C++ :: Runtime Speed Integer Versus Double
May 27, 2013
Using integers faster than using floating points? Or more precise: what do you estimate as the chance that writing a custom floating point class is worth the effort?
I need to examine some C++ code for an ARM7 or ARM9 processor. Instead of using floating points, the coder had chosen to use integers only. To be able to fake floating points, a custom class was written. The coder states that he avoids using floating points as these are much how much slower. "Have you measured this?", I asked. "No, but it is known to be so", he replied.
Google taught me that most people state integers are faster than using doubles, because their operations (addition, multiplication) take less assembler instructions. But if you need those floating points, what do you estimate as the chance that writing a custom floating point class is worth the effort?
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Jun 27, 2014
A while ago i was asked to write a program for a class that used a "Double ended queue with a current-position marker."
An example of some of the functions that i created are:
boolean atFirst() // Returns true if first element is current. Pre: !isEmpty().
boolean atLast() // Returns true if last element is current. Pre: !isEmpty().
void makeEmpty() // Sets this List to the empty state. Post: isEmpty().
void moveFirst() // Sets current marker to first element.
void movePrev() // Moves current marker one step toward first element.
void moveNext() // Moves current marker one step toward last element.
void insertBeforeFirst(int data) // Inserts new element before first element.
My question is whether a double ended queue with pointer is the same thing as a "doubly linked list" in this case. The terminology is throwing me of a little. If the two concepts are different, how is a doubly linked list different?
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Feb 24, 2013
Given this code
Code:
double x=1.00,y=2,z=4;
if (y/z||++x)
x+=y/z;
printf("%f
",x); So (y/z||++x)
is true if at least one expression is true, that is either (y/z)!=0 or (++x)!=0 or both. I wonder how the comparison is done? Is (y/z) be truncated to integer or 0 be promoted to double?
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Nov 22, 2014
#include <iostream>
#define show(variable) std::cout << #variable << " = " << variable << std::endl;
class LivingBeing {
protected:
struct Speed {
[Code] ....
Though the above works, memory is being wasted for speed types that do not pertain to many animals (a snail only crawls, a human never flies, etc...). Saving and loading their files will involve a lot of useless zeros. The problem seems simple, but I can't think of a good redesign to encapsulate speed properly for each of the many, many types of animals. Note that main() works with speed from the base class LivingBeing.
Should there be polymorphic Speed types within each Animal subtype? Then there will be a lot of identical Speed subtypes (e.g. many animals can only swim).
Something like:
class AnimalsThatOnlySwimOrCrawl : LivingBeing {
protected:
struct Speed : LivingBeing::Speed {
int swimmingSpeed, crawlingSpeed;
virtual void increase() override {swimmingSpeed *= 2; crawlingSpeed *= 2;}
[Code] .....
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Feb 16, 2012
Any example code to convert a velocity vector to speed in C++?
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Jun 26, 2014
I understand that the dot operator is:
Code: a.b "a"
is the actual object (not a memory location) and "b" is the member. I also understand the arrow to mean:
Code: a->b "a"
is a pointer to a struct and "b" is it's member so "a" is dereferenced then "b" is given.
Here is where I get a little confused. I have a class:
exampleclass.h
Code:
#ifndef EXAMPLECLASS_H_INCLUDED
#define EXAMPLECLASS_H_INCLUDED
class exampleclass{
[Code].....
Also if ec1 had a public variable and I wanted to access it would it be referenced the same way as the method I call in ec1?
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Jun 26, 2014
On a project I'm working on, I need to update many QLabels very quickly. Each label needs to be updated at about 20 to 50 hertz and there can be over 50 labels at any given time. The problem I'm having is after running the program for about a minute, the labels freeze and the whole program crashes about 10 seconds later. If I comment out the setText() and setNum() calls and reroute the outputs to the console, it runs fine and never crashes. Why does calling SetText() and setNum() so quickly cause the program to crash and how can I prevent this?
