mORMot 2 Generics and Collections

Generics are a clever way of writing some code once, then reuse it for several types.
They are like templates, or compiler-time shortcuts for type definitions.

In the last weeks, we added a new mormot.core.collections.pas unit, which features:

  • JSON-aware IList<> List Storage;
  • JSON-aware IKeyValue<> Dictionary Storage.

In respect to Delphi or FPC RTL generics.collections, this unit uses interfaces as variable holders, and leverage them to reduce the generated code as much as possible, as the Spring4D 2.0 framework does, but for both Delphi and FPC. It publishes TDynArray and TSynDictionary high-level features like indexing, sorting, JSON/binary serialization or thread safety as Generics strong typing.

Resulting performance is great, especially for its enumerators, and your resulting executable size won't blow up as with the regular RTL unit.

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New move/fillchar optimized sse2/avx asm version

Our Open Source framework includes some optimized asm alternatives to RTL's move() and fillchar(), named MoveFast() and FillCharFast().

We just rewrote from scratch the x86_64 version of those, which was previously taken from third-party snippets.
The brand new code is meant to be more efficient and maintainable. In particular, we switched to SIMD 128-bit SSE2 or 256bit AVX memory access (if available), whereas current version was using 64-bit regular registers. The small blocks (i.e. < 32 bytes) process occurs very often, e.g. when processing strings, so has been tuned a lot. Non temporal instructions (i.e. bypassing the CPU cache) are used for biggest chunks of data. We tested ERMS support, but it was found of no benefit in respect to our optimized SIMD, and was actually slower than our non-temporal variants. So ERMS code is currently disabled in the source, and may be enabled on demand by a conditional.

FPC move() was not bad. Delphi's Win64 was far from optimized - even ERMS was poorly introduced in latest RTL, since it should be triggered only for blocks > 2KB. Sadly, Delphi doesn't support AVX assembly yet, so those opcodes would be available only on FPC.

Resulting numbers are talking by themselves. Working on Win64 and Linux, of course.

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