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  • Slow performance by PHP directory operations on virtual machine (Ubuntu libvirt)

    - by thonixx
    Some days ago I installed an Ubuntu server and two running virtual machines with libvirt. Everything works fine except one performance problem. Everytime when I call a PHP script with directory operations the operations are very slow and not performant. Here is an example: http://zother.white-tiger.ch/ And here you see an example without a directory operation and how fast it is: http://michaeltanner.ch/ It's all on the same virtual server. The virtual machine uses 6 cores (8 are available) and 7500 megabytes RAM (8 Gigabyte are available). The disk image format is qcow2. How can I improve the performance?

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  • Offloading Cable Modem operations to Router

    - by Matt
    I may be crazy here, but I seem to recall a conversation in the past stating that it was possible to offload some of the operations taken by one's cable modem to one's router. The logic was that since the cable modem is often equipped with a cheaper processor as it is supplied by your provider, that it often chokes even crashes when you start a torrent or something else with a lot of connections. I seem to recall that some routers offered the ability to take some of the modem's operations. Is this possible or have I imagined the whole thing? I ask because my modem seems to have many issues when I start torrents.

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  • Node.js server crashes , Database operations halfway?

    - by Ranadeep
    I have a node.js app with mongodb backend going to production in a week and i have few doubts on how to handle app crashes and restart . Say i have a simple route /followUser in which i have 2 database operations /followUser ----->Update User1 Document.followers = User2 ----->Update User2 Document.followers = User1 ----->Some other mongodb(via mongoose)operation What happens if there is a server crash(due to power failure or maybe the remote mongodb server is down ) like this scenario : ----->Update User1 Document.followers = User2 SERVER CRASHED , FOREVER RESTARTS NODE What happens to these operations below ? The system is now in inconsistent state and i may have error everytime i ask for User2 followers ----->Update User2 Document.followers = User1 ----->Some other mongodb(via mongoose)operation Also please recommend good logging and restart/monitor modules for apps running in linux

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  • All Tasks..Advanced Operations option missing from Certificaces MMC Snap-In

    - by JohnFx
    I am trying to follow the instructions in this article to create a custom certificate to support SSL on a web server. I'm stick on the following step: Click on Personal – All Tasks – Advanced Operations – Create Custom request The problem is that on the web server (Windows Server 2003 R2) I don't have an "Advanced Operations" option under "All Tasks". I do on my desktop machine (Windows 7), but not on the server. All the documentation I can find indicates that it should be available on WS-2003-R2, but it just isn't. Note: I'm going through this manual process because I need to specify a alternate host names in the CSR, which you can't do through the IIS 6.0 console certificate managment functionality. Any suggestions for how to make this option show up?

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  • Order of operations in C. ++ vs |=, which occurs first?

    - by chris
    I have the following code that I'm reading through: if( (i%2) == 0 ){ *d = ((b & 0x0F) << 4); } else{ *d++ |= (b & 0x0F); }; I'm looking specifically at the else statement and wondering in what order this occurs? I don't have a regular C compiler, so I can't test this. When we are performing *d++ |= (b & 0x0F);, what order does this occur in?

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  • Security for university research lab systems

    - by ank
    Being responsible for security in a university computer science department is no fun at all. And I explain: It is often the case that I get a request for installation of new hw systems or software systems that are really so experimental that I would not dare put them even in the DMZ. If I can avoid it and force an installation in a restricted inside VLAN that is fine but occasionally I get requests that need access to the outside world. And actually it makes sense to have such systems have access to the world for testing purposes. Here is the latest request: A newly developed system that uses SIP is in the final stages of development. This system will enable communication with outside users (that is its purpose and the research proposal), actually hospital patients not so well aware of technology. So it makes sense to open it to the rest of the world. What I am looking for is anyone who has experience with dealing with such highly experimental systems that need wide outside network access. How do you secure the rest of the network and systems from this security nightmare without hindering research? Is placement in the DMZ enough? Any extra precautions? Any other options, methodologies?

