General C++ Programming - March 2024

Hi, I have this code: vector<string> coll1 = { "Hello", "this", "is", "an", "example" }; list<string> coll2; move(coll1.begin(), coll1.end(), back_...

[9 replies] Last: thank you all!! (by JUANDENT)

by JamieAl

1D FFTs of an Eigen tensor

So I am trying to take an FFT along a specific direction of an Eigen tensor, similarly to my code in MATLAB. In MATLAB: Nx = 8; Ny = 6; Nz= 8; Lx =6; Ly =...

[10 replies] Last: I was trying to take the 1D FFT along each direction separately to un... (by JamieAl)

by deleted account xyzzy

C++23 Formatting Ranges

C++23 added the ability to "print out" using formatting options a container directly instead of having to use some form of a loop to access each element individ...

[5 replies] Last: I would recommend two books, one on C++20 and the other on C++23, by t... (by deleted account xyzzy)

by Zaap

vector push_back passing size from 0 to overflow

Hi, please see the following code and the associated prints. I also add the Argument class below. Basically, it crashes the second time it goes in the loop b...

[3 replies] Last: Bumping this to just give some insight that might be generally helpful... (by Ganado)

by JUANDENT

The object itself (this) is it a leak if its constructor throws?

if the ctor throws, then the object this has already received the memory (some new or alloc has been executed)... so, does the object this leak? the only possi...

[7 replies] Last: Excellent comments! Thank you again!! (by JUANDENT)

by JamieAl

Convert MATLAB function to C++

I have a function from a textbook: https://people.maths.ox.ac.uk/trefethen/spectral.html Basically it calculates the Chebyshev differentiation matrix and I hav...

[14 replies] Last: @mbozzi I think the problem is that duyk is too small to hold the en... (by JamieAl)

by Zaap

Threading: changing processor count does not change performances

Hi, I've been doing some multi-threading in my program. This program essentially iterates over a dataset and for each line computes some stuff. My multi-t...

[8 replies] Last: [quote=Zaap]I think using a for_each in my code will create an excessi... (by TheIdeasMan)

by JamieAl

Why is my fft function not working as expected?

Trying to take the fft of 2D array along one direction (x for example and not y) so it's a 1D FFT of 2D array. I have done this successfully before using Eigen ...

[9 replies] Last: it makes no difference whether you store your matrix row or column maj... (by jonnin)

by JUANDENT

Cyclic dependencies - how to deal with them?

Hi, I have a class GridCtrl that delegates to GridCtrlHandler but GridCtrlHandler must also be able to call methods on GridCtrl. I cannot have GridCtrl.h ...

[6 replies] Last: Heh, I created a circular dependency issue using modules and Visual St... (by deleted account xyzzy)

by JUANDENT

why use decltype(auto) return type instead of auto?

Hi, I have this code namespace detail { template <class F, class Tuple, std::size_t... I> decltype(auto) apply_impl(F&& f, Tuple&& t, std::index_sequence<I....

[3 replies] Last: I swear modern C++ is a minefield Too bad there's no golden idol acr... (by deleted account xyzzy)

by Cplusc

MPI Blocking and Non_Blocking Communication

I'm currently working on a lattice Boltzmann code (D3Q27) employing MPI for parallelization. I've implemented MPI 3D topology for communication, and my code sni...

[7 replies] Last: @mbozzi thanks for your help. In your algorithm, I assume there's a ... (by Cplusc)

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