ftp.nice.ch/pub/next/unix/audio/cmusic.bs.N.tar.gz#/src/lib/libran/SCCS/s.onefrand.c

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c switched to random().

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c original distributed version

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/* %M%	%I%	(CARL)	%G%	%U% */

/*
 * 1/f noise according to Voss' algorithm.
 * Sequence length (seq) may be any number, but is truncated to the
 * nearest power of 2.
 * The algorithm:
 * Select log2(sequence) separate white noise generators, i.e.,
 * one for each bit of a binary number.
 * Initialize a counting register.
 * In a loop, add 1 to the counting register, determine which
 * bits have changed from its previous value.  For each changed
 * bit, invoke the appropriate generator to produce a new number.
 * Sum the normalized output of all generators as the current number.
 * The procedure f1init() is used to reset the sequence length.
 * On the next call to onefrand(), the new value of seq will be used.
 */

#include<math.h>
#include<stdio.h>

static f1ini;
static double seq = 32.0*1024.0;

double onefrand(lb, ub)
	double lb, ub;
{
	double tmp;
	register int i, dif;
	static int gens;
	static double *sums; 
	double sum; 
	static double div;
	static int cnt = -1, ocnt;

	if (f1ini == 0) 
		{
		f1ini++;
		if (seq <= 1.0) seq = 2.0;
		gens = log(seq) / log(2.0);
		if (sums != NULL) free(sums);
		sums = (double *) malloc(sizeof(double)*gens);
		for (i = 0; i < gens; i++) sums[i] = 0;
		div = pow(2.0, (double) ((sizeof(int) * 8) - 1)) - 1.0;
		}

	ocnt = cnt++;				/* increment count */
	dif = cnt ^ ocnt;			/* set sums to change */

	for ( i = 0; i < gens; i++ )		/* form new sums */
		{
		if (dif & (1 << i))

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			sums[i] = rand();

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			sums[i] = random();

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		}

	for ( sum = i = 0; i < gens; i++ )	/* sum them all */
		sum += sums[i];

	sum /= gens * div;
	sum = (sum * (ub - lb)) + lb;		/* norm to spec */
	return(sum);
	}

f1init(sequence)
	double sequence;
{
	f1ini = 0;
	seq = sequence;
}

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