Questions tagged [c++]
A powerful object oriented programming language.
-2
votes
0answers
34 views
Clion “Cannot Find Any CMake Profile” [closed]
I just downloaded clion for my computer science class at Andrews. I got it for free using my student benefits, so now I'm trying to run the simple program that it has compiled beforehand--the "Hello ...
2
votes
2answers
140 views
Best software to do big number calculations quickly
I am trying to do some work on some math conjecture. I am testing the conjecture numbers using very large math numbers (100+ digits ). I am currently using python to test these numbers.
In the ...
-1
votes
0answers
25 views
Non-Linear Optimization Using NLOPT library in C++
NLOPT (Non-linear optimisation library) clearly mentions that non-linear constraints may not be satisfied at an intermediate step of optimisation, but if one uses maxeval() function as stopping ...
1
vote
0answers
141 views
Good C++ optimization library for BFGS
To implement maximum likelihood estimators, I am looking for a good C++ optimization library that plays nicely with Eigen's matrix objects. Eigen has some capability of interfacing of its own but if ...
1
vote
0answers
37 views
FFTW on subarray with MPI
With the guru interfaces of FFTW, I can apply transforms only to parts of a multidimensional array by modifying the fftw_iodim ...
1
vote
0answers
64 views
$ A * B $ computation when B is a symmetric matrix in armadillo [closed]
Is there any way to multiply a symmetric matrix by a dense one in armadillo(and use the fact that we have a symmetric matrix)? I know about DSYMM Routine in BLAS,...
-1
votes
2answers
249 views
Does armadillo library slow down the execution of matrix operations?
I've converted a MATLAB code to C++ to speed it up, using the Armadillo library to handle matrix operations in C++, but surprisingly it is 10 times slower than the MATLAB code!
So I test the ...
4
votes
3answers
381 views
Efficient eigen-decomposition of covariance matrix
I am looking for an C/C++/Python algorithm implementation that calculates eigenvalues and eigenvectors of a symmetric, positive semidefinite covariance matrix.
A general-purpose eigen-decomposition ...
0
votes
1answer
79 views
Looking for a converter of AMPL/GAMS models into C code
I've done an extensive web search, but could not find an option. Conversion between model formats is available, but conversion of objective function and constraint equations into C code seems absent. ...
2
votes
2answers
138 views
Integration of a diverge function in c++ GSL Library
I am trying to perform an Integral of Hypergeometric function 2F1(a,b,c,x) from -1 to 1 for some good values of $a,b,c$ (lets say $a=1,b=2,c=3$) .
I did it in ...
3
votes
1answer
69 views
MD Simulation: Reference for the Neighbor's List Method
With a rather basic knowledge in C++, I have written my own MD simulation code. Currently, I calculate forces in the most naive way: I go through all the atoms and account for their interactions. This ...
1
vote
0answers
52 views
Dense decomposition of very non-square matrices
I have inherited code that solves Eigen::Matrix problems using the code shown on this page:
...
0
votes
1answer
279 views
I've developed a derivative-free optimization method, looking for comments
Here is the URL: https://github.com/avaneev/biteopt
I've tested it on numerous global optimization benchmarking functions (included), and on real-world hyperparameter optimization problems I have. ...
2
votes
0answers
48 views
Looking for a version of DSDP that is less prone to integer overflows than the original
I am working on a problem that involves semidefinite programming (constrained optimization of fairly large positive definite matrices). The software is written in C++ and calls DSDP 5.8 to solve the ...
1
vote
2answers
257 views
2D Ising Model, heat capacity decreases with lattice size
The problem
I'm trying to make a metropolis simulation of the 2D Ising model.
Basically, it's the following, for each monte-carlo step:
Visit each lattice site,
Compute energy required to flip ...
0
votes
1answer
58 views
Wanting an explanation of the variables in Iterative PCA algorithm
I've been trying to implement the CPU GS-PCA algorithm in this paper .
The code starts on page 28
I have a program written a script in python which gives the same output as the C++ program in the ...
0
votes
1answer
25 views
combinatory exploration c++ [closed]
I have n spots with 2 possible positions each.
I would like to explore all of this possibilities in C++ using loops (or something else if there is a better option).
I was thinking of looping from 0 ...
