[all-commits] [llvm/llvm-project] 51b8c6: [libc++] Extend the scope of radix sorting inside ...

Дмитрий Изволов via All-commits all-commits at lists.llvm.org
Wed Apr 16 02:34:32 PDT 2025


  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 51b8c66b0867154730d07e1ee4016b5116440293
      https://github.com/llvm/llvm-project/commit/51b8c66b0867154730d07e1ee4016b5116440293
  Author: Дмитрий Изволов <dmitriy at izvolov.ru>
  Date:   2025-04-16 (Wed, 16 Apr 2025)

  Changed paths:
    M libcxx/docs/ReleaseNotes/21.rst
    M libcxx/include/__algorithm/radix_sort.h
    M libcxx/include/__algorithm/stable_sort.h
    M libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/stable_sort.pass.cpp

  Log Message:
  -----------
  [libc++] Extend the scope of radix sorting inside std::stable_sort to floating-point types (#129452)

These changes speed up `std::stable_sort` in the case of sorting
floating-point types.
This applies only to IEEE 754 floats.
The speedup is similar to that achieved for integers in PR #104683 (see
benchmarks below).

Why does this worth doing?
Previously, `std::stable_sort` had almost no chance of beating
`std::sort`.
Now there are cases when `std::stable_sort` is preferrable, and the
difference is significant.
```
---------------------------------------------------------------------------
Benchmark             |  std::stable_sort  |   std::sort | std::stable_sort
                      | without radix_sort |             | with radix_sort 
---------------------------------------------------------------------------
float_Random_1        |       1.62 ns      |     2.15 ns |          1.61 ns
float_Random_4        |       18.0 ns      |     2.71 ns |          16.3 ns
float_Random_16       |        118 ns      |      113 ns |           112 ns
float_Random_64       |        751 ns      |      647 ns |           730 ns
float_Random_256      |       4715 ns      |     2937 ns |          4669 ns
float_Random_1024     |      25713 ns      |    13172 ns |          5959 ns <--
float_Random_4096     |     131307 ns      |    56870 ns |         19294 ns <--
float_Random_16384    |     624996 ns      |   242953 ns |         64264 ns <--
float_Random_65536    |    2895661 ns      |  1027279 ns |        288553 ns <--
float_Random_262144   |   13285372 ns      |  4342593 ns |       3022377 ns <--
float_Random_1048576  |   60595871 ns      | 19087591 ns |      18690457 ns <--
float_Random_2097152  |  131336117 ns      | 38800396 ns |      52325016 ns
float_Random_4194304  |  270043042 ns      | 79978019 ns |     102907726 ns
double_Random_1       |       1.60 ns      |     2.15 ns |          1.61 ns
double_Random_4       |       15.2 ns      |     2.70 ns |          16.9 ns
double_Random_16      |        104 ns      |      112 ns |           119 ns
double_Random_64      |        712 ns      |      614 ns |           755 ns
double_Random_256     |       4496 ns      |     2966 ns |          4820 ns
double_Random_1024    |      24722 ns      |    12679 ns |          6189 ns <--
double_Random_4096    |     126075 ns      |    54484 ns |         20999 ns <--
double_Random_16384   |     613782 ns      |   232557 ns |        110276 ns <--
double_Random_65536   |    2894972 ns      |   988531 ns |        774302 ns <--
double_Random_262144  |   13460273 ns      |  4278059 ns |       5115123 ns
double_Random_1048576 |   61119996 ns      | 18408462 ns |      27166574 ns
double_Random_2097152 |  132511525 ns      | 37986158 ns |      54423869 ns
double_Random_4194304 |  272949862 ns      | 77912616 ns |     147670834 ns
```

