C/C++ :: Optimizing Equation For Cases Of 0
Feb 19, 2015
I'm writing an algorithm on a microcontroller in C.
One of the iterations that takes a long time involves the following equation, summing the product of pairs of variables:
signed char VarA;
signed char VarA;
signed long VarA;
Total+=VarA*VarB;
The vast majority of cases, at least one of the variables VarA and VarB will be 0, so nothing will be added to Total.
Is there a way to check for this condition which might give me a performance increase over doing a lot of multiplying-by-zeros?
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Jan 16, 2014
I was getting errors and I looked into the error and it told me to fix it by adding Code: { } in my case statements. I did, it compiled but fell through the whole thing. Lets say I enter 1, it outputs the was not found 5 times in a row.
Code:
void addressbook::EditNameOrDate() {
std::cout << "Enter 1 to Edit the contacts First Name: " << "
";
std::cout << "Enter 2 to Edit the contacts Last Name: " << "
";
std::cout << "Enter 3 to Edit the contacts Street Address: " << "
[Code] .....
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Aug 14, 2012
I have an issue with switch case. There are about 32 cases to be handled in switch. each case just assigns a hexadecimal to a local variable.
#define ADFV 0x0301
Switch(error_index)
{
case 1:
var = ADFV;
........
}
}
can i use jump table for above issue to reduce the code size.
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Jan 18, 2013
I've written a timer function in c/c++, but it still has performance problems. how to optimize this further (atm works with delay to perform timing):
#include "headers/types.h" //Basic types!
#include "headers/timers.h" //Timer support function data!
#include "headers/emu/threads.h" //Thread for timer item!
//Timer step in ms! Originally 100ms
#define TIMER_STEP 10000
[code]....
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May 25, 2014
Today I came across a problem that I've never had before and haven't thought about. Until now, The optimizing and speed in a program. I've created a small and very easy user input based "Word Generator" just to test and compare other programs.
I have compared my program to another program that works on the same concept that is programmed in C#. What I've heard is that C++ is one of the fastest languages, but still. The C# program I compared to was about 15 seconds faster when both generating 100 000 words.
optimize this program down below and describe what you've done.
#include <iostream>
#include <ctime>
#include <string>
#include "conio.h"
[Code]....
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Jan 21, 2013
I'm taking a CS course and we've been tasked with creating a program that recovers jpegs from a formatted CF card which uses the FAT file system with a block size of 512 bytes, the jpegs in the card are block aligned which means that the beginning of a jpeg marks the end of the former.
I've wrote the program and it works nicely and recovers the 51 jpegs in the CF card (actually just an image of some 4-5 megabytes of the actual card which can be downloaded here) but I'm looking for ways to optimize/improve my code so I need a second look from experienced programmers.
Here's my code:
Code:
/*
* filename : recover.c
* description : Recovers jpegs from a forensic image
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#define BLOCK 512 // fat file system block size
int main(void) {
// open CF card image
[Code] .....
My questions are:
1) What are the possible optimizations that can make my code faster/better/more concise?
2) I'm not handling slack space, since trailing zeros at the end of a jpeg won't affect rendering it (we were told it won't contain any garbage values)... how may I approach the problem?
3) Can I enhance my if else constructs? or even replace them with something more elegant?
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Mar 25, 2013
how to take two variables with values such as a 1; and b 2;. Now you take cout << a + b; and you will get 3, but I want to somehow have a 1; b 2; and c num; then have a + b = c. So what ever I have the user input is for a and be added together will become the value of the c variable.
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Oct 18, 2013
This is my code:
Code:
#include <math.h>
#include <stdio.h>
int main(void) {
float a,b,c,root_1,root_2;
printf("Please enter value a from the quadratic equation
[Code] ......
And I keep getting this error:
Code:
/tmp/ccgtUIun.o: In function `main':
assign345.c:(.text+0xc7): undefined reference to `sqrt'
assign345.c:(.text+0xef): undefined reference to `sqrt'
collect2: ld returned 1 exit status
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Oct 30, 2014
I have a small project for school due today but i cant get my head around programming
Ive to create a program where ive to get the values from the user and add them to an equation. I have also to add a selection statement where it will ask for the material being tested which will have its value set in the program.
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Apr 14, 2013
Write a program that creates the output shown in the Output Layout section below. The program should create 2 points with x and y coordinates as integers, prompt the user to input the x and y values for one of the points and randomly set the other (-99 to 99 range) and output the length of the radius line segment and the area of the circle that radius defines. The program should then end. Include an SDM for the program and any other appropriate documentation.
Special Calculations:
Distance between 2 points equation:
√((p0x – p1x)2 + (p0y – p1y)2) (This requires use of the math library)
Output Layout: (bold text represents user input)
Please enter the location of your first point.
Enter a value from -99 to 99 for your x coordinate: -2
Enter a value from -99 to 99 for your y coordinate: 17
The location of your second randomly set point.
Your x coordinate: 45
Your y coordinate: -89
The length of the radius line segment from point one to point two is 115.
The area of the circle with a radius of 115 is 41546.33.
Other:
int pAx;
int pAy;
int pBx;
int pBy;
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Jul 4, 2014
soo quadratic equation solver. output is "x=nan x=nan".
#include <iostream>
#include <string>
#include <cmath>
using namespace std;
//prototyping
double ans_1(double,double,double)
[code].....
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Feb 3, 2013
I am creating a program that solves the quadratic equation ax^2 + bx +c.
I have this program almost complete except the output of the equation in the function called display_quadratic. I need the program to display the variables a,b,c in the equation ax^2 + bx + c but I am having 2 problems. My first problem is that I cannot get the right addition and subtraction signs for the equation.
