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  • Rounding issue when adding floats in python, is this normal?

    - by thepearson
    I just wanted to know if this behavior is expected. If so, can someone explain to me why. This has probably been answered elsewhere I can't seem to find it using Google. Probably not searching with the right terms. I am running Ubuntu 10.04. Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56) [GCC 4.4.3] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> var = 10.0 >>> var 10.0 >>> var + 5 15.0 >>> var + 5.1 15.1 >>> var + 5.2 15.199999999999999 >>>

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  • How can I add floats together in different orders, and always get the same total?

    - by splicer
    Let's say I have three 32-bit floating point values, a, b, and c, such that (a + b) + c != a + (b + c). Is there summation algorithm, perhaps similar to Kahan summation, that guarantees that these values can be summed in any order and always arrive at the exact same (fairly accurate) total? I'm looking for the general case (i.e. not a solution that only deals with 3 numbers). Is arbitrary precision arithmetic the only way to go? I'm dealing with very large data sets, so I'd like to avoid the overhead of using arbitrary precision arithmetic if possible. Thanks!

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  • Floats not clearing properly in IE - how to fix?

    - by Stomped
    I've been banging my head for about an hour now, and I've distilled the problem down to the simplest example I can think of that shows the problem. The CSS/HTML <style> #T div { float: left; } ._b { clear: left; } </style> <div id='T'> <div class='_a'>*</div> <div class='_b'>*</div> <div class='_c'>*</div> <div class='_d'>*</div> </div> IE7 *** * FF, Chrome, Opera * *** The result in FF/Chrome/Opera is what I'd expect. There's no adding more mark-up to fix this and I'm absolutely befuddled on to how to make it work properly in IE. It gets really ugly when you have say, 3 all on a row to themselves and then 3 meant to be on the same line -- the extra 2 end up on the first row. I really hope someone knows the work-around for this.

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  • Python: How can I read in the characters from a line in a file and convert them to floats and strs, depending on if they are numbers or letters?

    - by user1467577
    I have a file that looks like: 1 1 C C 1.9873 2.347 3.88776 1 2 C Si 4.887 9.009 1.21 I would like to read in the contents of the file, line-by-line. When I only had numbers on the lines I used: for line in readlines(file): data = map(float, line.split) But this only works when all the elements of line.split are numbers. How can I make it store the letters as strings and the numbers as floats?

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  • How to transform gameObjects in array?

    - by user1764781
    I have an array of available gameObjects in the scene. An array of GO should be transformed according to received floats through UDP connection. I know it is simple, but can't figure it out how to accomplish the transformation an array of GO according to received unique floats for each GO, any help will be appreciated. Here is a transformation floats, it might be helpful I guess: x =ReadSingleBigEndian(data, signalOffset); signalOffset+=4; y= ReadSingleBigEndian(data, signalOffset); signalOffset+=4; z= ReadSingleBigEndian(data, signalOffset); signalOffset+=4; alpha= ReadSingleBigEndian(data, signalOffset); signalOffset+=4; theta= ReadSingleBigEndian(data,signalOffset); signalOffset+=4; phi= ReadSingleBigEndian(data,signalOffset); signalOffset+=4;

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  • Should I use float, double, or decimal for stats, position, etc?

    - by Ryan Peschel
    The problem with float and double is that they are not exact. If you are to do something like store replays, the values would have to be exact. The problems with decimal is that they are approximately 16x slower (confirmed by searching and personal testing) than floats and doubles. Couldn't Vector2s be another problem because they use floats internally for all the components? How do other games solve this problem? I'm sure they must use floats and doubles but aren't they not deterministic across platforms and different architecture? The replay files for games like SC2 run in a linear fashion so you cannot skip ahead so how do they solve the determinism issue with floating point numbers?

