Commit 0840efc
morelos
Update base for Update on "[ET-VK][Ops] torchao.choose_qparams_affine vulkan impl and shader (buffer only) and cleanup"
# Changes
* Implement `torchao.choose_qparams_affine` operator in Vulkan backend with comprehensive buffer storage support
* Add block-wise quantization parameter computation in `choose_qparams_buffer.glsl` shader for configurable tensor block analysis
* Extend quantization parameter infrastructure in `ChooseQParams.cpp` to handle affine transformations with configurable block sizes and multiple mapping types
* Support three quantization mapping strategies: ASYMMETRIC, SYMMETRIC, and SYMMETRIC_NO_CLIPPING_ERR for optimal parameter selection
* Consolidated the logic for choosing scale and zero point between affine cases and regular quantized_decomposed cases.
BE: Improved the documentation in the shader logic which is more detailed and clear
# Motivation
The existing Vulkan quantization infrastructure lacked support for the `torchao.choose_qparams_affine` operator, which is essential for computing optimal quantization parameters in dynamic quantization workflows. The `choose_qparams_affine` operator provides flexible block-wise parameter computation that analyzes statistical distributions within tensor blocks, enabling:
* **Block-wise Parameter Computation**: Analyzes configurable tensor blocks to compute optimal scale and zero-point values, improving quantization accuracy for heterogeneous data distributions
* **Multiple Mapping Types**: Supports ASYMMETRIC, SYMMETRIC, and SYMMETRIC_NO_CLIPPING_ERR quantization strategies for different precision-performance trade-offs
# Operator Description
The `choose_qparams_affine` operator computes optimal quantization parameters (scale and zero_point) from floating-point tensor blocks using statistical analysis of data distributions. Block-wise parameter computation divides tensors into blocks and analyzes each block independently to determine the best quantization mapping for subsequent quantization operations.
The parameter calculation varies by mapping type:
- **ASYMMETRIC**: `scale = (max - min) / (quant_max - quant_min)`, `zero_point = quant_min - round(min / scale)`
- **SYMMETRIC**: `scale = max_abs / ((quant_max - quant_min) / 2)`, `zero_point = midpoint`
- **SYMMETRIC_NO_CLIPPING_ERR**: `scale = max(abs(min)/abs(quant_min), max/quant_max)`, `zero_point = midpoint`
**Storage Requirements**: Input tensors must be floating-point (kFloat) with width-packed layout. Output scale/zero_point tensors use buffer storage.
NOTE: Texture storage implementation is not supported due to complexity of block-wise coordinate mapping in 3D texture space. This will likely be necessary for better efficiency in the future.
# Block-wise Parameter Computation Implementation
Block-wise parameter computation enables fine-grained quantization analysis by dividing tensors into blocks and computing separate scale/zero_point parameters for each block. The implementation uses several key data structures computed in `ChooseQParams.cpp`:
* **`block_size_vec`**: WHCN-ordered block dimensions converted from PyTorch NCHW layout (e.g., [3,3,2,1] for 3×3×2×1 blocks)
* **`tensor_size_whcn`**: Input tensor dimensions converted to WHCN layout using `utils::make_whcn_ivec4()`
* **`num_blocks_vec`**: Number of blocks per dimension calculated as `ceil(tensor_size_whcn / block_size_vec)` to handle non-divisible dimensions
* **`block_stride_vec`**: Pre-computed linear strides for block grid indexing `{1, #W, #W*#H, #W*#H*#C}` to enable efficient block ID calculation
* **`mapping_type`**: Integer encoding of quantization strategy (0=ASYMMETRIC, 1=SYMMETRIC, 2=SYMMETRIC_NO_CLIPPING_ERR)
The block coordinate calculation uses: `block_coord = block_id_to_coord(block_id)` which converts linear block IDs back to 4D WHCN coordinates, then computes element ranges: `t0 = block_coord * blockSize` and `tEnd = t0 + blockSize` for nested loop iteration.
# Shader Algorithm Overview
## Buffer Storage Implementation (`choose_qparams_buffer.glsl`)
**Workgroup Configuration**:
- **Global WG Size**: `{nBlocks, 1u, 1u}` where `nBlocks = total number of blocks` computed from `ceil(tensor_size / block_size)` for each dimension
- **Local WG Size**: `{1u, 1u, 1u}` (single thread per block for simplicity, though could be optimized for larger blocks)
**Block-wise Mode Algorithm**:
The shader uses a sophisticated multi-level nested approach to process tensor blocks efficiently. Each thread is assigned multiple blocks using strided access: `for (uint block_id = gl_GlobalInvocationID.x; block_id < TOTAL_BLOCKS; block_id += STRIDE)` where `STRIDE = gl_WorkGroupSize.x * gl_NumWorkGroups.x`.
