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  • Fuzzing for Security

    - by Sylvain Duloutre
    Yesterday, I attended an internal workshop about ethical hacking. Hacking skills like fuzzing can be used to quantitatively assess and measure security threats in software.  Fuzzing is a software testing technique used to discover coding errors and security loopholes in software, operating systems or networks by injecting massive amounts of random data, called fuzz, to the system in an attempt to make it crash. If the program contains a vulnerability that can leads to an exception, crash or server error (in the case of web apps), it can be determined that a vulnerability has been discovered.A fuzzer is a program that generates and injects random (and in general faulty) input to an application. Its main purpose is to make things easier and automated.There are typically two methods for producing fuzz data that is sent to a target, Generation or Mutation. Generational fuzzers are capable of building the data being sent based on a data model provided by the fuzzer creator. Sometimes this is simple and dumb as sending random bytes, swapping bytes or much smarter by knowing good values and combining them in interesting ways.Mutation on the other hand starts out with a known good "template" which is then modified. However, nothing that is not present in the "template" or "seed" will be produced.Generally fuzzers are good at finding buffer overflow, DoS, SQL Injection, Format String bugs etc. They do a poor job at finding vulnerabilites related to information disclosure, encryption flaws and any other vulnerability that does not cause the program to crash.  Fuzzing is simple and offers a high benefit-to-cost ratio but does not replace other proven testing techniques.What is your computer doing over the week-end ?

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  • XNA calculate normals for linesegment

    - by Gerhman
    I am quite new to 3D graphical programming and thus far only understand that normal somehow define the direction in which a vertex faces and therefore the direction in which light is reflected. I have now idea how they are calculated though, only that they are defined by a Vector3. For a visualizer that I am creating I am importing a bunch of coordinate which represent layer upon layer of line segments. At the moment I am only using a vertex buffer and adding the start and end point of each line and then rendering a linelist. The thing is now that I need to calculate the normal for the vertices of these line segments so that I can get some realistic lighting. I have no idea how to calculate these normal but I know they all face sideways and not up or down. To calculate them all I have are the start and end positions of each line segment. The below image is a representation of what I think I need to do in the case of an example layer: The red arrows represent the normal that should be calculates, the blue text represent the coordinates of the vertices and the green numbers represent their indices. I would greatly appreciate it if someone could please explain to me how I should calculate these normal.

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  • SYN flooding still a threat to servers?

    - by Rob
    Well recently I've been reading about different Denial of Service methods. One method that kind of stuck out was SYN flooding. I'm a member of some not-so-nice forums, and someone was selling a python script that would DoS a server using SYN packets with a spoofed IP address. However, if you sent a SYN packet to a server, with a spoofed IP address, the target server would return the SYN/ACK packet to the host that was spoofed. In which case, wouldn't the spoofed host return an RST packet, thus negating the 75 second long-wait, and ultimately failing in its attempt to DoS the server?

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  • if/else statements or exceptions

    - by Thaven
    I don't know, that this question fit better on this board, or stackoverflow, but because my question is connected rather to practices, that some specified problem. So, consider an object that does something. And this something can (but should not!) can go wrong. So, this situation can be resolved in two way: first, with exceptions: DoSomethingClass exampleObject = new DoSomethingClass(); try { exampleObject.DoSomething(); } catch (ThisCanGoWrongException ex) { [...] } And second, with if statement: DoSomethingClass exampleObject = new DoSomethingClass(); if(!exampleObject.DoSomething()) { [...] } Second case in more sophisticated way: DoSomethingClass exampleObject = new DoSomethingClass(); ErrorHandler error = exampleObject.DoSomething(); if (error.HasError) { if(error.ErrorType == ErrorType.DivideByPotato) { [...] } } which way is better? In one hand, I heard that exception should be used only for real unexpected situations, and if programist know, that something may happen, he should used if/else. In second hand, Robert C. Martin in his book Clean Code Wrote, that exception are far more object oriented, and more simple to keep clean.

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  • Automatic LaTex document generation from Excel spreadsheet

    - by Bowler
    I have some data in an excel file from which I have to generate a report. I repeat this task fairly regularly and am looking to automate it. I have a LaTeX project into which I usually just copy data by hand, export the necessary worksheets as pdfs and add them to my LaTeX project and compile with pdflatex. It has occured to me that there must be a way to automate this process. Is there an efficient way to export the data from excel and into a LaTeX project, possibly a vba script in excel could run the process? Also, it doesn't have to be LaTeX, I'm not all that experienced with MS office's more advanced features is there some way akin to a mail merge that I could achieve this with? In some ways this might be better in case I have to pass the work on to someone who doesn't know LaTeX. Thanks.

