it is enough to find a string that results in the same hash. This is called a first preimage attack. As far as I could find, there are no preimage attacks against SHA-1. (A bruteforce attack would take 2160 operations, which means our theoretical attacker would need 1030 years to pull it off. Limits of theoretical possibility are around 260 operations, at which the attack would take a few years.) There are preimage attacks against reduced versions of SHA-1 with negligible effect (for the reduced SHA-1 which uses 44 steps instead of 80, attack time is down from 2160 operations to 2157). There are collision attacks against SHA-1 which are well within theoretical possibility (the best I found brings the time down from 280 to 252), but those are useless against password hashes, even without salting. In short, storing passwords with SHA-1 seems perfectly safe. Did I miss something?

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• AAC 256kbit to MP3 320kbit conversion. I know it's lossy, but how?

  - by Fabian Zeindl

  Has anyone ever transcoded music from a high-quality aac to an mp3 (or vice-versa). The internet is full of people who say this should never be done, but apart from the theoretical standpoint that you can only lose information, does it matter in practise? is the difference perceivable, except on studio-equipment? does the re-encoding actually lose much information? If, p.e., high frequences are chopped away by the initial compression, those frequencies aren't there anymore, so this part of the compression-algorithm won't touch the data during the second compression. Am i wrong?

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• How secure is the encryption used by Microsoft Office 2007?

  - by ericl42

  I've read various articles about Microsoft's Office 2007 encryption and from what I gather 2007 is secure using all default options due to it using AES, and 2000 and 2003 can be configured secure by changing the default algorithm to AES. I was wondering if anyone else has read any other articles or know of any specific vulnerabilities involved with how they implement the encryption. I would like to be able to tell users that they can use this to send semi-sensitive documents as long as they use AES and a strong password. Thanks for the information.

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• Single Sign On for intranet with Apache and Linux MIT Kerberos

  - by Beerdude26

  Greetings, I am looking for a way to do a single sign on to an intranet in the following manner: A Linux user logs on via a graphical frontend (for example, GNOME). He automatically requests a TGT for his username from the MIT Kerberos KDC. Via some way or another, the Apache server (which we'll assume is on the same server as the KDC), is informed that this user has logged in. When the user accesses the intranet, he is automatically granted access to his web applications. I don't think I've seen this kind of functionality while searching the net. I know the following possibilities exist: Using an authentication module such as mod_auth_kerb, a user is presented with a login prompt to enter his username and password, which are then authenticated against the MIT Kerberos server. (I would like this to be automatic.) IIS supports integrated Windows logon via ASP.Net when the user is part of an Active Directory. (I'm looking for the Linux / Apache equivalent.) Any suggestions, criticism and ideas are highly appreciated. This is for a school project to show a proof-of-concept, so every handy piece of information is more than welcome. :)

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• Bad results converting PDF to EPS on Linux

  - by Tim

  I'm having some trouble converting PDFs (created by Adobe Illustrator on a Mac) to EPS. I have tried several things but I am wondering if there is a better option. The following list is ordered by decreasing quality: inkscape --export-area-page --export-eps=out.eps in.pdf using the graphical program Inkscape works best, but is a bit slow; pdftops -eps in.pdf out.eps uses Poppler and works good and is fast; pdf2ps in.pdf out.eps uses ghostscript and works ok for simple documents; convert in.pdf out.eps uses ImageMagick and always rasterizes the image. I haven't tested the following: acroread -toPostScript use acroread (Linux only) Some issues I've found: Transparency is not supported in EPS, but instead of flattening the layers, most programs rasterize the image producing big files and ugly graphs. Inkscape does this best by only rasterizing the unsupported area. Gradients are rendered properly by Inkscape, but Poppler somehow chops up the gradient into many shapes of different colors. Greek symbols are seemingly not supported by Ghostscript and are rasterized (using pdf2ps). What are your experiences for this kind of task? Did I forgot certain programs and/or command line options that improve quality? I found some posts on this, but not a (thorough) comparison of possibilities, please correct me if I'm wrong. Related posts How to convert PDF to EPS? on TeX

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• The best cross platform (portable) arbitrary precision math library

