Function shard_take 

pub fn shard_take(take: usize, index: usize, count: usize) -> usize

2026-09-26: How many of a subset’s take drawn rows shard index of count gets; 0 for an index out of range or a count of 0. Rows are striped, row i going to shard i % count (shard_owns), not cut into contiguous blocks, so every shard gets a proportional slice of every subset, and membership depends on position alone.