Feat: Add dummy PSF support workload diagnostics

Add an opt-in DUMMY_PSF_SUPPORT_STATS mode to the diagnostic-only dummy
consumer. It records per-chunk cache-limited 16px support references,
touched tiles, 256-reference tasks, maximum tile list and first-pass
counting time, then reports percentiles. No HDR is produced and no
references are materialized or uploaded.

src/dummy_psf.c

@@ -7,13 +7,16 @@
 #include <stdlib.h>
 #include <string.h>
 
-enum { DUMMY_SELECTOR_TILE = 32 };
+enum { DUMMY_SELECTOR_TILE = 32, DUMMY_SUPPORT_TILE = 16,
+       DUMMY_TASK_EVENTS = 256 };
 
 typedef struct {
   size_t worker, events, triangles, occupied_tiles;
   double event_bbox_diagonal, triangle_bbox_diagonal;
   double maximum_triangle_jump;
   int adaptive_tile16;
+  size_t support_refs, support_tiles, support_tasks, maximum_tile_list;
+  double support_pass_seconds;
 } DummyChunkSample;
 
 struct DummyPsfSink {
@@ -21,6 +24,8 @@ struct DummyPsfSink {
   size_t count, capacity, event_capacity;
   size_t total_events;
   int width, height, tiles_x, tiles_y;
+  int support_tiles_x, support_tiles_y, support_stats;
+  double max_radius_pixels;
   int failed;
   omp_lock_t lock;
 };
@@ -28,6 +33,9 @@ struct DummyPsfSink {
 struct DummyPsfChunk {
   DummyPsfSink *sink;
   uint32_t *tile_generation;
+  PsfCachedEvent *support_events;
+  uint32_t *support_counts, *support_touched;
+  size_t support_touched_count;
   uint32_t generation;
   size_t worker, events, triangles, occupied_tiles;
   size_t last_triangle;
@@ -66,8 +74,9 @@ static int append_sample(DummyPsfSink *sink, DummyChunkSample sample) {
 }
 