  - by Siu Ching Pong - Asuka Kenji

  Dear ninjas / hackers / wizards, I'm looking for a good arbitrary precision math library in C or C++. Could you please give me some advices / suggestions? The primary requirements: It MUST handle arbitrarily big integers (my primary interest is on integers). In case that you don't know what the word arbitrarily big means, imagine something like 100000! (the factorial of 100000). The precision MUST NOT NEED to be specified during library initialization / object creation. The precision should ONLY be constrained by the available resources of the system. It SHOULD utilize the full power of the platform, and should handle "small" numbers natively. That means on a 64-bit platform, calculating 2^33 + 2^32 should use the available 64-bit CPU instructions. The library SHOULD NOT calculate this in the same way as it does with 2^66 + 2^65 on the same platform. It MUST handle addition (+), subtraction (-), multiplication (*), integer division (/), remainder (%), power (**), increment (++), decrement (--), gcd(), factorial(), and other common integer arithmetic calculations efficiently. Ability to handle functions like sqrt() (square root), log() (logarithm) that do not produce integer results is a plus. Ability to handle symbolic computations is even better. Here are what I found so far: Java's BigInteger and BigDecimal class: I have been using these so far. I have read the source code, but I don't understand the math underneath. It may be based on theories / algorithms that I have never learnt. The built-in integer type or in core libraries of bc / Python / Ruby / Haskell / Lisp / Erlang / OCaml / PHP / some other languages: I have ever used some of these, but I have no idea on which library they are using, or which kind of implementation they are using. What I have already known: Using a char as a decimal digit, and a char* as a decimal string and do calculations on the digits using a for-loop. Using an int (or a long int, or a long long) as a basic "unit" and an array of it as an arbitrary long integer, and do calculations on the elements using a for-loop. Booth's multiplication algorithm What I don't know: Printing the binary array mentioned above in decimal without using naive methods. Example of a naive method: (1) add the bits from the lowest to the highest: 1, 2, 4, 8, 16, 32, ... (2) use a char* string mentioned above to store the intermediate decimal results). What I appreciate: Good comparisons on GMP, MPFR, decNumber (or other libraries that are good in your opinion). Good suggestions on books / articles that I should read. For example, an illustration with figures on how a un-naive arbitrarily long binary to decimal conversion algorithm works is good. Any help. Please DO NOT answer this question if: you think using a double (or a long double, or a long long double) can solve this problem easily. If you do think so, it means that you don't understand the issue under discussion. you have no experience on arbitrary precision mathematics. Thank you in advance! Asuka Kenji

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• [SOLVED] Single Sign On for intranet with Apache and Linux MIT Kerberos

  - by Beerdude26

  EDIT: SOLVED! See my answer below. Greetings, I am looking for a way to do a single sign on to an intranet in the following manner: A Linux user logs on via a graphical frontend (for example, GNOME). He automatically requests a TGT for his username from the MIT Kerberos KDC. Via some way or another, the Apache server (which we'll assume is on the same server as the KDC), is informed that this user has logged in. When the user accesses the intranet, he is automatically granted access to his web applications. I don't think I've seen this kind of functionality while searching the net. I know the following possibilities exist: Using an authentication module such as mod_auth_kerb, a user is presented with a login prompt to enter his username and password, which are then authenticated against the MIT Kerberos server. (I would like this to be automatic.) IIS supports integrated Windows logon via ASP.Net when the user is part of an Active Directory. (I'm looking for the Linux / Apache equivalent.) Any suggestions, criticism and ideas are highly appreciated. This is for a school project to show a proof-of-concept, so every handy piece of information is more than welcome. :)

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• Spotlight actually searching every file on "This Mac"

  - by Cawas

  I know of 2 ways to search for any file in your machine using Finder (some say it's Spotlight) and no Terminal. To prevent answers / comments about Terminal, I consider it either for scripting something or as last resource. It's not practical for lots of usages. For instance, if you want to find something to attach to a mail, or embed in iTunes or any other app, you can just drag n' drop one or many of them. Definitely not practical to do under Terminal. There are many cases of use for any, but the focus here is Graphical User Interface. Well, the 2 ways basically are: Press Cmd + Opt + Spacebar and type in your search. Press the + button, select "System files" and "are included". This is so far my preferred way, but I'm not sure it will go through every file. Open Finder, press Cmd + Shift + G and/or select just one folder. Type in your search and select the folder rather than "This Mac". This will bring files not shown in "This Mac" if you select a folder outside of the default scope. Thing is, none of those is really convenient or have the nice presentation from regular Spotlight, which you get from Cmd + Spacebar and just typing. And, as far as I've heard, the default behavior on Spotlight in Tiger was actually being able to find files anywhere. So, is there any way to make the process significantly simpler? Maybe some tweak, configuration or really good Spotlight alternative? I'd rather keep it simple and tweak Spotlight.

