Black Hole (solitaire)
Encyclopedia
Black Hole is a solitaire
Solitaire
Solitaire is any tabletop game which one can play by oneself or with other people. The solitaire card game Klondike is often known as simply Solitaire....

 card game
Card game
A card game is any game using playing cards as the primary device with which the game is played, be they traditional or game-specific. Countless card games exist, including families of related games...

 that is akin to Golf and Tri Peaks
Tri Peaks
Tri Peaks is a solitaire card game that is akin to the solitaire games Golf and Black Hole. The game uses one deck and the object is to clear three peaks made up of cards....

, but its tableau is somewhat like that of La Belle Lucie
La Belle Lucie
La Belle Lucie is a Patience game where the object is to build the cards into the foundations.All cards are visible from the start, but this does not imply that this game is solvable with strategy. The default rule is very hard to win. The majority of games cannot be solved...

. Invented by David Parlett
David Parlett
David Parlett is a games scholar from South London, who has studied both card games and board games. His published works include many popular books on games and the more academic volumes "Oxford Guide to Card Games" and "Oxford History of Board Games", both now out of print...

, this game's objective is to compress the entire deck into one foundation.

The cards are dealt to the tableau in piles of three. The leftover card, dealt first or last, is placed as a single foundation called the Black Hole. This card usually is the Ace of Spades
Ace of Spades
At least in English-speaking countries, the ace of spades is traditionally seen as the highest card in the deck of playing cards, although the actual value of the card varies from game to game...

, but any card can do.

Only the top cards of each pile in the tableau are available for play and in order for a card to be placed in the Black Hole, it must be a rank higher or lower than the top card on the Black Hole. This is the only allowable move in the entire game.

The game ends if there are no more top cards that can be moved to the Black Hole. The game is won if all of the cards end up in the Black Hole.

Solvers and Solvability Statistics

Shlomi Fish has written an open-source solver for Black Hole Solitaire solver for Black Hole Solitaire first as a Perl
Perl
Perl is a high-level, general-purpose, interpreted, dynamic programming language. Perl was originally developed by Larry Wall in 1987 as a general-purpose Unix scripting language to make report processing easier. Since then, it has undergone many changes and revisions and become widely popular...

-based CPAN
CPAN
CPAN, the Comprehensive Perl Archive Network, is an archive of nearly 100,000 modules of software written in Perl, as well as documentation for it. It has a presence on the World Wide Web at and is mirrored worldwide at more than 200 locations...

 module, but which was later re-implemented in the C programming language
C (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....

. The solver was run on the first one million PySolFC
PySol
PySol is an open source and platform independent computer game that incorporates around 1,000 solitaire games, including card games and other types of single-player games.. It is written in the Python programming language. PySol was originated by Markus F.X.J...

 Black Hole Solitaire deals and generated some statistics of using its Depth-first search
Depth-first search
Depth-first search is an algorithm for traversing or searching a tree, tree structure, or graph. One starts at the root and explores as far as possible along each branch before backtracking....

(DFS) scan.

Out of the million deals 869,413 could be solved and the 130,587 others were fully traversed without a possible final solution. The search iterations counts of both the solved and unsolved deals had fairly large averages (roughly 292,400 and 553,884) and standard deviations which indicates that some deals result in many false ends. The median number of iterations for the solved states was also relatively high - about 79,000.
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