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axmol/thirdparty/astc/astcenc_compute_variance.cpp

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// SPDX-License-Identifier: Apache-2.0
// ----------------------------------------------------------------------------
// Copyright 2011-2022 Arm Limited
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy
// of the License at:
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations
// under the License.
// ----------------------------------------------------------------------------
#if !defined(ASTCENC_DECOMPRESS_ONLY)
/**
* @brief Functions to calculate variance per component in a NxN footprint.
*
* We need N to be parametric, so the routine below uses summed area tables in order to execute in
* O(1) time independent of how big N is.
*
* The addition uses a Brent-Kung-based parallel prefix adder. This uses the prefix tree to first
* perform a binary reduction, and then distributes the results. This method means that there is no
* serial dependency between a given element and the next one, and also significantly improves
* numerical stability allowing us to use floats rather than doubles.
*/
#include "astcenc_internal.h"
#include <cassert>
/**
* @brief Generate a prefix-sum array using the Brent-Kung algorithm.
*
* This will take an input array of the form:
* v0, v1, v2, ...
* ... and modify in-place to turn it into a prefix-sum array of the form:
* v0, v0+v1, v0+v1+v2, ...
*
* @param d The array to prefix-sum.
* @param items The number of items in the array.
* @param stride The item spacing in the array; i.e. dense arrays should use 1.
*/
static void brent_kung_prefix_sum(
vfloat4* d,
size_t items,
int stride
) {
if (items < 2)
return;
size_t lc_stride = 2;
size_t log2_stride = 1;
// The reduction-tree loop
do {
size_t step = lc_stride >> 1;
size_t start = lc_stride - 1;
size_t iters = items >> log2_stride;
vfloat4 *da = d + (start * stride);
ptrdiff_t ofs = -(ptrdiff_t)(step * stride);
size_t ofs_stride = stride << log2_stride;
while (iters)
{
*da = *da + da[ofs];
da += ofs_stride;
iters--;
}
log2_stride += 1;
lc_stride <<= 1;
} while (lc_stride <= items);
// The expansion-tree loop
do {
log2_stride -= 1;
lc_stride >>= 1;
size_t step = lc_stride >> 1;
size_t start = step + lc_stride - 1;
size_t iters = (items - step) >> log2_stride;
vfloat4 *da = d + (start * stride);
ptrdiff_t ofs = -(ptrdiff_t)(step * stride);
size_t ofs_stride = stride << log2_stride;
while (iters)
{
*da = *da + da[ofs];
da += ofs_stride;
iters--;
}
} while (lc_stride > 2);
}
/**
* @brief Compute averages for a pixel region.
*
* The routine computes both in a single pass, using a summed-area table to decouple the running
* time from the averaging/variance kernel size.
*
* @param[out] ctx The compressor context storing the output data.
* @param arg The input parameter structure.
*/
static void compute_pixel_region_variance(
astcenc_context& ctx,
const pixel_region_args& arg
) {
// Unpack the memory structure into local variables
const astcenc_image* img = arg.img;
astcenc_swizzle swz = arg.swz;
bool have_z = arg.have_z;
int size_x = arg.size_x;
int size_y = arg.size_y;
int size_z = arg.size_z;
int offset_x = arg.offset_x;
int offset_y = arg.offset_y;
int offset_z = arg.offset_z;
int alpha_kernel_radius = arg.alpha_kernel_radius;
float* input_alpha_averages = ctx.input_alpha_averages;
vfloat4* work_memory = arg.work_memory;