0
votes
2answers
516 views
Physics Simulation in C++
OK, I know a bit of C++ (very basic syntax), and I want to do physics simulation in C++, like stuff like (also the things mentioned here):
Ripples and waves over a 2-d surface
Vibrating string/...
0
votes
1answer
156 views
C++: Efficient library for dense linear algebra operations (determinant & principal minors)
I usually work with Python, but my basic knowledge of c++ allows me to switch when I need to increase the speed of my code.
Currently, I have a python script that (among other things) computes the ...
0
votes
1answer
82 views
How to do a Generalized Complex Schur (or QZ) Decomposition with Eigen C++? [closed]
I would like to do a Generalized Schur (or QZ) decomposition for a pair of complex matrices $A$ and $B$.
I found the following class:
...
6
votes
2answers
188 views
Recommended language/environment for large scale semi-continuous biological models
We have a fairly large (maybe 1000 equations) differential-algebraic equation model written in ACSLX, an obsolete modelling environment similar to Modelica. The model represents the evolution of a ...
2
votes
0answers
115 views
What could be causing multi-dimensional numerical integration inconsistency?
I'm trying to numerically integrate a multi-dimensional expression. The integrand is complicated; for example this is the integrand for $N=4$:
$$\begin{aligned}&x_1^6x_2^5x_3^3x_4^2(x_1-x_1x_2)(...
0
votes
1answer
69 views
Is the time step size of a Rosenbrock method for stiff systems iteratively calculated?
I have an ODE system of the general form
y' = k(y)(x) + q(z)(x)
x' = a(z)(x) + b(x)(x)
where k,q,a and b are also dependent on the states x and y. The ...
7
votes
2answers
137 views
Generating set of points on a surface defined by constraint
I'm writing a differential geometry library, and one minor convenience I'd like to offer is to generate a set of points on a surface given by a constraint. For example, for a sphere,
$$x^2+y^2+z^2-r^...
1
vote
0answers
131 views
Newton - Raphson method : maxima of function in 2 variables
I am computing the maximum of a function (with two-variables) using Newton-Raphson method. The function is : $e^{-(x \ - x_0)^2 - (y \ - y_0)^2}$, whose maxima exists at $(x_0,y_0)$.
The Jacobian ...
1
vote
2answers
222 views
C++ template design pattern for groups (algebra)
Having both programmed my share of c++ and studied some beginners group theory some year ago, I got curious about this...
Is there any particularly popular template based (object oriented) design ...
1
vote
2answers
850 views
Solving the 1D Particle-in-a-Box using C++
I've just finished learning the physics behind the problem and would like to write a program in C++ than can solve the problem. I'm actually stuck at the start. I've quite a bit of research, the ...
2
votes
2answers
166 views
Inverting big symmetric and singular matrices
In this post I found a very similar probem to the one I have, but not a satisfactory answer for my purposes.
I have a set of matrices $C_\ell$. They are exactly symmetric by construction. ...
3
votes
0answers
238 views
Using C/C++ for Markov chain Monte Carlo (MCMC) methods
I'm working on optimizing the parameters of a mathematical model to fit experimental data, using an existing formula for the likelihood of observing the data given a set of parameter values. At the ...
5
votes
1answer
112 views
Simple Monte Carlo in C++, result dependent from seed
I implemented as an exercise a program to sample the statistics of the escape time of a Brownian particle in a potential well. I used the Euler-Maruyama method to numerically integrate the ...
0
votes
1answer
320 views
Speeding up ODEINT stiff example [closed]
I am trying the implement the following odeint solver example but my differential equations are different.
https://github.com/headmyshoulder/odeint-v2/blob/master/examples/stiff_system.cpp
The ...
1
vote
2answers
131 views
Sign of integer determinant 4 by 4
I'm in the context of this publication: http://www.gilbertbernstein.com/resources/booleans2009.pdf
I applied quantization to my point coordinates: All coordinates are integer lying in [0, 2 power 20]....
4
votes
1answer
107 views
Using GSL for basic operations
I am learning C/C++ for Scientific Computing and I have a question regarding the usage of scientific libraries for basic operations.
Suppose I have to write a small program in C for a bioinformatics ...
0
votes
0answers
84 views
Inbuilt function in C++ to return the value of $c$ in from the CDF $F(c)$ in the case of $t-$ distribution?
I was coding for calculating the confidence interval for mean $\mu$ of the Normal Distribution with unknown $\sigma^{2}$.