Comparison for only `std::stable_sort`:
```
Benchmark                                                         Time      Time Old      Time New
--------------------------------------------------------------------------------------------------
BM_StableSort_float_Random_1024                                -0.7997         25438          5096
BM_StableSort_float_Random_4096                                -0.8731        128157         16260
BM_StableSort_float_Random_16384                               -0.9024        621271         60623
BM_StableSort_float_Random_65536                               -0.9081       2922413        268619
BM_StableSort_float_Random_262144                              -0.7766      13386345       2990408
BM_StableSort_float_Random_1048576                             -0.6954      60673010      18481751
BM_StableSort_float_Random_2097152                             -0.6026     130977358      52052182
BM_StableSort_float_Random_4194304                             -0.6252     271556583     101770500
BM_StableSort_float_Ascending_1024                             -0.6430          6711          2396
BM_StableSort_float_Ascending_4096                             -0.7979         38460          7773
BM_StableSort_float_Ascending_16384                            -0.8471        191069         29222
BM_StableSort_float_Ascending_65536                            -0.8683        882321        116194
BM_StableSort_float_Ascending_262144                           -0.8346       3868552        639937
BM_StableSort_float_Ascending_1048576                          -0.7460      16521233       4195953
BM_StableSort_float_Ascending_2097152                          -0.5439      21757532       9922776
BM_StableSort_float_Ascending_4194304                          -0.7525      67847496      16791582
BM_StableSort_float_Descending_1024                            -0.6359         15038          5475
BM_StableSort_float_Descending_4096                            -0.7090         62810         18278
BM_StableSort_float_Descending_16384                           -0.7763        311844         69750
BM_StableSort_float_Descending_65536                           -0.7228       1270513        352202
BM_StableSort_float_Descending_262144                          -0.6785       5484173       1763045
BM_StableSort_float_Descending_1048576                         -0.5084      20223149       9941852
BM_StableSort_float_Descending_2097152                         -0.7646      60523254      14247014
BM_StableSort_float_Descending_4194304                         -0.5638      95706839      41748858
BM_StableSort_float_SingleElement_1024                         +0.3715          1732          2375
BM_StableSort_float_SingleElement_4096                         -0.1685          9357          7781
BM_StableSort_float_SingleElement_16384                        -0.3793         47307         29362
BM_StableSort_float_SingleElement_65536                        -0.4925        227666        115536
BM_StableSort_float_SingleElement_262144                       -0.4271       1075853        616387
BM_StableSort_float_SingleElement_1048576                      -0.3736       5097599       3193279
BM_StableSort_float_SingleElement_2097152                      -0.2470       9854161       7420158
BM_StableSort_float_SingleElement_4194304                      -0.3384      22175964      14670720
BM_StableSort_float_PipeOrgan_1024                             -0.4885         10664          5455
BM_StableSort_float_PipeOrgan_4096                             -0.6340         50095         18337
BM_StableSort_float_PipeOrgan_16384                            -0.7078        238700         69739
BM_StableSort_float_PipeOrgan_65536                            -0.6740       1102419        359378
BM_StableSort_float_PipeOrgan_262144                           -0.7460       4698739       1193511
BM_StableSort_float_PipeOrgan_1048576                          -0.5657      18493972       8032392
BM_StableSort_float_PipeOrgan_2097152                          -0.7116      41089206      11850349
BM_StableSort_float_PipeOrgan_4194304                          -0.6650      83445011      27955737
BM_StableSort_float_QuickSortAdversary_1024                    -0.6863         17402          5460
BM_StableSort_float_QuickSortAdversary_4096                    -0.7715         79864         18247
BM_StableSort_float_QuickSortAdversary_16384                   -0.7800        317480         69839
BM_StableSort_float_QuickSortAdversary_65536                   -0.7400       1357601        352967
BM_StableSort_float_QuickSortAdversary_262144                  -0.6450       5662094       2009769
BM_StableSort_float_QuickSortAdversary_1048576                 -0.5092      21173627      10392107
BM_StableSort_float_QuickSortAdversary_2097152                 -0.7333      61748178      16469993
BM_StableSort_float_QuickSortAdversary_4194304                 -0.5607      98459863      43250182
