def _fifi2fid(x):
x = kept_within(0.0, x)
cdf = chyperexpo(means, qumul, x)
pdf = dhyperexpo(means, qumul, x)
fi = cdf - prob
if pdf <= 0.0:
if fi == 0.0: fi2fid = 1.0
else: fi2fid = MAXFLOAT
else:
fi2fid = fi/pdf
return fi, fi2fid
def rhyperexpo(self, means, qumul, xmax=float('inf'), pmax=1.0):
"""
Generates a random number from the hyperexponential distribution
f = sumk pk * exp(x/mk) / mk, F = sumk pk * (1-exp(x/mk))
NB Input to the function is the list of CUMULATIVE FREQUENCIES !
"""
assert xmax >= 0.0, "xmax must be a non-negative float in rhyperexpo!"
self._checkpmax(pmax, 'rhyperexpo')
pmx = pmax
if xmax < float('inf'):
pmx = min(pmax, chyperexpo(means, qumul, xmax))
p = pmx * self.runif01()
x = ihyperexpo(p, means, qumul)
return x
