attach the sample usage here: dT = jitter*$rdist_normal(seed,0,1);

I have attached one sample code from this website, why author chose seed=286, not other number?

module osc2 (out);

output out; voltage out;                  // output signal
parameter real freq=1 from (0:inf);            // output frequency
parameter real vl=-1;                        // high output voltage
parameter real vh=1;                        // low output voltage
parameter real tt=0.01/freq from (0:inf);      // transition time of output
parameter real jitter=0 from [0:0.1/freq);      // white period jitter
integer n, seed;
real next, dT;

analog begin
   @(initial_step) begin
     seed = 286;
     next = 0.5/freq + $abstime;
   end
   @(timer(next)) begin
     n = !n;
     dT = jitter*$rdist_normal(seed,0,1);
     next = next + 0.5/freq + `M_SQRT1_2*dT;
   end
   V(out) <+ transition(n ? vh : vl, 0, tt);
end
endmodule

Ken Kundert wrote on Nov 16^th, 2006, 7:20pm:


By "two different rdist functions" Ken does not mean to say that $rdist_normal() and $rdist_uniform will give the same sequence of random numbers.  I am fairly sure he meant "give the same seed to two different calls of the same rdist function":

Modifying the example:

integer n, seed, seed2;
real next, dT, dT2;

analog begin
 @(initial_step) begin
   seed = 286;
   seed2 = 286;
   next = 0.5/freq + $abstime;
 end
 @(timer(next)) begin
   n = !n;
   dT = jitter*$rdist_normal(seed,0,1);
   dT2 = jitter*$rdist_normal(seed2,0,1); // will have the same sequence of values as dT
  next = next + 0.5/freq + `M_SQRT1_2*dT;
 end
 V(out) <+ transition(n ? vh : vl, 0, tt);
end

dT2 will have the exact same sequence of random values as dT.  Also, seed and seed2 are changed by the $rdist function calls, and the sequence of their values will be the same.

I wonder: if you did
 rn1 = $rdist_normal(seed,0,1);
 rn2 = $rdist_uniform(seed2,-1,1);

will "seed" and "seed2" have the same sequence of (integer) values?  I guess you might or might not, since the LRM doesn't say.

-Geoffrey