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--- base:16bit_xorshift_random_generator [2019-05-10 02:45] – vsariola
+++ base:16bit_xorshift_random_generator [2019-08-12 15:41] (current) – Standardized format of the heading ftc
@@ Line 1: / Line 1: @@
-=== 16-bit "798" Xorshift ===
+====== 16-bit "798" Xorshift ======
   * original idea: [[https://www.jstatsoft.org/article/view/v008i14|George Marsaglia]]
   * idea for fast 8-bit implementation: [[http://www.retroprogramming.com/2017/07/xorshift-pseudorandom-numbers-in-z80.html|John Metcalf]]
   * ported by: Veikko Sariola
-Xorshift is a fast pseudorandom generator algorithm originally developed by [[https://www.jstatsoft.org/article/view/v008i14|George Marsaglia]]. [[http://www.retroprogramming.com/2017/07/xorshift-pseudorandom-numbers-in-z80.html|John Metcalf]] found a 16-bit version of the algorithm that is fast on 8-bit platforms with only single bit shifts available. It has a period of 65535 and passes reasonable tests for randomness, unlike most of the LFSRs on this site. His pseudocode is reprinted here:
+Xorshift is a fast pseudorandom generator algorithm originally developed by [[https://www.jstatsoft.org/article/view/v008i14|George Marsaglia]]. [[http://www.retroprogramming.com/2017/07/xorshift-pseudorandom-numbers-in-z80.html|John Metcalf]] found a 16-bit version of the algorithm that is fast on 8-bit platforms with only single bit shifts available. It has a period of 65535 and passes reasonable tests for randomness. His pseudocode is reprinted here:
 <code c>
@@ Line 31: / Line 32: @@
         STA rng_zp_high
         ...
-        ; the RNG, you can get 8-bit random numbers in A, leaves X/Y unchanged
+        ; the RNG. You can get 8-bit random numbers in A or 16-bit numbers
+        ; from the zero page addresses. Leaves X/Y unchanged.
 random  LDA rng_zp_high
         LSR
@@ Line 49: / Line 51: @@
 {{:base:xorshift_798_results.png?400|}}