179 lines
9.0 KiB
Markdown
179 lines
9.0 KiB
Markdown
# 4.x series change log
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This page summarizes the major functional and performance changes in each
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release of the 4.x series.
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All performance data on this page is measured on an Intel Core i5-9600K
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clocked at 4.2 GHz, running `astcenc` using AVX2 and 6 threads.
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<!-- ---------------------------------------------------------------------- -->
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## 4.2.0
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**Status:** November 2022
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The 4.2.0 release is an optimization release. There are significant performance
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improvements, minor image quality improvements, and library interface changes in
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this release.
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Reminder - the codec library API is not designed to be binary compatible across
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versions. We always recommend rebuilding your client-side code using the updated
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`astcenc.h` header.
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* **General:**
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* **Bug-fix:** Compression for RGB and RGBA base+offset encodings no
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longer generate endpoints with the incorrect blue-contract behavior.
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* **Bug-fix:** Lowest channel correlation calculation now correctly ignores
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constant color channels for the purposes of filtering 2 plane encodings.
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On average this improves both performance and image quality.
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* **Bug-fix:** ISA compatibility now checked in `config_init()` as well as
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in `context_alloc()`.
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* **Change:** Removed the low-weight count optimization, as more recent
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changes had significantly reduced its performance benefit. Option removed
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from both command line and configuration structure.
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* **Feature:** The `-exhaustive` mode now runs full trials on more
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partitioning candidates and block candidates. This improves image quality
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by 0.1 to 0.25 dB, but slows down compression by 3x. The `-verythorough`
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and `-thorough` modes also test more candidates.
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* **Feature:** A new preset, `-verythorough`, has been introduced to provide
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a standard performance point between `-thorough` and the re-tuned
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`-exhaustive` mode. This new mode is faster and higher quality than the
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`-exhaustive` preset in the 4.1 release.
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* **Feature:** The compressor can now independently vary the number of
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partitionings considered for error estimation for 2/3/4 partitions. This
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allows heuristics to put more effort into 2 partitions, and less in to
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3/4 partitions.
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* **Feature:** The compressor can now run trials on a variable number of
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candidate partitionings, allowing high quality modes to explore more of the
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search space at the expense of slower compression. The number of trials is
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independently configurable for 2/3/4 partition cases.
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* **Optimization:** Introduce early-out threshold for 2/3/4 partition
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searches based on the results after 1 of 2 trials. This significantly
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improves performance for `-medium` and `-thorough` searches, for a minor
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loss in image quality.
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* **Optimization:** Reduce early-out threshold for 3/4 partition searches
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based on 2/3 partition results. This significantly improves performance,
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especially for `-thorough` searches, for a minor loss in image quality.
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* **Optimization:** Use direct vector compare to create a SIMD mask instead
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of a scalar compare that is broadcast to a vector mask.
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* **Optimization:** Remove obsolete partition validity masks from the
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partition selection algorithm.
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* **Optimization:** Removed obsolete channel scaling from partition
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`avgs_and_dirs()` calculation.
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### Performance:
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Key for charts:
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* Color = block size (see legend).
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* Letter = image format (N = normal map, G = grayscale, L = LDR, H = HDR).
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**Relative performance vs 4.0 and 4.1 release:**
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<!-- ---------------------------------------------------------------------- -->
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## 4.1.0
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**Status:** August 2022
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The 4.1.0 release is a maintenance release. There is no performance or image
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quality change in this release.
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* **General:**
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* **Change:** Command line decompressor no longer uses the legacy
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`GL_LUMINANCE` or `GL_LUMINANCE_ALPHA` format enums when writing KTX
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output files. Luminance textures now use the `GL_RED` format and
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luminance_alpha textures now use the `GL_RG` format.
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* **Change:** Command line tool gains a new `-dimage` option to generate
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diagnostic images showing aspects of the compression encoding. The output
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file name with its extension stripped is used as the stem of the diagnostic
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image file names.
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* **Bug-fix:** Library decompressor builds for SSE no longer use masked store
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`maskmovdqu` instructions, as they can generate faults on masked lanes.