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Feb 14, 2015
I want to create a program in windows, it will search for a process/program by name or part of its name and monitor real-time at certain intervals the data speed at each moment that are received from the internet by this process/program. So that when no data is received by the process/program the speed will be zero and i will know it.
Can i do it in c or c++ , if yes then what libraries should i look into to do it and if i can not with these then what language and libraries should i look into to create the program?
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Feb 20, 2014
I'm trying to find the fastest method to find whether or not two rectangles intersect in an effort to streamline my code. I've built this function into a rectangle class I created below.
struct rectangle{
rectangle() :X1(0), Y1(0), X2(0), Y2(0) {};
rectangle(int X1, int Y1, int X2, int Y2)
:X1(X1), Y1(Y1), X2(X2), Y2(Y2) {};
[Code].....
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Jun 2, 2012
I heard that the speed of floating point multiplication is much faster than division. Is it still the case today?
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Apr 28, 2014
I tried to keep the coding style as similar as possible. I tested these with 4 million (4x1024x1024) 64 bit unsigned integers, Visual Studio 2005, 64 bit mode, Win XP X64, Intel 2600K 3.4ghz cpu. The average time for top down = 3.7 seconds, bottom up = 3.5 seconds.
Code: // tsorttd.h - top down merge sort
template <class T>
T * TopDownMergeSort(T a[], T b[], size_t n) {
TopDownMergeSortAtoA(a, b, 0, n);
[Code]....
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Feb 25, 2013
I am in a position to choose between function pointers and subclassed objects. To make it clear, say I have to notify some object of some action (a timer for example); refer to the following two choices (a very basic code for demo purposes):
Version 1
typedef void TimerCallback(void *args);
class Timer{
public:
Timer();
[Code] .....
Version 2:
class TimerTask{
public:
TimerTask();
virtual ~TimerTask();
void timedout()=0;
[Code] .....
which one is the standard C++ way and which one is efficient?
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Feb 27, 2013
there is a performance difference (e.g access time, speed, ...) between allocating static memory vs dynamic memory?
For example, if am reading data from a file, and storing them inside a huge buffer, what would be the differences between storing these data inside a static buffer vs a dynamic one?
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Feb 20, 2015
I'm using an animation program. In this program I've simulated a particle system. The particles are flying around at different and varying speeds. I've attached birds to the particles and I want to be able to control each bird's flapping animation based on its velocity; so birds moving faster will be flapping faster.
Initially, the bird's flapping animation is controlled by a parameter that goes from 0 to 100%. So not only do I need to drive the speed at which the animation goes from 0 to 100%, I need to set it on a loop so once it reaches 100%, it loops back to 0%. I'm extremely new to code so I don't think it would be wise for me to even provide a jumping off point, not that I could.
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May 11, 2014
In our Qt application, we have to load several files on application start-up starting from a root directory.
We are recursively scanning the directories and loading the files.
The total time it takes is about 12 seconds. Can we reduce this time if we use multi-threading?
I have heard that multi-threading does not work everywhere and it increases code complexity and debugging issues.
Would multi-threading solve the above problem? We want it to be platform independent (Mac, Linux, Windows).
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Nov 27, 2014
Basically what are the advantages and disadvantages of having an array implementation vs linked list implementation for a stack?
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Feb 10, 2015
I'm having trouble getting the program to calculate the percentage of times it flipped either heads versus tails. I realize what I currently have doesn't work because above I initialized heads and tails by giving them values of 0, but I'm unsure of how to fix it.
#include <iostream>
#include <cstdlib>
#include <ctime>
using namespace std;
int main () {
srand(time(0));
[Code] .....
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Feb 10, 2013
I have written my program and it works when I keep everything in the header files, and then have my main. I am now splitting them up into implementation files, but Eclipse keeps giving me errors. It gives me error at every opening brace of the constructor and functions. It says on all of them "Redefinition of (name of constructor or method), Previously declared here." What am I doing wrong, because it works in the header file?
