Questions tagged [reference-request]

This tag is for requests for books, papers, and citations.

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2 votes
0 answers
69 views

Solving systems of the form $y_i=UW x_i$ for $U,W$

I'm looking for pointers/examples of solving system of equations $y_i=f_W(f_U(x_i))$ for $W,U$ where $f_M(x) \approx M x$ $U,W$ are updated simultaneously $i\in (0, 10^{12})$ Simplest example is ...
2 votes
1 answer
299 views

Literature request covering Chebyshev's pseudospectral collocation method

I would like to request some literature recommendations covering Chebyshev's pseudospectral collocation method for solving space-time PDEs. It would be nice if it even contained some example problems ...
0 votes
0 answers
44 views

Which numerical method can I use to solve this system of hyperbolic PDEs?

Backround The mathematical model I am trying to numerically solve models wave propagation inside a cylinder with specific material properties suited for dynamic loading. The cylinder's upper base is ...
12 votes
2 answers
2k views

Why are systems with clustered eigenvalues easy to solve?

I came across the following slide by Theo Diamandis & Zachary Frangella on what makes the linear system $Ax=b$ easy to solve using the conjugate gradient method. Transcription: CG converges ...
2 votes
1 answer
95 views

references for optimization in the context of parameter identification with finite elements

i am performing parameter identification for a non-linear partial differential equation (elasticity) that I solve with finite elements. My optimization problem is a non-linear least squares data-...
1 vote
0 answers
44 views

Solution to the Liouville-Gibbs equation

What would be the approach to numerically solve for $\rho(x,t)$ the following equation with some initial conditions $$\frac{\partial\rho}{\partial t} +\sum_{i=1}^n\left(\frac{\partial(\rho g_i)}{\...
1 vote
0 answers
92 views

Closed formula to diagonalize discretized (perhaps randomized) Laplacians

I was wondering whether there is a closed formula for the eigenvalues and eigenvectors of the discretized Laplacian in (edit) $[0,1]^n$ with a uniform grid, using what I imagine is a $2n+1$ stencil. ...
4 votes
2 answers
363 views

Looking for references on this adaptive Runge–Kutta method (GSL’s rk2)

Background For a study that is beyond the scope of this question, I applied all of GSL’s adaptive Runge–Kutta methods to a certain problem. This includes a Runge–Kutta method of 2nd and 3rd order, ...
2 votes
1 answer
134 views

Truncated power series algebra implementation

1) I am looking for references for an efficient implementation and usage of TPSA. What sources exist besides Berz's 1989 original paper and the incomplete chapter in Dragt's book? 2) Are there ...
11 votes
5 answers
5k views

Memory efficient implementations of partial Singular Value Decompositions (SVD)

For model reduction, I want to compute the left singular vectors associated to the - say 20 - largest singular values of a matrix $A \in \mathbb R^{N,k}$, where $N\approx 10^6$ and $k\approx 10^3$. ...
5 votes
2 answers
313 views

Continuous vs discontinuous space-time FEM

What are some reasons for approximating a (e.g. parabolic) PDE using the space-time method, with continuous finite elements in time, vs discontinuous finite elements in time? Are there e.g. ...
6 votes
0 answers
119 views

References on the theory of Petrov-Galerkin methods for more "basic" problems

In my reading on various aspects of FEM, Petrov-Galerkin methods often arise in the study of solutions of convection-dominated systems, such as Hughes' work on Navier-Stokes, or systems where optimal ...
1 vote
0 answers
70 views

Has the arithmetic for exotic (unsigned float with positive exponent) number format been solved?

The data type is a doubly unsigned float. This is where the value and exponent are both strictly positive. The range of this number should include $0$ and $[1, ~2^{\text{exponent}})$, skipping all ...
1 vote
0 answers
88 views

Resource to learn assembly code

I'm a PhD student in mechanical engineering and I have to perform a lot of simulations for my project. In my lab we use several well-known libraries, from FEM to machine learning. As we're doing ...
0 votes
0 answers
48 views

Efficient cutting of mesh edges

I am looking for efficient algorithms to cut a mesh along edges. I have a (half-edge) mesh and a list of inner edges that I want to cut, such that both are new boundary edges. At each vertex there can ...
3 votes
3 answers
210 views

Stable finite elements for the mixed form of the elasticity equations

The mixed form of the elasticity equations is to find the unique critical point of the Hellinger-Reissner functional $$J(u, \sigma) = \int_\Omega\left\{\frac{1}{2}A\sigma : \sigma + u\cdot\left(\nabla\...
1 vote
1 answer
136 views

Could you recommend some books on FEM that explain various data-structures in FEM?

