SudokuSolver

This project contains

• a Grid object baked by a two dimensional array of int int[9][9].
• a Solver interface with a solve method that returns a solved Grid
• Some implementations of Solver with differents strategies like brut force or human style ones.

The Grid object is mutable by the getContent() method. Immutability behavior can be achieved with the clone() method. Feel free to implement your own method to clone the Grid.

Since this project is for experiment purpose, there are some test cases to valid various implementations and a SpeedTest to check performances.

Solver implementations by performances

1. BitBackedSolver.java [avg 1.5 ms]
   This solver behaves has human regular strategy trying to first identify cells with less possibilities.
2. BrutForceFlatSolver.java [avg 5 ms]
   This solver use brut force strategy with an history of Moves in order to rollback unsuccessful trees. This version is no more recursive and don't clone each Grid.
3. BrutForceRecursiveSolver.java [avg 83 ms]
   This solver use brut force strategy over an immutable grid that is cloned over recursive iteration. Each non ending trees rolls back in a recursive way by throwing Exceptions.
4. CleverSolver.java [avg 447 ms]
   This solver behaves has human regular strategy trying to first identify cells with less possibilities.

OpenJDK JMH Microbenchmark FWK SpeedTests results

Results computed on HP DV6 Core i5 4Go with Win7

Benchmark                                            (gridsToTest)  Mode  Samples    Score  Score error  Units
s.j.SolverBenchmarks.bitBackedSolverBenchmark          AL_ESCARGOT  avgt        5    1,725        0,108  ms/op
s.j.SolverBenchmarks.bitBackedSolverBenchmark          MEDIUM_GRID  avgt        5    1,042        0,035  ms/op
s.j.SolverBenchmarks.bitBackedSolverBenchmark            EASY_GRID  avgt        5    0,034        0,001  ms/op
s.j.SolverBenchmarks.brutForceFlatSolverBenchmark      AL_ESCARGOT  avgt        5    4,905        1,258  ms/op
s.j.SolverBenchmarks.brutForceFlatSolverBenchmark      MEDIUM_GRID  avgt        5    3,224        0,571  ms/op
s.j.SolverBenchmarks.brutForceFlatSolverBenchmark        EASY_GRID  avgt        5    0,035        0,008  ms/op
s.j.SolverBenchmarks.brutForceRecursiveBenchmark       AL_ESCARGOT  avgt        5   83,840       46,523  ms/op
s.j.SolverBenchmarks.brutForceRecursiveBenchmark       MEDIUM_GRID  avgt        5   55,528        4,822  ms/op
s.j.SolverBenchmarks.brutForceRecursiveBenchmark         EASY_GRID  avgt        5    0,482        0,167  ms/op
s.j.SolverBenchmarks.cleverSolverBenchmark             AL_ESCARGOT  avgt        5  447,568       87,966  ms/op
s.j.SolverBenchmarks.cleverSolverBenchmark             MEDIUM_GRID  avgt        5   33,032        8,530  ms/op
s.j.SolverBenchmarks.cleverSolverBenchmark               EASY_GRID  avgt        5    0,437        0,121  ms/op