Petrus Method

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Petrus method
Petrus method.gif
Information about the method
Proposer(s): Lars Petrus
Proposed: 1981
Alt Names: none
Variants: Petrus-W, LEOR
No. Steps: 7
No. Algs: 2 to 493 (for the last layer)
Avg Moves: ~45 (using ZBLL)
Purpose(s):


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Scrambled cube -> 2x2x2 Block -> 2x2x3 Block -> EO Petrus -> Petrus F2L -> LL+EO:CP -> LL+EO+CP:CO -> EPLL -> Solved cube


Petrus was the second most popular speedcubing method behind CFOP.

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The Petrus Method, invented by Lars Petrus, is a block-building method where the F2L is solved intuitively with no algorithms. Petrus used to be the second most popular speedcubing method behind Fridrich/CFOP; however nowadays it is often considered to be outdated as it has been steadily declining in popularity since the rise of the "Big Three" (CFOP, Roux and ZZ).

Petrus-like Blockbuilding is sometimes partially used in CFOP solves for creating an XCross.

The Steps

The following describes a standard approach to Petrus. Other ways to solve using the method can be found below, at #Petrus variations.

  1. Build a 2x2x2 block anywhere on the cube.
  2. Expand the 2x2x2 block to a 2x2x3 block; three ways are possible for each initial 2x2x2 block placement.
  3. Orient the remaining seven "bad" edges on the cube that have not been solved yet.
  4. Finish the First Two Layers by only turning two sides. The original Petrus approach is to create a 1x2x2 block and expand it to a 1x2x3 block to finish off the F2L, although a the more CFOP-like, but also less efficient approach of placing the cross edge and solving to corner-edge pairs can be used as well. The Last Layer edges will orientate themselves automatically.
  5. Solve the Last Layer using any LL method. Because the edges are already oriented, advanced solvers can make use of ZBLL. However, other approaches like OCLL+PLL and COLL+EPLL are also possible.

Pros

  • The Petrus Method uses fewer moves than the CFOP method and most, if not all, other non-block-building methods.
  • It is very intuitive and requires far fewer algorithms compared to CFOP.
  • It even requires fewer algorithms than some beginner methods (including the most popular one: Layer By Layer).
  • A variety of options exist for solving the the last layer, for example ZBLL, which solves the last layer in one look.

Cons

  • It can be sometimes hard (especially for a beginner) to optimize block building, and it's difficult to keep consistently turning throughout the solve.
  • Blockbuilding, even with good fingertricks, often tends to be unergonomic.
  • A rotation is required after Edge Orientation to solve the rest of F2L ergonomically.

Petrus variations

Petrus as a Beginner Method

Used as a beginner method, Petrus requires much more intuition, but also involves learning fewer algorithms. For example, the last layer can be split up into the three steps, CP, CO and EP, which Petrus was originally proposed for. For a full tutorial, see #External links.

Petrus on other puzzles

Methods based around the Petrus' idea of blockbuilding and then orienting the remaining edges have also been created for other puzzles. Here is a list of puzzles and Petrus-like methods for them:

External links