I know that you can split a power-of-two number in half like so: halfintR = some32bitint & 0xFFFF halfintL = some32bitint >> 16 can you do the same thing for an integer which is bounded by a non-power of two space? (say that you want your range to be limited to the set of integers that will fit into 4 digit base 52 space unsigned) ...
On a PHP & CodeIgniter-based web site, users can earn reputation for various actions, not unlike Stack Overflow. Every time reputation is awarded, a new entry is created in a MySQL table with the user_id, action being rewarded, and value of that bunch of points (e.g. 10 reputation). At the same time, a field in a users table, reputation_...
Logic error problem with the Gaussian Elimination code...This code was from my Numerical Methods text in 1990's. The code is typed in from the book- not producing correct output... Sample Run: SOLUTION OF SIMULTANEOUS LINEAR EQUATIONS USING GAUSSIAN ELIMINATION This program uses Gaussian Elimination to solve the s...
I've got about 100M value/count pairs in a text file on my Linux machine. I'd like to figure out what sort of formula I would use to generate more pairs that follow the same distribution. From a casual inspection, it looks power law-ish, but I need to be a bit more rigorous than that. Can R do this easily? If so, how? Is there somet...
I'm writing a vertex shader at the moment, and I need some random numbers. Vertex shader hardware doesn't have logical/bit operations, so I cannot implement any of the standard random number generators. Is it possible to make a random number generator using only standard arithmetic? the randomness doesn't have to be particularly good! ...
i want to resize cell's height according to the label's height and label's height according to text...?? or is there any way i can resize the cell's height according to the text entered in uitextview? ...
I am trying to include math.h in my Linux kernel module. If I use, #include '/usr/include/math.h' It give me theses errors: error: features.h: No such file or directory error: bits/huge_val.h: No such file or directory error: bits/mathdef.h: No such file or directory error: bits/mathcalls.h: No such file or directory Why is this? ...
Hi, Given: A 3d mesh defined with a set of vertices and triangles building up the mesh with these points. Problem: Find the 2d outline of the projected arbitrarily rotated mesh on an arbitrary plane. The projection is easy. The challenge lies in finding the "hull" of the projected triangle edges in the plane. I need some help with inp...
Just trying to figure out the proper and safer way to execute mathematic operation passed as string. In my scenario it is values fetched from image EXIF data. After little research I found two way of doing it. first, using eval: function calculator1($str){ eval("\$str = $str;"); return $str; } second, using create_function: ...
I've been having fun rendering charts and graphs from co-ordinates lately, and I'm fascinated by using matrices to transform co-ordinate spaces. I've been able to successfully scale and invert 2 dimensional co-ordinate spaces, but now my appetite is whetted. :) Where can I go for clear, informative, (free), educational material on matr...
In short: Given that a is coprime to b if GCD(a,b) = 1 (where GCD stands for great common divisor), how many positive integers below N are coprime to N? Is there a clever way? Not necessary stuff Here is the dumbest way: def count_coprime(N): counter = 0 for n in xrange(1,N): if gcd(n,N) == 1: counter +...
I have a task to draw a circle and then fill in with the most amount of circles without touching the sides. I can draw the circle, and I can make loops to pack the circle in a hexagonal/honeycomb format, but can't control whether they are inside or outside the circle. I have used this: g.drawOval(50, 50, 300, 300); to specify my circle....
I'm writing an application draws in another application's window (this is under OS X with Cocoa, but the question is general enough that I hope it won't be bogged down by operating system / framework issues), and I'm running into a problem which seems like it should have a simple answer, but it's driving me absolutely insane. Here's th...
I have a continuous value for which I'd like to calculate an exponential moving average. Normally I'd just use the standard formula for this: Sn = Y + (1-)Sn-1 where Sn is the new average, is the alpha, Y is the sample, and Sn-1 is the previous average. Unfortunately, due to various issues I don't have a consistent sample time. I m...
Given a large N, I need to iterate through all phi(k) such that 1 < k < N quickly. Since the values of N will be around 1012, it is important that the memory complexity is sub O(n). Is it possible? If so, how? ...
I need to evaluate if two sets of 3d points are the same (ignoring translations and rotations) by finding and comparing a proper geometric hash. I did some paper research on geometric hashing techniques, and I found a couple of algorithms, that however tend to be complicated by "vision requirements" (eg. 2d to 3d, occlusions, shadows, et...
sympy is a great tool for doing units conversions in python: >>> from sympy.physics import units >>> 12. * units.inch / units.m 0.304800000000000 You can easily roll your own: >>> units.BTU = 1055.05585 * units.J >>> units.BTU 1055.05585*m**2*kg/s**2 However, I cannot implement this into my application unless I can convert degrees ...
I'm writing a script where icons rotate around a given pivot (or origin). I've been able to make this work for rotating the icons around an ellipse but I also want to have them move around the perimeter of a rectangle of a certain width, height and origin. I'm doing it this way because my current code stores all the coords in an array ...
Hi What's the best, complex math library in c++? (I'd like to use it in graphics engine) EDIT: I should precise it a bit: it should have all 3d math, like planes, spheres, points, AABB, etc. and of course matrix, vector, quaternion support. ...
Math escapes me today. How do I find the X speed and the Y speed of an object if it is going at a defined speed (say, 5 pixels/second) at a 45 degree angle? ...