Implement parallel `cuda::std::sort` by miscco · Pull Request #8621 · NVIDIA/cccl

miscco · 2026-04-22T13:46:19Z

This implements the sort algorithm for the cuda backend.

std::sort see https://en.cppreference.com/w/cpp/algorithm/sort.html

It provides tests and benchmarks similar to Thrust and some boilerplate for libcu++

The functionality is publicly available yet and implemented in a private internal header

bernhardmgruber · 2026-04-24T12:38:41Z

The benchmark looks a bit negative, but the slowdowns are tiny. I am still wondering a bit whether we missed something. Maybe we should repeat the benchmark on a different machine.

This implements the sort algorithm for the cuda backend. * std::sort see https://en.cppreference.com/w/cpp/algorithm/sort.html It provides tests and benchmarks similar to Thrust and some boilerplate for libcu++ The functionality is publicly available yet and implemented in a private internal header Fixes NVIDIA#7376

miscco · 2026-05-12T09:02:18Z

I reevaluated on blackwell:

['thrust_sort.json', 'pstl_sort.json']
# base

## [0] NVIDIA RTX PRO 6000 Blackwell Workstation Edition

|  T   |  Elements  |  Entropy  |   Ref Time |   Ref Noise |   Cmp Time |   Cmp Noise |       Diff |   %Diff |  Status  |
|------|------------|-----------|------------|-------------|------------|-------------|------------|---------|----------|
|  I8  |    2^16    |     1     |  22.607 us |       4.24% |  22.571 us |       2.78% |  -0.036 us |  -0.16% |   SAME   |
|  I8  |    2^20    |     1     |  25.535 us |       5.35% |  26.550 us |       2.75% |   1.015 us |   3.97% |   SLOW   |
|  I8  |    2^24    |     1     |  86.938 us |       1.39% |  89.644 us |       1.10% |   2.706 us |   3.11% |   SLOW   |
|  I8  |    2^28    |     1     |   1.216 ms |       0.18% |   1.223 ms |       0.16% |   6.960 us |   0.57% |   SLOW   |
|  I8  |    2^16    |   0.201   |  22.452 us |       3.50% |  22.725 us |       4.41% |   0.273 us |   1.22% |   SAME   |
|  I8  |    2^20    |   0.201   |  24.060 us |       4.20% |  25.156 us |       4.92% |   1.096 us |   4.56% |   SLOW   |
|  I8  |    2^24    |   0.201   |  84.586 us |       1.48% |  87.429 us |       1.60% |   2.843 us |   3.36% |   SLOW   |
|  I8  |    2^28    |   0.201   |   1.219 ms |       0.58% |   1.226 ms |       0.16% |   6.706 us |   0.55% |   SLOW   |
| I16  |    2^16    |     1     |  28.044 us |       4.11% |  28.294 us |       2.49% |   0.250 us |   0.89% |   SAME   |
| I16  |    2^20    |     1     |  34.937 us |       2.65% |  35.308 us |       1.88% |   0.371 us |   1.06% |   SAME   |
| I16  |    2^24    |     1     | 150.464 us |       0.86% | 151.752 us |       0.77% |   1.288 us |   0.86% |   SLOW   |
| I16  |    2^28    |     1     |   1.951 ms |       0.35% |   1.975 ms |       0.48% |  24.316 us |   1.25% |   SLOW   |
| I16  |    2^16    |   0.201   |  27.493 us |       4.12% |  27.792 us |       2.80% |   0.298 us |   1.09% |   SAME   |
| I16  |    2^20    |   0.201   |  31.890 us |       3.20% |  32.395 us |       2.71% |   0.505 us |   1.58% |   SAME   |
| I16  |    2^24    |   0.201   | 130.327 us |       0.77% | 131.303 us |       0.80% |   0.976 us |   0.75% |   SAME   |
| I16  |    2^28    |   0.201   |   1.981 ms |       0.13% |   1.989 ms |       0.13% |   8.202 us |   0.41% |   SLOW   |
| I32  |    2^16    |     1     |  42.317 us |       1.79% |  42.660 us |       2.42% |   0.343 us |   0.81% |   SAME   |
| I32  |    2^20    |     1     |  58.572 us |       1.19% |  59.254 us |       1.06% |   0.681 us |   1.16% |   SLOW   |
| I32  |    2^24    |     1     | 309.775 us |       0.38% | 312.215 us |       0.36% |   2.440 us |   0.79% |   SLOW   |
| I32  |    2^28    |     1     |   6.841 ms |       0.07% |   6.847 ms |       0.07% |   5.874 us |   0.09% |   SLOW   |
| I32  |    2^16    |   0.201   |  41.666 us |       1.70% |  42.253 us |       2.73% |   0.587 us |   1.41% |   SAME   |
| I32  |    2^20    |   0.201   |  51.945 us |       2.36% |  52.548 us |       2.00% |   0.603 us |   1.16% |   SAME   |
