Resolve degenerate performance in create_structs_data

[SurajAralihalli]

Resolves issue #14716

• Eliminated unnecessary recursive self-calls in the superimpose_nulls_no_sanitize function, addressing performance issues in make_structs_column.
• Introduced STRUCT_CREATION_NVBENCH to assess the performance of the create_structs_data function.

Checklist

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

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[SurajAralihalli]

Example structure definition: STRUCT<STRUCT<INT32>> : [ {{Null}}, {Null}, Null, {{3}} ]

In the code:

P {
  type = STRUCT
  null_mask = [1, 1, 0, 1]
  null_count = 1
  children =
    C_1 {
      type = STRUCT
      null_mask = [1, 0, 0, 1]
      null_count = 2
      children =
        C_2 {
          type = INT32
          data =       [X, X, X, 3]
          null_mask  = [0, 0, 0, 1]
          null_count = 3
        }
    }
}

The make_structs_column function applies the null mask of the parent (P) to its immediate children (C_1) at line

cudf/cpp/src/structs/structs_column_factories.cu

Line 46 in 0710335

for (auto& child : child_columns) {

.
The superimpose_nulls_no_sanitize function recursively applies a correct null mask to all nested children (C_2) at line

cudf/cpp/src/structs/utilities.cpp

Line 266 in 0710335

std::for_each(content.children.begin(),

.
This function uses make_structs_column to reconstruct the parent column (P) which applies C_1's null mask to its children (C_2) at line

cudf/cpp/src/structs/utilities.cpp

Line 274 in 0710335

return cudf::make_structs_column(num_rows,

However, C_2's null_mask is already correct.

I believe this redundancy can be eliminated by removing the code at line 266.

[SurajAralihalli]

Before:

After:

Thank you @karthikeyann for sharing scope based NVTX ranges #11864 (comment). This utility greatly helped in debugging.

[davidwendt]

/ok to test

[davidwendt]

Is there a benchmark that could be run to show the performance improvement here?

[SurajAralihalli]

Is there a benchmark that could be run to show the performance improvement here?

I ran the rank_struct benchmark described by @GregoryKimball in #14716 (comment). I added the NVTX regions to superimpose_nulls_no_sanitize to compute the following results.

Before:

After:

[ttnghia]

/ok to test

[vuule]

How come there were 130k calls to superimpose_nulls_no_sanitize? It's more than even quadratic redundancy (not a thing, but hopefully you know what I meant :)) would cause.

I think this change should include a new benchmark.

[SurajAralihalli]

How come there were 130k calls to superimpose_nulls_no_sanitize? It's more than even quadratic redundancy (not a thing, but hopefully you know what I meant :)) would cause.

I think this change should include a new benchmark.

Absolutely @vuule! It would be interesting to derive the relationship between calls to make_structs_column and superimpose_nulls_no_sanitize in terms of depth. Also, I've created create_structs benchmark.

./STRUCT_CREATION_NVBENCH -b create_structs --axis NumRows=[10] --axis Depth=[16] --axis Nulls=[0]

[SurajAralihalli]

Comparing benchmarking results:

## [0] NVIDIA RTX A5000

|  NumRows  |  Depth  |  Nulls  |   Ref Time |   Ref Noise |   Cmp Time |   Cmp Noise |            Diff |   %Diff |  Status  |
|-----------|---------|---------|------------|-------------|------------|-------------|-----------------|---------|----------|
|   2^10    |    1    |    0    |  42.087 us |       7.79% |  39.435 us |       6.45% |       -2.651 us |  -6.30% |   PASS   |
|   2^18    |    1    |    0    |   7.681 ms |       3.37% |   7.582 ms |       2.55% |      -98.575 us |  -1.28% |   PASS   |
|   2^26    |    1    |    0    |    2.346 s |       0.23% |    2.357 s |       0.55% |       11.391 ms |   0.49% |   FAIL   |
|   2^10    |    8    |    0    |   8.984 ms |       1.35% | 824.409 us |       2.86% |    -8159.408 us | -90.82% |   FAIL   |
|   2^18    |    8    |    0    |  47.787 ms |       1.30% |  38.508 ms |       1.60% |    -9278.895 us | -19.42% |   FAIL   |
|   2^26    |    8    |    0    |   10.222 s |        inf% |   10.222 s |        inf% |       29.785 us |   0.00% |   PASS   |
|   2^10    |   16    |    0    |    2.455 s |       0.58% |   3.206 ms |       1.87% | -2452204.726 us | -99.87% |   FAIL   |
|   2^18    |   16    |    0    |    2.779 s |       0.23% |  75.308 ms |       1.82% | -2703843.785 us | -97.29% |   FAIL   |
|   2^26    |   16    |    0    |   26.935 s |        inf% |   19.043 s |        inf% | -7891943.359 us | -29.30% |   PASS   |
|   2^10    |    1    |    1    |  56.118 us |       5.24% |  56.982 us |       6.84% |        0.864 us |   1.54% |   PASS   |
|   2^18    |    1    |    1    |   7.839 ms |       1.51% |   7.985 ms |       3.48% |      146.030 us |   1.86% |   FAIL   |
|   2^26    |    1    |    1    |    2.447 s |       1.11% |    2.434 s |       0.48% |   -12658.447 us |  -0.52% |   FAIL   |
|   2^10    |    8    |    1    |   9.043 ms |       1.18% | 837.039 us |       2.92% |    -8206.161 us | -90.74% |   FAIL   |
|   2^18    |    8    |    1    |  48.371 ms |       1.75% |  38.803 ms |       1.66% |    -9568.242 us | -19.78% |   FAIL   |
|   2^26    |    8    |    1    |   10.312 s |        inf% |   10.285 s |        inf% |   -26727.539 us |  -0.26% |   PASS   |
|   2^10    |   16    |    1    |    2.411 s |       0.27% |   3.235 ms |       1.79% | -2407859.781 us | -99.87% |   FAIL   |
|   2^18    |   16    |    1    |    2.762 s |       0.40% |  75.156 ms |       0.44% | -2686969.612 us | -97.28% |   FAIL   |
|   2^26    |   16    |    1    |   27.152 s |        inf% |   19.126 s |        inf% | -8025222.656 us | -29.56% |   PASS   |

[ttnghia]

/ok to test

[SurajAralihalli]

/ok to test

[vuule]

/ok to test

[vuule]

/merge