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  • TSQL - make a literal float value

    - by David B
    I understand the host of issues in comparing floats, and lament their use in this case - but I'm not the table author and have only a small hurdle to climb... Someone has decided to use floats as you'd expect GUIDs to be used. I need to retrieve all the records with a specific float value. sp_help MyTable -- Column_name Type Computed Length Prec -- RandomGrouping float no 8 53 Here's my naive attempt: --yields no results SELECT RandomGrouping FROM MyTable WHERE RandomGrouping = 0.867153569942739 And here's an approximately working attempt: --yields 2 records SELECT RandomGrouping FROM MyTable WHERE RandomGrouping BETWEEN 0.867153569942739 - 0.00000001 AND 0.867153569942739 + 0.00000001 -- 0.867153569942739 -- 0.867153569942739 In my naive attempt, is that literal a floating point literal? Or is it really a decimal literal that gets converted later? If my literal is not a floating point literal, what is the syntax for making a floating point literal? EDIT: Another possibility has occurred to me... it may be that a more precise number than is displayed is stored in this column. It may be impossible to create a literal that represents this number. I will accept answers that demonstrate that this is the case. EDIT: response to DVK. TSQL is MSSQLServer's dialect of SQL. This script works, and so equality can be performed deterministically between float types: DECLARE @X float SELECT top 1 @X = RandomGrouping FROM MyTable WHERE RandomGrouping BETWEEN 0.839110948199148 - 0.000000000001 AND 0.839110948199148 + 0.000000000001 --yields two records SELECT * FROM MyTable WHERE RandomGrouping = @X I said "approximately" because that method tests for a range. With that method I could get values that are not equal to my intended value. The linked article doesn't apply because I'm not (intentionally) trying to straddle the world boundaries between decimal and float. I'm trying to work with only floats. This isn't about the non-convertibility of decimals to floats.

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  • uninitialized local variable

    - by blitzeus
    This code compiles and runs though gives a Microsoft compiler error that I cant fix warning C4700: uninitialized local variable 'ptr4D' used. This is in the last line of the code, I think #include <iostream> using namespace std; const int DIM0 = 2, DIM1 = 3, DIM2 = 4, DIM3 = 5; void TestDeclar(); int main(){ TestDeclar(); cout << "Done!\n"; return 0; } void TestDeclar(){ //24 - array of 5 floats float xa[DIM3], xb[DIM3], xc[DIM3], xd[DIM3], xe[DIM3], xf[DIM3]; float xg[DIM3], xh[DIM3], xi[DIM3], xj[DIM3], xk[DIM3], xl[DIM3]; float xm[DIM3], xn[DIM3], xo[DIM3], xp[DIM3], xq[DIM3], xr[DIM3]; float xs[DIM3], xt[DIM3], xu[DIM3], xv[DIM3], xw[DIM3], xx[DIM3]; //6 - array of 4 pointers to floats float *ya[DIM2] = {xa, xb, xc, xd}, *yb[DIM2] = {xe, xf, xg, xh}; float *yc[DIM2] = {xi, xj, xk, xl}, *yd[DIM2] = {xm, xn, xo, xp}; float *ye[DIM2] = {xq, xr, xs, xt}, *yf[DIM2] = {xu, xv, xw, xx}; //2 - array of 3 pointers to pointers of floats float **za[DIM1] = {ya, yb, yc}; float **zb[DIM1] = {yd, ye, yf}; //array of 2 pointers to pointers to pointers of floats float ***ptr4D[DIM0] = {za, zb}; cout << &***ptr4D[DIM0] << '\n'; }

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  • Should I Make These Vectors Classes or Structs in C#

    - by dewald
    I am creating a geometry library in C# and I will need the following immutable types: Vector2f (2 floats - 8 bytes) Vector2d (2 doubles - 16 bytes) Vector3f (3 floats - 12 bytes) Vector3d (3 doubles - 24 bytes) Vector4f (4 floats - 16 bytes) Vector4d (4 doubles - 32 bytes) I am trying to determine whether to make them structs or classes. MSDN suggests only using a struct if the size if going to be no greater than 16 bytes. That reference seems to be from 2005. Is 16 bytes still the max suggested size? I am sure that using structs for the float vectors would be more efficient than using a class, but what should I do about the double vectors? Should I make them structs also to be consistent, or should I make them classes?

