Exec policy/remove fast reduce

[SSoelvsten]

• As mentioned at the end of Fix 'fast reduce' variable incorrectly is set to 0 as its default #640 , experiments seem to indicate this optimisation is not really relevant for quantification. Hence, exec_policy::nested::fast_reduce has been removed and the optimisation is triggered at compile-time instead.
• Since it will now probably only be used for static variable reordering, the __reduce_level__fast has been simplified such that it is faster.
• Furthermore, this also fixes the issue, that the __reduce_level__fast algorithm turns the Reduce priority queue into a 2-level cut. So, the 3/2 bound has been applied.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.315%. Comparing base (5ac21d0) to head (6468467).
Report is 3 commits behind head on main.

Additional details and impacted files

@@              Coverage Diff              @@
##              main      #642       +/-   ##
=============================================
+ Coverage   97.306%   97.315%   +0.008%     
=============================================
  Files           90        90               
  Lines         6534      6480       -54     
=============================================
- Hits          6358      6306       -52     
+ Misses         176       174        -2     

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[github-actions]

🟢 Regression Test (12-Queens)

'origin/exec_policy/remove-fast_reduce' is a change in performance of 0.15% (stdev: 0.75%).

...	origin/main	origin/exec_policy/remove-fast_reduce
Mean	11446.50	11429.75
Standard Deviation	83.59	86.07

Number of samples: 4

[github-actions]

🟡 Regression Test (QBF 'breakthrough/3x4_19_bwnib')

'origin/exec_policy/remove-fast_reduce' is a change in performance of -1.27% (stdev: 2.00%).

...	origin/main	origin/exec_policy/remove-fast_reduce
Mean	24510.00	24822.33
Standard Deviation	167.20	497.55

Number of samples: 3

[github-actions]

🟡 Regression Test (Picotrav 'arbiter')

'origin/exec_policy/remove-fast_reduce' is a change in performance of -0.56% (stdev: 1.21%).

...	origin/main	origin/exec_policy/remove-fast_reduce
Mean	63140.67	63495.33
Standard Deviation	763.93	469.90

Number of samples: 3

[github-actions]

🟢 Regression Test (QBF 'connect4/4x4_9_connect3_bwnib')

'origin/exec_policy/remove-fast_reduce' is a change in performance of 0.23% (stdev: 2.73%).

...	origin/main	origin/exec_policy/remove-fast_reduce
Mean	1180.50	1177.75
Standard Deviation	32.19	22.87

Number of samples: 4

[github-actions]

🟡 Regression Test (Picotrav 'mem_ctrl')

'origin/exec_policy/remove-fast_reduce' is a change in performance of -0.88% (stdev: 1.01%).

...	origin/main	origin/exec_policy/remove-fast_reduce
Mean	113707.00	114713.00
Standard Deviation	918.74	1162.00

Number of samples: 3

[github-actions]

🟡 Regression Test (14-Queens)

'origin/exec_policy/remove-fast_reduce' is a change in performance of -1.30% (stdev: 2.27%).

...	origin/main	origin/exec_policy/remove-fast_reduce
Mean	268429.33	271905.67
Standard Deviation	690.88	6183.61

Number of samples: 3

[github-actions]

🟢 Regression Test (Picotrav 'adder')

'origin/exec_policy/remove-fast_reduce' is a change in performance of 0.24% (stdev: 9.49%).

...	origin/main	origin/exec_policy/remove-fast_reduce
Mean	9612.80	9589.60
Standard Deviation	912.34	896.32

Number of samples: 10