# All Questions

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### What features do users need from an MPI C++ interface?

The 3.0 version of the MPI standard formally deleted the C++ interface (it was previously deprecated). While implementations may still support it, features that are new in MPI-3 do not have a C++ ...
4k views

### Are there any famous problems/algorithms in scientific computing that cannot be sped up by parallelisation

Are there any famous problems/algorithms in scientific computing that cannot be sped up by parallelisation? It seems to me whilst reading books on CUDA that most things can be.
16k views

### Dealing with the inverse of a positive definite symmetric (covariance) matrix?

In statistics and its various applications, we often calculate the covariance matrix, which is positive definite (in the cases considered) and symmetric, for various uses. Sometimes, we need the ...
5k views

### Which package should I use to wrap Modern Fortran Code with Python?

I know of, and have used f2py2e to wrap some old Fortran 77 code, but my understanding is that it does not work with newer Fortran 95 code. I've researched what I should use, and have come across ...
21k views

### What is the fastest way to calculate the largest eigenvalue of a general matrix?

EDIT: I am testing if any eigenvalues have a magnitude of one or greater. I need to find the largest absolute eigenvalue of a large sparse, non-symmetric matrix. I have been using R's ...
712 views

### Recommendations and experiences on which license to choose for software?

Developers of software have the choice to choose an appropriate license in accordance with the goal(s) of the work. Can anyone give some recommendations/experiences on which license to pick for ...
7k views

### Robust algorithm for $2 \times 2$ SVD

What is a simple algorithm for computing the SVD of $2 \times 2$ matrices? Ideally, I'd like a numerically robust algorithm, but I'll like to see both simple and not-so-simple implementations. C code ...
6k views

### What is the computational cost of $\sqrt{x}$ in standard libraries?

One of the major issues that we have to deal with in molecular simulations is the calculation of distance-dependent forces. If we can restrict the force and distance functions to have even powers of ...
6k views

### Compressing floating point data

Are there any tools specifically designed for compressing floating point scientific data? If a function is smooth, there's obviously a lot of correlation between the numbers representing that ...
16k views

### Fastest Delaunay triangulation libraries for sets of 3D points

Which is the fastest library for performing delaunay triangulation of sets with millions if 3D points? Are there also GPU versions available? From the other side, having the voronoi tessellation of ...
5k views

### Is Crank-Nicolson a stable discretization scheme for Reaction-Diffusion-Advection (convection) equation?

I am not very familiar with the common discretization schemes for PDEs. I know that Crank-Nicolson is popular scheme for discretizing the diffusion equation. Is also a good choice for the advection ...
3k views

### What is the relationship of BLAS, LAPACK, and other linear algebra libraries?

I have been looking into C++ linear algebra libraries for a project I've been working on. Something that I still don't have any grasp on is the connection of BLAS and LAPACK to other linear algebra ...
16k views

### Permute a matrix in-place in numpy

I want to modify a dense square transition matrix in-place by changing the order of several of its rows and columns, using python's numpy library. Mathematically this corresponds to pre-multiplying ...
2k views

### How does one test a numerical ODE solver implementation?

I'm about to start working on a software library of numerical ODE solvers, and I'm struggling with how to formulate tests for the solver implementations. My ambition is that the library, eventually, ...
4k views

### How can the gravitational n-body problem be solved in parallel?

How can the gravitational n-body problem be solved numerically in parallel? Is precision-complexity tradeoff possible? How does precision influence the quality of the model?
643 views

### Is there software that can autogenerate numerically-accurate floating point C routines from symbolic formulae?

Given a real function of real variables, is there software available that can automatically generate numerically-accurate code to calculate the function over all inputs on a machine equipped with IEEE ...
19k views

### BFGS vs. Conjugate Gradient Method

What considerations should I be making when choosing between BFGS and conjugate gradient for optimization? The function I am trying to fit with these variables are exponential functions; however, the ...
49k views

### How should I install a Fortran compiler on a Mac? (OS X 10.x, x >= 4)

Related question: State of the Mac OS in Scientific Computing and HPC A significant number of software packages in computational science are written in Fortran, and Fortran isn't going away. A ...
6k views

### Visualizing very large link graphs

I am looking for a tool to visualize very large directional link graphs. I currently have ~2million nodes with ~10million edges. I have tried a few different things, but most take hours to even do ...
8k views

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### Using unconventional programming languages for scientific computation [closed]

Note: the following post may include controversial opinions, so please note that they are only my opinions, and not intended to offend anyone. I'm being programming in some form or the other since ...
760 views

### Solving $(G^TA^{-1}G)x = b$ without inverting $A$

I have matrices $A$ and $G$. $A$ is sparse and is $n\times n$ with $n$ very large (can be on the order of several million.) $G$ is an $n\times m$ tall matrix with $m$ rather small ($1 \lt m \lt 1000$) ...
2k views

### What simple methods are there for adaptively sampling a 2D function?

I have a two-dimensional function $f(x,y)$ whose values I would like to sample. The function is very expensive to compute and it has a complex shape, so I need to find a way to get the most ...
3k views

### Modern C++ in scientific computing?

I am looking for books or articles, or blog-posts, or any published material in general, that address specifically the uses of C++ modern features (move semantics, the STL, iterators, lazy evaluation, ...
9k views

### Libraries for solving sparse linear systems

There are a number of different libraries out there that solve a sparse linear system of equations, however I'm finding it difficult to figure out what the differences are. As far as I can tell there ...
I am looking to solve a constrained optimization problem where I know the bounds on some of the variables (specifically a boxed constraint). $$\arg \min_u f(u,x)$$ subject to $$c(u,x) = 0$$  ...