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  • .NET Geometry Library

    - by dewald
    Does anyone know of a good (efficient, nice API, etc.) geometry open source library for .NET? Some of the operations needed: Data Structures Vectors (2D and 3D with floats and doubles) Lines (2D and 3D) Rectangles / Squares / Cubes / Boxes Spheres / Circles N-Sided Polygon Matrices (floats and doubles) Algorithms Intersection calculations Area / Volume calculations

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  • jRuby's Float to represent in JTable's cell

    - by guai
    Hello. I need to represent floats in jTable formatted. When I do tbl.model.add_row [obj, 1.3524632478].to_java, obj is represented as it's to_s method's return value, but float do not. Overriding float's to_s method does nothing. I want floats to be formatted like this class Float def to_s sprintf("%.2f", self) end end in all my tables.

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  • JavaScript function to validate an integer value

    - by Psyche
    Hello, I'm building a shopping cart and I would like to use a JavaScript function to validate user input when entering the quantity value in the quantity text input. I would like to allow the entering of integer values only (no floats, no other characters). I know that I can apply this function using onKeyUp event and also I found isNaN() function, but it returns true even for floats (which is not ok). Can you guys help me out with this one? Thanks.

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  • Specifying formatting for csv.writer in Python

    - by user248237
    I am using csv.DictWriter to output csv files from a set of dictionaries. I use the following function: def dictlist2file(dictrows, filename, fieldnames, delimiter='\t', lineterminator='\n'): out_f = open(filename, 'w') # Write out header header = delimiter.join(fieldnames) + lineterminator out_f.write(header) # Write out dictionary data = csv.DictWriter(out_f, fieldnames, delimiter=delimiter, lineterminator=lineterminator) data.writerows(dictrows) out_f.close() where dictrows is a list of dictionaries, and fieldnames provides the headers that should be serialized to file. Some of the values in my dictionary list (dictrows) are numeric -- e.g. floats, and I'd like to specify the formatting of these. For example, I might want floats to be serialized with "%.2f" rather than full precision. Ideally, I'd like to specify some kind of mapping that says how to format each type, e.g. {float: "%.2f"} that says that if you see a float, format it with %.2f. Is there an easy way to do this? I don't want to subclass DictWriter or anything complicated like that -- this seems like very generic functionality. How can this be done? The only other solution I can think of is: instead of messing with the formatting of DictWriter, just use the decimal package to specify the decimal precision of floats to be %.2 which will cause to be serialized as such. Don't know if this is a better solution? thanks very much for your help.

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  • Understanding floating point problems

    - by Maxim Gershkovich
    Could someone here please help me understand how to determine when floating point limitations will cause errors in your calculations. For example the following code. CalculateTotalTax = function (TaxRate, TaxFreePrice) { return ((parseFloat(TaxFreePrice) / 100) * parseFloat(TaxRate)).toFixed(4); }; I have been unable to input any two values that have caused for me an incorrect result for this method. If I remove the toFixed(4) I can infact see where the calculations start to lose accuracy (somewhere around the 6th decimal place). Having said that though, my understanding of floats is that even small numbers can sometimes fail to be represented or have I misunderstood and can 4 decimal places (for example) always be represented accurately. MSDN explains floats as such... This means they cannot hold an exact representation of any quantity that is not a binary fraction (of the form k / (2 ^ n) where k and n are integers) Now I assume this applies to all floats (inlcuding those used in javascript). Fundamentally my question boils down to this. How can one determine if any specific method will be vulnerable to errors in floating point operations, at what precision will those errors materialize and what inputs will be required to produce those errors? Hopefully what I am asking makes sense.

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  • Fast sign in C++ float...are there any platform dependencies in this code?

