Perhaps you should just get some raw hardware random numbers from some place
like random.org or HotBits.
Then just do something like this:
void* p;
while ((p+8)<=size)
{
unsigned long long* LL = reintepret_cast<unsigned long long*>(void*
p);
long double r = double(1/LL);
p=p+8;
}
where p is a pointer to the random bits you loaded into ram somehow, maybe
with fread() or some kind of simple stream code, whatever you use doesn't
matter as long as it's binary mode.
That should be a little bit tricky, but extremely accurate way to get some
fractional numbers.
You could also do the same general thing a little less accurately and
randomly by making an array of shorts (up to 32767 is a short on i386)
containing the output of many rand() calls. Then accumulate every so many
shorts together into a long or long long with a pointer of some kind and
your friend reinterpret_cast<T>(x) and divide 1 by this value to make some
random fraction. Make sure you cast when you do the division just to make
sure the compiler uses floating point math, so you'll get an accurate
result.
If you do this, don't define the array with values any bigger than rand()
returns or you'll be adding predictable zeros to your random numbers, which
is a bad thing to do.
-----Original Message-----
From: dev...@li...
[mailto:dev...@li...]On Behalf Of Anton Zilman
Sent: Wednesday, February 16, 2005 2:05 PM
To: dev...@li...
Subject: [Dev-C++] random numbers with double precision
Hi,
I need to produce random numbes uniformly distributed between 0 and 1. I
can use (rand()%MAX_INT)/MAX_INT, but this gives me only 30 thousand
something different numbers, because rand() is an integer.
So, if I cannot simulate something probability of which is less than
1/MAX_INT. Is there an analog of drand() function in Dec C/C++?
If anyone can help, it is apprecated!
Anton
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