 int dummy_psf_sink_create(DummyPsfSink **out, int width, int height,
-                          size_t event_capacity) {
+                          size_t event_capacity, double max_radius_pixels) {
-  if (out == NULL || width <= 0 || height <= 0 || event_capacity == 0)
+  if (out == NULL || width <= 0 || height <= 0 || event_capacity == 0 ||
+      !isfinite(max_radius_pixels) || max_radius_pixels < 0)
     return -1;
   DummyPsfSink *sink = calloc(1, sizeof *sink);
   if (sink == NULL)
@@ -77,6 +86,14 @@ int dummy_psf_sink_create(DummyPsfSink **out, int width, int height,
   sink->tiles_x = (width + DUMMY_SELECTOR_TILE - 1) / DUMMY_SELECTOR_TILE;
   sink->tiles_y = (height + DUMMY_SELECTOR_TILE - 1) / DUMMY_SELECTOR_TILE;
   sink->event_capacity = event_capacity;
+  sink->support_tiles_x = (width + DUMMY_SUPPORT_TILE - 1) / DUMMY_SUPPORT_TILE;
+  sink->support_tiles_y = (height + DUMMY_SUPPORT_TILE - 1) / DUMMY_SUPPORT_TILE;
+  sink->max_radius_pixels = max_radius_pixels;
+  const char *support = getenv("DUMMY_PSF_SUPPORT_STATS");
+  if (support && strcmp(support, "0") && strcmp(support, "1")) {
+    free(sink); return -1;
+  }
+  sink->support_stats = support && !strcmp(support, "1");
   omp_init_lock(&sink->lock);
   *out = sink;
   return 0;
@@ -89,13 +106,24 @@ int dummy_psf_chunk_create(DummyPsfChunk **out, DummyPsfSink *sink,
   DummyPsfChunk *chunk = calloc(1, sizeof *chunk);
   if (chunk == NULL)
     return -1;
+  chunk->sink = sink;
   const size_t tile_count = (size_t)sink->tiles_x * sink->tiles_y;
   chunk->tile_generation = calloc(tile_count, sizeof *chunk->tile_generation);
   if (chunk->tile_generation == NULL) {
     free(chunk);
     return -1;
   }
-  chunk->sink = sink;
+  if (sink->support_stats) {
+    const size_t count = (size_t)sink->support_tiles_x * sink->support_tiles_y;
+    chunk->support_events = malloc(sink->event_capacity * sizeof *chunk->support_events);
+    chunk->support_counts = calloc(count, sizeof *chunk->support_counts);
+    chunk->support_touched = malloc(count * sizeof *chunk->support_touched);
+    if (!chunk->support_events || !chunk->support_counts ||
+        !chunk->support_touched) {
+      dummy_psf_chunk_destroy(chunk);
+      return -1;
+    }
+  }
   chunk->worker = worker_id;
   chunk->generation = 1;
   *out = chunk;
@@ -127,6 +155,40 @@ int dummy_psf_chunk_flush(DummyPsfChunk *chunk) {
   const double triangle_diagonal =
       hypot(chunk->triangle_max_x - chunk->triangle_min_x,
             chunk->triangle_max_y - chunk->triangle_min_y);
+  size_t support_refs = 0, support_tasks = 0, maximum_tile_list = 0;
+  double support_pass_seconds = 0.0;
+  if (chunk->sink->support_stats) {
+    const double start = omp_get_wtime();
+    for (size_t i = 0; i < chunk->support_touched_count; ++i)
+      chunk->support_counts[chunk->support_touched[i]] = 0;
+    chunk->support_touched_count = 0;
+    const int tiles_x = chunk->sink->support_tiles_x;
+    for (size_t i = 0; i < chunk->events; ++i) {
+      const PsfCachedEvent *event = &chunk->support_events[i];
+      const int support = (int)fmin(ceil(event->support_radius),
+                                    chunk->sink->max_radius_pixels);
+      const int bx = (int)floor(event->x), by = (int)floor(event->y);
+      const int x0 = fmax(0, bx - support);
+      const int x1 = fmin(chunk->sink->width - 1, bx + support);
+      const int y0 = fmax(0, by - support);
+      const int y1 = fmin(chunk->sink->height - 1, by + support);
+      if (x0 > x1 || y0 > y1) continue;
+      for (int y = y0 / DUMMY_SUPPORT_TILE; y <= y1 / DUMMY_SUPPORT_TILE; ++y)
+        for (int x = x0 / DUMMY_SUPPORT_TILE; x <= x1 / DUMMY_SUPPORT_TILE; ++x) {
+          const size_t tile = (size_t)y * tiles_x + x;
+          if (!chunk->support_counts[tile])
+            chunk->support_touched[chunk->support_touched_count++] = tile;
+          ++chunk->support_counts[tile];
+          ++support_refs;
+        }
+    }
+    for (size_t i = 0; i < chunk->support_touched_count; ++i) {
+      const size_t count = chunk->support_counts[chunk->support_touched[i]];
+      if (count > maximum_tile_list) maximum_tile_list = count;
+      support_tasks += (count + DUMMY_TASK_EVENTS - 1) / DUMMY_TASK_EVENTS;
+    }
+    support_pass_seconds = omp_get_wtime() - start;
+  }
   const DummyChunkSample sample = {
       .worker = chunk->worker,
       .events = chunk->events,
@@ -136,7 +198,12 @@ int dummy_psf_chunk_flush(DummyPsfChunk *chunk) {
       .triangle_bbox_diagonal = triangle_diagonal,
       .maximum_triangle_jump = chunk->maximum_triangle_jump,
       .adaptive_tile16 = chunk->events >= 8192 && chunk->occupied_tiles != 0 &&
-                         chunk->events / chunk->occupied_tiles >= 32};
+                         chunk->events / chunk->occupied_tiles >= 32,
+      .support_refs = support_refs,
+      .support_tiles = chunk->support_touched_count,
+      .support_tasks = support_tasks,
+      .maximum_tile_list = maximum_tile_list,
+      .support_pass_seconds = support_pass_seconds};
   const int result = append_sample(chunk->sink, sample);
   reset_chunk(chunk);
   return result;
@@ -150,6 +217,8 @@ int dummy_psf_chunk_emit(DummyPsfChunk *chunk, const PsfCachedEvent *event,
   if (chunk->events == chunk->sink->event_capacity &&
       dummy_psf_chunk_flush(chunk))
     return -1;
+  if (chunk->sink->support_stats)
+    chunk->support_events[chunk->events] = *event;
 
   if (!chunk->have_event) {
     chunk->event_min_x = chunk->event_max_x = event->x;
@@ -204,6 +273,9 @@ void dummy_psf_chunk_destroy(DummyPsfChunk *chunk) {
     return;
   (void)dummy_psf_chunk_flush(chunk);
   free(chunk->tile_generation);
+  free(chunk->support_events);
+  free(chunk->support_counts);
+  free(chunk->support_touched);
   free(chunk);
 }
 
