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  • OleDB Jet - Float issues in reading excel data

    - by Patrick
    When I read a sheet into a DataTable using the OleDbDataReader, floating point numbers loose their precision. I tried forcing OleDb to read the excel data as string, but although the data is now contained in a DataRow with each Column defined as System.String it looses precision (18.125 - 18.124962832). Any idea how to avoid this behaviour?

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  • Oracle: Is there a way to get the column data types for a view?

    - by rally25rs
    For a table in oracle, I can query "all_tab_columns" and get table column information, like the data type, precision, whether or not the column is nullable. In SQL Developer or TOAD, you can click on a view in the GUI and it will spit out a list of the columns that the view returns and the same set of data (data type, precision, nullable, etc). So my question is, is there a way to query this column definition for a view, the way you can for a table? How do the GUI tools do it?

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  • Efficient skeletal animation

    - by Will
    I am looking at adopting a skeletal animation format (as prompted here) for an RTS game. The individual representation of each model on-screen will be small but there will be lots of them! In skeletal animation e.g. MD5 files, each individual vertex can be attached to an arbitrary number of joints. How can you efficiently support this whilst doing the interpolation in GLSL? Or do engines do their animation on the CPU? Or do engines set arbitrary limits on maximum joints per vertex and invoke nop multiplies for those joints that don't use the maximum number? Are there games that use skeletal animation in an RTS-like setting thus proving that on integrated graphics cards I have nothing to worry about in going the bones route?

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  • Tree position terminology/naming

    - by wst
    This is a naming things question. I am processing trees (XML documents), and there are often special rules applied to nodes based on structure. It's been very difficult coming up with concise naming conventions for some cases, namely for nodes in the first position among their siblings, along with some recursive relationship: Given an arbitrary node, I want to describe its first child, and then that node's first child, and so on recursively. Given another arbitrary node, I want to describe its parent if the parent is first among its siblings, and that parent's parent if it's first, and so on recursively. Is there existing terminology to describe these tree positions? How would you name a variable or function that captures one of these cases so that it's intuitive to an unfamiliar developer trying to understand an algorithm?

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  • Efficient skeletal animation

    - by Will
    I am looking at adopting a skeletal animation format (as prompted here) for an RTS game. The individual representation of each model on-screen will be small but there will be lots of them! In skeletal animation e.g. MD5 files, each individual vertex can be attached to an arbitrary number of joints. How can you efficiently support this whilst doing the interpolation in GLSL? Or do engines do their animation on the CPU? Or do engines set arbitrary limits on maximum joints per vertex and invoke nop multiplies for those joints that don't use the maximum number? Are there games that use skeletal animation in an RTS-like setting thus proving that on integrated graphics cards I have nothing to worry about in going the bones route?

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  • A story of Murphy&ndash;my technical issues at TechDays Switzerland #chtd

