SAMG-MODFLOW

SAMG for groundwater simulation

Mesh-Agnostic yet fast

SAMG is a very efficient linear solver library based on algebraic multigrid (AMG) specifically developed for industrial applications. SAMG supports both serial and multi-core computations on single PCs, workstations or compute nodes.

LMG is an interface linking the SAMG library to MODFLOW. There are three versions of LMG: LMG-2kx supports MODFLOW-2000 and MODFLOW-2005, LMG-USG supports MODFLOW-USG and LMG-MF6 supports MODFLOW-6.

Key Features of SAMG:

State-of-the-art AMG performance – applicable for structured and unstructured meshes.
Optimized solver control including automated-setup-reuse and switching between different solvers.
Supports both multi-core and multi-node systems.

Advantages for MODFLOW:

„Big Models“: Allows increased modeling accuracy for both structured and unstructured models (as in MODFLOW-USG and MODFLOW-6), while keeping compute times manageable.
Handles strongly heterogeneous and unstructured models where standard solvers have problems. No additional knowledge about solvers needed.

The graph shows computing times for the MODFLOW 6 model test007_751x751 with roughly 600,000 grid-cells. While PCG is very sensitive to the relaxation factor used, LMG does not need additional parameters set by the user. LMG achieves a speed-up of 5.1 on a single core and a speed-up of 11.8 on 4 cores compared with PCG. Hence, the total runtime with LMG is reduced by a factor of 3.4 on a single core and a factor of 5.1 on 4 cores compared with the total runtime using PCG. The runtime of SAMG grows only linearly with the number of equations. For this reason, the speed-up of LMG compared to PCG will increase for bigger models.

User Comments

“...Without SAMG as our solver engine, it would have been impossible to solve [transport models with up to 30 million variables] in a practicable time.” – DHI-WASY GmbH

“[SAMG] was able to reduce the compute time of [one of] our simulations from 12 hours to 3 hours, so our engineers can now run multiple simulations a day.” – ITASCA DENVER Inc.

“In general, the SAMG solver is the fastest MODFLOW solver that [we] have used.” – Aquaveo LLC

“[SAMG] provided optimal runtime speed compared to public-domain solvers evaluated....” – GeoHydroScience LLC

“In general, the SAMG solver is the fastest MODFLOW solver that [we] have used. I have seen multiple models where the SAMG solver was not only faster but more stable than the standard MODFLOW solvers” – Aquaveo LLC