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3 votes
2 answers
200 views

I'm working on a project written in C that's going to be deployed on vintage systems with very limited resources. The target system has at minimum a 16 MHz Motorola 68030 processor with a 256 byte L1 ...
0 votes
3 answers
203 views

I have this code so far, which performs some kind of hashing. The goal is to map each ASCII string to a single Hangul Syllable unicode point: const HANGUL_START = 0xAC00; // Start of Hangul ...
0 votes
2 answers
97 views

I have a set of N integers in the range 0 to 255 which must be mapped using a minimally perfect hash function to the range [0, N-1]. However, this set of integers can grow dynamically. In the case ...
jeffreyveon's user avatar
  • 13.9k
2 votes
1 answer
247 views

I am developing a CANopen slave stack on a 200 MHz microcontroller and require a highly efficient lookup method to match a 16-bit object index (e.g., 0x603d) with a table index where the objects are ...
nowox's user avatar
  • 29.7k
2 votes
0 answers
71 views

I have a set of ~10.2 billion 64-bit elements that are: Constant and known before compile time (so no insertion, deletion, or modification). Classified into 3 categories, also constant and known ...
2 votes
1 answer
2k views

I need a very fast hash table in C (or C++). Conditions are like this: There exist N known keys which shall map to an object (with some state) There exist more unknown keys which do not map to ...
5 votes
2 answers
2k views

I have input keys that can cheaply be converted to a uint64_t (ie, the input contains less than or equal to 64 bits). Each unique key (not yet in the map) will be assigned some data (a pointer to an ...
1 vote
2 answers
715 views

Here's the problem: X is a positive integer (include 0) set which has n different elements I know in advance. All of them is less equal than m. And I want to have an occ-free hash function as simple ...
0 votes
1 answer
3k views

I've found that function in the golang's source code and want to know whether it's truly a perfect hash function or not. Is it the correct way to test that? package main import ( "fmt" ...
0 votes
1 answer
1k views

I'm currently writing my master thesis about clusterings in graphs. My prof said he wants the graph to be represented as a hash table. Because it needs less space than the adjency matrix and it is ...
0 votes
1 answer
256 views

I'm looking for a way to 'project' a series of 'ranges' into a series of values. Applications would be histograms with uneven bins or creation of lookup tables. An example: 0 to 14 => 0 15 to 234 =&...
0 votes
1 answer
138 views

The gperf info pages claims that if you specify -l then The keywords in the input file may contain NUL bytes, written in string syntax as 000円 or \x00, and the code generated by gperf will treat ...
1 vote
1 answer
670 views

What I need I need an algorithm that produces a bijective output. I have a 31-bit input and need a pseudo-random 31-bit output. What I have considered CRCs are bijective within their bit-width. I ...
15 votes
2 answers
8k views

I recently read this article Throw away the keys: Easy, Minimal Perfect Hashing about generating a minimal perfect hash table for a known set of keys. The article seems to assume that you need an ...
1 vote
0 answers
40 views

Consider the following list of permutations of {0,1,2,3,4,5,6,*,*,*} as generated with ordinary backtracking: Index Permutation 1. 0123456*** 2. 012345*6** 3. 012345**6* ...

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