Hash table value for a particular row and col?

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The description of sparseLoc.hash returns a value of type size_t. The description says it returns the hash value. My analog of the hash value is the index of the occupied cells. That is, if the three occupied cells (and array index) are 4, 8, & 12, then if I put in sparseLoc.hash(12), would it return 2 (0,1,2) or 3 (1,2,3)?

If this is 2 do I extract the value at that location with sparseLoc.value<float>(2)?

Thanks Ralph