I want to understand the data structure of elements, elements around elements, and so on, and various other data structures in FEM, could you please recommend some books?
5 votes
0 answers
91 views

How to get an "optimal point" for refinement in FEM adaptive mesh refinement?

Consider the following 1D problem \begin{align*} \begin{cases} \displaystyle -\frac{d^2u}{dx^2} = f(x), \hspace{0.5cm} x\in (a,b) \\[4mm] u(a) = u_{a}, \ \ u(b) = u_{b} \end{cases} \end{align*} I ...
1 vote
1 answer
169 views

Non-Uniform Grids: Approximation Quality: First Order Finite Difference vs. First Order Finite Volume

Consider the advection/transport equation in 1D with constant velocity $a(x) \equiv 1$ $$u_t(t,x) + u_x(t,x) = 0$$ on a, say, periodic domain. On uniform grids $$ \{x_i\}_{i = 1, \dots, N}, \quad x_{i ...
2 votes
1 answer
3k views

Introduction to Lattice Boltzmann methods [closed]

I am trying to learn the Lattice-Boltzmann method and was looking for some good beginner resources explaining the method. I have been looking at some codes online, but have been having trouble ...
3 votes
1 answer
169 views

Adaptive Lagrangian-Eulerian methods and practical benchmark results

Does anyone know of any published study that talks about the practical aspects of running Adaptive Lagrangian-Eulerian techniques for solid and/or fluid mechanics problems? I'm looking for things ...
7 votes
0 answers
279 views

Matrix-free FEM references

I've seen that many people are using matrix-free fem codes in my community (mechanical engineering). I have to admit that I googled a bit and I didn't manage to find a good reference for the subject. ...
1 vote
1 answer
97 views

Automatic Differentiation using foward mode on matrices

Whilst googling I see reverse mode automatic differentiation (AD) tends to be used when optimising neural networks. Would it not be better to use forward mode and treat your input as a single variable,...
2 votes
2 answers
126 views

Nonlinear Hyperbolic PDEs: Known solutions

I would like to collect some test-problems for nonlinear hyperbolic PDEs (Euler Equations, Shallow Water Equations, Ideal MHD, Acoustic Perturbation, ...) for which analytical solutions are known. A ...
1 vote
1 answer
533 views

Kolmogorov n-width

Could someone please point me to an understandable definition of the Kolmogorov n-width? I'm having a hard time figuring out what is the output of the definition - is it an integer? Edit: I realize ...
7 votes
3 answers
173 views

Reference request: Philosophy of Computational Science

Do you suggest any references (papers, monographs, books) about the philosophy of computational science? Recently, I found out about the following two: Winsberg, E. (2009). Computer simulation and ...
4 votes
1 answer
103 views

Stabilized Many Stage Runge-Kutta methods instead of Local/Multirate Time Stepping

Locally refined meshes are often inevitable for accurate, yet feasible computations. In the context of time-dependent PDEs, however, this comes at the cost that (due to the CFL condition) reducing the ...
0 votes
0 answers
57 views

Finding optimal values from multiple parameter estimation runs

I've performed a parameter estimation repeat (i.e. 1000 parallel runs with the same initial values of parameters). I am trying to estimate ~20 parameters using measurements from experiments. After ...
0 votes
2 answers
399 views

Searching for recent code source for "Parallel scientific computing in C++ and MPI "

I am learning C++ scientific computing with "Parallel scientific computing in C++ and MPI A Seamless Approach to Parallel Algorithms and their Implementation" since it kept coming up a lot ...
5 votes
0 answers
197 views

Dense least-squares with millions of variables

Suppose $X$ is a dense $m\times n$ data matrix and we seek to find $w$ by approximately iterating least-squares filter equation: $$w = w - \mu (X'X)^{-1}X'(Xw-b)$$ What are known approaches for $10^9&...
1 vote
1 answer
136 views

What are the prerequisites and resources to self-learn the Boundary Element Method for Contact Mechanics problems?

What are the prerequisites to learning BEM? In which order is it advisable to learn BEM and FEM - either one before the other, or does it not matter? What are some good resources to self-learn BEM? P....
7 votes
1 answer
3k views

4th order tensor rotation - sources to refer

I am trying to model a linear elastic material in Abaqus using a UMAT. For my application, I need to rotate the 6x6 compliance matrix for a given set of eigenvectors (or a rotation matrix). I came ...
1 vote
1 answer
87 views

A priori estimates in finite elements for inhomogeneous heat equation

Consider the problem $$\partial_t u-\Delta u = f\\ u(\Sigma_1)=f_D\\ \partial_\nu u (\Sigma_2)=f_N\\u(0)=u_0$$ where the sides of the space-time cylinder $\Sigma_i$ are disjoint (one of them could be ...
2 votes
0 answers
39 views

Unconstrained convex optimization: correlation between dimensionality and Lipschitz constant

The author of the SIAM News article "Optimization Theory and Perspectives on the Field of Machine Learning" mentions: ... For unconstrained convex optimization, GD (gradient descent) ...
3 votes
1 answer
124 views

Has there been a comparison bewteen SIMPLE/SIMPLER and JFNK for steady CFD?

