Make hit efficiency and hit purity counters more accurate

This MR makes hit efficiency and hit purity counters more accurate by:

• Storing in std::vector<double> all intermediate values.
• Calculating when printing the hit efficiency and purity in a double.

Not surprisingly, the references have changed for the basic pipeline.

• This MR contains an additional tiny change required to support compilation in macos.

Closes #283 (closed)