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Describe the bug
I was able to get the solution
[[0 0 Q 0]
[0 Q 0 0]
[0 0 0 Q]
[Q 0 0 0]]
For a 4x4 4-Queens problem. I believe this is because the "diagonal /" constraints are slightly off.
I believe the correct code is
diff --git a/benchmarks/queens-pulp.py b/benchmarks/queens-pulp.py
index 0768dbf..f6d5323 100644
--- a/benchmarks/queens-pulp.py+++ b/benchmarks/queens-pulp.py@@ -45,7 +45,7 @@ def gen_model(n):
if i - j == k) <= 1, 'diag1({})'.format(p)
# diagonal /
- for p, k in enumerate(range(3, n + n)):+ for p, k in enumerate(range(1, n + n - 2)):
queens += lpSum(x[i][j] for i in range(n) for j in range(n)
if i + j == k) <= 1, 'diag2({})'.format(p)
At least, this seemed to produce correct solutions to me.
To Reproduce
Solve the n-Queens problem with PuLP and the example will be present in the solutions.
Expected behavior
I was expecting no queens to share diagonals, like
[[0 Q 0 0]
[0 0 0 Q]
[Q 0 0 0]
[0 0 Q 0]]
Desktop (please complete the following information):
Operating System, version: Ubuntu 22.04
Python version: Python 3.9
Python-MIP version (we recommend you to test with the latest version): Latest commit 6044fc8
Additional context
I was looking for a PuLP n-Queens problem to test my SMT solvers backend.
The text was updated successfully, but these errors were encountered:
EthanJamesLew
changed the title
$n$-Queens Incorrect Constraints
$n$-Queens Incorrect Constraints?
Apr 8, 2023
EthanJamesLew
changed the title
$n$-Queens Incorrect Constraints?
Incorrect n-Queens Constraints?
Apr 8, 2023
Describe the bug
I was able to get the solution
[[0 0 Q 0]
[0 Q 0 0]
[0 0 0 Q]
[Q 0 0 0]]
For a 4x4 4-Queens problem. I believe this is because the "diagonal /" constraints are slightly off.
I believe the correct code is
At least, this seemed to produce correct solutions to me.
To Reproduce
Solve the n-Queens problem with PuLP and the example will be present in the solutions.
Expected behavior
I was expecting no queens to share diagonals, like
[[0 Q 0 0]
[0 0 0 Q]
[Q 0 0 0]
[0 0 Q 0]]
Desktop (please complete the following information):
Additional context
I was looking for a PuLP n-Queens problem to test my SMT solvers backend.
The text was updated successfully, but these errors were encountered: