... Eliminate CreateFromCopy, add new one-step constructor instead.
It was wasteful to create a copy only to re-create the Sequence at once.
Sequence::Copy is a factory returning a unique_ptr.
Some error checks are removed, but there will be exceptions instead later.
... and that they have equal width on the linear scale
... also simplify the logic involving zero padding factor
This is more preparation for constant-q.
... whenever they really describe the size of a buffer that fits in memory, or
of a block file (which is never now more than a megabyte and so could be fit in
memory all at once), or a part thereof.
... with run-time assertions.
I examined each place and reasoned that the narrowing was safe, and commented
why so.
Again, there are places where the sampleCount variable will later be changed
to have a different type, and they are not changed here.
... A non-narrowing conversion out to long long is a necessity, but the
conversions to float and double are simply conveniences.
Conversion from floating is explicit, to avoid unintended consequences with
arithmetic operators, when later sampleCount ceases to be an alias for an
integral type.
Some conversions are not made explicit, where I expect to change the type of
the variable later to have mere size_t width.
... This makes much code agnostic about how other things (functions and
arguments) are typed.
Many of these neeed to become size_t instead of sampleCount.
I confirmed that the currently used real FFT code in RealFFTf.cpp is faster
than the old one with a quick benchmark that calls PowerSpectrum() on 4-minute
audio file, with different sizes of computation windows:
Window_size: 256 method: new FFT time_s: 0.393
Window_size: 256 method: old FFT time_s: 1.065
Window_size: 1024 method: new FFT time_s: 0.38
Window_size: 1024 method: old FFT time_s: 0.958
Window_size: 4096 method: new FFT time_s: 0.413
Window_size: 4096 method: old FFT time_s: 1.084
Window_size: 16384 method: new FFT time_s: 0.518
Window_size: 16384 method: old FFT time_s: 1.338
Window_size: 65536 method: new FFT time_s: 0.655
Window_size: 65536 method: old FFT time_s: 1.524
Window_size: 262144 method: new FFT time_s: 0.735
Window_size: 262144 method: old FFT time_s: 1.873
