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Jungfraujoch/image_analysis/spot_finding/ImageSpotFinderCPU.cpp
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leonarski_fandClaude Opus 5.5 8e6ecedd5c CPU pixel loops: keep the ring sums and the vertical slide out of memory for real
Two fixes found in the post-merge profile, where the previous commit's loops did not do what they
were written to do:

- AccumulateRingsBlock: the ring_overflow.emplace_back call inside the loop left no callee-saved
  registers for the locals, so GCC kept sum/sum2/count on the stack and the store-reload chain was
  still there (29% of the function's samples on one stack add). The azint sums get a loop of their own
  over the block, and the out-of-histogram values are listed by a second loop run only when the block
  has any, in the same pixel order; now the sums live in registers. Same additions in the same order.
- DetectPass: inlined into DetectPass's main loop the vertical slide was not vectorised (the
  vectorised copies GCC made were for the other call sites). It is now a free function,
  SlideVertical, which GCC vectorises on its own.

Measured (perf, 75 s of myob, CPU-only, relative to the unchanged FlagRow/AnalyzeBlock):
AccumulateRingsBlock -4..-11%, DetectPass + SlideVertical -7..-14%. Byte-identical p.hkl, p.mtz,
p_P1.mtz, p_unmerged.mtz on myob, cytc, lyso, sparse (CPU) and myob (GPU); ImageSpotFinderCPU*,
AdaptiveSpotFinder, SpotFinding, AzimuthalIntegration and portable tests pass.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01D1G8gJVAy6gp1K5Dz3NE5C
2026-09-28 03:57:10 +02:00

313 lines
15 KiB
C++

// SPDX-FileCopyrightText: 2024 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
// SPDX-License-Identifier: GPL-3.0-only
#include <algorithm>
#include <bit>
#include <bitset>
#include <cmath>
#include "ImageSpotFinderCPU.h"
#include "StrongPixelSet.h"
ImageSpotFinderCPU::ImageSpotFinderCPU(int32_t in_width, int32_t in_height)
: ImageSpotFinder(in_width, in_height), first_pass_buffer(OutputSize(), 0) {}
void ImageSpotFinderCPU::Detect(const ImagePreprocessorBuffer &image,
const SpotFindingSettings &settings) {
// Two passes, as ImageSpotFinderGPU::Detect does. The second recomputes every local background
// with the pixels the first found strong taken out of it, and keeps those pixels strong. It
// matters because a spot wide enough to reach into its own background window inflates the mean
// and variance it is then tested against, so its outer pixels fail the SNR test on a single
// pass. The GPU has always done this; running one pass here made the two finders return
// different spot lists for the same frame.
DetectPass(image, settings, nullptr, first_pass_buffer);
DetectPass(image, settings, first_pass_buffer.data(), output_buffer);
}
namespace {
// The local-box SNR test of one pixel. sum/sum2/valid are its window's, centre pixel included.
bool StrongInWindow(int64_t pxl_val, int64_t sum, int64_t sum2, int64_t valid,
const SpotFindingSettings &settings, float strong2) {
const int64_t sum_local = sum - pxl_val;
const int64_t sum2_local = sum2 - pxl_val * pxl_val;
const int64_t valid_local = valid - 1;
const int64_t var = valid_local * sum2_local - (sum_local * sum_local);
const int64_t in_minus_mean = pxl_val * valid_local - sum_local;
return (pxl_val == INT32_MAX) // saturated pixel, or strong in the previous pass, is accepted always
|| ((pxl_val != INT32_MIN && // pixel is not bad pixel
valid_local > ImageSpotFinder::MIN_VALID_PIXELS && // too many bad pixels around will give poor statistics
(pxl_val > settings.photon_count_threshold) && // pixel is above count threshold
(in_minus_mean > 0) && // pixel value is larger than mean
(in_minus_mean * in_minus_mean > static_cast<int64_t>(std::ceil(var * strong2)))));
// pixel is above SNR threshold
}
// Adds row `in` to the vertical sums and takes row `out` out of them; nullptr is no row. A bad or
// saturated pixel adds 0. Written without branches, and as a function of its own so that the loop
// vectorises whatever it is inlined into; integer sums, so the same totals as pixel by pixel.
void SlideVertical(const int32_t *in, const int32_t *out, int32_t width,
int64_t *sum, int64_t *sum2, uint16_t *valid) {
for (int32_t col = 0; col < width; col++) {
const int64_t a = in ? in[col] : INT32_MIN;
const int64_t r = out ? out[col] : INT32_MIN;
const bool a_ok = a != INT32_MAX && a != INT32_MIN;
const bool r_ok = r != INT32_MAX && r != INT32_MIN;
const int64_t a_v = a_ok ? a : 0;
const int64_t r_v = r_ok ? r : 0;
sum[col] += a_v - r_v;
sum2[col] += a_v * a_v - r_v * r_v;
valid[col] += static_cast<uint16_t>(a_ok - r_ok);
}
}
} // namespace
void ImageSpotFinderCPU::DetectAt(const ImagePreprocessorBuffer &image, const SpotFindingSettings &settings,
const std::vector<uint32_t> &candidates,
const std::function<void(int32_t)> &fill_row) {
candidate_windows.clear();
// Filled in by DetectPass as the candidates of each row become known.
