{"record":{"id":"a1c14ca18e320914","repo":"huggingface/pytorch-image-models","slug":"a-progressive-schedule-requires-at-least-two-choic","errorCode":null,"errorMessage":"A progressive schedule requires at least two choices.","messagePattern":"A progressive schedule requires at least two choices\\.","errorType":"validation","errorClass":"ValueError","httpStatus":null,"severity":"error","filePath":"timm/data/scheduled_sampler.py","lineNumber":74,"sourceCode":"            schedule_epochs: Optional[int] = None,\n            schedule_spread: float = 0.65,\n            schedule_random_mix: float = 0.1,\n    ) -> None:\n        if not hasattr(sampler, '__len__'):\n            raise TypeError('ScheduledBatchSampler requires a sampler with a length.')\n        if len(sampler) <= 0:\n            raise ValueError('ScheduledBatchSampler requires a non-empty sampler.')\n        if not batch_sizes:\n            raise ValueError('batch_sizes must contain at least one value.')\n        if any(int(batch_size) != batch_size or batch_size <= 0 for batch_size in batch_sizes):\n            raise ValueError('All scheduled batch sizes must be positive integers.')\n        if num_batches is not None and (int(num_batches) != num_batches or num_batches <= 0):\n            raise ValueError('num_batches must be a positive integer when specified.')\n        if choice_schedule not in ('constant', 'progressive'):\n            raise ValueError(\"choice_schedule must be 'constant' or 'progressive'.\")\n        if choice_schedule == 'progressive':\n            if len(batch_sizes) < 2:\n                raise ValueError('A progressive schedule requires at least two choices.')\n            if schedule_epochs is None or int(schedule_epochs) != schedule_epochs or schedule_epochs <= 0:\n                raise ValueError('schedule_epochs must be a positive integer for a progressive schedule.')\n            if schedule_spread < 0:\n                raise ValueError('schedule_spread must be non-negative.')\n            if not 0 <= schedule_random_mix <= 1:\n                raise ValueError('schedule_random_mix must be between 0 and 1.')\n\n        self.sampler = sampler\n        self.batch_sizes = tuple(int(batch_size) for batch_size in batch_sizes)\n        self.choice_weights = self._normalize_choice_weights(choice_weights)\n        self._active_choices = tuple(\n            choice_index\n            for choice_index, choice_weight in enumerate(self.choice_weights)\n            if choice_weight > 0\n        )\n        self.seed = seed\n        self.drop_last = drop_last\n        self.shuffle_schedule = shuffle_schedule","sourceCodeStart":56,"sourceCodeEnd":92,"githubUrl":"https://github.com/huggingface/pytorch-image-models/blob/9a5261e31b3b5128526eb2658333b4c0a54464ae/timm/data/scheduled_sampler.py#L56-L92","documentation":"A progressive schedule interpolates between batch-size choices across epochs, so it needs at least two entries in batch_sizes to move between; with one (or zero) entries there is nothing to progress through and construction fails.","triggerScenarios":"choice_schedule='progressive' together with batch_sizes=[256] (single element) or [].","commonSituations":"Configs generated from a single base batch size where the progressive path was enabled by default; forgetting to add the smaller starting batch size.","solutions":["Provide >=2 sizes, ordered small->large, e.g. batch_sizes=[128, 256, 512].","If you only want one batch size, use choice_schedule='constant' with that single size."],"exampleFix":"# before\nScheduledBatchSampler(s, batch_sizes=[256], choice_schedule='progressive')\n\n# after\nScheduledBatchSampler(s, batch_sizes=[64, 256], choice_schedule='progressive', schedule_epochs=20)","handlingStrategy":"validation","validationCode":"if choice_schedule == 'progressive':\n    assert len(batch_sizes) >= 2, 'progressive needs >= 2 batch sizes'","typeGuard":null,"tryCatchPattern":null,"preventionTips":["Pair progressive mode with an ordered list of >=2 sizes.","Use 'constant' when a single batch size is intended."],"tags":["timm","sampler","progressive-schedule","validation"],"backgroundTag":"insufficient-config-choices","analyzedSha":"9a5261e31b3b5128526eb2658333b4c0a54464ae","analyzedAt":"2026-08-27T02:34:25.417Z","schemaVersion":2},"datasetVersion":"2026-08-27T03:17:27.898Z"}