From: janis_papanagnou+ng@hotmail.com   
      
   On 2025-12-25 06:09, BGB wrote:   
   > On 12/24/2025 5:22 AM, BGB wrote:   
   >>   
   >> Some people seem to really like using lookup tables.   
      
   Of course; they can speed up things significantly. And simplify   
   the operations for contemporary data sizes (bytes, 64 bit words,   
   etc.).   
      
   >   
   > I don't really get the point of lookup table driven RNGs.   
      
   In e.g. bit-oriented algorithms (e.g. based on LFSR) you can speed   
   up processing significantly by processing larger quantities (like   
   octets/bytes) and processing/accessing values then byte-wise.[*]   
      
   Someone already mentioned that a bit-wise operating PN-generator   
   for random numbers could make use of such a table driven approach.   
   (You can extend that principle to larger quantities than bits, e.g.   
   to gain from larger processor word lengths, especially it you need   
   those larger entities as result in the first place.)   
      
   > A lot of these ones are, say, a table with 256 spots, and an index.   
   > Each time one generates a random number (usually a byte), it returns the   
   > value at that location in the table and advances to the next index.   
   >   
   > Sometimes some get clever and use an algorithm to jitter the table index.   
   >   
   > I have mostly seen this strategy used in old game engines.   
   >   
   > These typically fail the image test as by design they give repeating   
   > patterns.   
   >   
   > [...]   
      
   Janis   
      
   [*] Here's some old "C" example for a CRC-16 using table-lookup...   
   http://random.gridbug.de/ccitt_crc16.c   
      
   --- SoupGate-Win32 v1.05   
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