break? 🤔

Doesnt work in my case.. or im just not doing it right.

Doesnt work in my case.. or im just not doing it right.

Show the code

??

What do you mean

Go and read the linux kernel if you want to see the best C program

nothing like that exists

Go and read the linux kernel if you want to see the best C program

Go and read the linux kernel if you want to see the best C program

Send link

Send link

https://github.com/torvalds/linux

https://github.com/torvalds/linux

If you understand even one line let us know

If you understand even one line let us know

😂😂

hi i can asking q on psudo code?

to find and return cyc in graph bfs methoud

?

to find and return cyc in graph bfs methoud

There are plenty of examples on the Internet for that like https://www.geeksforgeeks.org/detect-cycle-in-an-undirected-graph-using-bfs/

yes but i need to return the cyc not only i have or not

Hi guys, simple code for write/read from two different file .c with shm, IPC?

hi please can you tell me how to explain this code because im very bad at explaining something

If u r bad at explaining this piece of code , then it's not written by you , simple..

_Bool can hold either 0 or 1, so your condition is always true. Every non-zero number basically becomes 1. If you want to make sure either 0 or 1 is entered, read it as an integer and assign it to the bool after you validate the input. e.g. #include <stdio.h> int main() { printf("%d ", (_Bool)16); printf("%d ", (_Bool)0.5); printf("%d ", (_Bool)2000); printf("%d ", (_Bool)0.00000001); } this prints 1 1 1 1

int main() { int i=0, c=0, num; scanf("%d",&num); while(i<num){ if((num/i) == i) printf("Working"); } } Hi everyone, why this code doesn't execute but when you take the input as float, it works fine. Why is that?

int main() { int i=0, c=0, num; scanf("%d",&num); while(i<num){ if((num/i) == i) printf("Working"); } } Hi everyone, why this code doesn't execute but when you take the input as float, it works fine. Why is that?

What input do you provide in the console?

What input do you provide in the console?

Any input, like you take 25 as an example

int main() { int i=0, c=0, num; scanf("%d",&num); while(i<num){ if((num/i) == i) printf("Working"); } } Hi everyone, why this code doesn't execute but when you take the input as float, it works fine. Why is that?

Your code does not compile, as there is no n. Otherwise you divide by 0 and the behavior of dividing by zero differs when using float. https://stackoverflow.com/a/4480036/4416573

Oh sorry, I type it wrong here, it's i<num not i<n

Your code does not compile, as there is no n. Otherwise you divide by 0 and the behavior of dividing by zero differs when using float. https://stackoverflow.com/a/4480036/4416573

Can you explain it a little to make it simple!

Can you explain it a little to make it simple!

float have reserved values to store inf or 'NaN`, when using float even 0 can have a sign. This is not the case for int where dividing by 0 causes an hardware exception on many platforms , hence the result is different.

Thank you

Hi guys

Thank you very much

Hi guys

can anyone solve a programme about left rotation of an array in C ?

can anyone solve a programme about left rotation of an array in C ?

Solve it yourself

xD

Patient danya hehe

Patient danya hehe

He'll soon change his name to "Solve your own assignments or leave this group" 😂

He'll soon change his name to "Solve your own assignments or leave this group" 😂

Or he could develop a not that would do it automatically :D

xD

hello guys

I am trying to use "sort" on vectors but it shows error here's my code......

#include <iostream> #include <vector> using namespace std; int main() { vector<double>temps; double temp, sum = 0; while (cin >> temp) temps.push_back(temp); for (int i = 0; i < temps.size(); i++) sum += temps[i]; cout << "Average temperature: " << sum / temps.size() << endl; sort(temps.begin(), temps.end()); cout << "Median temperature: " << temps[temps.size() / 2] << endl; }

Maybe it would be nice to say what error

I would agree with Klimi. Show your error

sort identifier undefined

sort identifier not found

Severity Code Description Project File Line Suppression State Error (active) E0020 identifier "sort" is undefined

I dont know much about CPP but dont you need import for STD::sort? // like <algorithm>?

