C++ :: QLabels And High Speed Updating Causes Crash
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?
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).
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?
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?
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) {};
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.
whats wrong with this code, I'm trying to parse a .js file and replace all the ";" with "; " i.e add a new line after each ";". So I load the file into a char[] buffer then assign a string to this contents of this buffer. Then loop char by char through using an iterator and check for a ";", if found use replace. So int i gets to about 85898 then crashes with unknown error, 'i' should reach about 175653. It does work up till it crashes. And, is this not a simpler way to load a file into a buffer, there is in C.
Ive narrowed down my crashing problem ( using printf's ) to a malloc call I had to use printf's because when i ran the program in Codeblocks debugging mode, it did not crash and ran fine, but when i ran it normally, it would crash, giving me this error:
fatal signal segmentation fault (sdl parachute deployed)
Inside my code, I created a malloce function that checks malloc for me ( so i dont have to do it )
I have a function such that one of its parameters is a 2D array of type int. The parameter is defined as follows:
[code] int topoGraph [][MAX_VERTICES] [code]
However, the following code snippet from the body of the function crashes at the specified line:
Code : if( counter >= 4 && !adjMatrixAlreadySet) { if( edgeCost == 10 ) { topoGraph[srcVertex][dstVertex] = 1; <<<<<---------- The point of crash } else if( edgeCost == 100000 )//restricted link { topoGraph[srcVertex][dstVertex] = edgeCost;
[code]....
It seems like there is an undefined behaviour at the specified point of crash since it crashes with different values of srcVertex and dstVertex each time I run it.
I have a question about allocating 2MB memory then filling it...
@ Platform: => DOS, and application is compiled/linked via Watcom C + DOS32/A (...memory model is "flat" mode)
@ phenomenon: 1. I allocate 2M memory by calloc() function. Then I got "!NULL" and it means allocating 2MB memory is ok( right ? ) 2. then I tried to "fill" this 2MB memory by for loop(one byte by one byte) like below:
for( DWORD i=0; i<0x200000; i++) { *((BYTE *)(A[0].B[0]->C) + i ) = 0x5A; // C is 4-byte address value }
here : * DWORD means "unsigned long(4-byte)" and 0x200000 means "2MByte" * in actual case the value of pointer(to allocated memory) is 3019AF3C(~768MB) <- running in flat mode...
3. after filling this range of memory(2MB) the application crashed...
@ my observations: 1. if allocating 2MB and no fill(no write data to memory) => OK 2. if allocating 2MB and just fill the former 32 bytes => OK 3. if allocating 4KB and fill all => OK
my question is: why can't I filling this 2M memory totally "even memory allocation succeeds" ?
I suspect that C++11 would make it possible to declare high rank vectors such as Code: int N = 15; // chosen arbitrary rank vector<vector<vector<...<vector<double>>>>..> vec; // N layers of nested vectors Is there a way to declare such a vector of rank N (given a fixed integer rank N)?
Heuristically I would like to write the declaration like this: Code:
vector<double> A; vector<A> vec[0]; for(int i=1; i<N; i++) { vector<vec[i-1]> vec[i]; } Is there a way to use the new variadic templates to make this work?
I haven't tried to run my program yet, but maybe I will save some trouble if I ask this question first.I am using MC PIC16F690, and I could make a pin high or low by writing RCx = 1 or 0, where x is the pin in the C port. However, I want to use the counter variable from a for() loop as the pin number. Will RC(variablename) = 1 work, or is there another syntax?
The bottom three functions do not work. Nor are the finished to the extent. I do not know how the data members are being accessed and is only giving me the last output. The overall goal of this program is to output the highest grade with student name and age, lowest grade with student name and age, and the average of all grades. The file is given and is commented out for you to see what the file looks like.
// Header Files #include <iostream> #include <fstream> using namespace std; // Global Constants const int STD_STR_LEN = 10;
I have taken a keen interest in writing trading programs. I have some Python background, a little C# but no C++.
The example below was provided in a book on HFT and I would love to see how the results look. I was hoping that I would just compile it and away you go!
That didn't happen. To start with the author listed this as a function, so I converted it to a main program. Still having issues with my path and where to see the output. Here it is..
Write a program that allows a user to enter high scores of a game, keeping tracking of the name of the user and the score. Add the ability to show the highest score for each user, all scores for a particular user, all scores from all users, and the list of users.
This is the program I am trying to write, however I am having difficulty storing the users name and high score, I know I need to store an array for the score but getting confused because of the structure. (By the way I have to use structures as it is a problem from the structures chapter of the ebook I am doing). Below is my code so far. .
Code:
#include <iostream> #include <string> using namespace std; struct highScore { string user; int score; int highestScore; int allScores;
One of my programs I recently created, needs higher precision then what doubles can provide. So I am wondering how I install a library like this [URL] .... I don't quite understand exactly how to install them. Im using visual studio 2012 ultimate right now!
I basically have a listbox that has postcode areas i.e : AE,CW,GU etc etc.
The user selects this and then a postback occurs - an sql statement is builts and a database query operation is performed and the results are returned to a datatable called tempdata.
So far so good. I then need to loop through this datatable and copy the records to my main viewstate datatable which is the datasource for google maps api.
DataTable tempstore = GetData(querystring, ""); //check tempstore has rows otherwise add defaultcust as default otherwise map will be blank if (tempstore.Rows.Count == 0) {
[Code].....
So my main datatable can grow and grow as users add more postcodes. However when it gets to around 500 rows or so I get a huge memory spike only on postback and then it settles back down.
My ram usage goes from 2gb to 3gb and if even more postcodes is selected it maxes the memory and crashes my pc.
If I remove the:
dtpc.Importrow(row);
the memory spike goes completely, obviously because the main datatable has no rows. I thought you only run into memory issues when you have thousands of rows?
I am new to C. I've been trying to use C to code some statistical functions originally coded in R. I've encountered an interesting phenomenon. In the function foo1, I declared the array v1v2b using an actual value 1999000. The function runs fine when I call it in R.
Code: void foo1(double *x, double *y, int *nsamp){ int i, j, k, oper=2, l; double* v1v2=malloc(sizeof(double)*((*nsamp)*(*nsamp-1)/2 + 1)); outer_pos(x, y, nsamp, &v1v2[0]); double v1v2b[1999000]; //<-------HERE for(i=1; i<= 1999000]; i++){ v1v2b[i-1]=1; } }
However, in foo2, I first create an integer variable called index, and store the value 1999000 in it. I then use it to initialize the same array. When I tried calling this function in R, it either led to a stack overflow error, or completely crashed R.
Code: void foo2(double *x, double *y, int *nsamp){ int i, j, k, oper=2, l; double* v1v2=malloc(sizeof(double)*((*nsamp)*(*nsamp-1)/2 + 1));
I have a class which dynamically allocates memory for three data arrays, and as such in the destructor I told it to delete those data arrays.
However, when I've created a new class, and inherited the previous class - it will always crash AFTER running the program, unless I don't have the previous destructor present.
