Optimization: do std structures introduce significant overheads? about sperr HOT 3 CLOSED

Investigation 1:
std:;unique_ptr<> does have a negligible performance impact compared to raw pointers. In fact, in one test, gcc and clang report slightly faster speed than raw pointers. PGI seems to suffer from std::unique_ptr<> overhead though.

More detailed results can be found in this PDF:
Performance Impact of STL Structures - Sheet1.pdf

from sperr.

Investigation 2:
The vast majority of time consuming std::vector<> operations are on push_back's of the LIS and LSP lists.
More specifically, the data movement incurred when push_back causes a capacity increase.
PR #6 partially addressed this problem.

from sperr.

Investigation 3:
After implementing #11 , the performance characteristics changed a bit. It's now obvious that the cost from std::vector<> is mostly related to memory allocation/deallocation.

However, with the current state of the code, there are simply arrays with unknown sizes: LIS and LSP. I have already tweaked LIS so that it still reserves 2X capacity even when garbage collection, and LSP only grows but won't shrink. So, I don't think there's much I can wrt memory usage here.

from sperr.