    - by Laurent Bugnion
    I had two sessions at the recent Swiss TechDays. While the first one (Advanced Development for Windows Phone 8) went extremely well (I think), I had a very annoying technical issue in the beginning of my second session. First let me add that I talked to Microsoft about that and I hope they will change a few things in the room assignment for next year. My two sessions were one right after the other, with only 15 minutes break to change room. I don’t mind having two sessions so close from each other, but I would really like them to be in the same room in order to avoid having to move my laptops (plural, that will become important later) and redoing the tech check. That being said, I am guilty of not checking where my talks would be before the day before the conference, and when I did notice, it was too late to change it. After my first session, I quickly moved to the other room and setup my main laptop, a Dell Precision. We tested the video output (VGA) and didn’t notice anything special. The projectors are using a fairly high resolution (kudos to the Basel conference center for not having old school 1024x768 projectors anymore, that makes Blend really hard to demo ;) but since everything went great during the first talk, I was not worried. In fact I even had some time to chat with some early attendees about my Microsoft Surface and the Samsung Slate 7, which I had carried with me in addition to the Precision. I just thought it would be nice to show the hardware that Windows 8 can run on, without thinking any further. When the session started, I immediately noticed that the main screen was not showing anything. I thought I had just forgotten to switch to “duplicate” for the video output, and did that with a quick Win-P. However it didn’t “hold”. After 2 seconds, it reverted back to a black display for my attendees. Then I started to really worry. We tried everything, switching from VGA to HDMI, changing the resolution, setting the projector as primary display, but nothing did the trick. The projector was just refusing to show my screen. Now, to show you how despaired I started to be, I even considered using the “extend” setting (which worked just fine), and to use one of the feedback monitors on the floor but really it was super cumbersome. Eventually, my last resort arrived: I started my Samsung Slate 7, which by chance has Visual Studio 12 and Blend 5 installed, plugged the HDMI projector in the dock (yes, I had the dock with me, which I usually don’t!), connected it to internet (had to enter a long password for that), loaded the source code from my main machine using a USB stick and…. finally started to give my presentation. All in all I think we lost about 10 minutes. Amongst the most horrible minutes of my whole life, truly (yes I am blessed, I didn’t have that many horrible minutes in my life ;) I really want to apologize to my attendees. We joked a bit during the attempts to resolve the issue, the reactions I had after the session were all very nice and sympathetic. Only a handful of people left my session while I was having the issues, and I really don’t blame them (who knew how long the problem would last!!). But still, I probably talked at more than 60 sessions over the years, and this was by far my most painful moment. What did I learn? So what did I learn from this? Well from now on I will always have my slate ready with the latest source code, internet connection and every tool I might need during the presentation. This way, if I detect even a hint that the Precision might not work, I will just switch to the Slate. The experience of presenting on the slate is actually not bad at all, it is just a bit slow for my taste, but it does work. By the way, I will be posting the code and slides for my sessions very soon, I just need to “clean it and zip it”. Stay tuned, and thanks again for your patience in that horrible circumstance. Cheers Laurent   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • How are hash functions like MD5 unique?

    - by Aly
    Im aware that MD5 has had some collisions but this is more of a high level question about hashing functions. If MD5 hashes any arbitrary string into a 32-digit hex value, then according to the Pigeonhole Principle surely this can not be unique as there are more unique arbitrary strings than there are unique 32-digit hex values

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  • Optimizing spacing of mesh containing a given set of points

    - by Feynman
    I tried to summarize the this as best as possible in the title. I am writing an initial value problem solver in the most general way possible. I start with an arbitrary number of initial values at arbitrary locations (inside a boundary.) The first part of my program creates a mesh/grid (I am not sure which is the correct nuance), with N points total, that contains all the initial values. My goal is to optimize the mesh such that the spacing is as uniform as possible. My solver seems to work half decently (it needs some more obscure debugging that is not relevant here.) I am starting with one dimension. I intend to generalize the algorithm to an arbitrary number of dimensions once I get it working consistently. I am writing my code in fortran, but feel free to reply with pseudocode or the language of your choice. Allow me to elaborate with an example: Say I am working on a closed interval [1,10] xmin=1 xmax=10 Say I have 3 initial points: xmin, 5 and xmax num_ivc=3 known(num_ivc)=[xmin,5,xmax] //my arrays start at 1. Assume "known" starts sorted I store my mesh/grid points in an array called coord. Say I want 10 points total in my mesh/grid. N=10 coord(10) Remember, all this is arbitrary--except the variable names of course. The algorithm should set coord to {1,2,3,4,5,6,7,8,9,10} Now for a less trivial example: num_ivc=3 known(num_ivc)=[xmin,5.5,xmax or just num_ivc=1 known(num_ivc)=[5.5] Now, would you have 5 evenly spaced points on the interval [1, 5.5] and 5 evenly spaced points on the interval (5.5, 10]? But there is more space between 1 and 5.5 than between 5.5 and 10. So would you have 6 points on [1, 5.5] followed by 4 on (5.5 to 10]. The key is to minimize the difference in spacing. I have been working on this for 2 days straight and I can assure you it is a lot trickier than it sounds. I have written code that only works if N is large only works if N is small only works if it the known points are close together only works if it the known points are far apart only works if at least one of the known points is near a boundary only works if none of the known points are near a boundary So as you can see, I have coded the gamut of almost-solutions. I cannot figure out a way to get it to perform equally well in all possible scenarios (that is, create the optimum spacing.)

