Synopsis
		sfshstack < cmp.rsf velocity=velocity.rsf > stack.rsf offset=offset.rsf half=y slowness=n h0=0. eps=0.01 jump=1 niter=10 restart=niter tol=1e-5 flo= fhi= nplo=6 nphi=6

Parameters
		float eps=0.01 stretch regularization   float fhi= High frequency in band, default is Nyquist   float flo= Low frequency in band, default is 0   float h0=0. reference offset   bool half=y [y/n] if y, the second axis is half-offset instead of full offset   int jump=1 subsampling   int niter=10 number of iterations   int nphi=6 number of poles for high cutoff   int nplo=6 number of poles for low cutoff   string offset= auxiliary input file name   int restart=niter GMRES memory   bool slowness=n [y/n] if y, use slowness instead of velocity   float tol=1e-5 GMRES tolerance   file velocity= auxiliary input file name