
This modules shrinks a Fsignal $in$ of size $n$ into a Fsignal $out$ of size
$n'$, with 
$$1-\frac p{100}\leq \frac{n'}n \leq 1,
\eqno(1)$$ 
in order the complexity per sample
of the Fast Fourier Transform (FFT)\index{Fourierr ansform} of $out$
to be as small as possible. This amounts to minimize
$$C(n') = \sum_i (p_i-1),$$
where $n'=\prod_i p_i$ is the prime factor decomposition of $n'$, 
with the constraint (1). The new signal $out$ starts at index
$(n-n')/2$.
If the \verb+-v+ option is selected, the module writes on standart output
the initial and final complexity, and the speed-up ratio
$C(n)/C(n')$. 
\index{crop!a signal}