    - by Patrick Niedzielski
    Searching online, I have found the following routine for calculating the sign of a float in IEEE format. This could easily be extended to a double, too. // returns 1.0f for positive floats, -1.0f for negative floats, 0.0f for zero inline float fast_sign(float f) { if (((int&)f & 0x7FFFFFFF)==0) return 0.f; // test exponent & mantissa bits: is input zero? else { float r = 1.0f; (int&)r |= ((int&)f & 0x80000000); // mask sign bit in f, set it in r if necessary return r; } } (Source: ``Fast sign for 32 bit floats'', Peter Schoffhauzer) I am weary to use this routine, though, because of the bit binary operations. I need my code to work on machines with different byte orders, but I am not sure how much of this the IEEE standard specifies, as I couldn't find the most recent version, published this year. Can someone tell me if this will work, regardless of the byte order of the machine? Thanks, Patrick

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  • Transfer data between C++ classes efficiently

    - by David
    Hi, Need help... I have 3 classes, Manager which holds 2 pointers. One to class A another to class B . A does not know about B and vise versa. A does some calculations and at the end it puts 3 floats into the clipboard. Next, B pulls from clipboard the 3 floats, and does it's own calculations. This loop is managed by the Manager and repeats many times (iteration after iteration). My problem: Now class A produces a vector of floats which class B needs. This vector can have more than 1000 values and I don't want to use the clipboard to transfer it to B as it will become time consumer, even bottleneck, since this behavior repeats step by step. Simple solution is that B will know A (set a pointer to A). Other one is to transfer a pointer to the vector via Manager But I'm looking for something different, more object oriented that won't break the existent separation between A and B Any ideas ? Many thanks David

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  • Qt/C++ - confused about caller/callee, object ownership

    - by Isabel
    I am creating a GUI to manipulate a robot arm. The location of the arm can be described by 6 floats (describing the positions of the various arm joints. The interface consists of a QGraphicsView with a diagram of the arm (which can be clicked to change the arm position - adjusting the 6 floats). The interface also has 6 lineEdit boxes, to also adjust those values separately. When the graphics view is clicked, and when the line edit boxes are changed, I'd like the line edit boxes / graphics view to stay in synchronisation. This brings me to confusion about how to store the 6 floats, and trigger events when they're updated. My current idea is this: The robot arm's location should be represented by a class, RobotArmLocation. Objects of this class then have methods such as obj.ShoulderRotation() and obj.SetShoulderRotation(). The MainWindow has a single instance of RobotArmLocation. Next is the bit I'm more confused about, how to join everything up. I am thinking: The MainWindow has a ArmLocationChanged slot. This is signalled whenever the location object is changed. The diagram class will have a SetRobotArmLocation(RobotArmLocation &loc). When the diagram is changed, it's free to change the location object, and fire a signal to the ArmLocationChanged slot. Likewise, changing any of the text boxes will fire a signal to that ArmLocationChanged slot. The slot then has code to synchronise all the elements. This kind of seems like a mess to me, does anyone have any other suggestions? I've also thought of the following, does it have any merrit? The RobotArmLocation class has a ValueChanged slot, the diagram and textboxes can use that directly, and bypass the MainWindow directly (seems cleaner?) thanks for any wisdom!

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  • Seeking C Union clarity

    - by mustISignUp
    typedef union { float flts[4]; struct { GLfloat r; GLfloat theta; GLfloat phi; GLfloat w; }; struct { GLfloat x; GLfloat y; GLfloat z; GLfloat w; }; } FltVector; Ok, so i think i get how to use this, (or, this is how i have seen it used) ie. FltVector fltVec1 = {{1.0f, 1.0f, 1.0f, 1.0f}}; float aaa = fltVec1.x; etc. But i'm not really groking how much storage has been declared by the union (4 floats? 8 floats? 12 floats?), how? and why? Also why two sets of curly braces when using FltVector {{}}? Any pointers much appreciated (sorry for the pun)

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  • c++ specialized overload?

    - by acidzombie24
    -edit- i am trying to close the question. i solved the problem with boost::is_base_and_derived In my class i want to do two things. 1) Copy int, floats and other normal values 2) Copy structs that supply a special copy function (template T copyAs(); } the struct MUST NOT return int's unless i explicitly say ints. I do not want the programmer mistaking the mistake by doing int a = thatClass; -edit- someone mention classes dont return anything, i mean using the operator Type() overload. How do i create my copy operator in such a way i can copy both 1) ints, floats etc and the the struct restricted in the way i mention in 2). i tried doing template <class T2> T operator = (const T2& v); which would cover my ints, floats etc. But how would it differentiate from structs? so i wrote T operator = (const SomeGenericBase& v); The idea was the GenericBase would be unsed instead then i can do v.Whatever. But that backfires bc the functions i want wouldnt exist, unless i use virtual, but virtual templates dont exist. Also i would hate to use virtual I think the solution is to get rid of ints and have it convert to something that can do .as(). So i wrote something up but now i have the same problem, how does that differentiate ints and structs that have the .as() function template?