No. It compiles fine for me. sort is part of the std namespace

Your logic doesn't make a lot of sense though. Have you tried compiling with c++17? It works for me on that version

g++ -std=c++17 main.cpp

Seems to work fine for me but others sites I am looking at say to #include <algorithm>

I dont know much about CPP but dont you need import for STD::sort? // like <algorithm>?

Thank you. I used #include <algorithm> and it worked

No. It compiles fine for me. sort is part of the std namespace

i don't know what version of c++ this is, but it is visual studio 2019

Seems to work fine for me but others sites I am looking at say to #include <algorithm>

yeah it works with this thank you!!

why is my program skipping 1 of the 3 input sections?

why is my program skipping 1 of the 3 input sections?

Good question

I want to input name,number,address. But when i've input name, input directly to the address and pass the number

Show your code

#include <iostream> #include <string> #include <cstdlib> #include <cstdio> #include <conio.h> using namespace std; struct SIMPUL { char NIM[10]; char NAMA[20]; int Nilai; struct SIMPUL *LEFT; struct SIMPUL *RIGHT; }; SIMPUL *head; int isEmpty(){ if(head==NULL) return 1; else return 0; } void tambahdepan(char *nim,char *nama,int *nilai){ SIMPUL *baru; baru = new SIMPUL; baru ->NIM[10] = *nim; baru ->NAMA[20] = *nama; baru ->Nilai = *nilai; baru ->LEFT = NULL; baru ->RIGHT = NULL; if( head == NULL){ head=baru; head->RIGHT = baru; head->LEFT = baru;} else{ baru->RIGHT=head; baru->LEFT = head->LEFT; head->LEFT->RIGHT=baru; head->LEFT=baru; } cout<<"DATA MASUK !"<<endl; } void tambahbelakang(char *nim,char *nama,int *nilai){ SIMPUL *baru,*bantu; baru = new SIMPUL; baru -> NIM[10] = *nim; baru -> NAMA[20] = *nama; baru -> Nilai = *nilai; baru -> LEFT = baru->RIGHT = baru; if(isEmpty() == 1){ head=baru; head->RIGHT=head; head->LEFT=head; } else bantu = head -> LEFT; bantu->RIGHT = baru; baru->LEFT = bantu; baru->LEFT=bantu; cout<<"DATA MASUK !"<<endl; } void hapusdepan(){ SIMPUL *hapus,*bantu; char d,e; int f; if(isEmpty() == 0){ if(head->RIGHT != head){ hapus=head; d = hapus->NIM[10]; e = hapus->NAMA[20]; f = hapus->Nilai; bantu = head->LEFT; head = head->RIGHT; bantu->RIGHT = head; head->LEFT = bantu; delete hapus;} else { d = hapus->NIM[10]; e = hapus->NAMA[20]; f = hapus->Nilai; head = NULL; } } cout<<" DATA TERHAPUS !"<<endl; } void hapusbelakang(){ SIMPUL *hapus,*bantu; char d,e; int f; if (isEmpty()==0){ if(head->RIGHT != head){ bantu = head; while(bantu->RIGHT->RIGHT != head){ bantu = bantu->RIGHT; } hapus = bantu->RIGHT; d = hapus->NIM[10]; e = hapus->NAMA[20]; f = hapus->Nilai; bantu->RIGHT = head; delete hapus; } else { d = hapus->NIM[10]; e = hapus->NAMA[20]; f = hapus->Nilai; head = NULL; } cout<<"DATA TERHAPUS !"<<endl; }} void tampildepan(){ SIMPUL *bantu; bantu = head; if(isEmpty()==0){ do{ cout<<bantu->NIM<<" "<<endl; cout<<bantu->NAMA<<" "<<endl; cout<<bantu->Nilai<<" "<<endl; bantu=bantu->RIGHT; }while(bantu!=head); cout<<endl; } else cout<<"Masih kosong\n"; } void tampilbelakang(){ SIMPUL *bantu; bantu = head; if(isEmpty()==0){ do{ cout<<bantu->NIM<<" "<<endl; cout<<bantu->NAMA<<" "<<endl; cout<<bantu->Nilai<<" "<<endl; bantu=bantu->LEFT; }while(bantu!=head); cout<<endl; } else cout<<"Masih kosong\n"; } int main() { char ulang; int nil; char namasaya; char nim; menu: int pil; cout<<"\n CIRCULAR DOUBLY LINKED LIST\n"<<"======================================\n\n"; cout<<" 1. INSERT KIRI\n"; cout<<" 2. INSERT KANAN\n"; cout<<" 3. HAPUS KIRI\n"; cout<<" 4. HAPUS KANAN\n"; cout<<" 5. CETAK DARI KIRI\n"; cout<<" 6. CETAK DARI KANAN\n"; cout<<" 7. KELUAR\n\n"; cout<<"======================================\n\n"; cout<<"Pilihan ( 1-7 ) = ";cin>>pil; system("cls"); switch(pil){ case 1: cout<<"\nInsert Data dari Kiri\n"<<endl; //printf("\nMasukan Nama Mahasiswa : "); gets(&namasaya); cout<<"\nMasukan Nama Mahasiswa\t : ";gets(&namasaya); cout<<"\nMasukan NIM Mahasiswa \t : ";gets(&nim); cout<<"\nMasukan Nilai Mahasiswa\t : ";cin>>nil; tambahdepan(&nim, &namasaya, &nil); cout<<"Kembali ke menu (Y/N) ? : "; cin>>ulang; if(ulang=='Y'||ulang=='y'){ system("cls"); goto menu; } else exit(1); } cin.get(); return 0; }