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  • Float addition promoted to double?

    - by Andreas Brinck
    I had a small WTF moment this morning. Ths WTF can be summarized with this: float x = 0.2f; float y = 0.1f; float z = x + y; assert(z == x + y); //This assert is triggered! (Atleast with visual studio 2008) The reason seems to be that the expression x + y is promoted to double and compared with the truncated version in z. (If i change z to double the assert isn't triggered). I can see that for precision reasons it would make sense to perform all floating point arithmetics in double precision before converting the result to single precision. I found the following paragraph in the standard (which I guess I sort of already knew, but not in this context): 4.6.1. "An rvalue of type float can be converted to an rvalue of type double. The value is unchanged" My question is, is x + y guaranteed to be promoted to double or is at the compiler's discretion? UPDATE: Since many people has claimed that one shouldn't use == for floating point, I just wanted to state that in the specific case I'm working with, an exact comparison is justified. Floating point comparision is tricky, here's an interesting link on the subject which I think hasn't been mentioned.

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  • Get coordinates in parent, but not in stage.

    - by Bart van Heukelom
    I know about Flash's localToGlobal and globalToLocal methods to transform coordinates from the local system to the global system, but is there a way to achieve the intermediate? To transform coordinates from an arbitrary system to any other arbitrary system? I have a clickable object inside a Sprite, and the Sprite is a child of the stage. I want to retrieve the clicked point in the Sprite.

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  • How can I cast authoritatively in asp classic?

    - by Tchalvak
    In asp classic, the cint() function or procedure or whatever it is won't allow me to cast arbitrary strings, like "bob" or "null" or anything like that. Is there anything that will allow me to simply cast integers, numeric strings, and arbitrary strings to actual integers, with some sane default like 0 for strings?

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  • Bash: easy way to put a configurable load on a system?

    - by WizardOfOdds
    In order to test how a program reacts when system resources become scarce (mainly the CPU but I'm interested in disk I/O too), I'd like to put an arbitrary load on the system. Currently I'm doing something like this: #!/bin/bash while true do echo "a" >> a.txt md5 a.txt done I could also start mp3-encoding audio files, or whatever. What would be an easy and small Bash script that could be used to simulate an arbitrary load, ideally configurable using parameter(s)?

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  • Box 2d basic questions

    - by philipp
    I am a bit new to box2d and I am developing an game with type and letters. I am using an svg font and generate the box2d bodies direct from the glyphs path definition, using the convex hull of them. I also have an decomposition routine the decomposes this hull if necessary. All this it is more or less working, except that I got some strange errors which definitely are caused by the scale factors. The problem is caused by two factors: first: the world scale of box2d, second: the the precision of curve-approximation of the glyph vectors. So through scaling down the input vertices for box2d, it happens that they become equal caused by numerical precision, what causes errors in box2d. Through scaling the my glyphs a bit up, this goes away. I also goes away if I chose a different world scale factor, but this slows down the whole animation quite much! So if my view port is about 990px * 600px and i want to animate Glyphs in box2d which should have a size from about 50px * 50px up to 300px * 300px, which scale factor of the b2world should i choose? How small should the smallest distance from on vertex to another be, while approximating the glyph vectors? Thanks for help greetings philipp EDIT:: I continued reading the docs of box2d and after rethinking of the units system, which is designed to handle object from 0.1 up to 10 meters, I calculated a scale factor of 75. So Objects 600px width will are 8 meters wide in box2d and even small objects of about 20px width will become 0.26 meters width in box2d. I will go on trying with this values, but if there is somebody out there who could give me a clever advice i would be happy!

