Modernizing Titan2D, a Parallel AMR Geophysical Flow Code to Support Multiple Rheologies and Extendability

Abstract

In this work, we report on strategies and results of our initial approach for modernization of Titan2D code. Titan2D is a geophysical mass flow simulation code designed for modeling of volcanic flows, debris avalanches and landslides over a realistic terrain model. It solves an underlying hyperbolic system of partial differential equations using parallel adaptive mesh Godunov scheme. The following work was done during code refactoring and modernization. To facilitate user input two level python interface was developed. Such design permits large changes in C++ and Python low-level while maintaining stable high-level interface exposed to the end user. Multiple diverged forks implementing different material models were merged back together. Data storage layout was changed from a linked list of structures to a structure of arrays representation for better memory access and in preparation for further work on better utilization of vectorized instruction. Existing MPI parallelization was augmented with OpenMP parallelization. The performance of a hash table used to store mesh elements and nodes references was improved by switching from a linked list for overflow entries to dynamic arrays allowing the implementation of the binary search algorithm. The introduction of the new data layout made possible to reduce the number of hash table look-ups by replacing them with direct use of indexes from the storage class. The modifications lead to 8-9 times performance improvement for serial execution.

The Kestrel software for simulations of morphodynamic Earth-surface flows

“…There are many existing codes available for simulating these systems. The programs most closely related to ours are the open source codes D-CLAW (George & Barnhart, 2023;, TITAN2D (Patra et al, 2005(Patra et al, , 2020Simakov et al, 2019), r.avaflow (Mergili & Pudasaini, 2023;Pudasaini & Mergili, 2019), IMEX_SfloW2D (de 'Michieli Vitturi, Costa, et al, 2023;de'Michieli Vitturi, Ongaro, et al, 2023;de'Michieli Vitturi & Lari, 2023) and the debris flow components of the proprietary software packages RAMMS (Christen et al, 2010;Meyrat et al, 2022) and Flo-2D (Flo-2D, 2023). Each of these codes uses a slightly different description of the flow physics and underlying mathematical framework.…”

RobustCalibration: Robust Calibration of Computer Models in R

“…Simulating the outputs from computer models can be slow. For instance, the TITAN2D computer model of simulating pyroclastic flows for geological hazard quantification takes roughly 8 minutes per set of inputs (Simakov et al, 2019). As hundreds of thousands of model runs are sometimes required for model calibration, directly computing the computer model by numerical methods is often prohibitive.…”

GHub: Building a glaciology gateway to unify a community

“…VHub hosts complex, large-scale simulation tools developed and used by the volcanology community, such as a parallel adaptive mesh refinement mass flow simulator called Titan2D; 15,16 ensemble-based Bayesian approaches to uncertainty quantification; and probabilistic simulations of volcanic ash transport that are generated from multiple volcanic plume rise simulations. 17 The VHub gateway makes the complex interplay of data and simulation involved in these workflows seamlessly available to geophysical scientists.…”

“…VHub, a virtual scientific community for sharing knowledge, tools, and educational materials, has become a true hub for volcano researchers, with 20,000–25,000 unique visits per month, substantial international participation, and approximately 10,000 members. VHub hosts complex, large‐scale simulation tools developed and used by the volcanology community, such as a parallel adaptive mesh refinement mass flow simulator called Titan2D; 15,16 ensemble‐based Bayesian approaches to uncertainty quantification; and probabilistic simulations of volcanic ash transport that are generated from multiple volcanic plume rise simulations 17 . The VHub gateway makes the complex interplay of data and simulation involved in these workflows seamlessly available to geophysical scientists.…”