[Retros] Add pieces

[Theodore Hwa]

On Fri, 11 Mar 2011, Theodore Hwa wrote:


>

>

> On Sat, 12 Mar 2011, Noam Elkies wrote:

>

>> Theodore Hwa <hwatheod at cs.stanford.edu> writes:

>> 

>>>> it would be difficult to compose a problem in which it is not

>>>> possible to add an additional piece (although not impossible).

>> 

>>> Here's one possibility with 30 units, nobody in check:

>>> Starting from the initial position, remove the queens,

>>> and move the kings over to the queens' original squares.

>>> It is not possible to add any pieces.

>> 

>> Neat.  Possibly reducible to 28: move each King one square further,

>> removing the Bc1 and Bc8.  Or even 26, going back to T.Hwa's position

>> but putting a2,h2,a7,h7 on b3,g3,b6,g6 and removing all four Knights

>> (or some suitable combination of Knights and Rooks).  26 could then

>> also be attained by a mixture of the two techniques: put the Kings

>> back on c1 and c8, and play only h2xg3 and h7xg6; or put just wK on c1

>> and add a7xb6.

>

> Extend this technique to achieve 22:

>

> Remove all queens, knights, rooks.  Move kings to d1/d8.  Move a2,a7,h2,h7 to 

> c4,f4,c5,f5.


Does this work? (18 units)

Put all white pawns on 5th rank.
Put all black pawns on 4th rank.
Kings anywhere not in check.

Ted