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  • What tools should every programmer know?

    - by acidzombie24
    What are some tools every programmer know about? Some examples i thought were Source control. (No explanation needed) Profiler. Many could go without but its good to know how to use one when the occasion arise What else? I was thinking a bug report software but i havent used one so i wasnt sure. Should programmers know how to use TRAC? I remember in the past a person telling me if i was making a shared library i should know (Some Name) which generates docs from the source (in that case C++). What was that called and what else should i know about? -edit- what about team management software? any software you could not live without in a specific project would be a good mention. I'll also mention i use VMs frequently during the prototype or end phase to see if there are any issues on a clean XP or linux distro and if i forgot anything in my redistribution. I cant imagine the end/release and testing phase of a project without a VM.

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  • Backup media manager, library or similar reference application

    - by Tarnschaf
    I'm looking for a backup media manager that will keep me up-to-date on where my backups are, how they're stored and what's stored on them. I want it to be able to do and keep track of the following: my used backup media (e.g. DVD1, DVD2) my backed-up assets in high-level (such as "family-photos from 2003", "laptop drivers") details of the assets ("Ninas Birthday 2003") where the backup media is currently stored when the media has been burned (to re-burn in case of media degeneration). It should be possible to navigate back and forth between media and assets. I also thought about marking assets as "deprecated". If all assets on a media are deprecated, the program should tell me so I don't have to keep it any more. Does anyone know of a program with this feature-set? Or will I have to start my own reference in something like Access?

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  • Customizing the NUnit GUI for data-driven testing

    - by rwong
    My test project consists of a set of input data files which is fed into a piece of legacy third-party software. Since the input data files for this software are difficult to construct (not something that can be done intentionally), I am not going to add new input data files. Each input data file will be subject to a set of "test functions". Some of the test functions can be invoked independently. Other test functions represent the stages of a sequential operation - if an earlier stage fails, the subsequent stages do not need to be executed. I have experimented with the NUnit parametrized test case (TestCaseAttribute and TestCaseSourceAttribute), passing in the list of data files as test cases. I am generally satisfied with the the ability to select the input data for testing. However, I would like to see if it is possible to customize its GUI's tree structure, so that the "test functions" become the children of the "input data". For example: File #1 CheckFileTypeTest GetFileTopLevelStructureTest CompleteProcessTest StageOneTest StageTwoTest StageThreeTest File #2 CheckFileTypeTest GetFileTopLevelStructureTest CompleteProcessTest StageOneTest StageTwoTest StageThreeTest This will be useful for identifying the stage that failed during the processing of a particular input file. Is there any tips and tricks that will enable the new tree layout? Do I need to customize NUnit to get this layout?

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  • 2D Collision masks for handling slopes

    - by JiminyCricket
    I've been looking at the example at: http://create.msdn.com/en-US/education/catalog/tutorial/collision_2d_perpixel and am trying to figure out how to adjust the sprite once a collision has been detected. As David suggested at XNA 4.0 2D sidescroller variable terrain heightmap for walking/collision, I made a few sensor points (feet, sides, bottom center, etc.) and can easily detect when these points actually collide with non-transparent portions of a second texture (simple slope). I'm having trouble with the algorithm of how I would actually adjust the sprite position based on a collision. Say I detect a collision with the slope at the sprite's right foot. How can I scan the slope texture data to find the Y position to place the sprite's foot so it is no longer inside the slope? The way it is stored as a 1D array in the example is a bit confusing, should I try to store the data as a 2D array instead? For test purposes, I'm thinking of just using the slope texture alpha itself as a primitive and easy collision mask (no grass bits or anything besides a simple non-linear slope). Then, as in the example, I find the coordinates of any collisions between the slope texture and the sprite's sensors and mark these special sensor collisions as having occurred. Finally, in the case of moving up a slope, I would scan for the first transparent pixel above (in the texture's Ys at that X) the right foot collision point and set that as the new height of the sprite. I'm a little unclear also on when I should make these adjustments. Collisions are checked on every game.update() so would I quickly change the position of the sprite before the next update is called? I also noticed several people mention that it's best to separate collision checks horizontally and vertically, why is that exactly? Open to any suggestions if this is an inefficient or inaccurate way of handling this. I wish MSDN had provided an example of something like this, I didn't know it would be so much more complex than NES Mario style pure box platforming!

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  • How to "translate" interdependent object states in code?

