Synopsis
		sfcheckptdemo < Fv.rsf > Fw.rsf p1=Fp1.rsf p2=Fp2.rsf nb=20 nt= dt= fm=20.0 ft=0 jt=1 verb=n kt= nob=(int)log2f(nt)

The real value of checkpointing technology resides in the backpropagation with
viscoacoustic and viscoelastic wave equation, where the wavefield
reconstruction method using saved boundaries fails. Here, we only
demonstrate how to implement it in acoustic media without dissipation.

Parameters
		float dt= time sampling interval   float fm=20.0 dominant freq of Ricker wavelet   int ft=0 first recorded time   int jt=1 time interval   int kt= output px and pz component at kt   int nb=20 thickness of PML ABC   int nob=(int)log2f(nt) number of buffers, default=optimal value   int nt= number of time steps   file p1= auxiliary output file name   file p2= auxiliary output file name   bool verb=n [y/n] verbosity, if y, output px and pz