|No. of units||A||B||C||D||E||F|
compiled by Thierry Le Gleuher & Alain Brobecker, march 2007
This page shows retrograde analysis problems where the solver is asked to find the last N single moves played to reach the position. The design objective is to maximize N and minimize the total number of units, M. Records are positions where one can improve neither of M or N, without worsening the other.
This is an extension of the "Last move" task, discussed in several webpages. Records are classified in the following six categories:
The number in the first column is M. Then there is one column per problem type, T. The non-blank cells show the records: the cell (M, T) contains the value of N.
When a record also applies to a less restrictive type, then the cell instead contains the letter referring to the least restrictive type.
In some cases, a record for Type C, apart from the last move, can also apply as a record for Type B: this is denoted C or Cx depending on whether the last move was a capture.
The problems here are also available from Alain as a pdf.