NAME

     lsqrrad - perform conjugate gradient least square  inversion
     of  gamma  curve  radon  transform  using iterative calls to
     radgamma program.

SYNOPSIS

     lsqrrad [ -Nfile_data ] [ -Pfile_prior ] [  -iterniter  ]  [
     -decreasedecrease  ] [ -weightweight ] [ -subsub-directory ]
     [ -prevsuboldsub-directory ] [ -pwddirectory ] [  -nodelist-
     nodelist ] [ -FORWARDcmdforward ] [ -BACKWARDcmdbackward ] [
     -V ] [ -? ]

DESCRIPTION

     lsqrrad minimizes the folowing quadratic objective  function
     by means of conjugate gradient algorithm:
        J(m)  = J1(m) + J2(m)
        J1(m) = || Fm- d ||**2
        J2(m) = || m - m0 ||**2
        F  : the forward modeling operator
        d  : the data to be inverted
        m0 : an a priori model

     The only difference between lsqrrad and lsqr resides in  the
     possibilty to run this program on several nodes using spawn2
     program. You thus don't have to type the name of the program
     for the FORWARD and BACKWARD command line argument (which is
     in both cases radgamma).  Note that you can do the inversion
     in  the  radon  domain  or  (after  projection  in the radon
     domain) in the original domain.  The inversion is  performed
     using  the forward modeling program (radgamma or radgamma -R
     ) and its adjoint forward modeling program (radgamma  -R  or
     radgamma);  the  command line arguments of both this program
     is entered, between quote, on the  command  line  arguments.
     The  result  called  solution is written in the subdirectory
     specified on the command line. In this subdirectory we  find
     also  the objective function value for each iteration in the
     file MINIMIZER.process_id, the  forward  modeled  calculated
     data  of  the solution called data.calc, such that the solu-
     tion and corresponding forward modeled  calculated  data  of
     the    previous    iteration,    called   solution.old   and
     data.calc.old. This allows lsqrrad to restart from a  previ-
     ous  minimization by specifying on the command line the sub-
     directory name of the previous minimization  from  which  we
     wish to restart.

  Command line arguments
     -N file_data
          Enter the usp input file name that contains the data to
          be inverted (no default).

     -P file_prior
          Enter the usp a priori model that contains the data  to
          be inverted. Default is nothing.

     -iter niter
          Enter the number of iterations  of  conjugate  gradient
          algorithm. The default value is 4.

     -weight weight
          Enter the normalized weighting parameter of the  second
          term  of  the  objective function. The default value is
          0.05 which means that the influence of second  term  of
          the  objective  function  is 5% of the influence of the
          first term during the minimization.

     -decrease decrease
          Enter the stop test value for the algorithm. The  algo-
          rithm will stop before the given iteration number niter
          if the objective function is less than the norm of  the
          data  multipled  by  decrease or if the decrease of the
          objective function between two  consecutive  iterations
          is  less  than  the  norm  of  the  data  multipled  by
          decrease. The default value is 0.01  which  means  that
          the  minimization  stop if the objective function falls
          under 1% of the data norm or if  the  decrease  of  the
          objective  function  between two consecutive iterations
          is less than 1% of the data norm.

     -nodelist nodelist
          Enter the list of cpu to be used by the  program.  Each
          cpu  name  must  be  separated by ":". The list must be
          ended by ".".

     -pwd directory
          Enter the name of the root directory where the  program
          will  be runed. The default directory is ".". Note that
          if you run the program on several  nodes  you  need  to
          enter the full path name.

     -sub sub-directory
          Enter the name of the  subdirectory  where  the  result
          will   be   written.   The   default   subdirectory  is
          result.process_id. Note that sub-directory and  oldsub-
          directory can be the same (see below).

     -prevsub oldsub-directory
          Enter the name of the directory from which the  minimi-
          zation  will  restart. In this case niter correspond to
          the additional iteration number to perform. The default
          value is nothing.

     -FORWARD cmdforward
          Enter between quote, the command line argument  (execpt
          for the name of the program, the -O and -N options) for
          the forward modeling program (no default).

     -BACKWARD cmdbackward
          Enter between quote, the command line argument  (execpt
          for the name of the program, the -O and -N options) for
          the adjoint forward modeling program (no default).

     -V   Enter the command line argument '-V' to obtain  verbose
          output.

     -?   Enter the command line  argument  '-?'  to  get  online
          help.   The program terminates after the help screen is
          printed.

     NOTE1 : The program does system calls to  the  folowing  usp
     programs:  mrgrad,  vstak, vmult, linear, linear2, lnorm and
     putzero.

     NOTE2 : The program assumes that the input and output  files
     of both forward and adjoint program are real values.

BUGS

     No bugs known at present.

REFERENCES

     Duquet, B., 1996, Improvement of seismic imaging of  complex
     geologic structures: Ph.D. Thesis, Univ. of Paris XIII.

CONTRACT AGREEMENT

     This product is brought to you as a 4th quarter  deliverable
     (filtering  of  coherent  noise  in  the  depth  domain)  by
     Research Agreement D96-2518 (Seismic Signal Analysis). Thank
     you for your support.

AUTHORS

     Bertrand Duquet, Amoco EPTG, 1997.

COPYRIGHT

     copyright 2001, Amoco Production Company
               All Rights Reserved
          an affiliate of BP America Inc.