Refactor group_nunique.cu to use nullate::DYNAMIC for reduce-by-key functor

[davidwendt]

Description

Refactored the group_nunique.cu source to use the nullate::DYNAMIC for the equal operator and the unique-iterator. This improves the compile time by almost 2x without much change to performance by reducing the number of calls to thrust::reduce_by_key.

Found while investigating compile issues for #11437

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[davidwendt]

The benchmark from #11472 was used to check the change in performance.

# groupby_nunique

## [0] NVIDIA RTX A6000

|  T  |  num_rows  |  null_frequency  |   Ref Time |   Ref Noise |   Cmp Time |   Cmp Noise |       Diff |   %Diff | 
|-----|------------|------------------|------------|-------------|------------|-------------|------------|---------|
| I32 |    2^12    |        0         | 342.972 us |       1.60% | 345.004 us |       2.03% |   2.032 us |   0.59% | 
| I32 |    2^16    |        0         | 520.081 us |       0.33% | 516.265 us |       0.61% |  -3.816 us |  -0.73% |
| I32 |    2^20    |        0         |   2.630 ms |       0.50% |   2.653 ms |       0.44% |  22.267 us |   0.85% |
| I32 |    2^24    |        0         |  58.545 ms |       0.06% |  58.617 ms |       0.05% |  72.704 us |   0.12% |
| I32 |    2^12    |       0.5        | 420.704 us |       0.30% | 424.737 us |       0.30% |   4.033 us |   0.96% |
| I32 |    2^16    |       0.5        | 657.260 us |       0.62% | 664.688 us |       0.49% |   7.428 us |   1.13% |
| I32 |    2^20    |       0.5        |   2.633 ms |       0.29% |   2.656 ms |       0.31% |  23.650 us |   0.90% |
| I32 |    2^24    |       0.5        |  48.216 ms |       0.09% |  48.363 ms |       0.11% | 147.083 us |   0.31% |
| I64 |    2^12    |        0         | 400.970 us |       0.40% | 407.797 us |       0.35% |   6.827 us |   1.70% |
| I64 |    2^16    |        0         | 583.841 us |       0.28% | 587.126 us |       0.42% |   3.284 us |   0.56% |
| I64 |    2^20    |        0         |   3.725 ms |       0.38% |   3.751 ms |       0.37% |  25.333 us |   0.68% |
| I64 |    2^24    |        0         |  77.178 ms |       0.15% |  77.230 ms |       0.17% |  51.759 us |   0.07% |
| I64 |    2^12    |       0.5        | 463.510 us |       0.50% | 466.201 us |       0.82% |   2.691 us |   0.58% |
| I64 |    2^16    |       0.5        | 714.861 us |       0.51% | 710.432 us |       0.35% |  -4.429 us |  -0.62% |
| I64 |    2^20    |       0.5        |   2.960 ms |       0.50% |   2.960 ms |       0.40% |  -0.151 us |  -0.01% |
| I64 |    2^24    |       0.5        |  56.646 ms |       0.10% |  56.683 ms |       0.06% |  36.585 us |   0.06% |

All diffs are less than 2%

[bdice]

I have to say, I love nullate::DYNAMIC. Such a nice solution.

[codecov]

Codecov Report

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[davidwendt]

@gpucibot merge