Questions tagged [c++]

A powerful object oriented programming language.

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4
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0answers
222 views

Adaptive mesh data structure for Fast Marching Method to overcome RAM limit

On an uniform mesh of positions in space $\ (x_i,y_j,z_k)$: $$\ x_i = x_0 + i\Delta x,\quad i=0,\ldots,n_x$$ $$\ y_j = y_0 + j\Delta y,\quad j=0,\ldots,n_y$$ $$\ z_k = z_0 + k\Delta z,\quad k=0,\...
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3answers
282 views

Traveling Salesman Problem

First off some context. The Traveling Salesman Problem(TSP) is to find the most efficient route passing through a series of points only once. However, there is no perfect function to solve for this in ...
2
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2answers
296 views

Compiled c++ code runs much faster with double than float. Explanation?

I am still rather new on here and I hope question is suitable for this forum otherwise please help me migrate it to greener pastures. I am an electrical engineer specializing in applying mathematics ...
46
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7answers
12k views

Is it a good idea to use vector<vector<double>> to form a matrix class for high performance scientific computing code?

Is it a good idea to use vector<vector<double>> (using std) to form a matrix class for high performance scientific computing code? If the answer is no. ...
11
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3answers
867 views

Testing if two 12x12 matrices have the same determinant

I am given a $12 \times 12$ matrix $Q$ that is symmetric, invertible, positive definite and dense. I need to test if $$\det(Q) = \det(12I-Q-J) \; \; (1)$$ where $J$ is the all ones matrix. I am ...
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0answers
70 views

Metis: how to use and tutorial recommendation

I am new to METIS and trying to use it in my fortran code. I read the manual online. But still, I am not sure about how to implement it my code. I tried the test cases in the graphs directory. For ...
3
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2answers
605 views

I am searching for a C++ code implementing the complex polygamma function

I googled about some code on the complex polygamma function especially C++ code, but can't find anything. Does anyone know where to find such code? The complex digamma function does exist but not the ...
0
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1answer
104 views

Good C, C++ library for efficient grid search / tuples, ideally with bindings to Eigen

I have a $q$-dimensional grid, known at run, not compile-time, that has $50$ points in each direction and hence $50^3$ combinations that I would like to first build and then call a function with each ...
4
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3answers
273 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 ...
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0answers
46 views

How to integrate the contents of a vector using an adaptive quadrature routine [duplicate]

I have a function which requires the return type to be a container. The problem is that I need to integrate the contents of the container as efficiently as possible and was hoping to use adaptive ...
5
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1answer
157 views

Whittaker-Shannon interpolation: Accuracy dies with speedup; can it be fixed?

With a truncated Whitaker-Shannon series (cardinal series) $$ f(t) = \sum_{j = 0}^{n-1} y_{j} \frac{\sin\left(\pi( \frac{t-t_0}{h} -j)\right)}{\pi\left(\frac{t-t_0}{h}-j\right)} $$ we can naively ...
1
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2answers
2k 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
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3answers
164 views

Find a solution of large system of inequalities

I have a large system of homogenous inequalities involving 33 real unknowns of the form $$ \vec{F}(z_i)^T \cdot \vec{X}>0\, $$ where $\vec{X} = \left(x_1,...,x_{24}\right)^T$ are the unknowns and ...
1
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1answer
372 views

LAPACK equivalent on c++ , which is the best one? [duplicate]

I am following a course of computational material physics. The professor uses fortran to code and uses lapack to solve eigenvalue problems. So far I just know c++. There is an equivalent library that ...
3
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2answers
1k views

Developing a C++ solid mechanics program

I am a beginner in computational science and programming. I am doing research in non linear solid mechanics analysis and using C++ for coding. I have been exploring various finite element open source ...
3
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0answers
69 views

Structural Analysis Library

Can anyone recommend a structural analysis library that satisfies the following requirements: C++ API Simulate both beam elements and shell (slab) elements Both static and dynamic analysis Free and/...
3
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3answers
1k views

Simple way to store/read data from file in C++

I've been running various simulations with C++, and doing so has often involved saving lots of data to file (real/complex matrices, arrays, etc) and then reading them into other programs later. ...
2
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0answers
2k 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 ...
2
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2answers
338 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 ...
9
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3answers
2k views

How to use polylogarithm function in c++?

Is there any preprocessor directives that could be used to use the polylog function? Or is it included in cmath? If so, do you call it by Li or by polylog? EDIT: What I really am trying to do is give ...
9
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3answers
2k views

Are there any “light-weight” FEM packages around?

Basically, FEM seems to be a problem that is pretty much "solved". There are numerous powerful frameworks existing, like Trilinos, PETSc, FEniCS, Libmesh or MOOSE. One thing they have in common: They ...
3
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2answers
121 views

C++ library to mutate pdb residues

Are there any open source libraries available to mutate PDB protein residues? If so are do you have any examples of them?
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3answers
967 views

C++ mixed integer nonlinear programming (MINLP) solver

Doing research project in material involving (mixed integer nonlinear programming) MINLP problem, we want to implement MINLP based on C++, because the majority of our project is based on C++. What ...
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2answers
534 views

How does MPI differentiate between two computers?

I am starting to dabble in MPI. I am fairly new to this area and I am currently reading the MPI standard. I would like to write my first MPI program, a simple hello world program, on a cluster that ...
3
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2answers
1k views

Stabilizing a 3x3 real symmetric matrix eigenvalue calculation

I have many 3x3 real symmetric matrices for which I need to determine the eigenvalues. Wikipedia gives a nice non-iterative algorithm for this case, which I have translated into C++: ...
0
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2answers
1k 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 ...
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0answers
112 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,...
0
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1answer
64 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 ...
3
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0answers
951 views

total memory usage of MPI shared memory

I am trying to use the MPI share memory feature. I have several SMP nodes, and each of them has four cores. I need an array of size N for each node that should be accessed by all four cores in each ...
6
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3answers
1k 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
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1answer
174 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. ...
7
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0answers
250 views

Numerical integration using interval arithmetic, nowadays

Is there now a package for rigorous numerical integration that uses interval arithmetic and has access to a well-developed library of special functions? By "well-developed", I mean something that, at ...
2
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1answer
475 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 ...
0
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1answer
375 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
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0answers
53 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
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1answer
260 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 ...
4
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1answer
147 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 ...
1
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2answers
3k 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
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1answer
29 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
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1answer
357 views

Debugging in parallel mode using Netbeans

I want to debug a c++ code with Netbeans. I can use the debugger in sequential mode but I dont know how to debug it when I want to run it in parallel. I would be grateful if anyone help me on this ...
0
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1answer
217 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: ...
2
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0answers
148 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
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1answer
123 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 ...
6
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2answers
176 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^...
17
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6answers
3k views

To what extent is generic and meta-programming using C++ templates useful in computational science?

The C++ language provides generic programming and metaprogramming through templates. These techniques have found their way into many large-scale scientific computing packages (e.g., MPQC, LAMMPS, CGAL,...
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2answers
208 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. ...
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0answers
481 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
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2answers
432 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 ...
2
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0answers
468 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 ...
0
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1answer
709 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 ...