Missing Dereference in C++ Interface

[SSoelvsten]

CAL seems to use much more memory than would be expected. For the 14-Queens problem, where the largest BDD only is 4 GiB in size, CAL runs out of memory on my machine after having filled 16 GiB of RAM and 8 GiB of swap.

When running the Tic-Tac-Toe 22 benchmark, we get the following output. Please note the number of nodes that were garbage collected - specifically notice nothing has been garbage collected.

Tic-Tac-Toe with 22 crosses (CAL [BDD] 8096 MiB):

   CAL [BDD] initialisation:
   | time (ms):              1

   Initial decision diagram:
   | size (nodes):           990
   | time (ms):              0

   Applying constraints:
   | final size (nodes):     6560564
   | time (ms):              336215

   counting solutions:
   | number of solutions:    9734400
   | time (ms):              3444

   total time (ms):          339659

**** CAL modifiable parameters ****
Node limit: 0
Garbage collection enabled: yes
...
Repacking after GC Threshold: 0.750000
**** CAL statistics ****
Total BDD Node Usage : 256739576 nodes, 8215666432 Bytes
Peak BDD Node Usage : 202440128 nodes, 6478084096 Bytes
Number of nodes locked: 42457
...
Number of nodes garbage collected: 0
number of garbage collections: 13
...
garbage collection limit: 404880256

[SSoelvsten]

Just to confirm, here are some statistics on Tic-Tac-Toe 22 with CAL after the rebase merge.

Number of nodes garbage collected: 190829368
number of garbage collections: 20

This is roughly equivalent to 190829368 * 3 * 8 bytes, i.e. 4.8 GiB garbage collected. Specifically, if we look at its own reported unique node table size we see it has used about 4 GiB a tmost

Total BDD Node Usage : 66592604 nodes, 2130963328 Bytes
Peak BDD Node Usage : 125127046 nodes, 4004065472 Bytes

This seems quite reasonable. Looking at the System Monitor The peak memory was about 8 GiB. The remaining 3 GiB must be the OS, computation cache and the unreduced nodes. That seems realistic.

This is much less than the 14 GiB total usage (counting duplicates).