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  • How to define type-specific scripts when using a 'type object' programming pattern?

    - by Erik
    I am in the process of creating a game engine written in C++, using the C/C++ SQLite interface to achieve a 'type object' pattern. The process is largely similar to what is outlined here (Thank you Bob Nystrom for the great resource!). I have a generally defined Entity class that when a new object is created, data is taken from a SQLite database and then is pushed back into a pointer vector, which is then iterated through, calling update() for each object. All the ints, floats, strings are loaded in fine, but the script() member of Entity is proving an issue. It's not much fun having a bunch of stationary objects laying around my gameworld. The only solutions I've come up with so far are: Create a monolithic EntityScript class with member functions encompassing all game AI and then calling the corresponding script when iterating through the Entity vector. (Not ideal) Create bindings between C++ and a scripting language. This would seem to get the job done, but it feels like implementing this (given the potential memory overhead) and learning a new language is overkill for a small team (2-3 people) that know the entirety of the existing game engine. Can you suggest any possible alternatives? My ideal situation would be that to add content to the game, one would simply add a script file to the appropriate directory and append the SQLite database with all the object data. All that is required is to have a variety of integers and floats passed between both the engine and the script file.

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  • What's wrong with this Open GL ES 2.0. Shader?

    - by Project Dumbo Dev
    I just can't understand this. The code works perfectly on the emulator(Which is supposed to give more problems than phones…), but when I try it on a LG-E610 it doesn't compile the vertex shader. This is my log error(Which contains the shader code as well): EDITED Shader: uniform mat4 u_Matrix; uniform int u_XSpritePos; uniform int u_YSpritePos; uniform float u_XDisplacement; uniform float u_YDisplacement; attribute vec4 a_Position; attribute vec2 a_TextureCoordinates; varying vec2 v_TextureCoordinates; void main(){ v_TextureCoordinates.x= (a_TextureCoordinates.x + u_XSpritePos) * u_XDisplacement; v_TextureCoordinates.y= (a_TextureCoordinates.y + u_YSpritePos) * u_YDisplacement; gl_Position = u_Matrix * a_Position; } Log reports this before loading/compiling shader: 11-05 18:46:25.579: D/memalloc(1649): /dev/pmem: Mapped buffer base:0x51984000 size:5570560 offset:4956160 fd:46 11-05 18:46:25.629: D/memalloc(1649): /dev/pmem: Mapped buffer base:0x5218d000 size:5836800 offset:5570560 fd:49 Maybe it has something to do with that men alloc? The phone is also giving a constant error while plugged: ERROR FBIOGET_ESDCHECKLOOP fail, from msm7627a.gralloc Edited: "InfoLog:" refers to glGetShaderInfoLog, and it's returning nothing. Since I removed the log in a previous edit I will just say i'm looking for feedback on compiling shaders. Solution + More questions: Ok, the problem seems to be that either ints are not working(generally speaking) or that you can't mix floats with ints. That brings to me the question, why on earth glGetShaderInfoLog is returning nothing? Shouldn't it tell me something is wrong on those lines? It surely does when I misspell something. I solved by turning everything into floats, but If someone can add some light into this, It would be appreciated. Thanks.

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  • MIPS (or SPIM): Loading floating point numbers...

    - by James
    Hey hey, I am working on a little mini compiler while trying to learn some MIPS here. Here's my issue: MIPS has an instruction li (load immediate) which would work like this li $5,100 which would load 100 into register 5. However, I need to load floats into registers right now and am struggling with figuring out a way to do it...since li $5,2.5 does not work. Anyone have any advice? I am working in C, I was thinking I could somehow get the integer representation of the float I am working with (i.e. so the floats binary representation == the ints binary representation) then load the "integer" into the register and treat it like a float from then on. Maybe its too late but Im stuck right now.

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