Changed queue to set in AC3 (as in the pseudocode of the original algorithm) to reduce the number of consistency-check due to the redundancy of the same arcs in queue. For example, on the harder1 configuration of the Sudoku CSP the number consistency-check has been reduced from 40464 to 12562!

AC3 algorithm has non-optimal worst case time-complexity O(cd^3 ), while AC4 algorithm runs in O(cd^2) worst case time

…he constant propagation algorithm in mac inference

…eady present in test_csp.py

This reverts commit 20ab0e5.

This reverts commit f743146.

This reverts commit 9e0fa55.

… are already present in test_csp.py"

This reverts commit b3cd24c.

…oosing the constant propagation algorithm in mac inference"

This reverts commit 6986247.

This reverts commit 03551fb.

This reverts commit 93af259.

This reverts commit 6641c2c.

This reverts commit 9d37ae0.

This reverts commit 24041e9.

This reverts commit 6d229ce.

This reverts commit c74933a.

… fixed typo errors

This reverts commit c4139e5.