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Optimize touch_position_to_pixel_position performance by avoiding NumPy overhead for small 2D coordinate mapping. #349

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Merged
copybara-service merged 1 commit into from
Jun 23, 2026
Merged

Optimize touch_position_to_pixel_position performance by avoiding NumPy overhead for small 2D coordinate mapping. #349

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8 changes: 5 additions & 3 deletions android_env/components/pixel_fns.py
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Original file line number Diff line number Diff line change
Expand Up @@ -26,9 +26,11 @@ def touch_position_to_pixel_position(
width_height: Sequence[int],
) -> tuple[int, int]:
"""Maps touch position in [0,1] to the corresponding pixel on the screen."""
touch_pixels = (touch_position * width_height).astype(np.int32)
cap_idx = lambda v, idx_len: min(v, idx_len - 1)
return tuple(map(cap_idx, touch_pixels, width_height))
# Unpack and use pure Python math to avoid NumPy overhead for small 2D array.
# Also avoids map/lambda overhead.
x, y = touch_position
w, h = width_height
return (min(int(x * w), w - 1), min(int(y * h), h - 1))


def transpose_pixels(frame: np.ndarray) -> np.ndarray:
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30 changes: 12 additions & 18 deletions android_env/components/pixel_fns_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -137,8 +137,8 @@ def test_touch_position_to_pixel_position(self):
number = 100000
res = t.timeit(number=number)
print(
f'\ntouch_position_to_pixel_position: {res / number * 1e6:.3f} us per'
' loop'
f'BenchmarkTouchPositionToPixelPosition {number}'
f' {res / number * 1e9:.0f} ns/op'
)

def test_transpose_pixels(self):
Expand All @@ -151,17 +151,15 @@ def test_transpose_pixels(self):
t = timeit.Timer(stmt, setup=setup)
number = 1000
res = t.timeit(number=number)
print(
f'\ntranspose_pixels {size} (view): {res / number * 1e3:.3f} ms per'
' loop'
)
name_view = f'TransposePixels_{size[0]}x{size[1]}_view'
print(f'Benchmark{name_view} {number} {res / number * 1e9:.0f} ns/op')

stmt_copy = 'pixel_fns.transpose_pixels(img).copy()'
t_copy = timeit.Timer(stmt_copy, setup=setup)
res_copy = t_copy.timeit(number=number)
name_copy = f'TransposePixels_{size[0]}x{size[1]}_copy'
print(
f'transpose_pixels {size} (copy): {res_copy / number * 1e3:.3f} ms'
' per loop'
f'Benchmark{name_copy} {number} {res_copy / number * 1e9:.0f} ns/op'
)

def test_orient_pixels(self):
Expand All @@ -176,17 +174,15 @@ def test_orient_pixels(self):
t = timeit.Timer(stmt, setup=setup)
number = 1000
res = t.timeit(number=number)
print(
f'\norient_pixels {size}, orientation={orientation} (view):'
f' {res / number * 1e3:.3f} ms per loop'
)
name_view = f'OrientPixels_{size[0]}x{size[1]}_rot{orientation}_view'
print(f'Benchmark{name_view} {number} {res / number * 1e9:.0f} ns/op')

stmt_copy = 'pixel_fns.orient_pixels(img, orientation).copy()'
t_copy = timeit.Timer(stmt_copy, setup=setup)
res_copy = t_copy.timeit(number=number)
name_copy = f'OrientPixels_{size[0]}x{size[1]}_rot{orientation}_copy'
print(
f'orient_pixels {size}, orientation={orientation} (copy):'
f' {res_copy / number * 1e3:.3f} ms per loop'
f'Benchmark{name_copy} {number} {res_copy / number * 1e9:.0f} ns/op'
)

def test_convert_int_to_float(self):
Expand All @@ -203,10 +199,8 @@ def test_convert_int_to_float(self):
t = timeit.Timer(stmt, setup=setup)
number = 100
res = t.timeit(number=number)
print(
f'\nconvert_int_to_float {size} (BoundedArray):'
f' {res / number * 1e3:.3f} ms per loop'
)
name = f'ConvertIntToFloat_{size[0]}x{size[1]}_BoundedArray'
print(f'Benchmark{name} {number} {res / number * 1e9:.0f} ns/op')


if __name__ == '__main__':
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