# Automatic detection of equivalent edges and surfaces in scuff-em

scuff-em versions 0.96 (June 2018) and later include a new optimization that automatically detects and exploits two common symmetries in scuff-em surface-mesh geometries, namely

• For surface meshes that are highly structured (contain many pairs of identical triangles), scuff-em implements automatic detection of equivalent edge pairs. This can yield an enormous reduction (as much as 90% or more) in the cost of assembling the system matrix, as well as computing power, force, and torque via the EMTPFT algorithm.

• For geometries containing pairs of identical surface meshes, scuff-em implements implements automatic detection of equivalent surface pairs. This allows the assembly of entire blocks of the system matrix to be bypassed entirely.

## Equivalent edge-pair detection

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Note: In scuff-em version 0.96, equivalent edge-pair detection is disabled by default, but may be enabled by setting the environment variable SCUFF_MATRIX_2018=1.