[CUB] warpspeed kernel: make scan_resources_t copy by srinivasyadav18 · Pull Request #9751 · NVIDIA/cccl

srinivasyadav18 · 2026-07-08T15:10:33Z

Description

closes

This improves performance of warpspeed on sm90 using atomics (#9565).

It doesn't impact performance on current implementation for SM100+ .

Further it reduces SASS on

cub.bench.scan.exclusive.deterministic.base
cub.bench.scan.exclusive.sum.base
cub.bench.scan.exclusive.sum.lookahead.base

Checklist

New or existing tests cover these changes.
The documentation is up to date with these changes.

srinivasyadav18 · 2026-07-08T15:11:23Z

Performance Report

B200

deterministic — main → warpspeed_ker_scan_res_copy (avg %Diff: -0.05%)

|  T{ct}  |  OffsetT{ct}  |  Elements{io}  |   Ref Time |   Ref Noise |   Cmp Time |   Cmp Noise |      Diff |   %Diff |  Status  |
|---------|---------------|----------------|------------|-------------|------------|-------------|-----------|---------|----------|
|   F32   |      I64      |      2^16      |  11.164 us |       4.00% |  11.177 us |       3.67% |  0.012 us |   0.11% |  🔵 SAME  |
|   F32   |      I64      |      2^20      |  13.994 us |       6.96% |  13.962 us |       7.01% | -0.032 us |  -0.23% |  🔵 SAME  |
|   F32   |      I64      |      2^24      |  36.414 us |       2.92% |  36.412 us |       2.84% | -0.002 us |  -0.00% |  🔵 SAME  |
|   F32   |      I64      |      2^28      | 320.482 us |       0.47% | 320.347 us |       0.48% | -0.134 us |  -0.04% |  🔵 SAME  |
|   F64   |      I64      |      2^16      |  11.257 us |       0.64% |  11.266 us |       0.66% |  0.010 us |   0.08% |  🔵 SAME  |
|   F64   |      I64      |      2^20      |  15.501 us |       3.75% |  15.436 us |       2.93% | -0.064 us |  -0.41% |  🔵 SAME  |
|   F64   |      I64      |      2^24      |  56.555 us |       1.89% |  56.601 us |       1.89% |  0.046 us |   0.08% |  🔵 SAME  |
|   F64   |      I64      |      2^28      | 620.459 us |       0.18% | 620.348 us |       0.18% | -0.111 us |  -0.02% |  🔵 SAME  |

lookahead — main → warpspeed_ker_scan_res_copy (avg %Diff: -0.09%)