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  • Extreme Optimization –Mathematical Constants and Basic Functions

    - by JoshReuben
    Machine constants The MachineConstants class - contains constants for floating-point arithmetic because the CLS System.Single and Double floating-point types do not follow the standard conventions and are useless. machine constants for the Double type: machine precision: Epsilon , SqrtEpsilon CubeRootEpsilon largest possible value: MaxDouble , SqrtMaxDouble, LogMaxDouble smallest Double-precision floating point number that is greater than zero: MinDouble , SqrtMinDouble , LogMinDouble A similar set of constants is available for the Single Datatype  Mathematical Constants The Constants class contains static fields for many mathematical constants and common expressions involving small integers – if you are doing thousands of iterations, you wouldn't want to calculate OneOverSqrtTwoPi , Sqrt17 or Log17 !!! Fundamental constants E - The base for the natural logarithm, e (2.718...). EulersConstant - (0.577...). GoldenRatio - (1.618...). Pi - the ratio between the circumference and the diameter of a circle (3.1415...). Expressions involving fundamental constants: TwoPi, PiOverTwo, PiOverFour, LogTwoPi, PiSquared, SqrPi, SqrtTwoPi, OneOverSqrtPi, OneOverSqrtTwoPi Square roots of small integers: Sqrt2, Sqrt3, Sqrt5, Sqrt7, Sqrt17 Logarithms of small integers: Log2, Log3, Log10, Log17, InvLog10  Elementary Functions The IterativeAlgorithm<T> class in the Extreme.Mathematics namespace defines many elementary functions that are missing from System.Math. Hyperbolic Trig Functions: Cosh, Coth, Csch, Sinh, Sech, Tanh Inverse Hyperbolic Trig Functions: Acosh, Acoth, Acsch, Asinh, Asech, Atanh Exponential, Logarithmic and Miscellaneous Functions: ExpMinus1 - The exponential function minus one, ex-1. Hypot - The hypotenuse of a right-angled triangle with specified sides. LambertW - Lambert's W function, the (real) solution W of x=WeW. Log1PlusX - The natural logarithm of 1+x. Pow - A number raised to an integer power.

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  • System speakers not recognized

    - by Kyle Maxwell
    Since upgrading to Xubuntu 13.10, sound has not functioned properly (e.g. screeching when playing Skype notifications). Now, however, it does not function at all. pavucontrol only shows Dummy Output and does not recognize the built-in speakers on my Dell Precision M4600. Possibly related, the sound indicator applet does not come up when I click on it, only showing a small white bar underneath it. I have purged and reinstalled pulseaudio. lspci -v shows: 00:1b.0 Audio device: Intel Corporation 6 Series/C200 Series Chipset Family High Definition Audio Controller (rev 04) Subsystem: Dell Precision M4600 Flags: bus master, fast devsel, latency 0, IRQ 56 Memory at f2560000 (64-bit, non-prefetchable) [size=16K] Capabilities: <access denied> Kernel driver in use: snd_hda_intel 01:00.1 Audio device: NVIDIA Corporation GF106 High Definition Audio Controller (rev a1) Subsystem: Dell Device 14a3 Flags: bus master, fast devsel, latency 0, IRQ 17 Memory at f0080000 (32-bit, non-prefetchable) [size=16K] Capabilities: <access denied> Kernel driver in use: snd_hda_intel The "Capabilities: <access denied" line makes me wonder if there's a permissions issue, as the Log Out applet now shows "Restart" and "Shutdown" grayed out. groups shows me in: kmaxwell adm dialout cdrom sudo dip plugdev fuse lpadmin netdev sambashare vboxusers

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  • Confusion with floats converted into ints during collision detection

