#### Prime Power Delay-Line Lengths

When the delay-line lengths need to be varied in real time, or interactively in a GUI, it is convenient to choose each delay-line length as an integer power of a distinct prime number [457]:

Suppose we are initially given desired delay-line lengths arranged in ascending order so that

round

where is the desired length in samples. That is, can be
simply obtained by *rounding*to the nearest integer (max 1). The prime-power delay-line length approximation is then of course

This prime-power length scheme is used to keep 16 delay lines both
variable and mutually prime in Faust's `reverb_designer.dsp`
programming example (via the function `prime_power_delays` in
`effect.lib`).

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