For instance, if the program had the values for a,b,c as 2,2,3
it will display 2x^2 2x 3
How can I get it to display 2x^2 + 2x + 3? or if it was negative like 2x^2 - 2x - 3?
My next question is how do I get to not display the coefficients that are 1?
I had an if-else statement but no matter what I created it would overlap with another statement and print out twice. Here is the code:
Code:
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
void display_quadratic (float a, float b, float c);
float root1(float a, float b, float c);
[Code] ......
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Sep 10, 2013
I am having trouble understanding how this loops would work. Give the function (x*x*x*x) - (10*x*x*x) + (35*x*x) - (50*x) + 24 Write a program that will use bisection method to find the roots of this function. Define lower limit and upper limit (e.g. -1.05 and 6.05) Starting at the lower limit step along the X axis at intervals of 0.1 for H calculating the function values f(x) and f(x +h), then f(x+h) and f(x+2h) until the upper limit is exceeded. If sign of the function value changes this indicates a root between ranges. Apply bi sectional method to this range until root has been found with an epsilon of 0.000001, then continue on until upper limit has been exceeded and all 4 roots found. If the function is within 0.000001 of zero then root has been found therefore no need for bi sectional method.
Code:
#include "stdafx.h"
#include "math.h"
#define H 0.1
#define epsilon 0.000001
double F(double x);
int main(void)
[code]....
So we have a function and a range. Program requires to work along the X axis at 0.1 increments until it reaches a point where the value changes from positive to negative or negative to positive. Then apply bisection method within that range to a given accuracy then print that root. Then continue on X axis until the next change of sign is found.
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Jan 22, 2014
How do to calculate the following equation"5+((56+8)/2)" using expression builder
Note: the equation may change "50+((26+8)/12)"
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May 11, 2013
I am working on a program to find the value of the current in a coil. This value satisfies the following equation:
y'=sin(2t)-[(ey-1)/(ey+1)]
which is of the form y'=f(t,y)
I know that in order to solve this I need to use the trapezoidal method to solve a differential equation, the formula is:
yn+1=yn+.5*h(f(tn,yn)+f(tn+1,yn+1) where h=tn+1-tn
I have found examples of the standard trapezoidal method but I do not think they will work because of the difference in the formulas.
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Oct 7, 2013
This is my code for the quadratic equation. It keeps telling me that my else is illegal since no matching if statement and my else statement is missing a statement
#include <iostream>
#include <cmath>
#include <string>
#include <iomanip>
using namespace std;
int main() {
string Name;
[Code] .....
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Mar 29, 2013
My program is returning NaN even though the value in square root function is not negative -1*b + ((sqrt(pow(b,2) * -4 *(a*c))) / 2).
x = 10;
y = -1;
z = 1;
Heres the program:
main.cpp:
#include <iostream>
#include "Quad.h"
double x,y,z; // variable x = 'a', variable y = 'b' and variable z = 'c'.
[Code] ....
I would like it return the answer and not "NaN".
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May 14, 2014
I've written a program that finds the maximum of a function. I now want to change it a little so that instead of evaluating the function y=x^2-7x-18, the program will ask the user to input an equation and then evaluate that equation. I'm really not sure of how to do so.
#include <iostream>
#include <cmath>
#include <cstdlib>
using namespace std;
int main() {
int a, b, delta, x, y;
double max= -1.8 * pow(10, 308);
[Code] .....
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Mar 4, 2014
How do I enter the equation all at once instead of prompting for each piece separately?
#include <iostream>
using std::cin;
using std::cout;
using std::endl;
[Code].....
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Feb 8, 2014
I want to find the root of an equation f(x) by using the secant method [URL] .....
#include <math.h>
#include <iostream>
using namespace std;
//Define function f(x)
double f(double x, double a, double b) {
return sin((a*x)/(1+x*x))*atan(b*x)+atan(x);
[Code] ....
1) Do I have to keep the function f and RootFinderSMNew in different cpp files?
2) When compiling I get the following errors:
1>------ Build started: Project: Assignment2.1, Configuration: Debug Win32 ------
1> Find Roots Secant method.cpp
[Code] .....
What am I doing wrong ?
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Jul 6, 2014
So, I successfully made a program that will perform the quadratic equation on three numbers, imaginary or real. however, i am now trying to simplify the result, as to get rid of the "/2a" on the bottom. Hence the simplify() function. I just started to create the simplification function, and am attempting to divide the imaginary part of the solution as well as the real part of the solution by 2a. Somehow, it gives the error, "error:invalid operands of types 'int' and 'double *' to binary 'operator*'" on lines 105 and 106. I suspect it has to do with the pointers and references that i am passing as parameters. Also, just an aside, I have never actually seen "/=" be used. It can be, right? I know "+=" can be.
#include <iostream>
#include <string>
#include <cmath>
#include <cstdlib>//simplify the answer
using namespace std;
int count=0;
//prototyping
double ans_1(double,double,double);
[Code] ....
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Dec 22, 2012
I am using matlab R2o11 in which the programming medium is c++. I am having these variables=
T=373 t0 376
V=0.09 to 1
P=T/V
I just need a result showing ... First it should take T=373 and solve the equation using all volume values. Then it takes another temperature and do the same.
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Apr 9, 2013
I need an equation that determines the lowest possible cost for laying power line.
The variables are as follows:
1. The width of a river
2. The distance a factory is downstream from a station on the other side of the river.
3. The cost for laying line underwater.
4. The cost for laying line on land.
All these variables will be user input each use of program.
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