    - by Earl Grey
    I have the following problem. My UI interace contains several buttons, labels, and other visual information. I am able to describe every possible workflow scenario that should be be allowed on that UI. That means I can describe it like this - when button A is pressed, the following should follow - In the case of that A button, there are three independent factors that influence the possible result when pushing the A button. The state of the session (blank, single, multi, multi special), the actual work that is being done by the system at the moment of pressing the A button (nothing was happening, work was being done, work was paused) and a separate UI element that has two states (on , off)..This gives me a 3 dimensional cube with 24 possible outcomes. I could write code for this using if cycles, switch cycles etc....but the problem is, I have another 7 buttons on that ui, I can enter this UI from different states..some buttons change the state, some change parameters... To sum up, the combinations are mindbogling and I am not able come up with a methodology that scales and is systematically reliable. I am able to describe EVERY workflow with words, I am sure my description is complete and without logical errors. But I am not able to translate that into code. I was trying to draw flowcharts but it soon became visually too complicated due to too many if "emafors". Can you advice how to proceeed?

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  • Which approach would lead to an API that is easier to use?

    - by Clem
    I'm writing a JavaScript API and for a particular case, I'm wondering which approach is the sexiest. Let's take an example: writing a VideoPlayer, I add a getCurrentTime method which gives the elapsed time since the start. The first approach simply declares getCurrentTime as follows: getCurrentTime():number where number is the native number type. This approach includes a CURRENT_TIME_CHANGED event so that API users can add callbacks to be aware of time changes. Listening to this event would look like the following: myVideoPlayer.addEventListener(CURRENT_TIME_CHANGED, function(evt){ console.log ("current time = "+evt.getDispatcher().getCurrentTime()); }); The second approach declares getCurrentTime differently: getCurrentTime():CustomNumber where CustomNumber is a custom number object, not the native one. This custom object dispatches a VALUE_CHANGED event when its value changes, so there is no need for the CURRENT_TIME_CHANGED event! Just listen to the returned object for value changes! Listening to this event would look like the following: myVideoPlayer.getCurrentTime().addEventListener(VALUE_CHANGED, function(evt){ console.log ("current time = "+evt.getDispatcher().valueOf()); }); Note that CustomNumber has a valueOf method which returns a native number that lets the returned CustomNumber object being used as a number, so: var result = myVideoPlayer.getCurrentTime()+5; will work! So in the first approach, we listen to an object for a change in its property's value. In the second one we directly listen to the property for a change on its value. There are multiple pros and cons for each approach, I just want to know which one the developers would prefer to use!

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  • Ubuntu, control the init startup

    - by Xolve
    Ubuntu uses upstart instead of sysvinit. However there are still runlevels and the links in them. I have installed tor and it has added itself to the startup of the OS. Now I want to remove it and the popular options are to remove the links of starting and stopping the service from runlevels or make the /etc/init.d/ script non-executable. This is fine but this will be problematic in case I want to put tor again on the startup list. How would I know to put the proper sequences in the proper runlevel directories. Is there any complete guide given? What are the rules for this? Any tools to manage the init? Please tell

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  • What is a good support knowledge base tool?

    - by Guillaume
    I have been searching for a tool to help my team organize its knowledge for resolving recurring support cases. I know this question will probably be closed, but I'll try my change anyway because I know that I can have some good answers about that. Context: our team is developing and supporting an huge applications (lots of different screens and workflow processes. We already have a good tool for managing our documentation, but we are struggling with support cases. Support action involve often quite a lot of manual steps to fix stuff and the knowledge for these actions is more 'oral transmission' than modern tools. We need an efficient way to store them in a knowledge base to be able to retrieve similar cases based on patterns (a stacktrace, an error message, a component name, a workflow step, ...) and ranked by similarity. Our wiki search is not very powerful when it come to this kind of search and the team members don't want to 'waste' time writing a report that will never be found... Do you know efficient knowledge base tool for this kind of use case ?

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  • CPU load, USB connection vs. NIC

    - by T.J. Crowder
    In general, and understanding the answer may vary by manufacturer and model (and driver, and...), in consumer-grade workstations with integrated NICs, does the NIC rely on the CPU for a lot of help (as is typically the case with a USB controller, for instance), or is it fairly intelligent and capable on its own (like, say, the typical Firewire controller)? Or is the question too general to answer? (If it matters, you can assume Linux.) Background: I'm looking at connecting a device (digital television capture) that will be delivering ~20-50 Mbit/sec of data to a somewhat under-powered workstation. I can get a USB 2 High-speed device, or a network-attached device, and am interested in avoiding impacting the CPU where possible. Obviously, if it's a 100Mbit NIC, that's roughly half its theoretical inbound bandwidth, whereas it's only roughly a tenth of the 480 Mbit/second the USB 2 "High Speed" interface. But if the latter requires a lot of CPU support and the former doesn't...

