salijagic
91 lines
3.2 KiB
Markdown
91 lines
3.2 KiB
Markdown
# Optimization: Inlining
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- **Author**: Smail
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- **Predecessor**: variant_inlining_7_symmetry_1.cpp
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- **File(s)**: variants/variant_inlining_7_symmetry_2.cpp
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- **Status**: TBA
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## What this changes
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Instead of calculating the distance and norm vector between two pedestrians everytime,
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we created a LUT that only calculates the distances once and r_a_b_norm (with expensive sqrt flop `dx`, `dy`, `norm`).
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The forces are somewhat symmetric, however it would still require a lot of calculations,
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maybe this second symmetry optimization can be done at a later stage.
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When i > j we need the opposite vector which is $curr * -1$.
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## Code (relevant snippet)
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TBD - see `variants/variant_inlining_7_symmetry_1.cpp` for the final version, and the
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individual file headers for the incremental steps.
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## Benchmark
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Conditions: single run (TODO: switch to min-of-N), N_ITER=1000,
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-O3 -march=native -flto. Predecessor reference for the same config is the
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baseline row.
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### x86
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**Machine**:
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```
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Processors: 16 x AMD Ryzen AI 7 350 w/ Radeon 860M
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Memory: 32 GiB of RAM (30.6 GiB usable)
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Graphics Processor: AMD Radeon 860M Graphics
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Manufacturer: LENOVO
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Product Name: 83HX
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System Version: IdeaPad Slim 5 14AKP10
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```
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**Frequency**: 2 GHz
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Existing single-point measurement (N unspecified, kept from the previous
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OPTIMIZATIONS.md; W matches roughly N=120 at N_ITER=1000):
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| Variant | W(n) [Flops] | T(n) [Cycles] | Performance [Flops/Cycle] |
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| -------- | ---------------- | -------------- | ------------------------- |
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| Baseline | 1'058'400'000.00 | 850'352'900.00 | 1.24 |
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| Inlining | 1'058'400'000.00 | 756'088'260.00 | 1.40 |
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| Symmetry | | | |
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Inlining is about 12.9% faster on this point. A full N sweep with min-of-3 is TODO.
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Full sweep (TODO):
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| N | W(n) [Flops] | T(n) [Cycles] | Performance [Flops/Cycle] | Diff vs Predecessor |
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| ---- | ------------ | ------------- | ------------------------- | ------------------- |
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| 50 | | | | |
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| 100 | | | | |
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| 200 | | | | |
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| 500 | | | | |
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| 1000 | | | | |
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### ARM (Apple)
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**Machine**:
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```
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TBD
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```
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**Frequency**: TBD
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| N | W(n) [Flops] | T(n) [Cycles] | Performance [Flops/Cycle] | Diff vs Predecessor |
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| ---- | ------------ | ------------- | ------------------------- | ------------------- |
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| 50 | | | | |
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| 100 | | | | |
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| 200 | | | | |
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| 500 | | | | |
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| 1000 | | | | |
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## Analysis
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Speedup likely comes mainly from halving the number of `sqrt` flops.
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## Takeaway
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TBD
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