first_pass_needed.assign(static_cast<size_t>(height) * ((width + 31) / 32), 0);
DetectPass(image, settings, nullptr, first_pass_buffer, candidates.data(), fill_row);
std::fill(output_buffer.begin(), output_buffer.end(), 0);
const float strong2 = settings.signal_to_noise_threshold * settings.signal_to_noise_threshold;
const auto first_pass = [&](int32_t pxl) { return (first_pass_buffer[pxl / 32] >> (pxl % 32)) & 1U; };
for (const auto &c : candidate_windows) {
const int32_t line = c.pxl / width;
const int32_t col = c.pxl % width;
int64_t sum = c.sum, sum2 = c.sum2, valid = c.valid;
// Take out of the window what the second pass does not count: the first pass's strong pixels.
for (int32_t y = std::max(line - NBX, 0); y <= std::min(line + NBX, height - 1); y++) {
const int32_t first = y * width + std::max(col - NBX, 0);
const int32_t last = y * width + std::min(col + NBX, width - 1);
for (int32_t w = first / 32; w <= last / 32; w++) {
uint32_t bits = first_pass_buffer[w];
if (w == first / 32)
bits &= UINT32_MAX << (first % 32);
if (w == last / 32 && last % 32 != 31)
bits &= (1U << (last % 32 + 1)) - 1;
while (bits) {
const int32_t q = w * 32 + std::countr_zero(bits);
bits &= bits - 1;
const int64_t v = image[q];
if (v != INT32_MAX && v != INT32_MIN) {
sum -= v;
sum2 -= v * v;
valid -= 1;
}
}
}
}
const int64_t pxl_val = first_pass(c.pxl) ? INT32_MAX : image[c.pxl];
if (StrongInWindow(pxl_val, sum, sum2, valid, settings, strong2))
output_buffer[c.pxl / 32] |= 1U << (c.pxl % 32);
}
}
void ImageSpotFinderCPU::DetectPass(const ImagePreprocessorBuffer &image,
const SpotFindingSettings &settings,
const uint32_t *prev_strong,
std::vector<uint32_t> &out_buffer,
const uint32_t *candidates,
const std::function<void(int32_t)> &fill_row) {
for (int i = 0; i < OutputSize(); i++)
out_buffer[i] = 0;
// The first pass's bits are read only inside the window of a candidate (and at the candidate), so
// with candidates it tests only the pixels of the row/column blocks such a window reaches; the bits
// it leaves unset there are never read. Those blocks are marked from each row's candidates as the
// row enters the vertical sums below, which is before any row within NBX of it is tested - so the
// candidates themselves can be filled in a row at a time (fill_row), while the row is in cache.
const int32_t nblocks = (width + 31) / 32;
const auto new_row = [&](int32_t r) {
if (!candidates)
return;
if (fill_row)
fill_row(r);
const int32_t first = r * width;
const int32_t last = first + width - 1;
for (int32_t w = first / 32; w <= last / 32; w++) {
uint32_t bits = candidates[w];
if (w == first / 32)
bits &= UINT32_MAX << (first % 32);
if (w == last / 32 && last % 32 != 31)
bits &= (1U << (last % 32 + 1)) - 1;
for (; bits; bits &= bits - 1) {
const int32_t col = w * 32 + std::countr_zero(bits) - first;
for (int32_t y = std::max(r - NBX, 0); y <= std::min(r + NBX, height - 1); y++)
for (int32_t b = std::max(col - NBX, 0) / 32; b <= std::min(col + NBX, width - 1) / 32; b++)
first_pass_needed[static_cast<size_t>(y) * nblocks + b] = 1;
}
}
};
// A pixel found strong by the previous pass reads as INT32_MAX, which the accumulation below
// already skips and the acceptance test below already takes as strong - the same substitution
// the GPU kernel makes when it reads prev_out.
auto value_at = [&](int32_t pxl) -> int32_t {
if (prev_strong && (prev_strong[pxl / 32] & (1U << (pxl % 32))))
return INT32_MAX;
return image[pxl];
};
std::bitset<32> out = 0;
if (settings.signal_to_noise_threshold <= 0.0) {
if (settings.photon_count_threshold > 0) {
for (int pxl = 0; pxl < height * width; pxl++) {
int32_t bit = pxl % 32;
int32_t pxl_val = value_at(pxl);
if (pxl_val == INT32_MAX || (pxl_val > settings.photon_count_threshold && pxl_val != INT32_MIN))
out.set(bit);
if (bit == 31) {
out_buffer[pxl / 32] = out.to_ulong();
out.reset();
}
}
}
} else {
float strong2 = settings.signal_to_noise_threshold * settings.signal_to_noise_threshold;
// Sum and sum of squares of (2*NBY+1) vertical elements
// These are updated after each line is finished
// 64-bit integer guarantees calculations are made without rounding errors
std::vector<int64_t> sum_vert(width, 0);
std::vector<int64_t> sum2_vert(width, 0);
std::vector<uint16_t> valid_vert(width, 0);
// Add the row entering the window (line_in) and take out the one leaving it (line_out); -1 is
// no row. A pixel strong in the previous pass is not counted either; SlideVertical adds it with
// the rest of its row and it is taken out again below - there are few, and the sums are
// integers, so the totals are the same as never adding it.
