function y = wv_fftconv(a, b)
% WV_FFTCONV  Linear convolution of two real vectors, by FFT.
%
% The direct sum costs the product of the two lengths, which for a two-second
% sound and a one-second impulse response is about 4e9 operations; the FFT
% costs a few times n log n.  The result is the full convolution, of length
% numel(a) + numel(b) - 1, as a column.
a = a(:);
b = b(:);
n = numel(a) + numel(b) - 1;
nfft = 2 ^ nextpow2(n);
y = real(ifft(fft(a, nfft) .* fft(b, nfft)));
y = y(1:n);
end