Re: Short Vectors Versus Long Vectors

Lawrence D'Oliveiro wrote:

On Tue, 23 Apr 2024 02:14:32 +0000, MitchAlsup1 wrote:

CRAY machines stayed "in style" as long as memory latency remained
smaller than the length of a vector (64 cycles) and fell out of favor
when the cores got fast enough that memory could no longer keep up.

So why would conventional short vectors work better, then? Surely the latency discrepancy would be even worse for them.

Yes, the later NEC long vector machines grew their VRF up to 256 entries per register.
As to why RISC-V went shorter I can only imagine they think vector codes
can be compiled properly for a quicker memory hierarchy (i.e., hit in
L1 or L2 caches.).