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Comment by KingOfCoders | Hacker News Reader

Wouldn't you need a fixed length of the temps?

  00.1
 -10.3

  0.1 (with an ending space)

so you can look up 5 bytes in the map? (+/i, two digits, dot, one digit)

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you can create a perfect hash based on the presence of at least 4 characters. perfect hash is pre calculated based on possible inputs (-99.9 to 99.0 in bytes). the hash is usual byte*seed+hash. "seed" is chosen so that there is no clash (you can find a static seed in a single brute force from 1 to 1m in < 1 min)

I thought the lookup would just be a byte tree not a hash. Wouldn't a hash with it's calculation beat the purpose of being faster than parsing a number?

The idea would be, you have a tree of all values of 0.0 to 99.9 and then just use the bytes to iterate the tree (e.g. in an array) to come up with the int value of e.g. 45.5

parsing a number contains an (addition + multiplication) *(number of digits) for each row. if you do precalculated perfect hash then multiplication for each row can be avoided. ( you anyways need to read each byte)

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