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  • Get Your PhD in Googling [Slideshow]

    - by Asian Angel
    Think you know how to search Google with the best of them? Then put your knowledge to the test with this awesome slideshow where you can verify what you know and perhaps learn something new along the way. Note: The slideshow contains a total of 22 slides. Go Directly to the Slideshow Your PhD in Googling – Blog Post [via Geeks are Sexy] HTG Explains: What Is Two-Factor Authentication and Should I Be Using It? HTG Explains: What Is Windows RT and What Does It Mean To Me? HTG Explains: How Windows 8′s Secure Boot Feature Works & What It Means for Linux

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  • Would this violate any copyright issues?

    - by Farhad
    I am currently publishing a paper on skin detection. However, I need to find the appropriate histogram bin size for each colorspace. I recently came upon a paper that published what it found to be the ideal bin size. The paper can be found at: http://www.inf.pucrs.br/~pinho/CG/Trabalhos/DetectaPele/Artigos/OPTIMUM%20COLOR%20SPACES%20FOR%20SKIN%20DETECTION.pdf. I am specifically talking about Table 1. If I cite the source, would it be okay for me to use data from the table? Note that I cannot contact the author of the paper.

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  • Estimating cost of labor for a controlled experiment

    - by Lorin Hochstein
    Let's say you are a software engineering researcher and you are designing a controlled experiment to compare two software technologies or techniques (e.g., TDD vs. non-TDD, Python vs. Go) with respect to some qualities of interest (e.g., quality of resulting code, programmer productivity). According to your study design, participants will work alone to implement a non-trivial software system. You estimate it should take about six months for a single programmer to complete the task. You also estimate via power analysis that you will need around sixty study participants to obtain statistically significant results, assuming the technologies actually do yield different outcomes. To maximize external validity, you want to use professional programmers as study participants. Unfortunately, it isn't possible to find professional programmers who can volunteer for several months to work full-time on implementing a software system. You decide to go the simplest route and contract with a large IT consulting firm to obtain access to programmers to participate in the study. What is a reasonable estimate of the cost range, per person-month, for the programming labor? Assume you are constrained to work with a U.S.-based firm, but it doesn't matter where in the U.S. the firm itself or the programmers or located. Note: I'm looking for a reasonable order-of-magnitude range suitable for back-of-the-envelope calculations so that when people say "Why doesn't somebody just do a study to measure X", I can say, "Because running that study properly would cost $Y", and have a reasonable argument for the value of $Y.

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  • What are some great papers/publications relating to game programming?

    - by Archagon
    What are some of your favorite papers and publications that closely relate to game programming? I'm particularly looking for examples that are well-written and illustrated, and/or have had a profound influence on the industry. (Here's one example: in this GDC talk, Bungie's David Aldridge mentions that a paper called "The TRIBES Engine Networking Model" was the starting point for Halo's network code.)

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  • How common is it to submit papers to journals or conferences outside of academia?

    - by Furry
    I worked in academia a few years, but more on the D-side of R&D. The race for papers never appealed to me and I'm a practical not theoretical type, but I do like reading papers on certain topics (e.g. Google Papers, NLP, FB papers, ...) a lot. How common is it that normally working developers submit papers to conferences or even journals? It seems to be somewhat common in certain companies (it's not common or encouraged in mine). Do journals or conferences even take papers by an academic nobody (BSc) under consideration? I ask, because I have a few rough ideas and I would just like to bring them into form, one way or the other. Bonus question: Is there a list of CS (in the widest sense) conferences/journals with short descriptions? PS (Four out of five researchers I met published quite some fluffy stuff for my taste. I am no expert, but those people told me sometimes themselves, that the implementation does not matter, just the idea and the presentation. I always wondered about that. I probably could write about ideas all day long (not instantly but with a bit of preparation), but the implementation and the practical part is the really hard part, that academia just does not like to be concerned with. Also many papers actually scream: I was written so the publication list of my author gets longer - which is a waste of time for everyone, and often a waste of tax money, too. When I think of CS-ish papers, I think of running implementations or actual data, like e.g. Google's Map Reduce, Serving Large-scale Batch Computed Data with Project Voldemort or the like.)