    - by TheBroodian
    So in designing a 2D platformer, I decided that I should be using a Vector2 to track the world location of my world objects to retain some sub-pixel precision for slow-moving objects and other such subtle nuances, yet representing their bodies with Rectangles, because as far as collision detection and resolution is concerned, I don't need sub-pixel precision. I thought that the following line of thought would work smoothly... Vector2 wrldLocation; Point WorldLocation; Rectangle collisionRectangle; public void Update(GameTime gameTime) { Vector2 moveAmount = velocity * (float)gameTime.ElapsedGameTime.TotalSeconds wrldLocation += moveAmount; WorldLocation = new Point((int)wrldLocation.X, (int)wrldLocation.Y); collisionRectangle = new Rectangle(WorldLocation.X, WorldLocation.Y, genericWidth, genericHeight); } and I guess in theory it sort of works, until I try to use it in conjunction with my collision detection, which works by using Rectangle.Offset() to project where collisionRectangle would supposedly end up after applying moveAmount to it, and if a collision is found, finding the intersection and subtracting the difference between the two intersecting sides to the given moveAmount, which would theoretically give a corrected moveAmount to apply to the object's world location that would prevent it from passing through walls and such. The issue here is that Rectangle.Offset() only accepts ints, and so I'm not really receiving an accurate adjustment to moveAmount for a Vector2. If I leave out wrldLocation from my previous example, and just use WorldLocation to keep track of my object's location, everything works smoothly, but then obviously if my object is being given velocities less than 1 pixel per update, then the velocity value may as well be 0, which I feel further down the line I may regret. Does anybody have any suggestions about how I might go about resolving this?

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  • How to make sure you server NIC performance is at best on Windows?

    - by Bobb
    I realised that I followed some obscure paper on setting NICs on Windows for too long. It might be outdated with new hardware released in past couple of years and with W2008R2. I read a bit about offloading and RSS settings on Windows and I realiased that it is very much circumstantial. Noone can really say - enable that and disable this. etc. So what I really want is for my next server try and setup testing environment and measure how my particular application will behave with different settings. The target is going to be latency of TCP primarily. Please note I am talking about latency inside the box. Are there precision tools for Windows to measure latency (down to microseconds)? P.S. I know this is not easy question. Windows time drift is awful problem for any precision test but still I am sure I am not the fist person to need that... Please share your experience

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  • Moving a copied layer group precisely in GIMP to make a paper of business cards?

    - by rautamiekka
    I found a template with space for 10 business cards, without extra space anywhere. Using GIMP 2.8.10, I made the design in top left slot and now I need to get that to the other slots. What is the best way to achieve that ? Using mouse is out of question for lack of precision and keyboard takes too long and still isn't completely precise, where we obviously can't afford lack of precision. Though, I'm no artist. The problem is that the slot's contents aren't anywhere same size as the slot itself.

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  • What's better practice: objc_msgSendv or NSInvocation?

    - by Jared P
    So I'm working on something in obj-c (I'd rather not say what) where I need to be able to call arbitrary methods on arbitrary objects with arbitrary variables. The first two are easy enough to do, but I am unsure how to do the variable arguments. To be clear, this is not about a function/method receiving variable arguments, but about sending them. I have found two ways to do this: objc_msgSendv (and its variants) in the objective-c runtime, and NSInvocation. NSInvocation seems easier and more like it's the 'best practice', but objc_msgSendv sounds like it should be faster, and I need to do this many, many times over, with completely different messages each time. Which one should I choose? Is objc_msgSendv taboo for a good reason? (the docs say not to call the objc_msgsend functions.) P.S. I know the types of all the arguments, and not all of them are id-s Also, (not part of the main question,) there doesn't appear to be a way to message super from objc_msgSendv, but there doesn't seem to be a way to do that in NSInvocation either, so any help on that would be great too.