|  T{ct}  |  OffsetT{ct}  |  Elements{io}  |   Ref Time |   Ref Noise |   Cmp Time |   Cmp Noise |       Diff |   %Diff |  Status  |
|---------|---------------|----------------|------------|-------------|------------|-------------|------------|---------|----------|
|   I8    |      I64      |      2^16      |  11.264 us |       0.45% |  11.257 us |       0.50% |  -0.006 us |  -0.06% |  🔵 SAME  |
|   I8    |      I64      |      2^20      |  12.969 us |       5.78% |  13.020 us |       5.34% |   0.051 us |   0.40% |  🔵 SAME  |
|   I8    |      I64      |      2^24      |  27.817 us |       2.07% |  27.720 us |       1.42% |  -0.097 us |  -0.35% |  🔵 SAME  |
|   I8    |      I64      |      2^28      | 212.552 us |       0.44% | 209.279 us |       0.52% |  -3.273 us |  -1.54% |  🟢 FAST  |
|   I8    |      I64      |      2^32      |   3.223 ms |       0.35% |   3.171 ms |       0.29% | -52.714 us |  -1.64% |  🟢 FAST  |
|   I16   |      I64      |      2^16      |  11.246 us |       0.53% |  11.248 us |       0.98% |   0.002 us |   0.02% |  🔵 SAME  |
|   I16   |      I64      |      2^20      |  13.002 us |       5.62% |  13.025 us |       5.44% |   0.024 us |   0.18% |  🔵 SAME  |
|   I16   |      I64      |      2^24      |  29.896 us |       3.63% |  29.827 us |       3.60% |  -0.069 us |  -0.23% |  🔵 SAME  |
|   I16   |      I64      |      2^28      | 212.506 us |       0.56% | 212.013 us |       0.59% |  -0.493 us |  -0.23% |  🔵 SAME  |
|   I16   |      I64      |      2^32      |   3.414 ms |       1.92% |   3.400 ms |       2.09% | -14.589 us |  -0.43% |  🔵 SAME  |
|   I32   |      I64      |      2^16      |  10.450 us |       9.58% |  10.556 us |       9.22% |   0.106 us |   1.02% |  🔵 SAME  |
|   I32   |      I64      |      2^20      |  13.072 us |       5.08% |  12.930 us |       6.15% |  -0.142 us |  -1.08% |  🔵 SAME  |
|   I32   |      I64      |      2^24      |  35.231 us |       3.15% |  35.212 us |       3.18% |  -0.019 us |  -0.06% |  🔵 SAME  |
|   I32   |      I64      |      2^28      | 322.145 us |       0.51% | 322.235 us |       0.51% |   0.090 us |   0.03% |  🔵 SAME  |
|   I32   |      I64      |      2^32      |   5.205 ms |       1.13% |   5.189 ms |       1.23% | -15.545 us |  -0.30% |  🔵 SAME  |
|   I64   |      I64      |      2^16      |  12.142 us |       8.41% |  12.897 us |       6.56% |   0.754 us |   6.21% |  🔵 SAME  |
|   I64   |      I64      |      2^20      |  15.893 us |       5.71% |  16.201 us |       6.30% |   0.308 us |   1.94% |  🔵 SAME  |
|   I64   |      I64      |      2^24      |  54.198 us |       1.78% |  54.291 us |       1.83% |   0.093 us |   0.17% |  🔵 SAME  |
|   I64   |      I64      |      2^28      | 645.326 us |       2.23% | 643.963 us |       2.30% |  -1.363 us |  -0.21% |  🔵 SAME  |
|   I64   |      I64      |      2^32      |  10.614 ms |       1.12% |  10.611 ms |       1.05% |  -3.263 us |  -0.03% |  🔵 SAME  |
|  I128   |      I64      |      2^16      |  12.839 us |       6.67% |  12.848 us |       6.66% |   0.009 us |   0.07% |  🔵 SAME  |
|  I128   |      I64      |      2^20      |  21.656 us |       2.59% |  21.700 us |       2.86% |   0.044 us |   0.20% |  🔵 SAME  |
|  I128   |      I64      |      2^24      | 149.172 us |       0.79% | 147.993 us |       0.83% |  -1.179 us |  -0.79% |  🔵 SAME  |
|  I128   |      I64      |      2^28      |   2.056 ms |       0.15% |   2.055 ms |       0.15% |  -0.223 us |  -0.01% |  🔵 SAME  |