BM_StableSort_double_Random_1024                               -0.7657         24769          5802
BM_StableSort_double_Random_4096                               -0.8441        126449         19717
BM_StableSort_double_Random_16384                              -0.8269        614910        106447
BM_StableSort_double_Random_65536                              -0.7413       2905000        751427
BM_StableSort_double_Random_262144                             -0.6287      13449514       4994348
BM_StableSort_double_Random_1048576                            -0.5635      60863246      26568349
BM_StableSort_double_Random_2097152                            -0.5959     130293892      52654532
BM_StableSort_double_Random_4194304                            -0.4772     272616445     142526267
BM_StableSort_double_Ascending_1024                            -0.4870          6757          3466
BM_StableSort_double_Ascending_4096                            -0.7360         37592          9923
BM_StableSort_double_Ascending_16384                           -0.7971        183967         37324
BM_StableSort_double_Ascending_65536                           -0.7465        897116        227398
BM_StableSort_double_Ascending_262144                          -0.6764       4020980       1301033
BM_StableSort_double_Ascending_1048576                         -0.6407      16421799       5900751
BM_StableSort_double_Ascending_2097152                         -0.6380      29347139      10622419
BM_StableSort_double_Ascending_4194304                         -0.5934      70439925      28644185
BM_StableSort_double_Descending_1024                           -0.5988         15216          6105
BM_StableSort_double_Descending_4096                           -0.6857         65069         20449
BM_StableSort_double_Descending_16384                          -0.6922        329321        101381
BM_StableSort_double_Descending_65536                          -0.7038       1367970        405242
BM_StableSort_double_Descending_262144                         -0.6472       5361644       1891429
BM_StableSort_double_Descending_1048576                        -0.6656      22031404       7366459
BM_StableSort_double_Descending_2097152                        -0.7593      68922467      16591242
BM_StableSort_double_Descending_4194304                        -0.6392      96283643      34743223
BM_StableSort_double_SingleElement_1024                        +0.9128          1895          3625
BM_StableSort_double_SingleElement_4096                        +0.1475         10013         11490
BM_StableSort_double_SingleElement_16384                       -0.1901         52382         42424
BM_StableSort_double_SingleElement_65536                       -0.2096        254698        201313
BM_StableSort_double_SingleElement_262144                      -0.1833       1248478       1019648
BM_StableSort_double_SingleElement_1048576                     -0.1741       5703397       4710603
BM_StableSort_double_SingleElement_2097152                     -0.1751      10922197       9009835
BM_StableSort_double_SingleElement_4194304                     -0.1538      26571923      22485137
BM_StableSort_double_PipeOrgan_1024                            -0.4406         10752          6014
BM_StableSort_double_PipeOrgan_4096                            -0.5917         49456         20195
BM_StableSort_double_PipeOrgan_16384                           -0.6258        270515        101221
BM_StableSort_double_PipeOrgan_65536                           -0.7098       1159462        336457
BM_StableSort_double_PipeOrgan_262144                          -0.6591       4735711       1614433
BM_StableSort_double_PipeOrgan_1048576                         -0.6620      19353110       6541172
BM_StableSort_double_PipeOrgan_2097152                         -0.7288      49131812      13323391
BM_StableSort_double_PipeOrgan_4194304                         -0.5988      81958974      32878171
BM_StableSort_double_QuickSortAdversary_1024                   -0.6516         17948          6254
BM_StableSort_double_QuickSortAdversary_4096                   -0.7527         82359         20363
BM_StableSort_double_QuickSortAdversary_16384                  -0.7009        340410        101811
BM_StableSort_double_QuickSortAdversary_65536                  -0.6854       1487480        467928
BM_StableSort_double_QuickSortAdversary_262144                 -0.6386       5648460       2041377
BM_StableSort_double_QuickSortAdversary_1048576                -0.6127      22859142       8852587
BM_StableSort_double_QuickSortAdversary_2097152                -0.7161      68693975      19499381
BM_StableSort_double_QuickSortAdversary_4194304                -0.5909      95532179      39077491
OVERALL_GEOMEAN                                                -0.6472             0             0
```



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