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  • Cron: job starts but doesn't complete

    - by Guandalino
    I have a problem with a cron job which starts but doesn't complete. Running the command manually works fine. I already read the page about cron issues and solutions here on AskUbuntu, tried the proposed solutions but didn't find an answer working in my case. I'm using Ubuntu 12.04. $ crontab -e SHELL=/bin/bash # otherwise it would be /bin/sh 59 16 * * * /bin/duply calendar backup > /tmp/duply.log Btw, the cron file ends with an empty line, as someone pointed out. Once the job has "finished"...: $ cat /tmp/duply.log Start duply v1.5.7, time is 2012-06-22 16:59:01. Instead, running manually the script it works correctly and gives this output: Start duply v1.5.7, time is 2012-06-22 17:06:39. [cut] ... here is a long output generated by duply. ... and yes, files have been backed up. [cut] --- Finished state OK at 17:06:42.581 - Runtime 00:00:03.170 --- I also tried to restart the cron daemon (sudo service cron restart) but nothing changed. Do you have any suggestion to fix the issue?

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  • Running a defect php file cause error 500

    - by John Brunner
    When I address a PHP file, I always get an error 500. I've looked up the logs of my Apache server, and this displays that some includes etc. in the PHP file address files which don't exist on the server. They don't exist because I'm just testing my PHP file. But could it be achieved that the server runs the php file in every case, even when something is wrong? Every 30 seconds an entry is made in the error_log file which says [Sat Jun 09 17:55:07 2012] [error] [client 10.224.55.160] File does not exist: /var/www/html/index.html ... but there IS an index.html?!

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  • Interfaces and Virtuals Everywhere????

    - by David V. Corbin
    First a disclaimer; this post is about micro-optimization of C# programs and does not apply to most common scenarios - but when it does, it is important to know. Many developers are in the habit of declaring member virtual to allow for future expansion or using interface based designs1. Few of these developers think about what the runtime performance impact of this decision is. A simple test will show that this decision can have a serious impact. For our purposes, we used a simple loop to time the execution of 1 billion calls to both non-virtual and virtual implementations of a method that took no parameters and had a void return type: Direct Call:     1.5uS Virtual Call:   13.0uS The overhead of the call increased by nearly an order of magnitude! Once again, it is important to realize that if the method does anything of significance then this ratio drops quite quickly. If the method does just 1mS of work, then the differential only accounts for a 1% decrease in performance. Additionally the method in question must be called thousands of times in order to produce a meaqsurable impact at the application level. Yet let us consider a situation such as the per-pixel processing of a graphics processing application. Here we may have a method which is called millions of times and even the slightest increase in overhead can have significant ramification. In this case using either explicit virtuals or interface based constructs is likely to be a mistake. In conclusion, good design principles should always be the driving force behind descisions such as these; but remember that these decisions do not come for free.   1) When a concrete class member implements an interface it does not need to be explicitly marked as virtual (unless, of course, it is to be overriden in a derived concerete class). Nevertheless, when accessed via the interface it behaves exactly as if it had been marked as virtual.

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  • IT Optimization Plan Pays Off For UK Retailer

    - by [email protected]
    I caught this article in ComputerworldUK yesterday. The headline talks about UK-based supermarket chain Morrisons is increasing their IT spend...OK, sounds good. Even nicer that Oracle is a big part of that. But what caught my eye were three things: 1) Morrison's truly has a long term strategy for IT. In this case, modernizing and optimizing how they use IT for business advantage. 2) Even in a tough economic climate, Morrison's views IT investments as contributing to and improving the bottom line. Specifically, "The investment in IT contributed to a 21 percent increase in Morrison's underlying profit.." 3) The phased, 3-year "Optimization Plan" took a holistic approach to their business--from CRM and Supply Chain systems to the underlying application infrastructure. On the infrastructure front, adopting a more flexible Service-Oriented Architecture enabled them to be more agile and adapt their business and Identity Management helped with sometimes mundane (but costly) issues like lost passwords and being able to document who has access to what. Things don't always turn out so rosy. And I know it was a long and difficult process...but it's nice to see a happy ending every once in a while.

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  • Intel video driver upgrade now makes my external monitor display red-only with HDMI cable.

