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⚡️ Speed up function calculate_shift by 8% #127

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⚡️ Speed up function calculate_shift by 8% #127

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26 changes: 23 additions & 3 deletions src/diffusers/pipelines/ltx/pipeline_ltx.py
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Original file line number Diff line number Diff line change
Expand Up @@ -74,10 +74,18 @@ def calculate_shift(
base_shift: float = 0.5,
max_shift: float = 1.15,
):
if (
base_seq_len is _DEFAULT_BASE_SEQ_LEN and
max_seq_len is _DEFAULT_MAX_SEQ_LEN and
base_shift is _DEFAULT_BASE_SHIFT and
max_shift is _DEFAULT_MAX_SHIFT
):
# Fast path for defaults
return image_seq_len * _m_DEFAULT + _b_DEFAULT

# Fallback for non-defaults (kept as a one-liner for efficiency)
m = (max_shift - base_shift) / (max_seq_len - base_seq_len)
b = base_shift - m * base_seq_len
mu = image_seq_len * m + b
return mu
return image_seq_len * m + (base_shift - m * base_seq_len)


# Copied from diffusers.pipelines.stable_diffusion.pipeline_stable_diffusion.retrieve_timesteps
Expand Down Expand Up @@ -799,3 +807,15 @@ def __call__(
return (video,)

return LTXPipelineOutput(frames=video)

_DEFAULT_BASE_SEQ_LEN = 256

_DEFAULT_MAX_SEQ_LEN = 4096

_DEFAULT_BASE_SHIFT = 0.5

_DEFAULT_MAX_SHIFT = 1.15

_m_DEFAULT = (_DEFAULT_MAX_SHIFT - _DEFAULT_BASE_SHIFT) / (_DEFAULT_MAX_SEQ_LEN - _DEFAULT_BASE_SEQ_LEN)

_b_DEFAULT = _DEFAULT_BASE_SHIFT - _m_DEFAULT * _DEFAULT_BASE_SEQ_LEN