I cant input "Nama Mahasiswa" and straight to "NIM"

I cant input "Nama Mahasiswa" and straight to "NIM"

Try to send it in online compiler so they could help you better.

why spinlock is slower than pthread_mutex?

why spinlock is slower than pthread_mutex?

Quoted from Linus Torvalds' email: What happens is that (a) since you're spinning, you're using CPU time (b) at a random time, the scheduler will schedule you out (c) that random time might ne just after you read the "current time", but before you actually released the spinlock. So now you still hold the lock, but you got scheduled away from the CPU, because you had used up your time slice. The "current time" you read is basically now stale, and has nothing to do with the (future) time when you are actually going to release the lock. Somebody else comes in and wants that "spinlock", and that somebody will now spin for a long while, since nobody is releasing it - it's still held by that other thread entirely that was just scheduled out. At some point, the scheduler says "ok, now you've used your time slice", and schedules the original thread, and now the lock is actually released. Then another thread comes in, gets the lock again, and then it looks at the time and says "oh, a long time passed without the lock being held at all".__ [...] [...] [...] You need to use a realtime scheduler for that (or be the kernel: inside the kernel spinlocks are fine, because the kernel itself can say "hey, I'm doing a spinlock, you can't schedule me right now").

Quoted from Linus Torvalds' email: What happens is that (a) since you're spinning, you're using CPU time (b) at a random time, the scheduler will schedule you out (c) that random time might ne just after you read the "current time", but before you actually released the spinlock. So now you still hold the lock, but you got scheduled away from the CPU, because you had used up your time slice. The "current time" you read is basically now stale, and has nothing to do with the (future) time when you are actually going to release the lock. Somebody else comes in and wants that "spinlock", and that somebody will now spin for a long while, since nobody is releasing it - it's still held by that other thread entirely that was just scheduled out. At some point, the scheduler says "ok, now you've used your time slice", and schedules the original thread, and now the lock is actually released. Then another thread comes in, gets the lock again, and then it looks at the time and says "oh, a long time passed without the lock being held at all".__ [...] [...] [...] You need to use a realtime scheduler for that (or be the kernel: inside the kernel spinlocks are fine, because the kernel itself can say "hey, I'm doing a spinlock, you can't schedule me right now").

