Optimization of genBlockColumn and WeightsAt

[tehtelev]

Summary

Changes for genBlockColumn:

• Buffer for float[] data used.

Changes for WeightsAt:

• Loop replaced with immediate clearing of the output array, variables reused.

Performance numbers

Tested on the generation of 10200 chunk columns:

• genBlockColumn method execution time: reduced from 16152 ms to 14678 ms;
• genBlockColumn GC memory allocations: reduced from 639 MB to 90 MB;
• WeightsAt method execution time: reduced from 600 ms to 10 ms;

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