I'm looking for a comparison between the Jacobian-Free Newton-Krylov (JFNK) method performance compared to the conventional CFD nonlinear solution methodologies like SIMPLE. Does anyone know if such ...
4 votes
1 answer
125 views

A priori FEM estimates without $H^2$ regularity

In basic lectures on finite elements theory, people always assume $H^2$ regularity of the solution in order to derive $O(h^k)$ a priori estimates in the norms $H^{2-k}$, $k=1,2$. For simplicity let's ...
0 votes
0 answers
67 views

Reference request for finite elements theory

Consider a domain $\Omega \subseteq \mathbb{R}^{2,3}$ which is non convex and with $C^2$ boundary. Could you recommend a good reference where it is explained how: without needing isoparametric ...
7 votes
1 answer
3k views

How to directly compute the inverse of an ill-conditioned dense matrix

I know that it is generally a bad idea to compute the inverse matrix directly. However, if it is necessary to compute the inverse of an ill-conditioned invertible dense matrix, then what can I try? ...
3 votes
3 answers
2k views

Scalar vs. vector potential for magnetostatics

When trying to solve a magneto-static boundary-value problem (BVP) ($\nabla \times \mathbf{H} = \mathbf{J}$ and $\nabla \cdot \mathbf{B} = 0$), one can use either the magnetic vector potential $\...
1 vote
0 answers
83 views

Implementation of integration schemes for ordinary differential equations in Python and peformance comparison

I look for a book/manual where I can find implementations of different integration schemes for ordinary differential equations (like 4-th order Runge-Kutta) in Python with Numba. To be more specific, ...
1 vote
1 answer
233 views

About using SOCP solvers to solve QCQP

I have noticed that some commercial solvers transform QCQPs into SOCPs and use SOCP algorithms to solve the resulting problem. I am wondering if there is a benefit to this approach over using a pure ...
3 votes
1 answer
71 views

Requesting for Finite Difference Methods reference in Portuguese or English

Crossposted on Mathematics SE I have been assigned a group project for an introductory Linear Algebra subject on Finite Difference Methods and sparse matrices. Our professor advised we use Gilbert ...
1 vote
3 answers
574 views

Morley element implementation reference

I am looking for a detailed reference on the implementation of the Morley element for FEM, specifically for the biharmonic equation. By detailed, I mean that it should discuss the problems associated ...
0 votes
1 answer
184 views

Mesh refinement in the Finite Element Method

I need some good references on how to implement programmatically the hp-refinement of meshes in the Finite Element Method in two/three-dimension. I've searched the web a lot and read many articles and ...
6 votes
1 answer
222 views

Fast way of computing the action of a matrix power on a vector

For integer $k>0$, it is well-known that one can use binary exponentiation to evaluate the matrix power $\mathbf A^k$, where $\mathbf A$ is an $n\times n$ matrix. However, it is not clear to me if ...
1 vote
1 answer
92 views

How to Impose nonhomogeneous Neumann Boundary Condition in the DG Formulation

Consider the following partial differential equation \begin{align} \frac{\partial u}{\partial t}+\frac{\partial f}{\partial x} &= g(x,t), \ \ x\in \Omega = [x_{L},x_{R}] \\ u(x,0) &= u_{0}(x) ...
1 vote
1 answer
814 views

Simple particle-in-cell examples

I am studying about the 1D EM-PIC (Electro Magnetics using particle-in-cell) simulation. I want to have a simultaneous time-integration of the electric/magnetic fields plus the motion of free charges ...
10 votes
2 answers
690 views

FEM for vector valued problems: reference request

I'm a PhD working in a computational mechanics lab. I come from a Math department, and I have a good background for what concerns the basics of finite elements, like inf-sup conditions, DG, non-...
2 votes
1 answer
183 views

DG method for solving Hyperbolic Partial Differential Equation with Dirichlet Boundary Conditions

Consider the following partial differential equation \begin{align} \frac{\partial u}{\partial t}+\frac{\partial f}{\partial x} &= g(x,t), \ \ x\in \Omega = [x_{L},x_{R}] \\ u(x,0) &= u_{0}(x) ...
14 votes
4 answers
36k views

Difference between Nodes and CPUs when running software on a cluster?

I'm looking into moving some computations of mine to a data center to get more computation power. In the context of this process, I am getting confused by the differentiation of a computation node and ...

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