In between the algorithm I have to calculate $c$ in $F(c) = \frac{1 + \gamma}{...
4
votes
1answer
343 views
2D numerical integration with infinite limit (C++)
In order to integrate a two dimensional function of the form
$$\int_{1}^\infty \int_{-\sqrt{x^2-1}}^{\sqrt{x^2-1}} e^{-x} \rm{d}y \rm{d}x,$$
I have been attempting to use the following code (written ...
1
vote
1answer
280 views
LAPACK sorting eigenvalues differently each time
I'm using LAPACK zgeev routine to get eigenvalues and eigenvectors of a symmetric matrix in C++. Problem is zgeev is being called in a loop but it sorts eigenvalues (and eigenvectors) differently ...
1
vote
0answers
71 views
MPI_Finalize() only some processors
I want to develop a distributed algorithm with MPI which have load balancing capability. But there is a situation that I'm not very clear about, which is, when the number of tasks is less than the ...
0
votes
2answers
199 views
Matlab, Mathematica & LAPACK returning 3 different eigenvectors
(I'm not sure which of math.se / stackoverflow / scicomp.se is the right place to ask this question)
I have a C++ code which generates a complex matrix and then calculates its eigenvalues and ...
1
vote
0answers
71 views
lightweight implementation of semiempirical quantum chemistry (e.g. MNDO,AM-1,PM3)
I'm searching for semi-empirical quantum chemistry solver which would be easy to integrate into my own software. I found a few implementations which can be in principle used e.g. MOPAC, ORCA, SQM some ...
0
votes
2answers
106 views
Spherical volume integral from pre-calculated points - which algorithm is best?
I need a fast and accurate method to calculate 3d spherical volume integrals.
I have pre-calculated data of high precision that just needs a few trivial manipulations before each integration step - ...
0
votes
1answer
73 views
Questions about implementing an electromagnetism/photonics solver package
I am hoping to start (very slowly) on implementing some form of a computational photonics/electromagnetism package. I know things like Meep, S4, FDTD++, EMPy, and a host of other proprietary/free/...
-3
votes
1answer
2k views
C++ - Expression must be modifiable lvalue [closed]
I am new to C++.
I am trying to set up a very basic TCG game (with only minion with no text).
I think my issue might be linked with pointer.
Below are the functions and attributes:
...
2
votes
1answer
1k views
Simple open-source Quantum chemistry or DFT code in C/C++
I know lot of density functional packages in fortran, including one which we are developing in our group (Fireball-DFT) but I don't like fortran very much and I would like something which is easier ...
3
votes
3answers
1k views
A good, simple book/resource on Parallel Programming in C++ for scientific computing
I am a Mechanical Engineering grad student, currently working on a project which will be scaled up in the new future to require quite some processing power. I am using C++ for the code that I have, ...
1
vote
0answers
75 views
Problem in analyzing the program of Gauss Jordan Inverse problem
I had to code a program which calculates Inverse of a matrix by Gauss-Jordan Inverse method , I was trying to analyse the program and then code it myself.
the link
http://hullooo.blogspot.in/2011/...
1
vote
0answers
63 views
Is MATLAB feasible for app deployment versus lower level languages [duplicate]
MATLAB/Octave is a pretty useful language for prototyping scientific computation use cases, however I would like to know if the sheer nature of being a high level language bottlenecks how fast the ...
1
vote
1answer
484 views
Improve numeric stability of subtraction in C++ [closed]
I'm writing a matrix library in c++. After some debugging I found that a simple double difference is not zero for two "equals" numbers. This is due how double are represented in a computer of course. ...
4
votes
1answer
198 views
SLEPc eigensolvers take long time to converge for large sparse symmetric matrices
I am leveraging the SLEPc library for solving the first $k$ (where $k = 3$ or $4$) eigenvalues and their corresponding vectors for a matrix of size 200,000. The matrix is sparse and symmetric. I ...
7
votes
3answers
2k views
Method to check for positive definite matrices
I think it's already been asked, but I still can't figure out a way to do it computationally.
I had to check for positive definiteness of an $n \times n$ matrix $A$. I know that for any nonzero ...
1
vote
2answers
546 views
LU decomposition of large dense matrices
I wanted to generate LU decomposition of large size dense matrices ($N>10^7$), the LU decomposition I'm currently using is based on Adaptive Cross Approximation and is taking very long time to ...