// Compute memory sizes and dimensions that we need
int kernel_radius = alpha_kernel_radius;
int kerneldim = 2 * kernel_radius + 1;
int kernel_radius_xy = kernel_radius;
int kernel_radius_z = have_z ? kernel_radius : 0;
int padsize_x = size_x + kerneldim;
int padsize_y = size_y + kerneldim;
int padsize_z = size_z + (have_z ? kerneldim : 0);
int sizeprod = padsize_x * padsize_y * padsize_z;
int zd_start = have_z ? 1 : 0;
vfloat4 *varbuf1 = work_memory;
vfloat4 *varbuf2 = work_memory + sizeprod;
// Scaling factors to apply to Y and Z for accesses into the work buffers
int yst = padsize_x;
int zst = padsize_x * padsize_y;
// Scaling factors to apply to Y and Z for accesses into result buffers
int ydt = img->dim_x;
int zdt = img->dim_x * img->dim_y;
// Macros to act as accessor functions for the work-memory
#define VARBUF1(z, y, x) varbuf1[z * zst + y * yst + x]
#define VARBUF2(z, y, x) varbuf2[z * zst + y * yst + x]
// Load N and N^2 values into the work buffers
if (img->data_type == ASTCENC_TYPE_U8)
{
// Swizzle data structure 4 = ZERO, 5 = ONE
uint8_t data[6];
data[ASTCENC_SWZ_0] = 0;
data[ASTCENC_SWZ_1] = 255;
for (int z = zd_start; z < padsize_z; z++)
{
int z_src = (z - zd_start) + offset_z - kernel_radius_z;
z_src = astc::clamp(z_src, 0, (int)(img->dim_z - 1));
uint8_t* data8 = static_cast<uint8_t*>(img->data[z_src]);
for (int y = 1; y < padsize_y; y++)
{
int y_src = (y - 1) + offset_y - kernel_radius_xy;
y_src = astc::clamp(y_src, 0, (int)(img->dim_y - 1));
for (int x = 1; x < padsize_x; x++)
{
int x_src = (x - 1) + offset_x - kernel_radius_xy;
x_src = astc::clamp(x_src, 0, (int)(img->dim_x - 1));
data[0] = data8[(4 * img->dim_x * y_src) + (4 * x_src )];
data[1] = data8[(4 * img->dim_x * y_src) + (4 * x_src + 1)];
data[2] = data8[(4 * img->dim_x * y_src) + (4 * x_src + 2)];
data[3] = data8[(4 * img->dim_x * y_src) + (4 * x_src + 3)];
uint8_t r = data[swz.r];
uint8_t g = data[swz.g];
uint8_t b = data[swz.b];
uint8_t a = data[swz.a];
vfloat4 d = vfloat4 (r * (1.0f / 255.0f),
g * (1.0f / 255.0f),
b * (1.0f / 255.0f),
a * (1.0f / 255.0f));
VARBUF1(z, y, x) = d;
VARBUF2(z, y, x) = d * d;
}
}
}
}
else if (img->data_type == ASTCENC_TYPE_F16)
{
// Swizzle data structure 4 = ZERO, 5 = ONE (in FP16)
uint16_t data[6];
data[ASTCENC_SWZ_0] = 0;
data[ASTCENC_SWZ_1] = 0x3C00;
for (int z = zd_start; z < padsize_z; z++)
{
int z_src = (z - zd_start) + offset_z - kernel_radius_z;
z_src = astc::clamp(z_src, 0, (int)(img->dim_z - 1));
uint16_t* data16 = static_cast<uint16_t*>(img->data[z_src]);
for (int y = 1; y < padsize_y; y++)
{
int y_src = (y - 1) + offset_y - kernel_radius_xy;
y_src = astc::clamp(y_src, 0, (int)(img->dim_y - 1));
for (int x = 1; x < padsize_x; x++)
{
int x_src = (x - 1) + offset_x - kernel_radius_xy;
x_src = astc::clamp(x_src, 0, (int)(img->dim_x - 1));
data[0] = data16[(4 * img->dim_x * y_src) + (4 * x_src )];
data[1] = data16[(4 * img->dim_x * y_src) + (4 * x_src + 1)];
data[2] = data16[(4 * img->dim_x * y_src) + (4 * x_src + 2)];
data[3] = data16[(4 * img->dim_x * y_src) + (4 * x_src + 3)];
vint4 di(data[swz.r], data[swz.g], data[swz.b], data[swz.a]);
vfloat4 d = float16_to_float(di);
VARBUF1(z, y, x) = d;
VARBUF2(z, y, x) = d * d;
}
}
}
}
else // if (img->data_type == ASTCENC_TYPE_F32)
{
assert(img->data_type == ASTCENC_TYPE_F32);
// Swizzle data structure 4 = ZERO, 5 = ONE (in FP16)
float data[6];
data[ASTCENC_SWZ_0] = 0.0f;
data[ASTCENC_SWZ_1] = 1.0f;
for (int z = zd_start; z < padsize_z; z++)