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  • A New Experience

    - by Calum
    So a couple of weeks ago, after a fraction over 12 years, I bade farewell to the Solaris Desktop team to join the team whose blog you're reading now: Oracle's Systems Experience Design team, known internally as sxDesign, which has a wider but still largely Solaris-focused usability remit.1 There's been a good deal of overlap and collaboration between the two teams over the years anyway, so it's not exactly a step into the unknown. The elders among you might remember a GNOME 1.4 usability study I presented at GUADEC in 2001, for example, which was primarily the handiwork of a previous incarnation of sxDesign… I pretty much just turned up at the end to steal the glory for the Desktop team. In your face, people I'm going to be working with now!2 1 A move I was first approached about making in about 2003, I think… who says I'm rubbish at making snap decisions? 2 I'm not really. They all left years ago.

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  • Choosing a subject to create a site for

    - by Daniel
    For 6 years I'm working as web developer and I would like to finally create my own site. I thought I have everything needed: programming and administration skills, found a good designer, own servers and understanding how to operate site. But I've missed very important (or the most important) point: how do I find a subject for my site? My hobby and my work are the same: IT, but I don't want to create just another tech blog or news aggregator, I want something different. First I thought things like Google Trends or Google top 1000 could help, but I've got lost in thousands of options I can't see them all (I actually can, but it'll take at least a couple of month). So my question is: how did you start? Where did you get the idea?

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  • Does heavy JavaScript use adversely impact Googleability?

    - by A T
    I've been developing the client-side for my web-app in JavaScript. The JavaScript can communicate with my server over REST (HTTP)[JSON, XML, CSV] or RPC (XML, JSON). I'm writing writing this decoupled client in order to use the same code for both my main website and my PhoneGap mobile apps. However recently I've been worrying that writing the website with almost no static content would prevent search-engines (like Google) from indexing my web-page. I was taught about this restriction about 4 years ago, which is why I'm asking here, to see if this restriction is still in-place. Does heavy JavaScript use adversely impact Googleability?

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  • Adjusting server-side tickrate dynamically

    - by Stuart Blackler
    I know nothing of game development/this site, so I apologise if this is completely foobar. Today I experimented with building a small game loop for a network game (think MW3, CSGO etc). I was wondering why they do not build in automatic rate adjustment based on server performance? Would it affect the client that much if the client knew this frame is based on this tickrate? Has anyone attempted this before? Here is what my noobish C++ brain came up with earlier. It will improve the tickrate if it has been stable for x ticks. If it "lags", the tickrate will be reduced down by y amount: // GameEngine.cpp : Defines the entry point for the console application. // #ifdef WIN32 #include <Windows.h> #else #include <sys/time.h> #include <ctime> #endif #include<iostream> #include <dos.h> #include "stdafx.h" using namespace std; UINT64 GetTimeInMs() { #ifdef WIN32 /* Windows */ FILETIME ft; LARGE_INTEGER li; /* Get the amount of 100 nano seconds intervals elapsed since January 1, 1601 (UTC) and copy it * to a LARGE_INTEGER structure. */ GetSystemTimeAsFileTime(&ft); li.LowPart = ft.dwLowDateTime; li.HighPart = ft.dwHighDateTime; UINT64 ret = li.QuadPart; ret -= 116444736000000000LL; /* Convert from file time to UNIX epoch time. */ ret /= 10000; /* From 100 nano seconds (10^-7) to 1 millisecond (10^-3) intervals */ return ret; #else /* Linux */ struct timeval tv; gettimeofday(&tv, NULL); uint64 ret = tv.tv_usec; /* Convert from micro seconds (10^-6) to milliseconds (10^-3) */ ret /= 1000; /* Adds the seconds (10^0) after converting them to milliseconds (10^-3) */ ret += (tv.tv_sec * 1000); return ret; #endif } int _tmain(int argc, _TCHAR* argv[]) { int sv_tickrate_max = 1000; // The maximum amount of ticks per second int sv_tickrate_min = 100; // The minimum amount of ticks per second int sv_tickrate_adjust = 10; // How much to de/increment the tickrate by int sv_tickrate_stable_before_increment = 1000; // How many stable ticks before we increase the tickrate again int sys_tickrate_current = sv_tickrate_max; // Always start at the highest possible tickrate for the best performance int counter_stable_ticks = 0; // How many ticks we have not lagged for UINT64 __startTime = GetTimeInMs(); int ticks = 100000; while(ticks > 0) { int maxTimeInMs = 1000 / sys_tickrate_current; UINT64 _startTime = GetTimeInMs(); // Long code here... cout << "."; UINT64 _timeTaken = GetTimeInMs() - _startTime; if(_timeTaken < maxTimeInMs) { Sleep(maxTimeInMs - _timeTaken); counter_stable_ticks++; if(counter_stable_ticks >= sv_tickrate_stable_before_increment) { // reset the stable # ticks counter counter_stable_ticks = 0; // make sure that we don't go over the maximum tickrate if(sys_tickrate_current + sv_tickrate_adjust <= sv_tickrate_max) { sys_tickrate_current += sv_tickrate_adjust; // let me know in console #DEBUG cout << endl << "Improving tickrate. New tickrate: " << sys_tickrate_current << endl; } } } else if(_timeTaken > maxTimeInMs) { cout << endl; if((sys_tickrate_current - sv_tickrate_adjust) > sv_tickrate_min) { sys_tickrate_current -= sv_tickrate_adjust; } else { if(sys_tickrate_current == sv_tickrate_min) { cout << "Please reduce sv_tickrate_min..." << endl; } else{ sys_tickrate_current = sv_tickrate_min; } } // let me know in console #DEBUG cout << "The server has lag. Reduced tickrate to: " << sys_tickrate_current << endl; } ticks--; } UINT64 __timeTaken = GetTimeInMs() - __startTime; cout << endl << endl << "Total time in ms: " << __timeTaken; cout << endl << "Ending tickrate: " << sys_tickrate_current; char test; cin >> test; return 0; }