|  I128   |      I64      |      2^32      |  32.476 ms |       0.03% |  32.476 ms |       0.03% |   0.344 us |   0.00% |  🔵 SAME  |
|   F32   |      I64      |      2^16      |  11.101 us |       5.18% |  11.169 us |       3.79% |   0.068 us |   0.61% |  🔵 SAME  |
|   F32   |      I64      |      2^20      |  14.048 us |       7.21% |  14.238 us |       7.21% |   0.190 us |   1.35% |  🔵 SAME  |
|   F32   |      I64      |      2^24      |  36.750 us |       3.59% |  36.581 us |       3.50% |  -0.169 us |  -0.46% |  🔵 SAME  |
|   F32   |      I64      |      2^28      | 319.751 us |       0.50% | 319.751 us |       0.49% |  -0.000 us |  -0.00% |  🔵 SAME  |
|   F32   |      I64      |      2^32      |   4.897 ms |       0.81% |   4.891 ms |       0.72% |  -6.101 us |  -0.12% |  🔵 SAME  |
|   F64   |      I64      |      2^16      |  12.497 us |       7.96% |  11.439 us |       5.10% |  -1.057 us |  -8.46% |  🟢 FAST  |
|   F64   |      I64      |      2^20      |  15.875 us |       5.63% |  15.656 us |       4.64% |  -0.219 us |  -1.38% |  🔵 SAME  |
|   F64   |      I64      |      2^24      |  55.365 us |       2.02% |  55.103 us |       1.98% |  -0.262 us |  -0.47% |  🔵 SAME  |
|   F64   |      I64      |      2^28      | 621.310 us |       0.24% | 621.106 us |       0.22% |  -0.204 us |  -0.03% |  🔵 SAME  |
|   F64   |      I64      |      2^32      |  10.242 ms |       0.78% |  10.219 ms |       0.83% | -23.097 us |  -0.23% |  🔵 SAME  |
|   C32   |      I64      |      2^16      |  11.349 us |       3.58% |  11.451 us |       5.31% |   0.102 us |   0.90% |  🔵 SAME  |
|   C32   |      I64      |      2^20      |  15.401 us |       2.01% |  15.365 us |       1.15% |  -0.035 us |  -0.23% |  🔵 SAME  |
|   C32   |      I64      |      2^24      |  53.724 us |       2.24% |  53.719 us |       2.23% |  -0.005 us |  -0.01% |  🔵 SAME  |
|   C32   |      I64      |      2^28      | 621.488 us |       0.22% | 621.542 us |       0.23% |   0.054 us |   0.01% |  🔵 SAME  |
|   C32   |      I64      |      2^32      |   9.893 ms |       0.58% |   9.870 ms |       0.53% | -23.091 us |  -0.23% |  🔵 SAME  |
|   F16   |      I64      |      2^16      |  11.450 us |       5.29% |  11.586 us |       6.47% |   0.136 us |   1.19% |  🔵 SAME  |
|   F16   |      I64      |      2^20      |  13.343 us |       3.53% |  13.315 us |       3.50% |  -0.027 us |  -0.21% |  🔵 SAME  |
|   F16   |      I64      |      2^24      |  31.040 us |       3.59% |  30.913 us |       3.51% |  -0.127 us |  -0.41% |  🔵 SAME  |
|   F16   |      I64      |      2^28      | 224.782 us |       0.55% | 224.388 us |       0.50% |  -0.394 us |  -0.18% |  🔵 SAME  |
|   F16   |      I64      |      2^32      |   3.337 ms |       0.84% |   3.333 ms |       0.73% |  -4.908 us |  -0.15% |  🔵 SAME  |
|  BF16   |      I64      |      2^16      |  11.292 us |       2.31% |  11.286 us |       2.08% |  -0.006 us |  -0.05% |  🔵 SAME  |
|  BF16   |      I64      |      2^20      |  13.324 us |       1.92% |  13.330 us |       2.68% |   0.006 us |   0.05% |  🔵 SAME  |
|  BF16   |      I64      |      2^24      |  30.956 us |       3.84% |  31.217 us |       3.67% |   0.260 us |   0.84% |  🔵 SAME  |
|  BF16   |      I64      |      2^28      | 224.687 us |       0.52% | 224.329 us |       0.54% |  -0.358 us |  -0.16% |  🔵 SAME  |
|  BF16   |      I64      |      2^32      |   3.337 ms |       0.70% |   3.334 ms |       0.97% |  -3.218 us |  -0.10% |  🔵 SAME  |