{
int z_src = (z - zd_start) + offset_z - kernel_radius_z;
z_src = astc::clamp(z_src, 0, (int)(img->dim_z - 1));
float* data32 = static_cast<float*>(img->data[z_src]);
for (int y = 1; y < padsize_y; y++)
{
int y_src = (y - 1) + offset_y - kernel_radius_xy;
y_src = astc::clamp(y_src, 0, (int)(img->dim_y - 1));
for (int x = 1; x < padsize_x; x++)
{
int x_src = (x - 1) + offset_x - kernel_radius_xy;
x_src = astc::clamp(x_src, 0, (int)(img->dim_x - 1));
data[0] = data32[(4 * img->dim_x * y_src) + (4 * x_src )];
data[1] = data32[(4 * img->dim_x * y_src) + (4 * x_src + 1)];
data[2] = data32[(4 * img->dim_x * y_src) + (4 * x_src + 2)];
data[3] = data32[(4 * img->dim_x * y_src) + (4 * x_src + 3)];
float r = data[swz.r];
float g = data[swz.g];
float b = data[swz.b];
float a = data[swz.a];
vfloat4 d(r, g, b, a);
VARBUF1(z, y, x) = d;
VARBUF2(z, y, x) = d * d;
}
}
}
}
// Pad with an extra layer of 0s; this forms the edge of the SAT tables
vfloat4 vbz = vfloat4::zero();
for (int z = 0; z < padsize_z; z++)
{
for (int y = 0; y < padsize_y; y++)
{
VARBUF1(z, y, 0) = vbz;
VARBUF2(z, y, 0) = vbz;
}
for (int x = 0; x < padsize_x; x++)
{
VARBUF1(z, 0, x) = vbz;
VARBUF2(z, 0, x) = vbz;
}
}
if (have_z)
{
for (int y = 0; y < padsize_y; y++)
{
for (int x = 0; x < padsize_x; x++)
{
VARBUF1(0, y, x) = vbz;
VARBUF2(0, y, x) = vbz;
}
}
}
// Generate summed-area tables for N and N^2; this is done in-place, using
// a Brent-Kung parallel-prefix based algorithm to minimize precision loss
for (int z = zd_start; z < padsize_z; z++)
{
for (int y = 1; y < padsize_y; y++)
{
brent_kung_prefix_sum(&(VARBUF1(z, y, 1)), padsize_x - 1, 1);
brent_kung_prefix_sum(&(VARBUF2(z, y, 1)), padsize_x - 1, 1);
}
}
for (int z = zd_start; z < padsize_z; z++)
{
for (int x = 1; x < padsize_x; x++)
{
brent_kung_prefix_sum(&(VARBUF1(z, 1, x)), padsize_y - 1, yst);
brent_kung_prefix_sum(&(VARBUF2(z, 1, x)), padsize_y - 1, yst);
}
}
if (have_z)
{
for (int y = 1; y < padsize_y; y++)
{
for (int x = 1; x < padsize_x; x++)
{
brent_kung_prefix_sum(&(VARBUF1(1, y, x)), padsize_z - 1, zst);
brent_kung_prefix_sum(&(VARBUF2(1, y, x)), padsize_z - 1, zst);
}
}
}
int alpha_kdim = 2 * alpha_kernel_radius + 1;
// Compute a few constants used in the variance-calculation.
float alpha_rsamples;
if (have_z)
{
alpha_rsamples = 1.0f / (float)(alpha_kdim * alpha_kdim * alpha_kdim);
}
else
{
alpha_rsamples = 1.0f / (float)(alpha_kdim * alpha_kdim);
}
// Use the summed-area tables to compute variance for each neighborhood
if (have_z)
{
for (int z = 0; z < size_z; z++)
{
int z_src = z + kernel_radius_z;
int z_dst = z + offset_z;
int z_low = z_src - alpha_kernel_radius;
int z_high = z_src + alpha_kernel_radius + 1;
for (int y = 0; y < size_y; y++)
{
int y_src = y + kernel_radius_xy;
int y_dst = y + offset_y;
int y_low = y_src - alpha_kernel_radius;
int y_high = y_src + alpha_kernel_radius + 1;
for (int x = 0; x < size_x; x++)
{
int x_src = x + kernel_radius_xy;
int x_dst = x + offset_x;
int x_low = x_src - alpha_kernel_radius;
int x_high = x_src + alpha_kernel_radius + 1;
// Summed-area table lookups for alpha average
float vasum = ( VARBUF1(z_high, y_low, x_low).lane<3>()
- VARBUF1(z_high, y_low, x_high).lane<3>()
- VARBUF1(z_high, y_high, x_low).lane<3>()
+ VARBUF1(z_high, y_high, x_high).lane<3>()) -
( VARBUF1(z_low, y_low, x_low).lane<3>()
- VARBUF1(z_low, y_low, x_high).lane<3>()
- VARBUF1(z_low, y_high, x_low).lane<3>()