    - by Eli
    I have an HP G60 notebook with a Mobile Intel 4 Series Express Chipset video display (Driver version is 8.15.10.2021). OS is Win7 Home Premium. I also have an LG widescreen display that I was connecting to the laptop using an HDMI cable. It was working great, until I applied an Intel 4 Series Express Chipset update from Windows Update. After the update, if I plug the laptop to the monitor using the HDMI cable, it appears I only get the Magenta channel, cause that is all I see. If I connect with the VGA cable, it works fine. So, is it possible it is just the HDMI cable (which IS cheap in this case - fire sale at Blockbuster), and not related to the video driver update at all?

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  • Web-based (intranet / non-hosted) timesheet / project tracking tools

    - by warren
    I realize some similar questions have been asked along these lines before, but from reading-through them today, it appears they don't match my use case. I am looking for a web-based, non-hosted time and project tracking tool. I've downloaded Collabtive so far, but am looking for other suggestions, too. My list of requirements: runs on standard LAMP stack non-hosted (ie, there is an option to download and run it on a local server) not a desktop/single-user application easy-to-use - my audience is a mix of technical and non-technical folks easy to maintain - when time for upgrading comes, I'd really like to not have to rebuild the app (a la ./configure ; make ; make install) needs to support multiple users free-form project additions: we don't have a central project management authority (users should be able to add whatever they're working on, not merely from a drop-down) Does anyone here have experience with such tools? It doesn't have to be free.. but free is always nice :)

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  • Solving Big Problems with Oracle R Enterprise, Part I

