roboflow/supervision · error · ValueError

`overlap_wh` must be smaller than `slice_wh` in both…

Error message

`overlap_wh` must be smaller than `slice_wh` in both dimensions to keep a positive stride. Received overlap_wh={overlap_wh}, slice_wh={slice_wh}.

What it means

Raised by InferenceSlicer._validate_overlap when overlap_wh is greater than or equal to slice_wh in either dimension. Slice offsets advance by (slice_wh - overlap_wh) per tile; if overlap meets or exceeds the slice size the stride is zero or negative, which would produce an infinite or degenerate tiling, so it is rejected.

Solutions

1. Choose overlap strictly smaller than the slice in both dimensions, e.g. slice_wh=(512, 512), overlap_wh=(128, 128) — 20-25% of the slice is a common starting point.
2. If you intended full-image inference without tiling, do not use InferenceSlicer — call the callback on the whole image.
3. Add a config assertion: assert 0 <= overlap_w < slice_w and 0 <= overlap_h < slice_h.

Example fix

# before
slicer = sv.InferenceSlicer(callback=cb, slice_wh=640, overlap_wh=640)  # ValueError

# after
slicer = sv.InferenceSlicer(callback=cb, slice_wh=640, overlap_wh=128)

assert 0 <= overlap_w < slice_w and 0 <= overlap_h < slice_h, 'overlap must be < slice in both axes'
slicer = sv.InferenceSlicer(callback=cb, slice_wh=(slice_w, slice_h), overlap_wh=(overlap_w, overlap_h))

def is_valid_overlap_vs_slice(slice_wh, overlap_wh) -> bool:
    (sw, sh), (ow, oh) = slice_wh, overlap_wh
    return 0 <= ow < sw and 0 <= oh < sh

When it happens

Trigger: Passing overlap_wh=(640, 640) with slice_wh=(640, 640); any configuration where overlap_w >= slice_w or overlap_h >= slice_h, e.g. copying the slice size into the overlap parameter or a ratio/target-size mix-up.

Common situations: Setting overlap equal to slice size expecting 'maximum coverage'; config templates where the same number is pasted into both fields; computing overlap as a percentage of the image but sized in slice pixels.

Related errors

• Overlap values must be greater than or equal to 0. Received
• `batch_size` must be a positive integer. Received
• `overlap_wh` must be a non negative integer. Received
• `overlap_wh` must be an int or a tuple of two non negative…
• `overlap_wh` values must be non negative. Received

AI-assisted analysis of roboflow/supervision@7f254d9784 (2026-08-15). Data as JSON: /api/errors/283439aa7239e40e. Report an issue: GitHub.

Appendix: source

Thrown at src/supervision/detection/tools/inference_slicer.py:772

        return offsets

    @staticmethod
    def _validate_overlap(
        slice_wh: tuple[int, int],
        overlap_wh: tuple[int, int],
    ) -> None:
        overlap_w, overlap_h = overlap_wh
        slice_w, slice_h = slice_wh

        if overlap_w < 0 or overlap_h < 0:
            raise ValueError(
                "Overlap values must be greater than or equal to 0. "
                f"Received: {overlap_wh}"
            )

        if overlap_w >= slice_w or overlap_h >= slice_h:
            raise ValueError(
                "`overlap_wh` must be smaller than `slice_wh` in both dimensions "
                f"to keep a positive stride. Received overlap_wh={overlap_wh}, "
                f"slice_wh={slice_wh}."
            )

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