sum — main → warpspeed_ker_scan_res_copy (avg %Diff: +0.03%)

|  T{ct}  |  OffsetT{ct}  |  Elements{io}  |   Ref Time |   Ref Noise |   Cmp Time |   Cmp Noise |       Diff |   %Diff |  Status  |
|---------|---------------|----------------|------------|-------------|------------|-------------|------------|---------|----------|
|   I8    |      I32      |      2^16      |  11.263 us |       0.48% |  11.259 us |       0.48% |  -0.004 us |  -0.04% |  🔵 SAME  |
|   I8    |      I32      |      2^20      |  13.021 us |       5.32% |  13.045 us |       5.15% |   0.024 us |   0.19% |  🔵 SAME  |
|   I8    |      I32      |      2^24      |  27.830 us |       2.10% |  27.715 us |       1.36% |  -0.115 us |  -0.41% |  🔵 SAME  |
|   I8    |      I32      |      2^28      | 212.541 us |       0.46% | 209.390 us |       0.48% |  -3.151 us |  -1.48% |  🟢 FAST  |
|   I8    |      I64      |      2^16      |  11.262 us |       0.47% |  11.267 us |       0.67% |   0.005 us |   0.05% |  🔵 SAME  |
|   I8    |      I64      |      2^20      |  13.206 us |       3.11% |  13.162 us |       3.87% |  -0.044 us |  -0.33% |  🔵 SAME  |
|   I8    |      I64      |      2^24      |  28.041 us |       2.90% |  27.947 us |       2.60% |  -0.094 us |  -0.33% |  🔵 SAME  |
|   I8    |      I64      |      2^28      | 213.827 us |       0.40% | 210.611 us |       0.50% |  -3.216 us |  -1.50% |  🟢 FAST  |
|   I8    |      I64      |      2^32      |   3.223 ms |       0.36% |   3.170 ms |       0.25% | -52.660 us |  -1.63% |  🟢 FAST  |
|   I16   |      I32      |      2^16      |  11.260 us |       0.44% |  11.259 us |       0.45% |  -0.001 us |  -0.01% |  🔵 SAME  |
|   I16   |      I32      |      2^20      |  13.035 us |       5.47% |  13.143 us |       4.24% |   0.108 us |   0.83% |  🔵 SAME  |
|   I16   |      I32      |      2^24      |  28.245 us |       3.48% |  28.233 us |       3.46% |  -0.012 us |  -0.04% |  🔵 SAME  |
|   I16   |      I32      |      2^28      | 214.041 us |       0.61% | 213.652 us |       0.64% |  -0.390 us |  -0.18% |  🔵 SAME  |
|   I16   |      I64      |      2^16      |  11.264 us |       0.53% |  11.258 us |       0.49% |  -0.006 us |  -0.05% |  🔵 SAME  |
|   I16   |      I64      |      2^20      |  12.770 us |       7.04% |  12.867 us |       6.50% |   0.097 us |   0.76% |  🔵 SAME  |
|   I16   |      I64      |      2^24      |  29.790 us |       3.34% |  29.866 us |       3.61% |   0.076 us |   0.25% |  🔵 SAME  |
|   I16   |      I64      |      2^28      | 212.369 us |       0.60% | 211.778 us |       0.58% |  -0.592 us |  -0.28% |  🔵 SAME  |
|   I16   |      I64      |      2^32      |   3.337 ms |       1.80% |   3.329 ms |       1.80% |  -8.259 us |  -0.25% |  🔵 SAME  |
|   I32   |      I32      |      2^16      |   9.547 us |       7.95% |   9.640 us |       8.62% |   0.092 us |   0.97% |  🔵 SAME  |
|   I32   |      I32      |      2^20      |  13.125 us |       4.54% |  13.135 us |       4.57% |   0.010 us |   0.08% |  🔵 SAME  |
|   I32   |      I32      |      2^24      |  35.670 us |       3.01% |  35.801 us |       3.34% |   0.131 us |   0.37% |  🔵 SAME  |
|   I32   |      I32      |      2^28      | 322.490 us |       0.51% | 322.513 us |       0.53% |   0.023 us |   0.01% |  🔵 SAME  |
|   I32   |      I64      |      2^16      |   9.510 us |       7.59% |   9.523 us |       7.70% |   0.014 us |   0.14% |  🔵 SAME  |
|   I32   |      I64      |      2^20      |  12.843 us |       6.69% |  12.808 us |       6.87% |  -0.035 us |  -0.27% |  🔵 SAME  |
|   I32   |      I64      |      2^24      |  35.952 us |       3.23% |  35.966 us |       3.51% |   0.014 us |   0.04% |  🔵 SAME  |
|   I32   |      I64      |      2^28      | 322.340 us |       0.56% | 322.399 us |       0.52% |   0.059 us |   0.02% |  🔵 SAME  |
|   I32   |      I64      |      2^32      |   5.112 ms |       1.20% |   5.103 ms |       1.19% |  -8.932 us |  -0.17% |  🔵 SAME  |
|   I64   |      I32      |      2^16      |  12.405 us |       8.22% |  11.427 us |       4.83% |  -0.978 us |  -7.89% |  🟢 FAST  |