| I32  |    2^24    |   0.201   | 271.176 us |       0.36% | 273.037 us |       0.38% |   1.860 us |   0.69% |   SLOW   |
| I32  |    2^28    |   0.201   |   6.798 ms |       0.13% |   6.804 ms |       0.11% |   5.957 us |   0.09% |   SAME   |
| I64  |    2^16    |     1     |  69.310 us |       2.03% |  69.898 us |       1.05% |   0.588 us |   0.85% |   SAME   |
| I64  |    2^20    |     1     | 108.659 us |       1.28% | 109.246 us |       0.71% |   0.587 us |   0.54% |   SAME   |
| I64  |    2^24    |     1     |   1.488 ms |       0.19% |   1.484 ms |       0.15% |  -4.460 us |  -0.30% |   FAST   |
| I64  |    2^28    |     1     |  25.449 ms |       0.09% |  25.457 ms |       0.03% |   8.102 us |   0.03% |   SLOW   |
| I64  |    2^16    |   0.201   |  66.083 us |       1.86% |  66.768 us |       1.60% |   0.685 us |   1.04% |   SAME   |
| I64  |    2^20    |   0.201   | 101.069 us |       1.03% | 101.670 us |       0.66% |   0.602 us |   0.60% |   SAME   |
| I64  |    2^24    |   0.201   |   1.574 ms |       0.11% |   1.576 ms |       0.12% |   2.507 us |   0.16% |   SLOW   |
| I64  |    2^28    |   0.201   |  25.412 ms |       0.03% |  25.432 ms |       0.02% |  20.878 us |   0.08% |   SLOW   |
| I128 |    2^16    |     1     | 109.491 us |       1.38% | 110.220 us |       0.91% |   0.729 us |   0.67% |   SAME   |
| I128 |    2^20    |     1     | 247.203 us |       0.43% | 248.617 us |       0.39% |   1.414 us |   0.57% |   SLOW   |
| I128 |    2^24    |     1     |   6.127 ms |       0.07% |   6.124 ms |       0.06% |  -2.286 us |  -0.04% |   SAME   |
| I128 |    2^28    |     1     | 100.288 ms |       0.01% | 100.307 ms |       0.01% |  19.100 us |   0.02% |   SLOW   |
| I128 |    2^16    |   0.201   | 103.644 us |       0.87% | 104.662 us |       0.81% |   1.018 us |   0.98% |   SLOW   |
| I128 |    2^20    |   0.201   | 239.595 us |       0.40% | 241.232 us |       0.37% |   1.637 us |   0.68% |   SLOW   |
| I128 |    2^24    |   0.201   |   6.157 ms |       0.07% |   6.159 ms |       0.06% |   2.396 us |   0.04% |   SAME   |
| I128 |    2^28    |   0.201   |  99.330 ms |       0.01% |  99.272 ms |       0.01% | -57.574 us |  -0.06% |   FAST   |
| F32  |    2^16    |     1     |  42.369 us |       2.05% |  43.028 us |       2.31% |   0.659 us |   1.56% |   SAME   |
| F32  |    2^20    |     1     |  59.386 us |       1.64% |  60.291 us |       1.11% |   0.905 us |   1.52% |   SLOW   |
| F32  |    2^24    |     1     | 339.452 us |       0.40% | 340.858 us |       0.26% |   1.406 us |   0.41% |   SLOW   |
| F32  |    2^28    |     1     |   7.030 ms |       0.16% |   7.026 ms |       0.11% |  -4.677 us |  -0.07% |   SAME   |
| F32  |    2^16    |   0.201   |  40.731 us |       1.90% |  41.680 us |       2.63% |   0.948 us |   2.33% |   SLOW   |
| F32  |    2^20    |   0.201   |  54.109 us |       1.85% |  55.116 us |       2.14% |   1.007 us |   1.86% |   SLOW   |
| F32  |    2^24    |   0.201   | 302.259 us |       0.34% | 303.758 us |       0.40% |   1.499 us |   0.50% |   SLOW   |
| F32  |    2^28    |   0.201   |   6.903 ms |       0.06% |   6.902 ms |       0.10% |  -1.049 us |  -0.02% |   SAME   |
| F64  |    2^16    |     1     |  70.710 us |       1.35% |  71.603 us |       2.83% |   0.894 us |   1.26% |   SAME   |
| F64  |    2^20    |     1     | 109.874 us |       0.70% | 110.832 us |       0.79% |   0.958 us |   0.87% |   SLOW   |
| F64  |    2^24    |     1     |   1.478 ms |       0.14% |   1.472 ms |       0.17% |  -6.638 us |  -0.45% |   FAST   |
| F64  |    2^28    |     1     |  26.599 ms |       0.04% |  26.633 ms |       0.03% |  34.056 us |   0.13% |   SLOW   |
| F64  |    2^16    |   0.201   |  69.317 us |       1.24% |  70.636 us |       1.63% |   1.319 us |   1.90% |   SLOW   |
| F64  |    2^20    |   0.201   | 103.788 us |       0.71% | 104.977 us |       0.80% |   1.189 us |   1.15% |   SLOW   |
| F64  |    2^24    |   0.201   |   1.576 ms |       0.14% |   1.576 ms |       0.15% |  -0.037 us |  -0.00% |   SAME   |
| F64  |    2^28    |   0.201   |  25.739 ms |       0.02% |  25.738 ms |       0.02% |  -1.160 us |  -0.00% |   SAME   |

