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Minor fixes to kiss99

--- a/dnn/kiss99.c

+++ b/dnn/kiss99.c

@@ -45,6 +45,15 @@

   if(i-3<_ndata)_this->z^=_data[i-3];

   if(i-2<_ndata)_this->w^=_data[i-2];

   if(i-1<_ndata)_this->jsr^=_data[i-1];

+  /*Fix any potential short cycles that show up.

+    These are not too likely, given the way we initialize the state, but they

+     are technically possible, so let us go ahead and eliminate that

+     possibility.

+    See Gregory G. Rose: "KISS: A Bit Too Simple", Cryptographic Communications

+     No. 10, pp. 123---137, 2018.*/

+  if(_this->z==0||_this->z==0x9068FFFF)_this->z++;

+  if(_this->w==0||_this->w==0x464FFFFF)_this->w++;

+  if(_this->jsr==0)_this->jsr++;

 }

 uint32_t kiss99_rand(kiss99_ctx *_this){

@@ -56,8 +65,12 @@

   znew=36969*(_this->z&0xFFFF)+(_this->z>>16);

   wnew=18000*(_this->w&0xFFFF)+(_this->w>>16);

   mwc=(znew<<16)+wnew;

-  shr3=_this->jsr^(_this->jsr<<17);

-  shr3^=shr3>>13;

+  /*We swap the 13 and 17 from the original 1999 algorithm to produce a single

+     cycle of maximal length, matching KISS11.

+    We are not actually using KISS11 because of the impractically large (16 MB)

+     internal state of the full algorithm.*/

+  shr3=_this->jsr^(_this->jsr<<13);

+  shr3^=shr3>>17;

   shr3^=shr3<<5;

   cong=69069*_this->jcong+1234567;

   _this->z=znew;

--- a/dnn/kiss99.h

+++ b/dnn/kiss99.h

@@ -27,6 +27,10 @@

 # define _kiss99_H (1)

 # include <stdint.h>

+/*KISS PRNG from George Marsaglia (1999 version).

+  See https://en.wikipedia.org/wiki/KISS_(algorithm) for details.

+  This is suitable for simulations, but not for use in crytographic contexts.*/

+

 typedef struct kiss99_ctx kiss99_ctx;

 struct kiss99_ctx{

-- 

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