|   I64   |      I32      |      2^20      |  15.898 us |       5.70% |  17.614 us |       3.72% |   1.716 us |  10.80% |  🔴 SLOW  |
|   I64   |      I32      |      2^24      |  54.110 us |       1.69% |  54.560 us |       2.20% |   0.449 us |   0.83% |  🔵 SAME  |
|   I64   |      I32      |      2^28      | 624.114 us |       0.29% | 623.866 us |       0.30% |  -0.248 us |  -0.04% |  🔵 SAME  |
|   I64   |      I64      |      2^16      |  11.259 us |       0.43% |  11.248 us |       0.48% |  -0.011 us |  -0.10% |  🔵 SAME  |
|   I64   |      I64      |      2^20      |  15.528 us |       3.80% |  15.815 us |       5.50% |   0.287 us |   1.85% |  🔵 SAME  |
|   I64   |      I64      |      2^24      |  53.992 us |       1.80% |  54.005 us |       1.89% |   0.013 us |   0.02% |  🔵 SAME  |
|   I64   |      I64      |      2^28      | 624.598 us |       0.43% | 623.908 us |       0.29% |  -0.690 us |  -0.11% |  🔵 SAME  |
|   I64   |      I64      |      2^32      |  10.457 ms |       0.89% |  10.442 ms |       0.83% | -15.025 us |  -0.14% |  🔵 SAME  |
|  I128   |      I32      |      2^16      |  12.641 us |       7.61% |  12.737 us |       7.25% |   0.096 us |   0.76% |  🔵 SAME  |
|  I128   |      I32      |      2^20      |  21.685 us |       2.74% |  21.729 us |       3.05% |   0.045 us |   0.21% |  🔵 SAME  |
|  I128   |      I32      |      2^24      | 149.486 us |       0.78% | 149.000 us |       0.75% |  -0.486 us |  -0.33% |  🔵 SAME  |
|  I128   |      I32      |      2^28      |   2.053 ms |       0.15% |   2.054 ms |       0.15% |   0.423 us |   0.02% |  🔵 SAME  |
|  I128   |      I64      |      2^16      |  12.877 us |       6.50% |  12.957 us |       5.97% |   0.079 us |   0.62% |  🔵 SAME  |
|  I128   |      I64      |      2^20      |  22.481 us |       4.60% |  22.756 us |       4.48% |   0.275 us |   1.22% |  🔵 SAME  |
|  I128   |      I64      |      2^24      | 149.431 us |       0.75% | 149.926 us |       0.77% |   0.495 us |   0.33% |  🔵 SAME  |
|  I128   |      I64      |      2^28      |   2.054 ms |       0.15% |   2.054 ms |       0.16% |   0.142 us |   0.01% |  🔵 SAME  |
|  I128   |      I64      |      2^32      |  32.464 ms |       0.03% |  32.466 ms |       0.03% |   2.705 us |   0.01% |  🔵 SAME  |
|   F32   |      I32      |      2^16      |  10.371 us |       9.73% |  10.465 us |       9.52% |   0.094 us |   0.90% |  🔵 SAME  |
|   F32   |      I32      |      2^20      |  13.278 us |       2.42% |  13.292 us |       2.55% |   0.013 us |   0.10% |  🔵 SAME  |
|   F32   |      I32      |      2^24      |  36.467 us |       2.82% |  36.408 us |       2.90% |  -0.060 us |  -0.16% |  🔵 SAME  |
|   F32   |      I32      |      2^28      | 320.703 us |       0.48% | 320.793 us |       0.43% |   0.090 us |   0.03% |  🔵 SAME  |
|   F32   |      I64      |      2^16      |  10.597 us |       9.00% |  10.395 us |       9.72% |  -0.202 us |  -1.90% |  🔵 SAME  |
|   F32   |      I64      |      2^20      |  13.289 us |       3.41% |  13.270 us |       3.35% |  -0.019 us |  -0.15% |  🔵 SAME  |
|   F32   |      I64      |      2^24      |  36.619 us |       2.98% |  36.594 us |       2.94% |  -0.024 us |  -0.07% |  🔵 SAME  |
|   F32   |      I64      |      2^28      | 320.635 us |       0.42% | 320.559 us |       0.48% |  -0.076 us |  -0.02% |  🔵 SAME  |
|   F32   |      I64      |      2^32      |   4.873 ms |       0.63% |   4.858 ms |       0.73% | -15.410 us |  -0.32% |  🔵 SAME  |
|   F64   |      I32      |      2^16      |  11.343 us |       3.68% |  11.275 us |       1.74% |  -0.068 us |  -0.60% |  🔵 SAME  |
|   F64   |      I32      |      2^20      |  16.092 us |       6.12% |  15.925 us |       5.75% |  -0.167 us |  -1.04% |  🔵 SAME  |
|   F64   |      I32      |      2^24      |  56.621 us |       2.09% |  56.722 us |       2.11% |   0.101 us |   0.18% |  🔵 SAME  |
|   F64   |      I32      |      2^28      | 622.487 us |       0.23% | 622.716 us |       0.25% |   0.229 us |   0.04% |  🔵 SAME  |
|   F64   |      I64      |      2^16      |  11.263 us |       0.67% |  11.257 us |       0.44% |  -0.007 us |  -0.06% |  🔵 SAME  |