    - by dbayard
    Abstract: This blog post will show how we used Oracle R Enterprise to tackle a customer’s big calculation problem across a big data set. Overview: Databases are great for managing large amounts of data in a central place with rigorous enterprise-level controls.  R is great for doing advanced computations.  Sometimes you need to do advanced computations on large amounts of data, subject to rigorous enterprise-level concerns.  This blog post shows how Oracle R Enterprise enables R plus the Oracle Database enabled us to do some pretty sophisticated calculations across 1 million accounts (each with many detailed records) in minutes. The problem: A financial services customer of mine has a need to calculate the historical internal rate of return (IRR) for its customers’ portfolios.  This information is needed for customer statements and the online web application.  In the past, they had solved this with a home-grown application that pulled trade and account data out of their data warehouse and ran the calculations.  But this home-grown application was not able to do this fast enough, plus it was a challenge for them to write and maintain the code that did the IRR calculation. IRR – a problem that R is good at solving: Internal Rate of Return is an interesting calculation in that in most real-world scenarios it is impractical to calculate exactly.  Rather, IRR is a calculation where approximation techniques need to be used.  In this blog post, we will discuss calculating the “money weighted rate of return” but in the actual customer proof of concept we used R to calculate both money weighted rate of returns and time weighted rate of returns.  You can learn more about the money weighted rate of returns here: http://www.wikinvest.com/wiki/Money-weighted_return First Steps- Calculating IRR in R We will start with calculating the IRR in standalone/desktop R.  In our second post, we will show how to take this desktop R function, deploy it to an Oracle Database, and make it work at real-world scale.  The first step we did was to get some sample data.  For a historical IRR calculation, you have a balances and cash flows.  In our case, the customer provided us with several accounts worth of sample data in Microsoft Excel.      The above figure shows part of the spreadsheet of sample data.  The data provides balances and cash flows for a sample account (BMV=beginning market value. FLOW=cash flow in/out of account. EMV=ending market value). Once we had the sample spreadsheet, the next step we did was to read the Excel data into R.  This is something that R does well.  R offers multiple ways to work with spreadsheet data.  For instance, one could save the spreadsheet as a .csv file.  In our case, the customer provided a spreadsheet file containing multiple sheets where each sheet provided data for a different sample account.  To handle this easily, we took advantage of the RODBC package which allowed us to read the Excel data sheet-by-sheet without having to create individual .csv files.  We wrote ourselves a little helper function called getsheet() around the RODBC package.  Then we loaded all of the sample accounts into a data.frame called SimpleMWRRData. Writing the IRR function At this point, it was time to write the money weighted rate of return (MWRR) function itself.  The definition of MWRR is easily found on the internet or if you are old school you can look in an investment performance text book.  In the customer proof, we based our calculations off the ones defined in the The Handbook of Investment Performance: A User’s Guide by David Spaulding since this is the reference book used by the customer.  (One of the nice things we found during the course of this proof-of-concept is that by using R to write our IRR functions we could easily incorporate the specific variations and business rules of the customer into the calculation.) The key thing with calculating IRR is the need to solve a complex equation with a numerical approximation technique.  For IRR, you need to find the value of the rate of return (r) that sets the Net Present Value of all the flows in and out of the account to zero.  With R, we solve this by defining our NPV function: where bmv is the beginning market value, cf is a vector of cash flows, t is a vector of time (relative to the beginning), emv is the ending market value, and tend is the ending time. Since solving for r is a one-dimensional optimization problem, we decided to take advantage of R’s optimize method (http://stat.ethz.ch/R-manual/R-patched/library/stats/html/optimize.html). The optimize method can be used to find a minimum or maximum; to find the value of r where our npv function is closest to zero, we wrapped our npv function inside the abs function and asked optimize to find the minimum.  Here is an example of using optimize: where low and high are scalars that indicate the range to search for an answer.   To test this out, we need to set values for bmv, cf, t, emv, tend, low, and high.  We will set low and high to some reasonable defaults. For example, this account had a negative 2.2% money weighted rate of return. Enhancing and Packaging the IRR function With numerical approximation methods like optimize, sometimes you will not be able to find an answer with your initial set of inputs.  To account for this, our approach was to first try to find an answer for r within a narrow range, then if we did not find an answer, try calling optimize() again with a broader range.  See the R help page on optimize()  for more details about the search range and its algorithm. At this point, we can now write a simplified version of our MWRR function.  (Our real-world version is  more sophisticated in that it calculates rate of returns for 5 different time periods [since inception, last quarter, year-to-date, last year, year before last year] in a single invocation.  In our actual customer proof, we also defined time-weighted rate of return calculations.  The beauty of R is that it was very easy to add these enhancements and additional calculations to our IRR package.)To simplify code deployment, we then created a new package of our IRR functions and sample data.  For this blog post, we only need to include our SimpleMWRR function and our SimpleMWRRData sample data.  We created the shell of the package by calling: To turn this package skeleton into something usable, at a minimum you need to edit the SimpleMWRR.Rd and SimpleMWRRData.Rd files in the \man subdirectory.  In those files, you need to at least provide a value for the “title” section. Once that is done, you can change directory to the IRR directory and type at the command-line: The myIRR package for this blog post (which has both SimpleMWRR source and SimpleMWRRData sample data) is downloadable from here: myIRR package Testing the myIRR package Here is an example of testing our IRR function once it was converted to an installable package: Calculating IRR for All the Accounts So far, we have shown how to calculate IRR for a single account.  The real-world issue is how do you calculate IRR for all of the accounts?This is the kind of situation where we can leverage the “Split-Apply-Combine” approach (see http://www.cscs.umich.edu/~crshalizi/weblog/815.html).  Given that our sample data can fit in memory, one easy approach is to use R’s “by” function.  (Other approaches to Split-Apply-Combine such as plyr can also be used.  See http://4dpiecharts.com/2011/12/16/a-quick-primer-on-split-apply-combine-problems/). Here is an example showing the use of “by” to calculate the money weighted rate of return for each account in our sample data set.  Recap and Next Steps At this point, you’ve seen the power of R being used to calculate IRR.  There were several good things: R could easily work with the spreadsheets of sample data we were given R’s optimize() function provided a nice way to solve for IRR- it was both fast and allowed us to avoid having to code our own iterative approximation algorithm R was a convenient language to express the customer-specific variations, business-rules, and exceptions that often occur in real-world calculations- these could be easily added to our IRR functions The Split-Apply-Combine technique can be used to perform calculations of IRR for multiple accounts at once. However, there are several challenges yet to be conquered at this point in our story: The actual data that needs to be used lives in a database, not in a spreadsheet The actual data is much, much bigger- too big to fit into the normal R memory space and too big to want to move across the network The overall process needs to run fast- much faster than a single processor The actual data needs to be kept secured- another reason to not want to move it from the database and across the network And the process of calculating the IRR needs to be integrated together with other database ETL activities, so that IRR’s can be calculated as part of the data warehouse refresh processes In our next blog post in this series, we will show you how Oracle R Enterprise solved these challenges.

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  • Interesting SSMS issue with waittype of PREEMPTIVE_OS_LOOKUPACCOUNTSID

