Given a normalized floating point number f what is the next normalized floating point number after/before f. With bit twiddling, extracting mantissa and exponent I have: next_normalized(double&){ if mantissa is not all ones maximally denormalize while maintaining equality add 1 to mantissa normalize...
Hi, I've been pretty interested in coding a Mandelbrot Set zoom and have already done it twice. However there were problems with each one. The first time I thought it'd be cool to do it in javascript... but that was so damn slow. Then I did it in C++, which worked great until you zoomed so far that the units on the graph got to the sma...
Hello, John Carmack has a special function in the Quake III source code which calculates the inverse square root of a float, 4x faster than regular (float)(1.0/sqrt(x)), including a strange 0x5f3759df constant. See the code below. Can someone explain line by line what exactly is going on here and why this works so much faster than the r...
I have a application which needs to raise a number to a fractional power. The target platform is an FPGA and I can get estimates on an FPU size for it, but I need an algorithm for raising a number to a fractional power just for a feasibility study. I'm assuming floating point as a worst case, I expect in practice we will be able to use...
See this code: <html> <head> <script src="http://www.json.org/json2.js" type="text/javascript"></script> <script type="text/javascript"> var jsonString = '{"id":714341252076979033,"type":"FUZZY"}'; var jsonParsed = JSON.parse(jsonString); console.log(jsonString, jsonParsed); </script> </head> <body> </body> </html> Wh...
I have a code wriiten in C which is intended for a 16-bit microcontroller. The code essentially does lot of floating point arithmatic. The arithmatic works fine till the result is positive; but in case of subtraction if the expected result is negative; I get a zero. result = 0.005 - 0.001; is correctly computed as 0.004 result = 0...
Hi guys, look the follow code, why the result of Trunc function is different? procedure TForm1.Button1Click(Sender: TObject); var D: Double; E: Extended; I: Int64; begin D := Frac(101 / 100) * 100; E := Frac(101 / 100) * 100; I := Trunc(D); ShowMessage('Trunc(Double): ' + IntToStr(I)); // Trunc(Double): 1 I := Trunc(E)...
Can I rely on sqrt((float)a)*sqrt((float)a)==a or (int)sqrt((float)a)*(int)sqrt((float)a)==a to check whether a number is a perfect square? Why or why not? int a is the number to be judged. I'm using Visual Studio 2005. Edit: Thanks for all these rapid answers. I see that I can't rely on float type comparison. (If I wrote as a...
I'm trying to understand a paper on lossless compression of floating point numbers and get stuck on one particular step where the authors map a signed integer from a certain range into a range of half the size, losing information that I would think is required. I have a feeling that the authors are using some standard technique which is ...
I am seeing something odd with storing doubles in a dictionary, and am confused as to why. Here's the code: Dictionary<string, double> a = new Dictionary<string, double>(); a.Add("a", 1e-3); if (1.0 < a["a"] * 1e3) Console.WriteLine("Wrong"); if (1.0 < 1e-3 * 1e3) ...
#include <iostream> using namespace std; int main() { float s; s = 10 / 3; cout << s << endl; cout.precision(4); cout << s << endl; return 0; } Why the output does not show 3.333 but only 3 ?? ...
long long int A = 3289168178315264; long long int B = 1470960727228416; double D = sqrt(5); long long int out = A + B*D; printf("%lld",out); This gives result : -2147483648 I am not able to figure out why (it should be a positive result). Can somebody help? ...
I was trying my hand at Google Code Jam and there was a question that used double values... I had a hard time coding in C, always somehow my answer would differ from the actual answer in some cases... What I wanted to know is that which language has the best floating point implementation and handling? This has happened a numerous time...
Running a quick experiment related to Is double Multiplication Broken in .NET? and reading a couple of articles on C# string formatting, I thought that this: { double i = 10 * 0.69; Console.WriteLine(i); Console.WriteLine(String.Format(" {0:F20}", i)); Console.WriteLine(String.Format("+ {0:F20}", 6.9 - i)); Console....
How expensive is the conversion of a float to a double? Is it as trivial as an int to long conversion? EDIT: I'm assuming a platform where where float is 4 bytes and double is 8 bytes ...
I'm looking for a diff tool that can also compare floating point values (within some tolerance) in text files. This is in addition to typical text-comparison diff functions, with options to ignore whitespace, ignore case, etc. A GUI (or full-screen console UI) is okay, but I'd really prefer a stream-oriented (stdin/stdout) tool. Here's ...
In programming contests, floating point arithmetic related questions say "the error is answer must be less than 1e-6" or "The answer must be correct upto 6 decimal places". Does this mean that I can perform calculations on FP variables without worrying about the precision and only while printing I should write like printf("%.6lf",a); ...
I am trying to convert a double to a string in a native NT application, i.e. an application that only depends on ntdll.dll. Unfortunately, ntdll's version of vsnprintf does not support %f et al., forcing me to implement the conversion on my own. The aforementioned ntdll.dll exports only a few of the math.h functions (floor, ceil, log, p...
How can I declare a class variable as floating point in Moose? My (fictional) sample below produces errors for "Real", "Number" etc ... "Str" works but defeats the purpose .. searching/Google doesn't help, since I can't hit the correct search terms... PROBLEM.pm package PROBLEM; use strict; use warnings; use Moose; has 'PROBLEM'=> ...
I am writing an application where in a certain block I need to exponentiate reals around 3*500*500 times. When I use the exp(y*log(x)) algorithm, the program noticeably lags. It is significantly faster if I use another algorithm based on playing with data types, but that algorithm isn't very precise, although provides decent results for ...