> Thanks for the explanation! I have a few clarification questions about this. > If I understand correctly, B would represent the number of elements the > vector can have (for 128b vector operating on 32b elements, B == 4, but if > operating on 64b elements B == 2); however, I'm not too sure what A > represents.
The runtime size of a vector is a polynomial with a "base size" of A and "increments beyond A" of B. B is compile-time variable/indeterminate and runtime invariant. For (non-zve32) RVV it specifies the number of 64-bit chunks beyond the minimum size of 64 bits. The polynomial is [2 2] in that case and the "vector bit size" would be 64 * [2 2] = [128 128] = 128 + x * 128. For a runtime vector size of 256 bits, x would be 1 and so on and we determine it at runtime via csrr. > On the poly_int docs, it says > > An indeterminate value of 0 should usually represent the minimum possible > > runtime value, with c0 specifying the value in that case. > "minimum possible runtime value" doesn't make sense to me. Does it mean the > potential minimum bound of elements it will operate on? This refers to the minimum runtime size of a vector, the constant 2 * 64 bit above. So it doesn't talk about the number of elements. The number of elements can be deducted from the "vector size" polynomial by dividing it by the element size. The minimum number of elements for an element size S could e.g. be [128 128] / S = 128 / S + x * (128 / S). -- Regards Robin
