85 lines
2.1 KiB
Markdown
85 lines
2.1 KiB
Markdown
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# PyQtGraph Optimization Examples
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Real-world optimization case studies from piker.
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## Case Study: Gap Annotations (1285 gaps)
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### Before: Individual `pg.ArrowItem` + `SelectRect`
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```
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Total creation time: 6.6 seconds
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Per-item overhead: ~5ms
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Memory: 1285 ArrowItem + 1285 SelectRect objects
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```
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Each gap was rendered as two separate
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`QGraphicsItem` instances (arrow + highlight rect),
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resulting in 2570 Qt objects.
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### After: Single `GapAnnotations` batch renderer
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```
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Total creation time:
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104ms (server) + 376ms (client)
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Effective per-item: ~0.08ms
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Speedup: ~36x client, ~180x server
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Memory: 1 GapAnnotations object
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```
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All 1285 gaps rendered via:
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- One `PrimitiveArray` for all rectangles
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- One `QPainterPath` for all arrows
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- Shared pen/brush across all items
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### Profiler Output (Client)
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```
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> Entering markup_gaps() for 1285 gaps
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initial redraw: 0.20ms, tot:0.20
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built annotation specs: 256.48ms, tot:256.68
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batch IPC call complete: 119.26ms, tot:375.94
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final redraw: 0.07ms, tot:376.02
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< Exiting markup_gaps(), total: 376.04ms
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```
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### Profiler Output (Server)
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```
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> Entering Batch annotate 1285 gaps
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`np.searchsorted()` complete!: 0.81ms, tot:0.81
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`time_to_row` creation: 98.45ms, tot:99.28
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created GapAnnotations item: 2.98ms, tot:102.26
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< Exiting Batch annotate, total: 104.15ms
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```
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## Positioning/Update Pattern
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For annotations that need repositioning when the
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view scrolls or zooms:
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```python
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def reposition(self, array):
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'''
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Update positions based on new array data.
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'''
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# vectorized timestamp lookups (not linear!)
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time_to_row = self._build_lookup(array)
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# update rect array in-place
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rect_memory = self._rectarray.ndarray()
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for i, spec in enumerate(self._specs):
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row = time_to_row.get(spec['time'])
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if row:
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rect_memory[i, 0] = row['index']
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rect_memory[i, 1] = row['close']
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# ... width, height
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# trigger repaint (single call, not per-item)
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self.update()
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```
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**Key insight:** Update the underlying memory
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arrays directly, then call `.update()` once.
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Never create/destroy Qt objects during reposition.
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