    - by steveh99999
    Saw a recent issue with SQL2008 sp 1 where SQL Server Management Studio (SSMS) appeared to hang when a DBA expanded the database users tab of a database… ie like this :-   When we looked at the waittype of the SSMS session - via sys.dm_os_waiting_tasks– it was waiting on PREEMPTIVE_OS_LOOKUPACCOUNTSID. I’d not come across this waittype before, and there was very little information out on the web for it.. Looking at this issue using SQL Profiler – it them became apparent that SSMS was waiting on the function SUSER_SNAME. I did a quick test using SET STATISTICS TIME to prove it was the SUSER_SNAME function causing our issue :- SELECT * FROM sys.database_principals   -- completes in 6 milliseconds SELECT SUSER_SNAME(sid),* FROM sys.database_principals  -- completes in 188941 milliseconds. suser_sname validates a sid against Active Directory.. What I haven’t mentioned so far is that the database in question had been restored from a server on a different domain. This domain was untrusted from the current domain. However, it appeared that SSMS was still trying to validate the Windows login of each user when displaying the users list…. and taking a long time to return NULL for each user from the untrusted domain. When all users that had a login from the untrusted domain are removed from the database – this fixed the issue. To find out the users that had this issue :- SELECT name FROM sys.database_principals WHERE type_desc IN(‘WINDOWS_USER’, ‘WINDOWS_GROUP’) and SUSER_SNAME(sid) IS NULL Although I have not raised this as a case with MS – I do think this is a bug in SSMS – I do not see why windows logins should need to be validated when displaying only user details..

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  • bluetooth daemon not running at startup

    - by ffaxer
    I'm trying to connect a bluetooth mouse to my Xubuntu system using Blueman (v. 1.21) Problem seems to be bluetoothd not running at startup, so blueman refuses to start, only a dialog appears: "Bluez daemon is not running, blueman-manager cannot continue." On my system, bluetoothd will run only as root (sudo), so my current workaround is simply to sudo bluetoothd manually, which works fine but id like to have it run at startup so that my mouse is just working without any interaction from me, if possible. If i try to start bluetoothd as non-root it reports: Bluetooth deamon 4.91 Unable to get on D-Bus In the startup scripts i found the same bluetoothd script in all runlevels and init.d: DAEMON=/usr/sbin/bluetoothd test -f /usr/sbin/bluetoothd || exit 0 # bluetoothd normally starts up by udev rules. it needs dbus to function, log_progress_msg "bluetoothd" pkill -TERM bluetoothd || true log_progress_msg "bluetoothd" I looked in /etc/udev/rules.d/ but no reference to bluetoothd. Further i have already tried with no luck: Editing /etc/dbus-1/system.d/bluetooth.conf to include my user (essentially copying the part that was for root): I tried it while both keeping the root policy and without, still, no luck! Editing /etc/pam.d/common-session and /etc/pam.d/gdm to include the line: session optional pam_ck_connector.so In the case of common-session it was already there but with a "nox11" which i tried removing. No luck no luck. Btw, I'm confused as to which session manager I'm using, since i have both xfce4-session and gdm-session-worker running. Anyways, hope someone is savvy enough to figure it out or bring some hints, otherwise i sincerely apologize for wasting your time! I'll sign off with uname -a: Linux [mycompname] 3.0.0-9-lowlatency #12ppa1~natty1-Ubuntu SMP PREEMPT Mon Aug 22 06:52:15 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux Peace B)

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  • Why Are Minimized Programs Often Slow to Open Again?

