[PATCH] D54445: [llvm-exegesis] BitVectorVector: provide assign() method, use it.

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

I will cut this patchseries here for now.
Old walltime was around ~25sec, new is ~5.6sec, so -77.58%.

5 patches remain in need of review:

- https://reviews.llvm.org/D54383 `[llvm-exegesis] Analysis: writeMeasurementValue(): don't alloc string for double each time.` <- self-contained, pretty trivial
- https://reviews.llvm.org/D54388 `[llvm-exegesis] InstructionBenchmarkClustering::rangeQuery(): use llvm::SmallVector<size_t, 0> for storage.` <- was essentially replaced by https://reviews.llvm.org/D54415, but that was only possible after https://reviews.llvm.org/D54390, so it kind-of makes sense as an intermediate step.
- Small incremental improvements to the `dbScan()`:
  - https://reviews.llvm.org/D54381 `[llvm-exegesis] InstructionBenchmarkClustering::dbScan(): use llvm::SetVector<> instead of ILLEGAL std::unordered_set<>` <- very straight-forward replacement, nothing complicated
  - https://reviews.llvm.org/D54418 `[llvm-exegesis] InstructionBenchmarkClustering::dbScan(): replace SetVector with custom BitVectorVector`
  - https://reviews.llvm.org/D54445 `[llvm-exegesis] BitVectorVector: provide assign() method, use it.` <- trivial

The biggest remaining problem is within `isNeighbour`. It contains 99% of cache misses, due to that vector-within-vector storage.
I believe i will be able to get //some// improvement by

1. Precalculating (into `BitVector`) the `is neighbor` matrix. I actually already tried that, not much of an improvement, anoter 100ms i think, not worth it on it's own.

and

2. Parallelizing this computation. I have not *yet* tried this, but i'm **optimistic** about it.

Thanks!


Repository:
  rL LLVM

https://reviews.llvm.org/D54445