On Thursday, 2 January 2014 at 20:38:10 UTC, Jeroen Bollen wrote:
D provides a set of Random Number Generators in std.random. I
am writing an application which would create a 2D map of noise.
To do this though, I'll have to calculate the same random
numbers over and over again. (I cannot store them, that'd take
a horrible amount of RAM. )
Is it good to re-seed a generator for every coordinate, will
this be performance intensive? Is there maybe way to easily
implement Generator.at(uint x) in D?
I believe you fail to understand how the RNG's work.
You supply a seed(a value) and they generate a deterministic
sequence off that value that is pseudo-random relative to each
other..
If you re-seed the generator every time you are not doing
anything but wasting cycles since the new element will be random,
but the same as using the next element in the sequence in the
first case.
e.g.,
seed(k);
for(i = 1..10)
print(rnd(i));
and
for(i = 1..10)
{
seed(time);
print(rnd(i));
}
will both produce random sequences of numbers(and random
sequences of numbers are "identically random".
The nice thing about the first case is that you can save the seed
once time and produce the exact same sequence... which would save
you memory. In the second case you would have to record every
seed to recover the sequence.