|   F64   |      I64      |      2^20      |  16.120 us |       6.20% |  16.015 us |       6.02% |  -0.105 us |  -0.65% |  🔵 SAME  |
|   F64   |      I64      |      2^24      |  56.425 us |       1.94% |  56.460 us |       1.82% |   0.035 us |   0.06% |  🔵 SAME  |
|   F64   |      I64      |      2^28      | 622.403 us |       0.24% | 622.571 us |       0.24% |   0.168 us |   0.03% |  🔵 SAME  |
|   F64   |      I64      |      2^32      |  10.143 ms |       0.84% |  10.095 ms |       0.84% | -48.044 us |  -0.47% |  🔵 SAME  |
|   C32   |      I32      |      2^16      |  11.285 us |       2.33% |  11.285 us |       2.05% |   0.000 us |   0.00% |  🔵 SAME  |
|   C32   |      I32      |      2^20      |  15.577 us |       4.16% |  15.606 us |       4.37% |   0.029 us |   0.19% |  🔵 SAME  |
|   C32   |      I32      |      2^24      |  54.680 us |       2.03% |  54.758 us |       1.91% |   0.078 us |   0.14% |  🔵 SAME  |
|   C32   |      I32      |      2^28      | 622.448 us |       0.23% | 622.397 us |       0.22% |  -0.052 us |  -0.01% |  🔵 SAME  |
|   C32   |      I64      |      2^16      |  11.258 us |       0.48% |  11.265 us |       0.50% |   0.007 us |   0.06% |  🔵 SAME  |
|   C32   |      I64      |      2^20      |  15.450 us |       2.95% |  15.524 us |       3.77% |   0.074 us |   0.48% |  🔵 SAME  |
|   C32   |      I64      |      2^24      |  54.506 us |       1.82% |  54.653 us |       1.91% |   0.147 us |   0.27% |  🔵 SAME  |
|   C32   |      I64      |      2^28      | 622.271 us |       0.22% | 622.440 us |       0.21% |   0.170 us |   0.03% |  🔵 SAME  |
|   C32   |      I64      |      2^32      |   9.832 ms |       0.46% |   9.789 ms |       0.45% | -42.450 us |  -0.43% |  🔵 SAME  |
|   F16   |      I32      |      2^16      |  11.258 us |       1.17% |  11.293 us |       2.58% |   0.035 us |   0.31% |  🔵 SAME  |
|   F16   |      I32      |      2^20      |  13.300 us |       2.34% |  13.264 us |       2.85% |  -0.035 us |  -0.27% |  🔵 SAME  |
|   F16   |      I32      |      2^24      |  28.913 us |       3.91% |  29.151 us |       3.93% |   0.238 us |   0.82% |  🔵 SAME  |
|   F16   |      I32      |      2^28      | 225.601 us |       0.53% | 225.448 us |       0.51% |  -0.153 us |  -0.07% |  🔵 SAME  |
|   F16   |      I64      |      2^16      |  11.261 us |       0.45% |  11.261 us |       0.44% |   0.001 us |   0.01% |  🔵 SAME  |
|   F16   |      I64      |      2^20      |  13.278 us |       2.56% |  13.244 us |       2.70% |  -0.034 us |  -0.26% |  🔵 SAME  |
|   F16   |      I64      |      2^24      |  28.816 us |       3.86% |  28.934 us |       4.04% |   0.119 us |   0.41% |  🔵 SAME  |
|   F16   |      I64      |      2^28      | 225.466 us |       0.54% | 225.222 us |       0.50% |  -0.244 us |  -0.11% |  🔵 SAME  |
|   F16   |      I64      |      2^32      |   3.338 ms |       0.81% |   3.333 ms |       0.69% |  -4.784 us |  -0.14% |  🔵 SAME  |
|  BF16   |      I32      |      2^16      |  11.260 us |       0.43% |  11.263 us |       0.52% |   0.003 us |   0.03% |  🔵 SAME  |
|  BF16   |      I32      |      2^20      |  13.280 us |       2.14% |  13.293 us |       1.87% |   0.013 us |   0.10% |  🔵 SAME  |
|  BF16   |      I32      |      2^24      |  28.984 us |       3.95% |  29.137 us |       3.79% |   0.153 us |   0.53% |  🔵 SAME  |
|  BF16   |      I32      |      2^28      | 225.525 us |       0.50% | 225.271 us |       0.48% |  -0.255 us |  -0.11% |  🔵 SAME  |
|  BF16   |      I64      |      2^16      |  11.259 us |       0.59% |  11.264 us |       0.47% |   0.004 us |   0.04% |  🔵 SAME  |
|  BF16   |      I64      |      2^20      |  13.269 us |       2.33% |  13.278 us |       2.07% |   0.009 us |   0.07% |  🔵 SAME  |
|  BF16   |      I64      |      2^24      |  29.016 us |       3.96% |  29.100 us |       3.71% |   0.084 us |   0.29% |  🔵 SAME  |
|  BF16   |      I64      |      2^28      | 225.656 us |       0.55% | 225.304 us |       0.51% |  -0.353 us |  -0.16% |  🔵 SAME  |
|  BF16   |      I64      |      2^32      |   3.338 ms |       0.74% |   3.333 ms |       0.71% |  -4.640 us |  -0.14% |  🔵 SAME  |

