Metric
From Speedsolving.com Wiki
A metric (more specifically, move count metric or turn metric) is a convention for counting moves. The same sequence of moves can have different move counts depending on the metric used.
Summary of different metrics
For more details, see the respective articles.
- HTM; Half Turn Metric (or Face Turn Metric): Any face turn of any angle counts as 1 turn.
- QTM; Quarter Turn Metric: Only quarter (90-degree) face turns count as 1 turn.
- STM; Slice Turn Metric: Any turn of any layer, by any angle, counts as 1 turn.
- QSTM; Quarter Slice Turn Metric: Only quarter turns of any layer, by any angle, counts as 1 turn.
- ATM; Axial Turn Metric: Any movement within the same axis counts as 1 turn.
- ETM; Execution Turn Metric: Any perceived movement counts as 1 turn.
- OBTM; Outer Block Turn Metric: The official metric of the WCA in which all non-slice moves on all twisty puzzles are considered 1 move and rotations are 0 moves
- BTM; Block Turn Metric: A metric for measuring movecounts on Bigcubes
Uses
Metrics are used to measure the length of move sequences such as Algorithms or Reconstructions. God's number is known to be 20 in HTM and 26 in QTM. From a mathematical standpoint, however, QTM seems a more natural choice; half-turns are visibly redundant as generators.
Debate over metric in FMC
WCA uses HTM in FMC. There has been a number of debates arguing for different metrics.