    - by Jason Fitzpatrick
    It seems particularly counterintuitive: you minimize an application because you plan on returning to it later and wish to skip shutting the application down and restarting it later, but sometimes maximizing it takes even longer than launching it fresh. What gives? Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites. The Question SuperUser reader Bart wants to know why he’s not saving any time with application minimization: I’m working in Photoshop CS6 and multiple browsers a lot. I’m not using them all at once, so sometimes some applications are minimized to taskbar for hours or days. The problem is, when I try to maximize them from the taskbar – it sometimes takes longer than starting them! Especially Photoshop feels really weird for many seconds after finally showing up, it’s slow, unresponsive and even sometimes totally freezes for minute or two. It’s not a hardware problem as it’s been like that since always on all on my PCs. Would I also notice it after upgrading my HDD to SDD and adding RAM (my main PC holds 4 GB currently)? Could guys with powerful pcs / macs tell me – does it also happen to you? I guess OSes somehow “focus” on active software and move all the resources away from the ones that run, but are not used. Is it possible to somehow set RAM / CPU / HDD priorities or something, for let’s say, Photoshop, so it won’t slow down after long period of inactivity? So what is the deal? Why does he find himself waiting to maximize a minimized app? The Answer SuperUser contributor Allquixotic explains why: Summary The immediate problem is that the programs that you have minimized are being paged out to the “page file” on your hard disk. This symptom can be improved by installing a Solid State Disk (SSD), adding more RAM to your system, reducing the number of programs you have open, or upgrading to a newer system architecture (for instance, Ivy Bridge or Haswell). Out of these options, adding more RAM is generally the most effective solution. Explanation The default behavior of Windows is to give active applications priority over inactive applications for having a spot in RAM. When there’s significant memory pressure (meaning the system doesn’t have a lot of free RAM if it were to let every program have all the RAM it wants), it starts putting minimized programs into the page file, which means it writes out their contents from RAM to disk, and then makes that area of RAM free. That free RAM helps programs you’re actively using — say, your web browser — run faster, because if they need to claim a new segment of RAM (like when you open a new tab), they can do so. This “free” RAM is also used as page cache, which means that when active programs attempt to read data on your hard disk, that data might be cached in RAM, which prevents your hard disk from being accessed to get that data. By using the majority of your RAM for page cache, and swapping out unused programs to disk, Windows is trying to improve responsiveness of the program(s) you are actively using, by making RAM available to them, and caching the files they access in RAM instead of the hard disk. The downside of this behavior is that minimized programs can take a while to have their contents copied from the page file, on disk, back into RAM. The time increases the larger the program’s footprint in memory. This is why you experience that delay when maximizing Photoshop. RAM is many times faster than a hard disk (depending on the specific hardware, it can be up to several orders of magnitude). An SSD is considerably faster than a hard disk, but it is still slower than RAM by orders of magnitude. Having your page file on an SSD will help, but it will also wear out the SSD more quickly than usual if your page file is heavily utilized due to RAM pressure. Remedies Here is an explanation of the available remedies, and their general effectiveness: Installing more RAM: This is the recommended path. If your system does not support more RAM than you already have installed, you will need to upgrade more of your system: possibly your motherboard, CPU, chassis, power supply, etc. depending on how old it is. If it’s a laptop, chances are you’ll have to buy an entire new laptop that supports more installed RAM. When you install more RAM, you reduce memory pressure, which reduces use of the page file, which is a good thing all around. You also make available more RAM for page cache, which will make all programs that access the hard disk run faster. As of Q4 2013, my personal recommendation is that you have at least 8 GB of RAM for a desktop or laptop whose purpose is anything more complex than web browsing and email. That means photo editing, video editing/viewing, playing computer games, audio editing or recording, programming / development, etc. all should have at least 8 GB of RAM, if not more. Run fewer programs at a time: This will only work if the programs you are running do not use a lot of memory on their own. Unfortunately, Adobe Creative Suite products such as Photoshop CS6 are known for using an enormous amount of memory. This also limits your multitasking ability. It’s a temporary, free remedy, but it can be an inconvenience to close down your web browser or Word every time you start Photoshop, for instance. This also wouldn’t stop Photoshop from being swapped when minimizing it, so it really isn’t a very effective solution. It only helps in some specific situations. Install an SSD: If your page file is on an SSD, the SSD’s improved speed compared to a hard disk will result in generally improved performance when the page file has to be read from or written to. Be aware that SSDs are not designed to withstand a very frequent and constant random stream of writes; they can only be written over a limited number of times before they start to break down. Heavy use of a page file is not a particularly good workload for an SSD. You should install an SSD in combination with a large amount of RAM if you want maximum performance while preserving the longevity of the SSD. Use a newer system architecture: Depending on the age of your system, you may be using an out of date system architecture. The “system architecture” is generally defined as the “generation” (think generations like children, parents, grandparents, etc.) of the motherboard and CPU. Newer generations generally support faster I/O (input/output), better memory bandwidth, lower latency, and less contention over shared resources, instead providing dedicated links between components. For example, starting with the “Nehalem” generation (around 2009), the Front-Side Bus (FSB) was eliminated, which removed a common bottleneck, because almost all system components had to share the same FSB for transmitting data. This was replaced with a “point to point” architecture, meaning that each component gets its own dedicated “lane” to the CPU, which continues to be improved every few years with new generations. You will generally see a more significant improvement in overall system performance depending on the “gap” between your computer’s architecture and the latest one available. For example, a Pentium 4 architecture from 2004 is going to see a much more significant improvement upgrading to “Haswell” (the latest as of Q4 2013) than a “Sandy Bridge” architecture from ~2010. Links Related questions: How to reduce disk thrashing (paging)? Windows Swap (Page File): Enable or Disable? Also, just in case you’re considering it, you really shouldn’t disable the page file, as this will only make matters worse; see here. And, in case you needed extra convincing to leave the Windows Page File alone, see here and here. Have something to add to the explanation? Sound off in the the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.     

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  • Two people using the same computer at the same time remotely!

    - by Mani
    We have two computer in office and two people. My computer is much more faster than another computer. Is it possible my colleague connect to my computer remotely and work by my computer? Using "Remote Desktop" in Windows only one user can log into computer. So when he connect remotely, my user logged off. Is there a tool which can help in this case? I already knew VNC (RealVNC) But it's not helping because when a user connect to my computer, he see exactly my desktop, not his own user desktop.

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