+ VARBUF1(z_low, y_high, x_high).lane<3>());
int out_index = z_dst * zdt + y_dst * ydt + x_dst;
input_alpha_averages[out_index] = (vasum * alpha_rsamples);
}
}
}
}
else
{
for (int y = 0; y < size_y; y++)
{
int y_src = y + kernel_radius_xy;
int y_dst = y + offset_y;
int y_low = y_src - alpha_kernel_radius;
int y_high = y_src + alpha_kernel_radius + 1;
for (int x = 0; x < size_x; x++)
{
int x_src = x + kernel_radius_xy;
int x_dst = x + offset_x;
int x_low = x_src - alpha_kernel_radius;
int x_high = x_src + alpha_kernel_radius + 1;
// Summed-area table lookups for alpha average
float vasum = VARBUF1(0, y_low, x_low).lane<3>()
- VARBUF1(0, y_low, x_high).lane<3>()
- VARBUF1(0, y_high, x_low).lane<3>()
+ VARBUF1(0, y_high, x_high).lane<3>();
int out_index = y_dst * ydt + x_dst;
input_alpha_averages[out_index] = (vasum * alpha_rsamples);
}
}
}
}
void compute_averages(
astcenc_context& ctx,
const avg_args &ag
) {
pixel_region_args arg = ag.arg;
arg.work_memory = new vfloat4[ag.work_memory_size];
int size_x = ag.img_size_x;
int size_y = ag.img_size_y;
int size_z = ag.img_size_z;
int step_xy = ag.blk_size_xy;
int step_z = ag.blk_size_z;
int y_tasks = (size_y + step_xy - 1) / step_xy;
// All threads run this processing loop until there is no work remaining
while (true)
{
unsigned int count;
unsigned int base = ctx.manage_avg.get_task_assignment(16, count);
if (!count)
{
break;
}
for (unsigned int i = base; i < base + count; i++)
{
int z = (i / (y_tasks)) * step_z;
int y = (i - (z * y_tasks)) * step_xy;
arg.size_z = astc::min(step_z, size_z - z);
arg.offset_z = z;
arg.size_y = astc::min(step_xy, size_y - y);
arg.offset_y = y;
for (int x = 0; x < size_x; x += step_xy)
{
arg.size_x = astc::min(step_xy, size_x - x);
arg.offset_x = x;
compute_pixel_region_variance(ctx, arg);
}
}
ctx.manage_avg.complete_task_assignment(count);
}
delete[] arg.work_memory;
}
/* See header for documentation. */
unsigned int init_compute_averages(
const astcenc_image& img,
unsigned int alpha_kernel_radius,
const astcenc_swizzle& swz,
avg_args& ag
) {
unsigned int size_x = img.dim_x;
unsigned int size_y = img.dim_y;
unsigned int size_z = img.dim_z;
// Compute maximum block size and from that the working memory buffer size
unsigned int kernel_radius = alpha_kernel_radius;
unsigned int kerneldim = 2 * kernel_radius + 1;
bool have_z = (size_z > 1);
unsigned int max_blk_size_xy = have_z ? 16 : 32;
unsigned int max_blk_size_z = astc::min(size_z, have_z ? 16u : 1u);
unsigned int max_padsize_xy = max_blk_size_xy + kerneldim;
unsigned int max_padsize_z = max_blk_size_z + (have_z ? kerneldim : 0);
// Perform block-wise averages calculations across the image
// Initialize fields which are not populated until later
ag.arg.size_x = 0;
ag.arg.size_y = 0;
ag.arg.size_z = 0;
ag.arg.offset_x = 0;
ag.arg.offset_y = 0;
ag.arg.offset_z = 0;
ag.arg.work_memory = nullptr;
ag.arg.img = &img;
ag.arg.swz = swz;
ag.arg.have_z = have_z;
ag.arg.alpha_kernel_radius = alpha_kernel_radius;
ag.img_size_x = size_x;
ag.img_size_y = size_y;
ag.img_size_z = size_z;
ag.blk_size_xy = max_blk_size_xy;
ag.blk_size_z = max_blk_size_z;
ag.work_memory_size = 2 * max_padsize_xy * max_padsize_xy * max_padsize_z;
// The parallel task count
unsigned int z_tasks = (size_z + max_blk_size_z - 1) / max_blk_size_z;
unsigned int y_tasks = (size_y + max_blk_size_xy - 1) / max_blk_size_xy;
return z_tasks * y_tasks;
}
#endif
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