Fix assertion error in UniPC scheduler for high step counts #126
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This fixes an edge case in the FlowUniPCMultistepScheduler where using high sampling step counts (> 50) would cause an assertion error in the last step. The issue was that with lower_order_final=True, the order calculation could become 0 when step_index equals len(timesteps), causing 'assert self.this_order > 0' to fail. The fix ensures this_order is always at least 1, maintaining stability while allowing higher quality generation with increased step counts. 🤖 Generated with Claude Code Co-Authored-By: Claude [email protected]
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We were unable to reproduce this bug. Could you please provide detailed information on how to reproduce this bug? |
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On ComfyUI i tested with 100 steps UniPC and Wan2.1 works fine. Here is the screenshot
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This fixes an edge case in the FlowUniPCMultistepScheduler where using high sampling step counts (> 50) would cause an assertion error in the last step. The issue was that with lower_order_final=True, the order calculation could become 0 when step_index equals len(timesteps), causing 'assert self.this_order > 0' to fail.
The fix ensures this_order is always at least 1, maintaining stability while allowing higher quality generation with increased step counts.
I verified that with this fix generation works if setting "--sample-steps" to 100. Without this change, it fails at the last step.
🤖 Generated with Claude Code
Co-Authored-By: Claude [email protected]