HI, I am trying to use the robust predicates for computational geometry from Jonathan Richard Shewchuk. I am not a programmer, so I am not even sure of what I am saying, I may be doing some basic mistake. The point is the predicates should allow for precise aritmthetic with adaptive floating point precision. On my computer: Asus p...
Since TIMESTAMP in mysql is stored as a 32bit value representing the time interval from 1970-jan-1 0:00:00 in seconds, I assumed that using minus (-) operator on TIMESTAMP values would give the difference of these values in seconds. Actually not: +---------------------------------------------------------------------+ | TIMESTAMP("2010-0...
Hey all, I have defined a scalar UDF in SQL Server 2005, which does some calculations on the input variables and returns a float as a result. This UDF needs to be called from within a select statement to have that calculation result in the query output for each record. Now, due to the nature of the calculation, an arithmetic overflow ...
How can one add two long values in Java so that if the result overflows then it is clamped to the range Long.MIN_VALUE..Long.MAX_VALUE? For adding ints one can perform the arithmetic in long precision and cast the result back to an int, e.g.: int saturatedAdd(int x, int y) { long sum = (long) x + (long) y; long clampedSum = Math.ma...
public class MaxHeap<T extends Comparable<T>> implements Heap<T>{ private T[] heap; private int lastIndex; private static final int defaultInitialCapacity = 25; public void add(T newItem) throws HeapException{ if (lastIndex < Max_Heap){ heap[lastIndex] = newItem; int place = lastIndex; int parent = (place – 1)/2; //ERROR ...
Today I found the following: #include <stdio.h> int main(){ char x = 255; int z = ((int)x)*2; printf("%d\n", z); //prints -2 return 0; } So basically I'm getting an overflow because the size limit is determined by the operands on the right side of the = sign?? Why doesn't casting it to int before multiplying work? In this case I...
I'm calculating fixedpoint reciprocals in Q22.10 with Goldschmidt division for use in my software rasterizer on ARM. This is done by just setting the numerator to 1, i.e the numerator becomes the scalar on the first iteration. To be honest, I'm kind of following the wikipedia algorithm blindly here. The article says that if the denomina...
I have been trying to solve this problem for a while, but couldn't with just integer arithmetic and bitwise operators. However, I think its possible and it should be fairly easy. What am I missing? The problem: to get an integer value of arbitrary length (this is not relevant to the problem) with it's X least significant bits sets to 1 ...
Hi, I am trying to implement my own version of pow() and sqrt() function as my custom library doesn't have pow()/sqrt() floating point support. Can anyone help? ...
What's the best way to do base36 arithmetic in Perl? To be more specific, I need to be able to do the following: Operate on positive N-digit numbers in base 36 (e.g. digits are 0-9 A-Z) N is finite, say 9 Provide basic arithmetic, at the very least the following 3: Addition (A+B) Subtraction (A-B) Whole division, e.g. floor(A/B). S...
Hi, I am just trying to implement multi-precision arithmetic on native MIPS. Assume that one 64-bit integer is in register $12 and $13 and another is in registers $14 and $15. The sum is to be placed in registers $10 and $11. The most significant word of the 64-bit integer is found in the even-numbered registers, and the least significa...
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 a 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 ...
Hi I am displaying a colour as a hex value in php . Is it possible to vary the shade of colour by subtracting a number from the hex value ? What I want to do it display vivid web safe colour but if selected I want to dull or lighten the colour. I know I can just use two shades of colour but I could hundred of potential colours . to be ...
Hi, I'm writing a small bignum library for a homework project. I am to implement Karatsuba multiplication, but before that I would like to write a naive multiplication routine. I'm following a guide written by Paul Zimmerman titled "Modern Computer Arithmetic" which is freely available online. On page 4, there is a description of an a...
Has anyone found it strange that the default context for uint and ulong is unchecked rather than checked considering that they are meant to represent values that can never be negative? So if some code is trying to violate that constraint it seems to me the natural and preferred behaviour would be to throw an exception rather than return...
How the heck does Ruby do this? Does Jörg or anyone else know what's happening behind the scenes? Unfortunately I don't know C very well so bignum.c is of little help to me. I was just kind of curious it someone could explain (in plain English) the theory behind whatever miracle algorithm its using. irb(main):001:0> 999**999 3680...
Should you use Int32 in places where you know the value is not going to be higher than 32,767? I'd like to keep memory down, hoever, using casts everywhere just to perform simple arithmetic is getting annoying. short a = 1; short result = a + 1; // Error short result = (short)(a + 1); // works but looks ugly when does lots of times ...
Hi, I am trying to find the easiest way to add, subtract a scalar value with a opencv 2.0 cv::Mat class. Most of the existing function allows only matrix-matrix and matrix-scalar operations. I am looking for a scalar-matrix operations. I am doing it currently by creating a temporary matrix with the same scalar value and doing require...
Right now I'm going to have to write a method that looks like this: public String Calculate(String Operator, Double Operand1, Double Operand2) { if (Operator.equals("+")) { return String.valueOf(Operand1 + Operand2); } else if (Operator.equals("-")) { return String.valueOf...
Is it possible to perform date arithmetic using JPA/Hibernate? For example, I have an entity with a java.util.Date field indicating when the row was created. Is it possible to perform a query using JPQL and include date arithmetic on that field? For example, can I perform a COUNT(*) of rows and then GROUP BY the month in that field? ...