For each assigned block, the algorithm performs several key steps:
**1. Block Coordinate Conversion**:
The `block_id_to_coord(block_id)` function converts linear block IDs to 4D WHCN coordinates using modular arithmetic.
**2. Element Range Calculation**: Computes the inclusive start coordinate `t0 = bc * blockSize` and exclusive end coordinate `tEnd = t0 + blockSize` to define the block's element boundaries in tensor space.
**3. Nested Loop Min/Max Scan**: Uses four nested loops to iterate through all elements within the block:
`for (int n = t0.w; n < tEnd.w; ++n) for (int c = t0.z; c < tEnd.z; ++c) for (int h = t0.y; h < tEnd.y; ++h) for (int w = t0.x; w < tEnd.x; ++w)`
Each element is accessed using `tidx_to_bufi(ivec4(w,h,c,n), t_in_strides)` to convert 4D tensor coordinates to linear buffer indices with proper stride handling.
**4. Parameter Calculation**: Calls `calc_scale_zp(lo, hi, quant_min, quant_max, mapping_type, eps, scale, zp)` which implements the three mapping strategies:
* **ASYMMETRIC (mapping_type=0)**: Maps full range [min, max] to [quant_min, quant_max] preserving data distribution
* **SYMMETRIC (mapping_type=1)**: Centers around zero using `max_abs = max(abs(min), abs(max))` for balanced quantization
* **SYMMETRIC_NO_CLIPPING_ERR (mapping_type=2)**: Computes separate scales for positive/negative ranges and uses the maximum to prevent clipping
**Future Improvements**: Implement workgroup-level reduction for large blocks, optimize memory access patterns for better cache utilization, and explore texture storage implementation with simplified block alignment constraints.
Differential Revision: [D78436638](https://our.internmc.facebook.com/intern/diff/D78436638/)
cc SS-JIA manuelcandales cbilgin
[ghstack-poisoned]File tree
42 files changed
+1088
-105
lines changed- .github/workflows
- backends
- arm
- _passes
- test
- ops
- tester
- cadence
- aot
- tests
- hifi/operators
- tests
- nxp/tests
- ir/converter/node_converter
- vulkan/runtime
- api
- graph
- ops/glsl
- vk_api
- xnnpack
- partition/config
- test
- ops
- passes
- examples/models/llama
- exir/program
- extension
- apple/ExecuTorch/Exported
- llm
- runner/io_manager
- test
- scripts
- tools/cmake
Some content is hidden
Large Commits have some content hidden by default. Use the searchbox below for content that may be hidden.
42 files changed
+1088
-105
lines changed| Original file line number | Diff line number | Diff line change | |
|---|---|---|---|
| |||
302 | 302 | | |
303 | 303 | | |
304 | 304 | | |
| 305 | + | |
| 306 | + | |
| 307 | + | |
| 308 | + | |
| 309 | + | |
| 310 | + | |
| 311 | + | |
| 312 | + | |
| 313 | + | |
| 314 | + | |
| 315 | + | |
| 316 | + | |
| 317 | + | |
| 318 | + | |
| 319 | + | |
| 320 | + | |
| 321 | + | |
| 322 | + | |
| 323 | + | |
| 324 | + | |
| 325 | + | |
| 326 | + | |
| 327 | + | |
| 328 | + | |
| 329 | + | |
| 330 | + | |
| 331 | + | |
| 332 | + | |
| 333 | + | |
| 334 | + | |
| 335 | + | |
305 | 336 | | |
306 | 337 | | |
307 | 338 | | |
| |||
| Original file line number | Diff line number | Diff line change | |
|---|---|---|---|
| |||
15 | 15 | | |
16 | 16 | | |
17 | 17 | | |
18 | | - | |
| 18 | + | |
| 19 | + | |
19 | 20 | | |
20 | 21 | | |
21 | 22 | | |
| |||
| Original file line number | Diff line number | Diff line change | |
|---|---|---|---|
| |||
85 | 85 | | |
86 | 86 | | |
87 | 87 | | |
| 88 | + | |
