# All Questions

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### How to measure the overall performance of a PETSc program using the -log_summary flag?

When I run a PETSc example in parallel with the flag "-log_summary", the first two tables of information look something like this: ...
434 views

### How effective is the 'tendrils of knowledge' approach to Comp. Sci?

I was reading this on Math SE. The basic question is : Assume that someone wishes to study something advanced; one way to do this would be to start off from basics and build up. But the "bigger ...
590 views

### What are some applications which require interval arithmetic?

I have a very basic notion about interval arithmetic (IA), but it seems to be a very interesting branch of computational science both theoretically and practically. It is clear that the obvious ...
3k views

### Analyzing Numerical Error in C++ Function

Suppose that I have a function that takes as input several floating-point values (single or double), does some computation, and produces output floating-point values (also single or double). I am ...
29k views

### How does the MATLAB backslash operator solve $Ax=b$ for square matrices?

I was comparing a few of my codes to "stock" MATLAB codes. I am surprised at the results. I ran a sample code (Sparse Matrix) ...
1k views

### Problems running a PETSc example in parallel

After configuring and building PETSc, I have successfully been able to run several examples. In particular, I am working with this example. I have been able to run the program using the following ...
340 views

### Enumeration of graphs deriving from Delaunay tessellations in 3D

Is there an algorithm that enumerates the graphs that correspond to some Delaunay tessellation of points in 3D? If so, is there an efficient parameterization of geometries that correspond to any "...
6k views

### FLOP counting for library functions

When evaluating the number of FLOPs in a simple function, one can often just go down the expression tallying basic arithmetic operators. However, in the case of mathematical statements involving even ...
183 views

### Texture analysis methods modern survey paper

I want to study the methods of analyzing textured images. So i searched google scholor but only found very old papers statistical and structural approaches to texture 1979 haralick Image Texture ...
279 views

### Approximately “solving” a linear system of equations without a feasible solution

A linear system of equations has the form $Ax = b$, where a matrix $A$ and a vector $b$ are given, and I wish to find a solution vector $x$. Suppose that the system $Ax = b$ has no feasible solution. ...
5k views

### Linear programming feasibility problem with strict positivity constraints

There is a system of linear constraints ${\bf Ax} \leq {\bf b}$ . I wish to find a strictly positive vector ${\bf x} > 0$ that satisfies these constraints. That means, $x_i > 0$ is required for ...
1k views

777 views

### Library for Fourier transform on triangle lattice

I am looking for reasonably fast implementations of the discrete Fourier transform (DFT) on a 2D triangular or hexagonal lattice. I would appreciate pointers to such implementations (especially ones ...
2k views

### Can a Krylov subspace method be used as a smoother for multigrid?

As far as I am aware, multigrid solvers use iterative smoothers such as Jacobi, Gauss-Seidel, and SOR to dampen the error at various frequencies. Could a Krylov subspace method (like conjugate ...