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• SASL + postfixadmin - SMTP authentication with hashed password

  - by mateo

  Hi all, I'm trying to set up the mail server. I have problem with my SMTP authentication using sasl. I'm using postfixadmin to create my mailboxes, the password is in some kind of md5, postfixadmin config.inc.php: $CONF['encrypt'] = 'md5crypt'; $CONF['authlib_default_flavor'] = 'md5raw'; the sasl is configured like that (/etc/postfix/sasl/smtpd.conf): pwcheck_method: auxprop auxprop_plugin: sql sql_engine: mysql mech_list: plain login cram-md5 digest-md5 sql_hostnames: 127.0.0.1 sql_user: postfix sql_passwd: **** sql_database: postfix sql_select: SELECT password FROM mailbox WHERE username = '%u@%r' log_level: 7 If I want to authenticate (let's say from Thunderbird) with my password, I can't. If I use hashed password from MySQL I can authenticate and send an email. So I think the problem is with hash algorithm. Do you know how to set up the SASL (or postfixadmin) to work fine together. I don't want to store my passwords in plain text...

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• How to give ASP.NET access to a private key in a certificate in the certificate store?

  - by thames

  I have an ASP.NET application that accesses private key in a certificate in the certificates store. On Windows Server 2003 I was able to use winhttpcertcfg.exe to give private key access to the NETWORK SERVICE account. How do I give permissions to access a Private Key in a certificate in the certificate store (Local Computer\Personal) on a Windows Server 2008 R2 in an IIS 7.5 website? I've tried giving Full Trust access to "Everyone", "IIS AppPool\DefaultAppPool", "IIS_IUSRS", and everyother security account I could find using the Certificates MMC (Server 2008 R2). However the below code demonstrates that the code does not have access to the Private Key of a certificate that was imported with the private key. The code instead throws and error everytime the private key property is accessed. Default.aspx <%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %> <%@ Import Namespace="System.Security.Cryptography.X509Certificates" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head runat="server"> <title></title> </head> <body> <form id="form1" runat="server"> <div> <asp:Repeater ID="repeater1" runat="server"> <HeaderTemplate> <table> <tr> <td> Cert </td> <td> Public Key </td> <td> Private Key </td> </tr> </HeaderTemplate> <ItemTemplate> <tr> <td> <%#((X509Certificate2)Container.DataItem).GetNameInfo(X509NameType.SimpleName, false) %> </td> <td> <%#((X509Certificate2)Container.DataItem).HasPublicKeyAccess() %> </td> <td> <%#((X509Certificate2)Container.DataItem).HasPrivateKeyAccess() %> </td> </tr> </ItemTemplate> <FooterTemplate> </table></FooterTemplate> </asp:Repeater> </div> </form> </body> </html> Default.aspx.cs using System; using System.Security.Cryptography; using System.Security.Cryptography.X509Certificates; using System.Web.UI; public partial class _Default : Page { public X509Certificate2Collection Certificates; protected void Page_Load(object sender, EventArgs e) { // Local Computer\Personal var store = new X509Store(StoreLocation.LocalMachine); // create and open store for read-only access store.Open(OpenFlags.ReadOnly); Certificates = store.Certificates; repeater1.DataSource = Certificates; repeater1.DataBind(); } } public static class Extensions { public static string HasPublicKeyAccess(this X509Certificate2 cert) { try { AsymmetricAlgorithm algorithm = cert.PublicKey.Key; } catch (Exception ex) { return "No"; } return "Yes"; } public static string HasPrivateKeyAccess(this X509Certificate2 cert) { try { string algorithm = cert.PrivateKey.KeyExchangeAlgorithm; } catch (Exception ex) { return "No"; } return "Yes"; } }

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• Why a 10 years old software still is so slow even today?