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  • Reconstructing trees from a "fingerprint"

    - by awshepard
    I've done my SO and Google research, and haven't found anyone who has tackled this before, or at least, anyone who has written about it. My question is, given a "universal" tree of arbitrary height, with each node able to have an arbitrary number of branches, is there a way to uniquely (and efficiently) "fingerprint" arbitrary sub-trees starting from the "universal" tree's root, such that given the universal tree and a tree's fingerprint, I can reconstruct the original tree? For instance, I have a "universal" tree (forgive my poor illustrations), representing my universe of possibilities: Root / / / | \ \ ... \ O O O O O O O (Level 1) /|\/|\...................\ (Level 2) etc. I also have tree A, a rooted subtree of my universe Root / /|\ \ O O O O O / Etc. Is there a way to "fingerprint" the tree, so that given that fingerprint, and the universal tree, I could reconstruct A? I'm thinking something along the lines of a hash, a compression, or perhaps a functional/declarative construction? Big-O analysis (in time or space) is a plus. As a for-instance, a nested expression like: {{(Root)},{(1),(2),(3)},{(2,3),(1),(4,5)}...} representing the actual nodes present at each level in the tree is probably valid, but can it be done more efficiently?

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  • IMAP protocol support in different email servers

    - by raticulin
    Having to interact with several different email servers via IMAP (using javamail), I have found that there is a very different level of support for IMAP features among them. The lack of support of some features has resulted in more developing time, more complicated code to deal with different support, worse perforamance due to not being able to SEARCH etc. So I would like to get some info on other servers and what level of support they provide. So far I have dealt with Lotus Domino and Novell GroupWise (and to a lesser extend Exchange 2003 and 2007). I am particularly interested in most used one in unix/linux (Courier, Cyrus, Dovecot, UW IMAP) and also Zimbra, but feel free to add any you know. Also welcomed info about online services like gmail. Features that I consider (comment if you are interested in others and I'll add them. Custom flags Searching Custom flags Searching arbitrary headers Partial fetching Proxy authentication And what I have found so far (correct if I am wrong anywhere): Lotus Domino Custom flags yes Searching Custom flags yes Searching arbitrary headers yes Partial fetching ? Proxy authentication sort of, you can give some user permissions to access other users mailboxes and he will see them under his '\Other Users' folder Novell GroupWise Custom flags No Searching Custom flags No Searching arbitrary headers No Partial fetching ? Proxy authentication yes, you can use what is called a Trusted Application

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  • Plotting an Arc in Discrete Steps

    - by phobos51594
    Good afternoon, Background My question relates to the plotting of an arbitrary arc in space using discrete steps. It is unique, however, in that I am not drawing to a canvas in the typical sense. The firmware I am designing is for a gcode interpreter for a CNC mill that will translate commands into stepper motor movements. Now, I have already found a similar question on this very site, but the methodology suggested (Bresenham's Algorithm) appears to be incompatable for moving an object in space, as it only relies on the calculation of one octant of a circle which is then mirrored about the remaining axes of symmetry. Furthermore, the prescribed method of calculation an arc between two arbitrary angles relies on trigonometry (I am implementing on a microcontroller and would like to avoid costly trig functions, if possible) and simply not taking the steps that are out of the range. Finally, the algorithm only is designed to work in one rotational direction (e.g. counterclockwise). Question So, on to the actual question: Does anyone know of a general-purpose algorithm that can be used to "draw" an arbitrary arc in discrete steps while still giving respect to angular direction (CW / CCW)? The final implementation will be done in C, but the language for the purpose of the question is irrelevant. Thank you in advance. References S.O post on drawing a simple circle using Bresenham's Algorithm: "Drawing" an arc in discrete x-y steps Wiki page describing Bresenham's Algorithm for a circle http://en.wikipedia.org/wiki/Midpoint_circle_algorithm Gcode instructions to be implemented (see. G2 and G3) http://linuxcnc.org/docs/html/gcode.html

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