@@ -284,6 +356,51 @@ static void report_group(const DummyPsfSink *sink, int full_only,
   free(events);
 }
 
+static void report_support_group(const DummyPsfSink *sink, int full_only,
+                                 const char *label) {
+  size_t count = 0, total_refs = 0, total_tasks = 0;
+  double total_pass = 0.0;
+  for (size_t i = 0; i < sink->count; ++i)
+    if (!full_only || sink->samples[i].events == sink->event_capacity)
+      ++count;
+  if (!count || count > SIZE_MAX / (5 * sizeof(double))) return;
+  double *values = malloc(5 * count * sizeof *values);
+  if (!values) { fputs("Dummy PSF support report allocation failed\n", stderr); return; }
+  const char *names[] = {"support_16px_references", "support_16px_tiles",
+                         "support_16px_tasks", "maximum_tile_list",
+                         "support_first_pass_ms"};
+  size_t next = 0;
+  for (size_t i = 0; i < sink->count; ++i) {
+    const DummyChunkSample *sample = &sink->samples[i];
+    if (full_only && sample->events != sink->event_capacity) continue;
+    values[next] = sample->support_refs;
+    values[count + next] = sample->support_tiles;
+    values[2 * count + next] = sample->support_tasks;
+    values[3 * count + next] = sample->maximum_tile_list;
+    values[4 * count + next] = 1000.0 * sample->support_pass_seconds;
+    total_refs += sample->support_refs;
+    total_tasks += sample->support_tasks;
+    total_pass += sample->support_pass_seconds;
+    ++next;
+  }
+  for (size_t field = 0; field < 5; ++field) {
+    double *series = values + field * count;
+    qsort(series, count, sizeof *series, compare_double);
+    fprintf(stderr,
+            "Dummy PSF %s %s: min=%.3f p10=%.3f p25=%.3f p50=%.3f "
+            "p75=%.3f p90=%.3f p99=%.3f max=%.3f\n",
+            label, names[field], series[0],
+            percentile(series, count, 0.10), percentile(series, count, 0.25),
+            percentile(series, count, 0.50), percentile(series, count, 0.75),
+            percentile(series, count, 0.90), percentile(series, count, 0.99),
+            series[count - 1]);
+  }
+  fprintf(stderr,
+          "Dummy PSF %s support totals: references=%zu tasks=%zu summed_first_pass=%.3f s\n",
+          label, total_refs, total_tasks, total_pass);
+  free(values);
+}
+
 void dummy_psf_sink_report(const DummyPsfSink *sink) {
   if (sink == NULL)
     return;
@@ -298,6 +415,11 @@ void dummy_psf_sink_report(const DummyPsfSink *sink) {
           sink->event_capacity, DUMMY_SELECTOR_TILE);
   report_group(sink, 0, "all");
   report_group(sink, 1, "full");
+  if (sink->support_stats) {
+    fputs("Dummy PSF support diagnostic: 16px rectangular cache-limited first pass only; no references were materialized or uploaded.\n", stderr);
+    report_support_group(sink, 0, "all");
+    report_support_group(sink, 1, "full");
+  }
 }
 
 void dummy_psf_sink_destroy(DummyPsfSink *sink) {

src/dummy_psf.h

@@ -11,7 +11,7 @@ typedef struct DummyPsfChunk DummyPsfChunk;
 /* Diagnostic-only consumer for the production PSF event stream. It preserves
  * per-worker chunk boundaries but never accumulates or writes an HDR image. */
 int dummy_psf_sink_create(DummyPsfSink **out, int width, int height,
-                          size_t event_capacity);
+                          size_t event_capacity, double max_radius_pixels);
 int dummy_psf_chunk_create(DummyPsfChunk **out, DummyPsfSink *sink,
                            size_t worker_id);
 int dummy_psf_chunk_emit(DummyPsfChunk *chunk, const PsfCachedEvent *event,