# with_predicate

## [0] NVIDIA RTX PRO 6000 Blackwell Workstation Edition

|  T   |  Elements  |  Entropy  |   Ref Time |   Ref Noise |   Cmp Time |   Cmp Noise |       Diff |   %Diff |  Status  |
|------|------------|-----------|------------|-------------|------------|-------------|------------|---------|----------|
|  I8  |    2^16    |     1     |  32.676 us |       2.50% |  33.116 us |       2.80% |   0.441 us |   1.35% |   SAME   |
|  I8  |    2^20    |     1     |  76.569 us |       0.68% |  77.141 us |       0.70% |   0.572 us |   0.75% |   SLOW   |
|  I8  |    2^24    |     1     | 397.458 us |       0.50% | 398.535 us |       0.52% |   1.077 us |   0.27% |   SAME   |
|  I8  |    2^28    |     1     |   7.975 ms |       0.23% |   8.015 ms |       0.24% |  39.424 us |   0.49% |   SLOW   |
|  I8  |    2^16    |   0.201   |  31.805 us |       2.00% |  32.313 us |       3.27% |   0.508 us |   1.60% |   SAME   |
|  I8  |    2^20    |   0.201   |  74.753 us |       0.77% |  75.371 us |       1.21% |   0.618 us |   0.83% |   SLOW   |
|  I8  |    2^24    |   0.201   | 396.979 us |       0.49% | 397.752 us |       0.53% |   0.772 us |   0.19% |   SAME   |
|  I8  |    2^28    |   0.201   |   7.942 ms |       0.20% |   7.981 ms |       0.21% |  38.748 us |   0.49% |   SLOW   |
| I16  |    2^16    |     1     |  34.222 us |       2.58% |  34.825 us |       2.47% |   0.602 us |   1.76% |   SAME   |
| I16  |    2^20    |     1     |  78.926 us |       1.55% |  79.486 us |       1.68% |   0.561 us |   0.71% |   SAME   |
| I16  |    2^24    |     1     | 399.217 us |       0.81% | 406.097 us |       7.81% |   6.880 us |   1.72% |   SLOW   |
| I16  |    2^28    |     1     |  14.122 ms |       0.11% |  14.142 ms |       0.22% |  19.868 us |   0.14% |   SLOW   |
| I16  |    2^16    |   0.201   |  33.821 us |       1.56% |  34.476 us |       1.52% |   0.655 us |   1.94% |   SLOW   |
| I16  |    2^20    |   0.201   |  78.864 us |       1.65% |  79.827 us |       1.68% |   0.963 us |   1.22% |   SAME   |
| I16  |    2^24    |   0.201   | 390.449 us |       0.60% | 395.891 us |       1.02% |   5.442 us |   1.39% |   SLOW   |
| I16  |    2^28    |   0.201   |  14.089 ms |       0.10% |  14.107 ms |       0.18% |  17.938 us |   0.13% |   SLOW   |
| I32  |    2^16    |     1     |  33.602 us |       1.66% |  34.395 us |       1.42% |   0.793 us |   2.36% |   SLOW   |
| I32  |    2^20    |     1     |  83.763 us |       0.84% |  84.078 us |       0.70% |   0.314 us |   0.38% |   SAME   |
| I32  |    2^24    |     1     | 540.429 us |       0.37% | 542.771 us |       1.48% |   2.342 us |   0.43% |   SLOW   |
| I32  |    2^28    |     1     |  26.143 ms |       0.05% |  26.153 ms |       0.06% |   9.072 us |   0.03% |   SAME   |
| I32  |    2^16    |   0.201   |  33.310 us |       1.95% |  33.986 us |       2.41% |   0.676 us |   2.03% |   SLOW   |
| I32  |    2^20    |   0.201   |  81.204 us |       0.64% |  82.193 us |       0.98% |   0.989 us |   1.22% |   SLOW   |