How can i control the scheduler

How can i control the scheduler

Be the kernel

I use multi-core cpu

I do not really know how to do that in userspace. But, Linus said you have to be the kernel for doing spinlock.

Quoted from Linus Torvalds' email: What happens is that (a) since you're spinning, you're using CPU time (b) at a random time, the scheduler will schedule you out (c) that random time might ne just after you read the "current time", but before you actually released the spinlock. So now you still hold the lock, but you got scheduled away from the CPU, because you had used up your time slice. The "current time" you read is basically now stale, and has nothing to do with the (future) time when you are actually going to release the lock. Somebody else comes in and wants that "spinlock", and that somebody will now spin for a long while, since nobody is releasing it - it's still held by that other thread entirely that was just scheduled out. At some point, the scheduler says "ok, now you've used your time slice", and schedules the original thread, and now the lock is actually released. Then another thread comes in, gets the lock again, and then it looks at the time and says "oh, a long time passed without the lock being held at all".__ [...] [...] [...] You need to use a realtime scheduler for that (or be the kernel: inside the kernel spinlocks are fine, because the kernel itself can say "hey, I'm doing a spinlock, you can't schedule me right now").

Maybe we should study "realtime scheduler" from his sentence.

#include "../util/Timer.hpp" #include <atomic> #include <functional> #include <iostream> #include <thread> #include <mutex> using namespace std; class SpinLock { public: SpinLock () { _flag.store(false); } bool TryLock() { bool expect = false; return _flag.compare_exchange_weak(expect, true); } void Lock() { bool expect = false; while(!_flag.compare_exchange_weak(expect, true)) expect = false; } void UnLock() { _flag.store(false); } private: atomic<bool> _flag; }; SpinLock g_lock; void func(int &arg, int total) { while(total-- > 0) { g_lock.Lock(); ++arg; g_lock.UnLock(); } } mutex g_mutex; void func2(int &arg, int total) { while(total-- > 0) { g_mutex.lock(); ++arg; g_mutex.unlock(); } } const int kAddNum = 1000000; const int kRoundNum = 100; int main() { Timer t; t.TimerBeg(); for(int i = 0; i < kRoundNum; i++) { int value = 0; thread a(func, ref(value), kAddNum); //thread b(func, ref(value), kAddNum); a.join(); //b.join(); } t.TimerEnd(); cout << t << endl; t.TimerBeg(); for(int i = 0; i < kRoundNum; i++) { int value2 = 0; thread c(func2, ref(value2), kAddNum); //thread d(func2, ref(value2), kAddNum); c.join(); //d.join(); } t.TimerEnd(); cout << t << endl; return 0; }

here is my code

func2 is faster than func

I don't know why

I don't know why

Linus explained it in detail here: https://www.realworldtech.com/forum/?threadid=189711&curpostid=189723 Check it up.

ok， I'll check

Hello guys! I'm trying to return a value to main from a function called within a function but the output I get is 0 https://pastebin.pl/view/8db37ebc The value I'm trying to return is "comparisons" Any help is much appreciated!

/helllo

in a scroll bar, the thumb size is only set when 1. the document width and/or height changes. 2. the window width and/or height changes. or 3. the scroll bar width and/or height changes. right?

Severity Code Description Project File Line Suppression State Error (active) E0020 identifier "sort" is undefined

You may read a litle bit more about the compilation process. You may check which sources are used in your Translation Unit and figure out the problem. The link is vg-blog .tech /archives / 27

Be the kernel

ahahahahahah

in a scroll bar, the thumb size is only set when 1. the document width and/or height changes. 2. the window width and/or height changes. or 3. the scroll bar width and/or height changes. right?

Is that c/cpp related question?

Can someone help me analyze a question?