  - by Cawas

  I just noted this question due to a game (which happens to be Diablo 2), but the matter of fact is: why is my brand new mac book pro, made in 2009 with latest technology (tho it's the cheapest one) can't rival my computer which used to run this much faster back in 2000? Really, it was much faster on my AMD K6 450 back in those days, and I could even run two clients at same time with no slow down. I've always had the feeling this machine was slow, but this is a very odd way to attest it. Granted, the machine is smaller, runs on wifi and "boots" way faster thanks to sleep mode. But other than that, what have we evolved after all?! I'm pretty sure this shouldn't be graphical card's fault. Sure if I buy latest technology it will run fast, and probably most people here can confirm this and won't even understand my question. But the thing is, all the hardware is supposedly much faster and better than the stuff from 10 years ago. The software and operating system became more complex, but also more well refined. Now I'm trying a piece of software that is actually 10 years old and it's not getting any better results! Why?

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• Ubuntu root privs installation issue

  - by Pam

  I am a fairly new Ubuntu user (and Linux user, for that matter) and I just downloaded a program whose installer was a .sh file. Not thinking, I copied the installer to an /opt subdirectory, thinking that I was going to install the application there: sudo cp ~/Downloads/fooInstaller.sh /opt/someDir I can't remember, but I either had to use sudo because /opt required it, or I just used it without thinking, but in any case, I prefixed with sudo. Once in /opt/someDir, I executed the installer again, using sudo: sudo sh fooInstaller.sh The terminal went crazy, and a few seconds later, a graphical install wizard popped up that guided me through the rest of the process. At the end of the wizard I was prompted to launch the program, and I did, and everything was great. Until... I closed the program, and attempted to add it to my Ubuntu "panel" (the icon panel at the top of the screen). The program was installed to /usr/local/foo/theProgram, and so I specified that URL as the command in the custom app launcher. When I open the program through the panel/launcher (at the top of the screen), the program doesn't load or operate correctly. I get a lot of error messages complaining about being denied permissions. I'm assuming that this is a "superuser/installation/privs" issue, and not a problem with the application (hence this post at superuser.com instead of the application's forums), because when I launch the program from the terminal with sudo, it opens and executes perfectly fine, just like it did the first time around after the install wizard finished. I realize I'm probably going to have to uninstall the program completely, and re-install it differently. Finally, my question: After uninstalling, can I avoid all these issue by just running the installer (sh fooInstaller.sh) right out of my Downloads directory, sans the sudo prefix? If not, how do I get the program to install without root privs so that I can add it to my panel/launcher and get it executing correctly? Sorry for the long post but I didn't want to omit any details because, as I'm sure you can tell, I'm not really sure I know what I'm doing. Thanks for any help here!

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• Corrupted .WAR file after transfer from 32-64 bit Windows Server to Desktop or vice versa

  - by Albert Widjaja

  Hi All, Does anyone experience this problem of corrupted .WAR file after it has been copied over the network share ? this is .WAR file (Web Archive) the J2EE application file (.WAR file is compressed with the same zip algorithm i think ?) Scenario 1: Windows Server 2008 x64 transfer into Windows XP using RDP client (Local Devices and Resources) Scenario 2: Windows XP 32 bit transfer into Windows Server 2003 x64 using shared network drive (port 445 SMB ?) for both of the scenario it always failed / corrupted (the source code seems to be duplicated at the end of line when you open up in the Eclipse / Java IDE). but when in both scenario i compressed the file into .ZIP file everything is OK. can anyone explains why this problem happens ? Thanks, Albert

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• Messed up USB stick doesn't show in blkid

  - by Felix

  I was playing around with a USB stick (booting archlinux with qemu off of it and trying to perform an installation on the same stick at the same time -- brave, I know, but I was just messing around). Now, after failing to boot and install at the same time, it seems I have sort of messed up my stick. What I think happened is that I used cfdisk to wipe everything on it and create one big partition, but formatting it then failed, so now there's a big partition with no filesystem. Just to make it clear: I'm not worried for my stick, I know I can recover it at any point. What I find intriguing is that after plugging the stick into my computer (using Ubuntu), there's no (terminal) way to find out what block device (/dev/sdx) it has associated. The only way I could determine that was with GParted: But blkid shows the following: /dev/sda1: UUID="12F695CFF695B387" LABEL="System Reserved" TYPE="ntfs" /dev/sda2: UUID="A0BAA6EABAA6BC62" TYPE="ntfs" /dev/sdb1: UUID="546aec8b-9ad6-4571-b07a-adba63e25820" TYPE="ext4" /dev/sdb2: UUID="2a8b82d8-6c6e-4053-a446-bab970d93d7c" TYPE="swap" /dev/sdb3: UUID="7cbede7d-c930-4e59-9d1b-01f2d79bd092" TYPE="ext4" No trace of /dev/sdc. My question is: if I didn't have a graphical interface (to use GParted), how would I have known which block device is my stick?