#include "KeyValuePair.h"
template<typename Key,typename Value>
KeyValuePair<Key,Value>::KeyValuePair()
[Code] .....
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Jul 30, 2014
I just wrote a code that reads in a text file called "policies.txt" which looks like this:
Pol1 M N 20 100000 1 .04 99
Pol2 F S 30 100000 1 .05 99
Pol3 M S 72 750000 1 .03 99
Pol4 F N 45 1000000 1 .05 99
This works perfectly fine, but what if I want each element of the table to be separated by commas. For example:
Pol1,M,N,20,100000,1,.04,99
Pol2,F,S,30,100000,1,.05,99
Pol3,M,S,72,750000,1,.03,99
Pol4,F,N,45,1000000,1,.05,99
or better yet, what if I want it to not matter whether the columns are separated by commas or spaces? is there any way to do this? If there is no way to read in both comma-separated and space-separated elements simultaneously then I would prefer just comma, rather than the space separated which my code is able to read now. What modifications would I have to make to my code to make this work? This is my code to reference.
double ratesmn[86] = {
#include "MaleNonSmoker.txt"
- 1
};
double ratesms[86] = {
#include "MaleSmoker.txt"
[Code] ....
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Oct 25, 2013
I am trying to assign the integer value to unsigned char array. But it is not storing the integer values. It prints the ascii values. Here the code snippet
Code: uchar uc[100];
for(i=0;i<100;i++)
{
uc[i] = i;
}
The values which are stored in uc[] is ascii values.I need the integer values to be stored in uc[]. I tried to do it with sprintf. but the output is not as expected. if I print the uc[i] it should diplay the value as 0,1,2....99.
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Jun 15, 2014
changing a 9 digit integer into a new 9 digit integer through simple mathematical operations. For example, I need to change 123456789 into the new digit 456123789. Sometimes I need to change a 9 digit integer into an 8 digit integer. An example is 789062456 into 62789456. I can ONLY use simple mathematical operations (addition, subtraction, multiplication, division and modulo).
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Oct 15, 2014
Complete the function myitohex so that its converts 8-byte integer to string based hexadecimals.
Ex: printf("0x%s",myitohex(64,hex)); should printout "0x40" on the screen
char *myitohex(uint8_t i, char *result){
???
return result;
}
I wrote:
#include <stdio.h>
#include <stdint.h>
char *myitohex(uint8_t i, char *result){
*result = i + '0';
[Code] ....
0xp gets printed out which is wrong. I think *result = i + '0'; is wrong. What changes should i do on this row ?
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Apr 4, 2013
class Base
{
.....
.....
.....
virtual void display();
[code]....
in the above polymorphism why is it called runtime polymorphism when i can say seeing the code itself that display() function in derived gets executed with ptr->display(),so how does it become runtime polymorphism when i could get decide at compile itself ???
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Jun 5, 2013
Here is my error message: Warning1warning C4717: 'getx' : recursive on all control paths, function will cause runtime stack overflow
and here is my code I will Bold the part that is giving me problems!
class point
{
public:
point();
[Code]....
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May 2, 2015
While running a Doc/View SDI, is there any way to switch from text mode to rtf mode during runtime? Search reveals nothing.
Say I have an editor and I want the app to use text, I can set the ctor as follows.
Code:
CEditorDoc::CEditorDoc() {
// TODO: add one-time construction code here
m_bRTF = FALSE;
}
But once I've done that and compiled the app, while it's running, is there a way for the user (or programmer) to change the mode back to RTF? One solution that occurred to me is to use 2 document classes, but that's a hassle.
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Oct 21, 2012
I can not set the size of my array while running porgrama. Is there any way to do this in C + +?
---- code ------
#include <iostream>
#include <string>
using namespace std;
[Code].....
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