# Computational Science Stack Exchange Community Digest

## Top new questions this week:

### Numerical flux and source term in FVM (Burger's like equation)

I'm trying to solve the following equation with FVM $$u_t + f(u)_x = g(u)$$ where $g$ is some smooth function of $u$ and $f(u) = \frac{u^2}{2}$. This is really similar to Burger's equation, except ...

numerics finite-volume discretization numerical-modelling hyperbolic-pde
 asked by VoB 5 votes
 answered by Maxim Umansky 1 vote

### Sparse Matrix Matrix multiplication using Intel MKL

Let $D$ be a sparse matrix. I want to compute $D\times D^T$. As $D$ is fairly large, so I am row-slicing $D$. That means for a range $(i,j)$, I am computing $C = D(i:j,:) \times D^T$ and performing ...

sparse-matrix intel-mkl
 asked by user2104150 2 votes

### Does BFGS preserve the bandedness of the inverse hessian?

In the BFGS method we perform iterations by calculating an approximation $\boldsymbol{H}_k$ to the inverse Hessian $\boldsymbol{H}$ of the objective function. This method belongs to a family of ...

optimization banded-matrix quasi-newton
 asked by DanielRch 2 votes

### Adaptive Runge-Kutta for Stochastic (Projected) Gross-Pitaevskii Equation

I am using the XMDS library for solving the stochastic (projected) Gross-Pitaevskii equation i \hbar \partial \Phi\left(\mathbf{r},t\right)_t=\hat{\mathcal{P}}\left\{(1-i ...

runge-kutta integration stochastic adaptive-timestepping stochastic-ode
 asked by Jack G 2 votes
 answered by Jack G 0 votes

### C++ book recommendation- Scientific computing and C++

I'm a master's student in Math interested in Numerical Analysis. I know there are lots of questions like that on this site, but I think this is the best place to ask. So, I'm looking for an ...

c++ reference-request
 asked by andereBen 1 vote
 answered by Herling G.A. 0 votes

### Setting up optimization problem in GEKKO

I have the following dynamical system, $\frac{d \phi}{dt} = -M^TDM\phi \tag{1}\label{1}$ $\frac{d \hat\phi}{dt} = -M^T\tilde{D}M\hat \phi \tag{2} \label{2}$ $\eqref{1}$ represents the exact ...

python constrained-optimization nonlinear-programming constraints gekko
 asked by Natasha 1 vote

### Convolution in Python

I have an integral of a convolution between two functions. How can I calculate this in Python? It is a continuum convolution.

python integral-equations convolution
 asked by Brenda Pinheiro 1 vote
 answered by nicoguaro 1 vote

## Greatest hits from previous weeks:

### Linear interpolation in Fortran

Is there a Fortran subroutine which performs linear interpolation in one-dimenional data? I need something similar to MATLAB function interp1.

fortran interpolation
 asked by kyperros 6 votes

### Which software and workflow is recommend for publication of scientific data and graphs?

Which software provides a good workflow from simple plotting of a few datapoints up to the creation of publication level graphics with detailed styles, mathematical typesetting and "professional ...

visualization data-management
 asked by Alexander 41 votes
 answered by GertVdE 31 votes

### What's the fastest software(open source) to solve mixed integer programming problem

I have a mixed integer programming problem. And I am current using GLPK as my solver. But I found that GLPK is good for Linear Programming problem, but for Mixed Integer programming, it requires much ...

optimization software linear-programming mixed-integer-programming
 asked by Yu Hao 14 votes
 answered by Geoff Oxberry 14 votes

### Fastest PCA algorithm for high-dimensional data

I would like to perform a PCA on a dataset composed of approximately 40 000 samples, each sample displaying about 10 000 features. Using Matlab princomp function consistently takes over half an hour ...

high-dimensional data-analysis
 asked by mellow 11 votes
 answered by Alexander 11 votes

### Python vs FORTRAN

Which one is better: FORTRAN or Python? And I guess that in both cases you need Gnuplot, am I right? I'm working on a Windows machine at the moment. I'd like to use it to get numerical solutions for ...

python fortran
 asked by Nick 17 votes
 answered by Geoff Oxberry 29 votes

### How to code in Matlab: If an argument is empty, then default to "x" value?

I have a function with a number of arguments, but some of them are optional. 1.) If when the function is called, some are left empty, how do I code it so that it defaults to a specific value? 2.) ...

matlab
 asked by AlanH 7 votes
 answered by Nat Wilson 7 votes

### How to formulate lumped mass matrix in FEM

When solving time dependent PDE's using the finite element method, for example say the heat equation, if we use explicit time stepping then we have to solve a linear system because of the mass matrix. ...

finite-element time-integration navier-stokes
 asked by James 11 votes
 answered by nicoguaro 12 votes

## Can you answer this question?

### What is the state-of-the-art in parallel sparse matrix and dense vector multiplication?

For sure, there has been many highly optimized library on this. But I am working on a matrix-free context since the problem size does not allow explicit storage of sparse matrix elements. I'd love ...

parallel-computing sparse-matrix
 asked by Izzy Vang 1 vote
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