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  • Who are the most influential computer scientists today? [closed]

    - by Banana
    Possible Duplicate: Which individuals are having the greatest impact on software developers today? Computer science has changed dramatically during the last decades, and new fields that recently arose in the scientific community are completely different with respect to classical cs related topics (for example, social network analysis). I'd like to have an overview of the most influential computer scientists in activity, or at least, who have been working during the last 10/15 years, possibly listed according to their specific field of study.

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  • Best practices for Persona development

    - by user12277104
    Over the years, I have created a lot of Personas, I've co-authored a new method for creating them, and I've given talks about best practices for creating your own, so when I saw a call for participation in the OpenPersonas project, I was intrigued. While Jeremy and Steve were calling for persona content, that wasn't something I could contribute -- most of the personas I've created have been proprietary and specific to particular domains of my employers. However, I felt like there were a few things I could contribute: a process, a list of interview questions, and what information good personas should contain. The first item, my process for creating data-driven personas, I've posted as a list of best practices. My next post will be the list of 15 interview questions I use to guide the conversations with people whose data will become the personas. The last thing I'll share is a list of items that need to be part of any good persona artifact -- and if I have time, I'll mock them up in a template or two. 

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  • What is the biggest weakness of students graduating with degrees in Computer Science?

    - by akobre01
    This question is directed more toward employers and graduate student advisors/professors but all opinions are welcome. What do you find is a common weakness of new hires and/or new grad students? Is it entirely variable dependent on the student and his or her university? Is there a particular skill or skillset that you wish new hires/researchers had expertise in and how can we remedey this deficiency? I realize that this question is general and really encapsulates two questions, one more about the weaknesses of new software engineers and one about the weaknesses of new researchers. However, both types of people tend to come from similar courses of study so I'm wondering if there is any overlap. Note: I am not a professor but I'm interested in how best to revise the undergraduate curriculum in CS.

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  • Help deciding on an area of study for a PhD [closed]

    - by ale
    I am going to start a PhD in about 1 year. My undergraduate degree is in computer science and my master's is in artificial intelligence. I want to get ideas about what's going to be hot in say 5 years i.e. what could I spend 3-4 years studying to potentially have expertise that will be applicable to industry and the computing world ? Impossible to answer factually but some ideas and thoughts would be great. I have narrowed my ideas down to AI (yes, even more AI) and information security. AI seems to becoming popular again but security is always a going to be useful. From a career point of view, if I were to stay working in software development then this might actually be the best move but I've always wanted to do a PhD! Many thanks :).

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  • The best programmer is N times more effective than the worst? Who Cares?