| 89 | + | |
88 | 90 | | |
89 | 91 | | |
90 | 92 | | |
91 | | - | |
92 | | - | |
93 | | - | |
94 | 93 | | |
95 | 94 | | |
96 | 95 | | |
| |||
| Original file line number | Diff line number | Diff line change | |
|---|---|---|---|
| |||
205 | 205 | | |
206 | 206 | | |
207 | 207 | | |
208 | | - | |
209 | 208 | | |
210 | 209 | | |
| Original file line number | Diff line number | Diff line change | |
|---|---|---|---|
| |||
| 1 | + | |
| 2 | + | |
| 3 | + | |
| 4 | + | |
| 5 | + | |
| 6 | + | |
| 7 | + | |
| 8 | + | |
| 9 | + | |
| 10 | + | |
| 11 | + | |
| 12 | + | |
| 13 | + | |
| 14 | + | |
| 15 | + | |
| 16 | + | |
| 17 | + | |
| 18 | + | |
| Original file line number | Diff line number | Diff line change | |
|---|---|---|---|
| |||
43 | 43 | | |
44 | 44 | | |
45 | 45 | | |
| 46 | + | |
46 | 47 | | |
47 | 48 | | |
48 | 49 | | |
| |||
332 | 333 | | |
333 | 334 | | |
334 | 335 | | |
| 336 | + | |
| 337 | + | |
335 | 338 | | |
336 | 339 | | |
337 | 340 | | |
| |||
| Original file line number | Diff line number | Diff line change | |
|---|---|---|---|
| |||
861 | 861 | | |
862 | 862 | | |
863 | 863 | | |
| 864 | + | |
| 865 | + | |
| 866 | + | |
864 | 867 | | |
865 | 868 | | |
866 | 869 | | |
867 | 870 | | |
868 | 871 | | |
869 | 872 | | |
870 | | - | |
871 | | - | |
872 | | - | |
873 | | - | |
874 | | - | |
875 | | - | |
876 | 873 | | |
877 | 874 | | |
878 | 875 | | |
| |||
887 | 884 | | |
888 | 885 | | |
889 | 886 | | |
| 887 | + | |
890 | 888 | | |
891 | 889 | | |
892 | 890 | | |
| |||
900 | 898 | | |
901 | 899 | | |
902 | 900 | | |
903 | | - | |
| 901 | + | |
904 | 902 | | |
905 | 903 | | |
906 | 904 | | |
| |||
| Original file line number | Diff line number | Diff line change | |
|---|---|---|---|
| |||
539 | 539 | | |
540 | 540 | | |
541 | 541 | | |
| 542 | + | |
542 | 543 | | |
543 | 544 | | |
| 545 | + | |
544 | 546 | | |
545 | 547 | | |
546 | 548 | | |
| Original file line number | Diff line number | Diff line change | |
|---|---|---|---|
| |||
19 | 19 | | |
20 | 20 | | |
21 | 21 | | |
22 | | - | |
| 22 | + | |
| 23 | + | |
| 24 | + | |
| 25 | + | |
23 | 26 | | |
24 | 27 | | |
25 | 28 | | |
| |||
95 | 98 | | |
96 | 99 | | |
97 | 100 | | |
98 | | - | |
| 101 | + | |
| 102 | + | |
| 103 | + | |
99 | 104 | | |
100 | 105 | | |
101 | 106 | | |
| |||
169 | 174 | | |
170 | 175 | | |
171 | 176 | | |
172 | | - | |
| 177 | + | |
| 178 | + | |
| 179 | + | |
173 | 180 | | |
174 | 181 | | |
175 | 182 | | |
| |||
| Original file line number | Diff line number | Diff line change | |
|---|---|---|---|
| |||
12 | 12 | | |
13 | 13 | | |
14 | 14 | | |
15 | | - | |
16 | 15 | | |
17 | 16 | | |
18 | 17 | | |
| |||
30 | 29 | | |
31 | 30 | | |
32 | 31 | | |
33 | | - | |
34 | 32 | | |
35 | 33 | | |
36 | 34 | | |
| |||
178 | 176 | | |
179 | 177 | | |
180 | 178 | | |
181 | | - | |
182 | | - | |
183 | | - | |
184 | | - | |
185 | | - | |
186 | | - | |
187 | | - | |
188 | | - | |
189 | | - | |
190 | | - | |
191 | | - | |
192 | | - | |
193 | | - | |
194 | | - | |
195 | | - | |
196 | | - | |
197 | | - | |
198 | | - | |
199 | | - | |
200 | | - | |
201 | | - | |
202 | | - | |
203 | | - | |
204 | | - | |
205 | | - | |
206 | | - | |
207 | | - | |
208 | | - | |
209 | | - | |
210 | | - | |
211 | | - | |
212 | | - | |
213 | | - | |
214 | | - | |
215 | | - | |
216 | | - | |
217 | | - | |
218 | 179 | | |
219 | 180 | | |
220 | 181 | | |
| |||
0 commit comments