ASTC decoding part 3: Benchmarks

[Erik-White]

Prerequisites

• I have written a descriptive pull-request title
• I have verified that there are no overlapping pull-requests open
• I have verified that I am following the existing coding patterns and practice as demonstrated in the repository. These follow strict Stylecop rules 👮.
• I have provided test coverage for my change (where applicable)

Description

The third part of ASTC (Adaptive scalable texture compression) decoding. ASTC is used with KTX containers to compress texture data.
This adds benchmarking to ImageSharp.Textures. It currently only contains ASTC related benchmarks, but could easily be extended with others in future. Benchmarks include direct comparison with the ARM C++ decoder that is used as a reference implementation.

Prerequisites

• Test infrastructure improvements and fixes
• Base decoder and LDR support
• High dynamic range support

To follow

• Fuzz testing

Test data

Everything used is either created by myself, or sourced from
https://github.com/KhronosGroup/KTX-Software (Apache 2.0 license)
https://github.com/KhronosGroup/KTX-Software-CTS (Apache 2.0 license)
https://github.com/ARM-software/astc-encoder (Apache-2.0 license)

Example output

AstcReferenceComparisonBenchmark

| Method         | Categories | Mean      | Error     | StdDev    | Ratio | RatioSD | Allocated | Alloc Ratio |
|--------------- |----------- |----------:|----------:|----------:|------:|--------:|----------:|------------:|
| Reference_Hdr  | HDR        |  7.204 ms | 0.1393 ms | 0.1604 ms |  1.00 |    0.03 |     460 B |        1.00 |
| ImageSharp_Hdr | HDR        |  1.965 ms | 0.0379 ms | 0.0389 ms |  0.27 |    0.01 |     288 B |        0.63 |
|                |            |           |           |           |       |         |           |             |
| Reference_Ldr  | LDR        | 10.623 ms | 0.2005 ms | 0.1875 ms |  1.00 |    0.02 |     616 B |        1.00 |
| ImageSharp_Ldr | LDR        |  2.723 ms | 0.0389 ms | 0.0364 ms |  0.26 |    0.01 |     384 B |        0.62 |

AstcReferencePersistenceBenchmark

Method	Categories	Mean	Error	StdDev	Ratio	Allocated	Alloc Ratio
Reference_Hdr	HDR	931.4 us	4.73 us	3.95 us	1.00	-	NA
ImageSharp_Hdr	HDR	1,915.3 us	5.28 us	4.13 us	2.06	288 B	NA
Reference_Ldr	LDR	2,381.4 us	5.92 us	4.95 us	1.00	-	NA
ImageSharp_Ldr	LDR	2,724.1 us	26.91 us	25.17 us	1.14	384 B	NA