coderabbitai · 2026-07-08T15:15:22Z

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cub/cub/device/dispatch/kernels/kernel_scan_lookahead.cuh

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Summary by CodeRabbit

Bug Fixes
- Improved internal scan handling to make lookahead processing more reliable and consistent.
- Reduced the risk of issues caused by shared state being accessed indirectly during device-side scan operations.

Walkthrough

The res member of lookahead_scan_closure in kernel_scan_lookahead.cuh changes from a reference type (scan_resources_t&) to a value type (scan_resources_t), affecting how the closure accesses shared scan resources during kernel dispatch.

Changes

Scan closure resource ownership

Layer / File(s)	Summary
Closure member type change `cub/cub/device/dispatch/kernels/kernel_scan_lookahead.cuh`	`lookahead_scan_closure`'s `res` field changes from `scan_resources_t&` to `scan_resources_t`, so the closure now stores a copy rather than an alias to the externally created resources.

critical: This changes res from a reference to a value copy, meaning the closure now operates on a separate copy of scan_resources_t instead of the shared instance. If scan_resources_t holds mutable state (e.g., counters, tile status) meant to be shared/mutated across the squad, this silently breaks that sharing — dispatch_squad and other closures using the original res object will no longer see updates made through this closure's copy. Verify scan_resources_t is trivially copyable and that no shared mutable state is lost; otherwise revert to reference semantics.

_{Comment @coderabbitai help to get the list of available commands.}

github-actions · 2026-07-08T17:49:05Z

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🟩 Finished in 2h 36m: Pass: 100%/287 | Total: 11d 17h | Max: 2h 34m | Hits: 20%/955032

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use scan_resources_t by copy

273a050

srinivasyadav18 requested a review from a team as a code owner July 8, 2026 15:10

srinivasyadav18 requested a review from NaderAlAwar July 8, 2026 15:10

github-project-automation Bot added this to CCCL Jul 8, 2026

github-project-automation Bot moved this to Todo in CCCL Jul 8, 2026

cccl-authenticator-app Bot moved this from Todo to In Review in CCCL Jul 8, 2026

srinivasyadav18 requested a review from bernhardmgruber July 8, 2026 15:36

bernhardmgruber approved these changes Jul 8, 2026

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bernhardmgruber merged commit 6b2c2b6 into NVIDIA:main Jul 8, 2026
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[CUB] warpspeed kernel: make scan_resources_t copy#9751

[CUB] warpspeed kernel: make scan_resources_t copy#9751
bernhardmgruber merged 1 commit into
NVIDIA:mainfrom
srinivasyadav18:warpspeed_ker_scan_res_copy

srinivasyadav18 commented Jul 8, 2026 •

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Description

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srinivasyadav18 commented Jul 8, 2026

Performance Report

B200

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coderabbitai Bot commented Jul 8, 2026

Summary by CodeRabbit

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github-actions Bot commented Jul 8, 2026

🥳 CI Workflow Results

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srinivasyadav18 commented Jul 8, 2026 •

edited

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