const int32_t *img = image.data();
const int32_t w = width;
int64_t *sv = sum_vert.data();
int64_t *sv2 = sum2_vert.data();
uint16_t *vv = valid_vert.data();
auto slide_vert = [&](int line_in, int line_out) {
SlideVertical(line_in >= 0 ? img + static_cast<size_t>(line_in) * w : nullptr,
line_out >= 0 ? img + static_cast<size_t>(line_out) * w : nullptr, w, sv, sv2, vv);
if (!prev_strong)
return;
// sign = +1 takes out what line_in added, -1 puts back what line_out took out.
const auto uncount_strong = [&](int line, int64_t sign) {
const int32_t first = line * w, last = first + w - 1;
for (int32_t word = first / 32; word <= last / 32; word++) {
uint32_t bits = prev_strong[word];
if (word == first / 32)
bits &= UINT32_MAX << (first % 32);
if (word == last / 32 && last % 32 != 31)
bits &= (1U << (last % 32 + 1)) - 1;
for (; bits; bits &= bits - 1) {
const int32_t pxl = word * 32 + std::countr_zero(bits);
const int64_t v = img[pxl];
if (v == INT32_MAX || v == INT32_MIN)
continue;
sv[pxl - first] -= sign * v;
sv2[pxl - first] -= sign * v * v;
vv[pxl - first] -= static_cast<uint16_t>(sign);
}
}
};
if (line_in >= 0)
uncount_strong(line_in, 1);
if (line_out >= 0)
uncount_strong(line_out, -1);
};
for (int line = 0; line < NBX; line++) {
new_row(line);
slide_vert(line, -1);
}
for (int line = 0; line < height; line++) {
if (line < height - NBX)
new_row(line + NBX);
slide_vert(line < height - NBX ? line + NBX : -1, line >= NBX + 1 ? line - (NBX + 1) : -1);
if (candidates) {
// Only the runs of 32-column blocks whose result is read (first_pass_needed; every
// candidate lies in one). Each run starts its window from the vertical sums over the
// columns it covers there - integers, so the same sums the running window holds at
// that column - and slides it as below; the bits outside the runs stay 0, as below.
const uint8_t *needed = first_pass_needed.data() + static_cast<size_t>(line) * nblocks;
for (int32_t b = 0; b < nblocks;) {
if (!needed[b]) { b++; continue; }
const int32_t c0 = b * 32;
while (b < nblocks && needed[b]) b++;
const int32_t c1 = std::min(b * 32, width);
int64_t sum = 0, sum2 = 0, valid = 0;
for (int32_t c = std::max(c0 - NBX, 0); c <= std::min(c0 + NBX, width - 1); c++) {
sum += sum_vert[c];
sum2 += sum2_vert[c];
valid += valid_vert[c];
}
for (int32_t col = c0; col < c1; col++) {
if (col > c0) {
if (col < width - NBX) {
sum += sum_vert[col + NBX];
sum2 += sum2_vert[col + NBX];
valid += valid_vert[col + NBX];
}
if (col >= NBX + 1) {
sum -= sum_vert[col - NBX - 1];
sum2 -= sum2_vert[col - NBX - 1];
valid -= valid_vert[col - NBX - 1];
}
}
const int32_t pxl = line * width + col;
if (candidates[pxl / 32] & (1U << (pxl % 32)))
candidate_windows.push_back({pxl, sum, sum2, valid});
if (StrongInWindow(value_at(pxl), sum, sum2, valid, settings, strong2))
out_buffer[pxl / 32] |= 1U << (pxl % 32);
}
}
continue;
}
int64_t sum = 0;
int64_t sum2 = 0;
int64_t valid = 0;
for (int col = 0; col < NBX; col++) {
sum += sum_vert[col];
sum2 += sum2_vert[col];
valid += valid_vert[col];
}
for (int col = 0; col < width; col++) {
if (col < width - NBX) {
sum += sum_vert[col + NBX];
sum2 += sum2_vert[col + NBX];
valid += valid_vert[col + NBX];
}
if (col >= NBX + 1) {
sum -= sum_vert[col - NBX - 1];
sum2 -= sum2_vert[col - NBX - 1];
valid -= valid_vert[col - NBX - 1];
}
const int32_t pxl = line * width + col;
const int32_t bit = pxl % 32;
if (StrongInWindow(value_at(pxl), sum, sum2, valid, settings, strong2))
out.set(bit);
if (bit == 31) {
out_buffer[pxl / 32] = out.to_ulong();
out.reset() ;
}
}
}
}
if (height * width % 32 != 0)
out_buffer[OutputSize() - 1] |= out.to_ulong(); // zeroed above; the candidates path sets its bits directly
}