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• Creating hard drive backup images efficiently

  - by Arrieta

  We are in the process of pruning our directories to recuperate some disk space. The 'algorithm' for the pruning/backup process consists of a list of directories and, for each one of them, a set of rules, e.g. 'compress *.bin', 'move *.blah', 'delete *.crap', 'leave *.important'; these rules change from directory to directory but are well known. The compressed and moved files are stored in a temporary file system, burned onto a blue ray, tested within the blue ray, and, finally, deleted from their original locations. I am doing this in Python (basically a walk statement with a dictionary with the rules for each extension in each folder). Do you recommend a better methodology for pruning file systems? How do you do it? We run on Linux.

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• Incremental PCA

  - by smichak

  Hi, Lately, I've been looking into an implementation of an incremental PCA algorithm in python - I couldn't find something that would meet my needs so I did some reading and implemented an algorithm I found in some paper. Here is the module's code - the relevant paper on which it is based is mentioned in the module's documentation. I would appreciate any feedback from people who are interested in this. Micha #!/usr/bin/env python """ Incremental PCA calculation module. Based on P.Hall, D. Marshall and R. Martin "Incremental Eigenalysis for Classification" which appeared in British Machine Vision Conference, volume 1, pages 286-295, September 1998. Principal components are updated sequentially as new observations are introduced. Each new observation (x) is projected on the eigenspace spanned by the current principal components (U) and the residual vector (r = x - U(U.T*x)) is used as a new principal component (U' = [U r]). The new principal components are then rotated by a rotation matrix (R) whose columns are the eigenvectors of the transformed covariance matrix (D=U'.T*C*U) to yield p + 1 principal components. From those, only the first p are selected. """ __author__ = "Micha Kalfon" import numpy as np _ZERO_THRESHOLD = 1e-9 # Everything below this is zero class IPCA(object): """Incremental PCA calculation object. General Parameters: m - Number of variables per observation n - Number of observations p - Dimension to which the data should be reduced """ def __init__(self, m, p): """Creates an incremental PCA object for m-dimensional observations in order to reduce them to a p-dimensional subspace. @param m: Number of variables per observation. @param p: Number of principle components. @return: An IPCA object. """ self._m = float(m) self._n = 0.0 self._p = float(p) self._mean = np.matrix(np.zeros((m , 1), dtype=np.float64)) self._covariance = np.matrix(np.zeros((m, m), dtype=np.float64)) self._eigenvectors = np.matrix(np.zeros((m, p), dtype=np.float64)) self._eigenvalues = np.matrix(np.zeros((1, p), dtype=np.float64)) def update(self, x): """Updates with a new observation vector x. @param x: Next observation as a column vector (m x 1). """ m = self._m n = self._n p = self._p mean = self._mean C = self._covariance U = self._eigenvectors E = self._eigenvalues if type(x) is not np.matrix or x.shape != (m, 1): raise TypeError('Input is not a matrix (%d, 1)' % int(m)) # Update covariance matrix and mean vector and centralize input around # new mean oldmean = mean mean = (n*mean + x) / (n + 1.0) C = (n*C + x*x.T + n*oldmean*oldmean.T - (n+1)*mean*mean.T) / (n + 1.0) x -= mean # Project new input on current p-dimensional subspace and calculate # the normalized residual vector g = U.T*x r = x - (U*g) r = (r / np.linalg.norm(r)) if not _is_zero(r) else np.zeros_like(r) # Extend the transformation matrix with the residual vector and find # the rotation matrix by solving the eigenproblem DR=RE U = np.concatenate((U, r), 1) D = U.T*C*U (E, R) = np.linalg.eigh(D) # Sort eigenvalues and eigenvectors from largest to smallest to get the # rotation matrix R sorter = list(reversed(E.argsort(0))) E = E[sorter] R = R[:,sorter] # Apply the rotation matrix U = U*R # Select only p largest eigenvectors and values and update state self._n += 1.0 self._mean = mean self._covariance = C self._eigenvectors = U[:, 0:p] self._eigenvalues = E[0:p] @property def components(self): """Returns a matrix with the current principal components as columns. """ return self._eigenvectors @property def variances(self): """Returns a list with the appropriate variance along each principal component. """ return self._eigenvalues def _is_zero(x): """Return a boolean indicating whether the given vector is a zero vector up to a threshold. """ return np.fabs(x).min() < _ZERO_THRESHOLD if __name__ == '__main__': import sys def pca_svd(X): X = X - X.mean(0).repeat(X.shape[0], 0) [_, _, V] = np.linalg.svd(X) return V N = 1000 obs = np.matrix([np.random.normal(size=10) for _ in xrange(N)]) V = pca_svd(obs) print V[0:2] pca = IPCA(obs.shape[1], 2) for i in xrange(obs.shape[0]): x = obs[i,:].transpose() pca.update(x) U = pca.components print U

