Multi-Threaded SDF Analysis

A previous post showed that, when compared to a couple of brute force approaches, using the sdfResponse command is the most computationally efficient approach to generating an earthquake response spectrum. During an OpenSees Cafe, Dr. Silvia Mazzoni suggested taking a more intelligent approach by "batching" the brute force SDF analyses. Instead of analyzing one oscillator … Continue reading Multi-Threaded SDF Analysis

I Missed Again

When I come up with "great" exam questions, only a handful of students get the correct answer while the remaining students misunderstand the question. Same thing happens on social media. Prior to Twitter's full-on death spiral, I tweeted a quiz on the MVLEM element, a formulation available in OpenSees for modeling shear walls. Only 5 … Continue reading I Missed Again

How to Profile OpenSees

Where does the time in a nonlinear finite element analysis go? For large models, solving equations dominates the analysis time, while for small to moderate models, constitutive models (state determination) dominate. It is impossible to know the relative cost of state determination and solving equations prior to an analysis. Profiling tools can tell you after … Continue reading How to Profile OpenSees

Don’t Invert the Matrix

A common issue with linear algebra textbooks is the depiction of $latex {\bf x}={\bf A}^{-1}{\bf b}$ as the solution to the linear system of equations $latex {\bf A}{\bf x}={\bf b}$. Find the inverse of the matrix $latex {\bf A}$, then multiply that inverse with the right-hand side vector, $latex {\bf b}$. Theoretically correct? Yes. Practical? … Continue reading Don’t Invert the Matrix

Single Quotes or Double?

Python, like many other languages, uses single (') and double quotes (") for multi-character strings. This was a bit for me to digest coming from the C++ world where single and double quotes have distinct uses: single quotes for a character and double quotes for strings. Functionally, there's no difference between single and double quotes … Continue reading Single Quotes or Double?

Stop Hogging All the RAM

While writing a previous post on elastic shear beams available in OpenSees, I noticed that the ElasticTimoshenkoBeam3d class stores the element stiffness matrix, along with several other matrices, as private data. As a result, each instance of this class keeps its own copy of several 12x12 matrices for the element response instead of writing to … Continue reading Stop Hogging All the RAM