Computer Science questions and answers

Computer Science

What is the naming convention used in ScaLAPACK?

I see that there are many files in the ScaLAPACK library without any immediately obvious naming convention... I'm sure that if the first letter is "p", it means parallel. But I'm not sure how to make sense of the rest of the names as seen here ( ....

Nathan Nathan: 2 hours ago

Computer Science

Numerically computing the advection equation

I am trying to write a program to compute the advection equation. $$u_t +u_x = 0$$ I use the spectral method for the spatial derivative $u_x$ and the leapfrog method for the time derivative $u_t$. That will give the an equation for the next time step: $$u_{j}^{k+1} = u_{j}^{k-1} - ....

Benjamin Benjamin: 3 hours ago

Computer Science

Definition of Lagrange nodes in Gmsh

When gmsh uses higher-order tetrahedral elements, there is an underlying Lagrange basis used to specify the map from reference space to the element. I'm trying to load a gmsh mesh of 3rd degree tetrahedral elements, but I can't seem to find any precise documentation on the location of the nodes ....

Charlotte Charlotte: 4 hours ago

Computer Science

Does the k-th approximate solution of a stationary iteration belong to the k-th Krylov subspace?

For an stationary iteration method solving $Ax=b$ as follows: $$ Mx_k = Nx_{k-1}+b, $$ I have known that when $M = I$, i.e., the Richardson iteration, the k-th solution $x_k = x_{k-1}+r_{k-1}$ is in the k-th Krylov subspace $K_k(A,b)$ with $x_0=0$. So, if we use a Krylov subspace method e.g., ....

Harper Harper: 5 hours ago

Computer Science

Periodic Green's functions in integral equation methods in different frequency regimes

I'm asking about the solution of the Helmholtz equation on a periodic domain with piecewise constant wavespeed in different frequency regimes. One possible approach is to solving this problem is to write down integral equations on the boundary surfaces in terms of the Green's function of the system. Since the ....

Raelynn Raelynn: 17 hours ago

Computer Science

Is there a complexity between $O(n)$ and $O(n \log n)$

Is there a complexity degree that is bigger than $O(n)$ and smaller than $O(n \log n)$? ....

Jordan Jordan: 21 hours ago

Computer Science

Software to build a mesh of a surface from points on the surface

I have a set of points $(x_i,y_i,u(x_i,y_i))\in\mathbb{R}^3$, $i=1,\dots N$, over a surface $S$ (from experimental data). I need to calculate the integral of a function $F$ over that surface. If the points were points over a volume I could use some mesh software (tetgen, for example) and build a mesh, ....

Naomi Naomi: 21 hours ago

Computer Science

For which statistical methods are GPUs faster than CPUs?

I have just installed a Nvidia GT660 graphic card on my desktop and, after some struggle, I manage to interface it with R. I have been playing with several R packages that use GPUs, especially gputools, and I was comparing the time taken by my GPU and CPU to perform ....

Austin Austin: yesterday

Computer Science

scipy optimize fsolve or root

I have a function: delt=1 #trial def f(z): return ((1-2*z)*np.exp(-delt/z))/(((1-z)**(2+delt))*(z**(2-delt))) I also have a variable: import scipy.integrate as integrate var=integrate.quad(f,0,0.5) # equals 0.040353419593637516 Now I am trying to find the value p such that integrate.quad(f,0.5,p)= var and manually I can check that it is around 0.605 I define the following ....

Elizabeth Elizabeth: 2 days ago

Computer Science

adaptive Gauss-Kronrod quadrature with vector-valued integrand

So I'm trying to implement a Gauss-Kronrod adaptive quadrature. That is, I want to calculate $$\int_a^b f(x) dx = \sum_i f(x_i) w_i$$ where f(x) is evaluated at multiple points at once for efficiency. A key point to bear in mind is that $f$ is also vector-valued (possible risk of confusion ....

Stella Stella: 2 days ago