3 ms·
I thought about hashing, but found that hashing would be enormously slow to compute compared to a perfectly crafted tree.
by netr0ute 1y ago
I thought about hashing, but found that hashing would be enormously slow to compute compared to a perfectly crafted tree.
- dafelst 1y agoBut did you think about using a perfect hash function and table? Based on my prior research, it seems like they are almost universally faster on small strings than trees and tries due to lower cache miss rates.
- dist1ll 1y agoDitto. Perfect hashing strings smaller than 8 bytes has been the fastest lookup method in my experience.
- netr0ute 1y agoProblem is, there are a lot of RISC-V instruction way longer than that (like th.vslide1down.vx) so hashing is going to be slow.
- ashdnazg 1y agoYou could copy the instruction to a 16 byte sized buffer and hash the one/two int64s. Looking at the code sample in the article, there wasn't a single instruction longer than 5 characters, and I suspect that in general instructions with short names are more common than those with long names. This last fact might actually support the current model, as it grows linearly-ish in the size of the instruction, instead of being constant like hash.
- snvzz 1y agoNote th.vslide1down.vx is a T-Head instruction, a vendor custom extension. It is not part of RISC-V, nor supported by any CPUs outside of that vendors' own.
- Lerc 1y agoIs there a handy list of all RISC-V instructions?