| I32  |    2^24    |   0.201   | 556.023 us |       0.44% | 557.285 us |       0.50% |   1.262 us |   0.23% |   SAME   |
| I32  |    2^28    |   0.201   |  26.144 ms |       0.06% |  26.162 ms |       0.06% |  18.180 us |   0.07% |   SLOW   |
| I64  |    2^16    |     1     |  38.438 us |       0.99% |  39.301 us |       2.15% |   0.862 us |   2.24% |   SLOW   |
| I64  |    2^20    |     1     | 100.603 us |       2.06% | 101.776 us |       2.09% |   1.173 us |   1.17% |   SAME   |
| I64  |    2^24    |     1     |   2.686 ms |       0.09% |   2.689 ms |       0.11% |   2.673 us |   0.10% |   SLOW   |
| I64  |    2^28    |     1     |  57.319 ms |       0.04% |  57.350 ms |       0.04% |  31.231 us |   0.05% |   SLOW   |
| I64  |    2^16    |   0.201   |  38.588 us |       1.22% |  39.566 us |       1.58% |   0.978 us |   2.53% |   SLOW   |
| I64  |    2^20    |   0.201   | 100.140 us |       2.05% | 100.933 us |       2.15% |   0.793 us |   0.79% |   SAME   |
| I64  |    2^24    |   0.201   |   2.685 ms |       0.09% |   2.688 ms |       1.29% |   3.426 us |   0.13% |   SLOW   |
| I64  |    2^28    |   0.201   |  57.308 ms |       0.04% |  57.340 ms |       0.04% |  31.794 us |   0.06% |   SLOW   |
| I128 |    2^16    |     1     |  40.601 us |       1.23% |  41.249 us |       1.06% |   0.647 us |   1.59% |   SLOW   |
| I128 |    2^20    |     1     | 146.193 us |       0.54% | 147.176 us |       0.68% |   0.984 us |   0.67% |   SLOW   |
| I128 |    2^24    |     1     |   5.735 ms |       0.08% |   5.737 ms |       0.07% |   1.688 us |   0.03% |   SAME   |
| I128 |    2^28    |     1     | 119.009 ms |       0.03% | 119.071 ms |       0.03% |  62.212 us |   0.05% |   SLOW   |
| I128 |    2^16    |   0.201   |  41.776 us |       1.12% |  42.762 us |       3.68% |   0.986 us |   2.36% |   SLOW   |
| I128 |    2^20    |   0.201   | 146.139 us |       0.56% | 147.163 us |       0.71% |   1.024 us |   0.70% |   SLOW   |
| I128 |    2^24    |   0.201   |   5.734 ms |       0.08% |   5.734 ms |       0.08% |   0.469 us |   0.01% |   SAME   |
| I128 |    2^28    |   0.201   | 118.975 ms |       0.03% | 119.045 ms |       0.03% |  69.785 us |   0.06% |   SLOW   |
| F32  |    2^16    |     1     |  33.631 us |       1.27% |  34.499 us |       1.71% |   0.868 us |   2.58% |   SLOW   |
| F32  |    2^20    |     1     |  83.276 us |       0.52% |  84.346 us |       0.85% |   1.071 us |   1.29% |   SLOW   |
| F32  |    2^24    |     1     | 541.899 us |       0.34% | 543.406 us |       0.41% |   1.507 us |   0.28% |   SAME   |
| F32  |    2^28    |     1     |  26.130 ms |       0.05% |  26.118 ms |       0.05% | -12.110 us |  -0.05% |   SAME   |
| F32  |    2^16    |   0.201   |  33.128 us |       1.05% |  34.000 us |       2.73% |   0.872 us |   2.63% |   SLOW   |
| F32  |    2^20    |   0.201   |  81.558 us |       0.80% |  82.460 us |       0.81% |   0.902 us |   1.11% |   SLOW   |
| F32  |    2^24    |   0.201   | 558.632 us |       0.40% | 559.986 us |       0.41% |   1.354 us |   0.24% |   SAME   |