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• x display problems in centos 5.5

  - by John Ruiz

  I have a Dell E510 desktop with a geForce 7200 instead of the ATI x600 it came with. I have attempted to install CentOS 5.4 x86_64 (DVD), CentOS 5.5 (net install), and CentOS 5.5 x86_64 (DVD). Gnome desktop. All of these run into the same issue. When I put the DVD into the machine and reboot, the installer begins and I select "graphical install". I see text that say anaconda is starting, and then my screen goes nuts. It's not black, but rather a screen full of diagonal stripes or multiple colors. So I attempted to do a text install of CentOS 5.5 (DVD) and got it installed. When I booted for the first time, I logged into the virtual console and started X (startx). The desktop came up and it already had the display properties GUI up. I changed it from 800x600 to 1680x1050, saw that there were updates available, installed them, and then rebooted. When I start X from the virtual console this time, I get exactly the same display problem as I described before. Does anyone know what might be causing this and what I can do about it? edit: I should also mention that I'm capable of installing Windows 7 and Ubuntu 10.04 onto this machine with absolutely no issues at all.

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• Logmein does not work at home?

  - by Littlet-ENG

  I've been using logmein successfully for may situations and have had very good success. Our company has an Log me in Pro account. I have used this to share my desktop with customers. At work, I have had no problem with my laptop. At home, one program (solid-works) that I need to share with my customers, will not display the active screen. I spent 45 min on the phone with both the software for the cad system and logmein support with not help. I need help in narrowing down what the problem is on my computer. The support guys at Solid-works got another remote software to work, so its not the program. I can get the logmein to work at the office so its not the settings of the logmein pro account. The LMI people say its a setting on my computer.? -internet is fast enough at home -can't narrow down the problem -changed graphical settings and that didn't work. Any Suggestions?

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• Reducing video mode switching during Linux boot

  - by Zack

  When I boot up my desktop computer, which only has Linux on it, the video mode and/or console font gets switched four times: When GRUB starts, it switches from 80x25 text to a graphical mode so it can draw a pretty background behind its menu; GRUB then goes back to 80x25 text after I pick something from the menu; When the KMS driver for my video card loads, it switches to a much higher-resolution text mode (I don't know if this is a hardware text mode or not); Finally X starts and it goes graphics and stays that way. I think this last switch does not change the resolution of the video mode, only the graphicalness. I'd like to get rid of as many of these mode switches as possible. Ideally, when GRUB takes over from the BIOS it would go directly to the same high-resolution text mode that the KMS driver selects, and the display would stay in that mode till X starts and brings up graphics. I am under the impression that this is possible by mucking with the kernel command line and/or the GRUB console module load parameters, but I don't know the details. GRUB 1.98+20100706, kernel 2.6.32.15 using Nouveau video drivers. Distro is Debian unstable. Please no answers that involve recompiling anything or cobbling together bleeding-edge kernel/driver combinations, I don't care enough about this to go to that much trouble. EDIT: Tobu suggests setting GRUB_GFXMODE to the full pixel resolution of the monitor, and GRUB_GFXPAYLOAD_LINUX=keep to avoid the mode switch after the menu goes away. This does part of what I want, but winds up being worse overall. There's no mode switch after the menu, but there's still a painfully-slow screen repaint (I should probably just give up on GRUB's gfxmode, it's waaaay too slow at 1920x1200). More seriously, there's now a double mode switch when nouveaufb loads, along with fun-looking error messages in dmesg [ 5.923798] [drm] nouveau 0000:02:00.0: allocated 1920x1200 fb: 0x40250000, bo ffff8801ba5f4600 [ 5.923802] fb: conflicting fb hw usage nouveaufb vs EFI VGA - removing generic driver [ 5.923821] [drm] nouveau 0000:02:00.0: PFIFO_INTR 0x00000010 - Ch 1 ("PFIFO_INTR" message repeats 400+ times) [ 5.925609] Console: switching to colour dummy device 80x25 [ 5.925802] Console: switching to colour frame buffer device 240x75