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* **Bug-fix:** Command line decompressor now correctly uses sized type enums
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for the internal format when writing output KTX files.
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* **Bug-fix:** Command line compressor now correctly loads 16 and 32-bit per
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component input KTX files.
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* **Bug-fix:** Fixed GCC9 compiler warnings on Arm aarch64.
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<!-- ---------------------------------------------------------------------- -->
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## 4.0.0
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**Status:** July 2022
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The 4.0.0 release introduces some major performance enhancement, and a number
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of larger changes to the heuristics used in the codec to find a more effective
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cost:quality trade off.
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* **General:**
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* **Change:** The `-array` option for specifying the number of image planes
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for ASTC 3D volumetric block compression been renamed to `-zdim`.
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* **Change:** The build root package directory is now `bin` instead of
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`astcenc`, allowing the CMake install step to write binaries into
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`/usr/local/bin` if the user wishes to do so.
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* **Feature:** A new `-ssw` option for specifying the shader sampling swizzle
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has been added as convenience alternative to the `-cw` option. This is
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needed to correct error weighting during compression if not all components
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are read in the shader. For example, to extract and compress two components
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from an RGBA input image, weighting the two components equally when
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sampling through .ra in the shader, use `-esw ggga -ssw ra`. In this
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example `-ssw ra` is equivalent to the alternative `-cw 1 0 0 1` encoding.
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* **Feature:** The `-a` alpha weighting option has been re-enabled in the
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backend, and now again applies alpha scaling to the RGB error metrics when
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encoding. This is based on the maximum alpha in each block, not the
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individual texel alpha values used in the earlier implementation.
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* **Feature:** The command line tool now has `-repeats <count>` for testing,
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which will iterate around compression and decompression `count` times.
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Reported performance metrics also now separate compression and
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decompression scores.
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* **Feature:** The core codec is now warning clean up to /W4 for both MSVC
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`cl.exe` and `clangcl.exe` compilers.
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* **Feature:** The core codec now supports arm64 for both MSVC `cl.exe` and
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`clangcl.exe` compilers.
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* **Feature:** `NO_INVARIANCE` builds will enable the `-ffp-contract=fast`
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option for all targets when using Clang or GCC. In addition AVX2 targets
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will also set the `-mfma` option. This reduces image quality by up to 0.2dB
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(normally much less), but improves performance by up to 5-20%.
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* **Optimization:** Angular endpoint min/max weight selection is restricted
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to weight `QUANT_11` or lower. Higher quantization levels assume default
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0-1 range, which is less accurate but much faster.
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* **Optimization:** Maximum weight quantization for later trials is selected
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based on the weight quantization of the best encoding from the 1 plane 1
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partition trial. This significantly reduces the search space for the later
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trials with more planes or partitions.
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* **Optimization:** Small data tables now use in-register SIMD permutes
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rather than gathers (AVX2) or unrolled scalar lookups (SSE/NEON). This can
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be a significant optimization for paths that are load unit limited.
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* **Optimization:** Decompressed image block writes in the decompressor now
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use a vectorized approach to writing each row of texels in the block,
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including to ability to exploit masked stores if the target supports them.
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* **Optimization:** Weight scrambling has been moved into the physical layer;
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the rest of the codec now uses linear order weights.
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* **Optimization:** Weight packing has been moved into the physical layer;
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the rest of the codec now uses unpacked weights in the 0-64 range.
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* **Optimization:** Consistently vectorize the creation of unquantized weight
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grids when they are needed.
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* **Optimization:** Remove redundant per-decimation mode copies of endpoint
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and weight structures, which were really read-only duplicates.
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* **Optimization:** Early-out the same endpoint mode color calculation if it
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cannot be applied.
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* **Optimization:** Numerous type size reductions applied to arrays to reduce
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both context working buffer size usage and stack usage.
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### Performance:
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Key for charts:
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* Color = block size (see legend).
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* Letter = image format (N = normal map, G = grayscale, L = LDR, H = HDR).
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**Relative performance vs 3.7 release:**
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- - -
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_Copyright © 2022, Arm Limited and contributors. All rights reserved._
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