Program sfadjgradient2d_gpu | 2D ISOTROPIC wave-equation finite-difference migration on GPU 
[SYNOPSIS]
sfadjgradient2d_gpu < Fvel.rsf xig=Fxig.rsf swf=Fswf.rsf rwf=Frwf.rsf > Fgrd.rsf nxtap=40 verbose=n gpu=0
[PARAMETERS]
int     | gpu | =0 |   | 	ID of the GPU to be used 
int     | nxtap | =40 |   | 	TAPER size 
file    | rwf | = |   | 	auxiliary input file name
file    | swf | = |   | 	auxiliary input file name
bool    | verbose | =n |  [y/n] | 	VERBOSITY flag 
file    | xig | = |   | 	auxiliary input file name
[DIRECTORY]
user/rweiss