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• Windows7 shows a drive as full in summary but files, including backup folder, shown on drive are ver

  - by Rob

  I have a drive partitioned so it is seen by Windows as 2 drives: C:\ and D:\ Windows7 shows D:\ as full up in the graphical summary in 'My Computer' summary of all the drives, e.g. the bar graph indicates full and nearly all of the drive's capacity, 108Gb, is full. So I go into the D:\ drive to look at the files, I see several folders. I select them all and the right click menu Properties to count their size, expecting the value to be about the same as what Windows reports in the summary, i.e. nearly 108Gb. But the properties shows the files are very small, Kbs and Mbs, nowhere near 108Gbs. One of the folders is a backup, but its size is very small. I've checked the folder options to show all system files and hidden files too - and counted these in the properties. Something invisible is holding the space. What is happening here? I'm afraid to delete anything if it removes valuable backups. Have I got huge backups here? Why can't I see them? How do I see them?

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• Turn off monitor (energy saving) while in text console mode (in Linux)

  - by Denilson Sá

  How to configure Linux text console to automatically turn of the monitor after some time? And by "text console" I mean that thing that you get on ctrl+alt+F[1-6], which is what you get whenever X11 is not running. And, no, I'm not using any framebuffer console (it's a plain, good and old 80x25 text-mode). Many years ago, I was using Slackware Linux, and it used to boot up in text-mode. Then you would manually run startx after the login. Anyway, the main login "screen" was the plain text-mode console, and I remember that the monitor used to turn off (energy saving mode, indicated by a blinking LED) after some time. Now I'm using Gentoo, and I have a similar setup. The machine boots up in text-mode, and only rarely I need to run startx. I say this because this is mostly my personal Linux server, and there is no need to keep X11 running all the time. (which means: I don't want to use GDM/KDM or any other graphical login screen) But now, in this Gentoo text-mode console, the screen goes black after a while, but the monitor does not enter any energy-saving mode (the LED is always lit). Yes, I've waited long enough to verify this. Thus, my question is: how can I configure my current system to behave like the old one? In other words, how to make the text console trigger energy-saving mode of the monitor? (maybe I should (cross-)post this question to http://unix.stackexchange.com/ )

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• Home Server: cpu 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 VM (or compute instance) management and what would best suit my needs. (I have another question related to the storage management). My use cases are: A backup server: rsync and other services running. A personal cloud server: a kind of owned dropbox system, à la ownCloud. " users foreseen. A media server: streaming videos and displaying photos. Here my environement and wishes: Server: HP Proliant MicroServer with 8 GB RAM (AMD Turion dual core with AMD-V technology) 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 2-3 VMs foreseen: backup server, owncloud server and media server (optional). Those are only servers, so no graphical console needed (I don't need VirtualBox) By VM I mean a virtualised environment like KVM, Xen, etc. or a compute instance like with OpenStack storage should be "virtualised/cloudified" see my other question. VM should be able to be migrated to another server in the future if performance cannot be fullfilled anymore by the current server It does not matter if installation of such setup is complicated as long as management tools allow for easy maintenance I don't have Windows at home, so solution should be Linux friendly and would be nice to be web based. But native apps are OK too. System should be easy to enhance: by adding a new server to migate some of the VMs to it. So it's really a kind of private cloud on which I could run some Linux OS. 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. So Xen, KVM, VitualBox or OpenStack? What would you recommend?

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• HAProxy NGInx SSL setup

  - by Niclas

  I've been looking around different setups for a server cluster supporting SSL and I would like to benchmark my idea with you. Requirements: All servers in the cluster should be under the same full domain name. (http and https) Routing to subsystems is done on URI matching in HA proxy. All URIs have support for SSL support. Wish: Centralizing routing rules ---<----http-----<-- | | Inet -->HA--+---https--->NGInx_SSL_1..N | | +---http---> Apache_1..M | +---http---> NodeJS Idea: Configure HA to route all SSL traffic (mode=tcp,algorithm=Source) to an NGInx cluster turning https traffic into http. Re-pass the http traffic from NGInx to the HA for normal load-balancing which performs load balancing based on HA config. My question is simply: Is this the best way to to configure based on requirements above?

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