Unsolved Grids

Here are some grids which the solver cannot currently complete.

Example 1

This example is from the Sudoku Players' Forums Benchmark Sudoku List. It is listed under Extremely tough puzzles, with the code:

000070940070090005300005070087400100463080000000007080800700000700000028050268000

The grid shown below is as close to a solution as the solver can get, as currently implemented. Actually, the solver can solve this puzzle, but only by allowing the Nishio solver to run for longer than the currently imposed time limit. As Nishio is, by its nature, an open ended process, the solver sets a timer running as Nishio commences. This is to avoid excessive CPU usage. I am investigating solver alogorithms which will solve this puzzle more efficiently.

1 2 5
6

1 2

1 2 5
8

1 3 6
8

 7 

1 2 3
6

 9   4 

1 2 3
6

1 2 6

 7 

1 2 4
8

1 3 6
8

 9 

1 2 3
4 6

2 3 6
8

1 3 6

 5 
 3 

1 2 4
9

1 2 4
8 9

1 6 8

1 2 4

 5 

2 6 8

 7 

1 2 6

2 5 9

 8   7   4 

2 3 5

2 3 6
9

 1 

3 5 6
9

2 3 6
9

 4   6   3 

1 5 9

 8 

1 2 9

2 5 7

5 9

2 7 9

1 2 5
9

1 2 9

1 2 5
9

3 5 6
9

2 3 5

 7 

2 3 4
5 6

 8 

2 3 4
6 9

 8 

1 2 3
4 9

1 2 4
6 9

 7 

1 3 4
5

1 3 4
9

4 5 6

1 5 6
9

1 4 6
9

 7 

1 3 4
9

1 4 6
9

1 3 5
9

1 3 4
5

1 3 4
9

4 5 6

 2   8 

1 9

 5 

1 4 9

 2   6   8 

3 4 7

1 3 9

1 3 4
7 9

You may view the output of the solver running with unrestricted Nishio.

Example 2

This example is also from the Sudoku Players' Forums Benchmark Sudoku List. It is listed under Extremely tough puzzles, with the code:

700000400020070080003008009000500300060020090001007006000300900030040060009001005

The grid shown below is as close to a solution as the solver can get, as currently implemented. Actually, the solver can solve this puzzle, but only by allowing the Nishio solver to run for longer than the currently imposed time limit. As Nishio is, by its nature, an open ended process, the solver sets a timer running as Nishio commences. This is to avoid excessive CPU usage. I am investigating solver alogorithms which will solve this puzzle more efficiently.

 7 

1 5 8
9

5 6 8

1 2 6
9

1 3 5
6 9

2 3 5
6 9

 4 

1 2 5

1 2 3

1 4 5
6 9

 2 

4 5 6

1 4 6
9

 7 

3 4 5
6 9

1 5 6

 8 

1 3

1 4 5
6

1 4 5

 3 

1 2 4
6

1 5 6

 8 

1 2 5
6 7

1 2 5
7

 9 

2 4 8
9

4 7 8
9

2 4 7
8

 5 

1 6 8
9

4 6 9

 3 

1 2 4
7

1 2 4
7 8

3 4 5
8

 6 

4 5 7
8

1 4 8

 2 

3 4

1 5 7
8

 9 

1 4 7
8

2 3 4
5 8 9

4 5 8
9

 1 

4 8 9

3 8 9

 7 

2 5 8

2 4 5

 6 

1 2 5
6 8

1 5 7
8

2 5 6
7 8

 3 

5 6 8

2 5 6

 9 

1 2 4
7

1 2 4
7 8

1 2 5
8

 3 

2 5 7
8

2 7 8
9

 4 

2 5 9

1 2 7
8

 6 

1 2 7
8

2 4 6
8

4 7 8

 9 

2 6 7
8

6 8

 1 

2 7 8

 3 

 5 

You may view the output of the solver running with unrestricted Nishio.

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