ut3_reciprocal_weights

t3toolbox.backend.ut3_operations.ut3_reciprocal_weights(weights)

def ut3_reciprocal_weights(
        weights: UT3WeightsData,  # (tucker_weight_supercore, tt_weight_supercore, masks)
) -> UT3WeightsData:              # 1/w on the real slots; padding a canonical, finite 0; masks unchanged

Elementwise 1/w on the real slots (masks unchanged) – e.g. to form inverse-singular-value weights.

Not just ``1/w``, because a canonical weight’s padding is zero and 1/0 = inf, which then poisons every masked reduction downstream (0 * inf = nan). That is the headline path, not a corner case: the Grasedyck-Kramer metric is from_ut3svd(x).reciprocal(). The real slots are left alone (see _ut3_map_real_weights() for how the padding is handled).

The real slots are deliberately unprotected: a genuinely zero singular value gives inf here, exactly as in the ragged layer. It is a real weight, not a padding artifact, so it is the caller’s to avoid – silently clamping it would hide a rank-deficient point.

Parameters:

weights (UT3WeightsData)

Return type:

UT3WeightsData