| F32  |    2^28    |   0.201   |  26.128 ms |       0.06% |  26.116 ms |       0.06% | -11.864 us |  -0.05% |   SAME   |
| F64  |    2^16    |     1     |  42.750 us |       1.08% |  43.513 us |       0.99% |   0.763 us |   1.79% |   SLOW   |
| F64  |    2^20    |     1     | 113.864 us |       1.53% | 114.964 us |       1.80% |   1.100 us |   0.97% |   SAME   |
| F64  |    2^24    |     1     |   2.738 ms |       0.10% |   2.739 ms |       0.10% |   0.882 us |   0.03% |   SAME   |
| F64  |    2^28    |     1     |  58.106 ms |       0.04% |  58.140 ms |       0.04% |  34.494 us |   0.06% |   SLOW   |
| F64  |    2^16    |   0.201   |  41.966 us |       1.37% |  42.978 us |       2.02% |   1.012 us |   2.41% |   SLOW   |
| F64  |    2^20    |   0.201   | 113.604 us |       1.63% | 114.703 us |       1.59% |   1.099 us |   0.97% |   SAME   |
| F64  |    2^24    |   0.201   |   2.736 ms |       0.09% |   2.738 ms |       0.10% |   2.570 us |   0.09% |   SLOW   |
| F64  |    2^28    |   0.201   |  58.101 ms |       0.04% |  58.112 ms |       0.04% |  11.206 us |   0.02% |   SAME   |
| C32  |    2^16    |     1     |  37.408 us |       1.49% |  38.620 us |       1.85% |   1.212 us |   3.24% |   SLOW   |
| C32  |    2^20    |     1     | 100.506 us |       2.08% | 101.264 us |       1.98% |   0.758 us |   0.75% |   SAME   |
| C32  |    2^24    |     1     |   2.679 ms |       0.10% |   2.680 ms |       0.09% |   0.834 us |   0.03% |   SAME   |
| C32  |    2^28    |     1     |  57.247 ms |       0.04% |  57.263 ms |       0.04% |  15.995 us |   0.03% |   SAME   |
| C32  |    2^16    |   0.201   |  38.359 us |       2.74% |  39.284 us |       2.60% |   0.926 us |   2.41% |   SAME   |
| C32  |    2^20    |   0.201   | 100.125 us |       1.94% | 101.225 us |       2.45% |   1.100 us |   1.10% |   SAME   |
| C32  |    2^24    |   0.201   |   2.678 ms |       0.10% |   2.681 ms |       0.11% |   2.847 us |   0.11% |   SLOW   |
| C32  |    2^28    |   0.201   |  57.241 ms |       0.04% |  57.249 ms |       0.04% |   8.605 us |   0.02% |   SAME   |

# Summary

- Total Matches: 120
  - Pass    (diff <= min_noise): 52
  - Unknown (infinite noise):    0
  - Failure (diff > min_noise):  68

bernhardmgruber · 2026-05-12T09:09:08Z

Please create a tracking issue to investigate the small performance difference to Thrust.

github-actions · 2026-05-12T10:38:39Z

🥳 CI Workflow Results

🟩 Finished in 1h 27m: Pass: 100%/395 | Total: 4d 13h | Max: 1h 27m | Hits: 92%/667828

See results here.

miscco requested review from a team as code owners April 22, 2026 13:46

miscco requested a review from oleksandr-pavlyk April 22, 2026 13:46

github-project-automation Bot added this to CCCL Apr 22, 2026

miscco requested review from ericniebler and gevtushenko April 22, 2026 13:46

github-project-automation Bot moved this to Todo in CCCL Apr 22, 2026

cccl-authenticator-app Bot moved this from Todo to In Review in CCCL Apr 22, 2026

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miscco force-pushed the parallel_sort branch from 5878a17 to 814405a Compare April 22, 2026 13:48