    - by StevenWilkins
    There is a latent belief in programming that the best programmer is N times more effective than the worst. Where N is usually between 10 and 100. Here are some examples: http://www.devtopics.com/programmer-productivity-the-tenfinity-factor/ http://www.joelonsoftware.com/articles/HighNotes.html http://haacked.com/archive/2007/06/25/understanding-productivity-differences-between-developers.aspx There is some debate as to whether or not it's been proven: http://morendil.github.com/folklore.html I'm confident in the accuracy of these statements: The best salesmen in the world are probably 10-100 times better than the worst The best drivers in the world are probably 10-100 times better than the worst The best soccer players in the world are probably 10-100 times better than the worst The best CEOs in the world are probably 10-100 times better than the worst In some cases, I'm sure the difference is greater. In fact, you could probably say that The best [insert any skilled profession here] in the world are probably 10-100 times better than the worst We don't know what N is for the rest of these professions, so why concern ourselves with what the actual number is for programming? Can we not just say that the number is large enough so that it's very important to hire the best people and move on already?

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  • How to maintain Motivation and enthusiasm once you have figured out the solution needed

    - by Pocket_Pie
    I am currently undertaking a software project on my own time. When I first got the project I put in many hours working out how to do the "tricky" parts of the solution. I spent many hours googling and reading up on classes available on MSDN that I could use for the project. I was madly excited and passionate about doing this work. However once, I got a working samples of how I could get around the "tricky" parts and got to the part where all that I needed to do was "grunt" work to finish the project, I lost all interest and desire to work on he project. Suddenly instead of looking forward to sitting down and working on this project it became a chore and a major hassle to motivate myself. I am now fast approaching the deadline and I am getting the work done now, but it is under very high pressure as I have left it almost too close to the deadline! I will manage to get it done but it will involve several all-nighters. (BTW I completely despise doing these all-nighters and would love to eliminate these by maintaining my motivation and working at the project continuously.) So my questions are is this normal? Does everyone else notice such spikes and troughs in their enthusiasm for projects? Anyone more experienced have any advice on how to keep the motivation going? Or am I just not designed to work on a full project lifecycle, should i and people like me being doing an R&D type role where I can do the fun figuring out part of the projects and leave it for someone else to finish the "les interesting/mundane" coding?

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  • networked storage for a research group, 10-100 TB

    - by Marc
    this is related to this post: http://serverfault.com/questions/80854/scalable-24-tb-nas-for-research-department but perhaps a little more general. Background: We're a research lab of around 10 people who do a lot of experiments that involve taking pictures at one of several lab setups and then analyzing it an one of several lab computers. Each experiment may produce 2 or 3 GB of data, and we are generating data at the rate of about 10 TB/year. Right now, we are storing the data on a 6-bay netgear readynas pro, but even with 2 TB drive, this only gives us 10 TB of storage. Also, right now we are not backing up at all. Our short term backup plan is to get a second readynas, put it in a different building and mirror the one drive onto the other. Obviously, this is somewhat non-ideal. Our options: 1) We can pay our university $400/ TB /year for "backed up" online storage. We trust them more than we trust us, but not a whole lot. 2) We can continue to buy small NASs and mirror them between offices. One limit, although stupid, is that we don't have an unlimited number of ethernet jacks. 3) We can try to implement our own data storage solution, which is why I'm asking you guys. One thing to consider is that we're a very transient population and none of us are network administration experts. I will probably be here only another year or so, and graduate students, who are here the longest, have a 5-6 year time scale. So nothing can require expert oversight. Our data transfer rates are low - most of the data will just sit on the server waiting for someone to look at it once or twice - so we don't need a really high speed system. Given these contraints, can someone recommend a fairly low-cost, scalable, more or less turn key shared data storage system with backup in a separate physical location. Does such a thing exist or should we just pay the university to take care of it for us? As a second question, our professor just got tenure and is putting together a budget. Here the goal is to ask for as much as you can and hope you get a fraction of it. So the same question, minus the low-cost. Without budget constraints, can you recommend a scalable turn-key backed up storage system. Thanks

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  • system center operations manager (SCOM) role combinations

    - by KAPes
    We are evaluating system center operations manager 2007 R2 product, and would like to know what all roles can be combined onto single server. Like root management server and reporting servers can be on one box or not? my environment is like 450 servers mostly Exchange and Domain Controllers plus few OCS servers.

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