[src/Pythia.cxx at Athena 9.0.3]
***** hard code as below
  m_msel=6;
  this->pysubs().msel() = m_msel;
  //  this->pysubs().ckin(3)=20.;
  //  this->pypars().mstp(43)=2;
  this->pydat2().pmas(6,1)=175.; // top quark mass
  // new set up some ATLAS default parameters.
  // this is change for version 6.203. 
  this->pypars().mstp(2)=1; // order of alpha_s; cdf uses 2
  this->pypars().mstp(33) =0; // no k factors, cdf uses 2 here!!
  this->pypars().mstp(128)=2; //fix junk output for documentary particles
  this->pypars().mstp(82) =4; //  multiple interactions on with varying impact param
  //  this->pypars().parp(82) =1.; // changed from default of 1.55. Use default with 6.203
  this->pydat1().mstj(11) =3; // non-standard b-quark fragementation
  ///  this->pydat1().mstj(27) =1; 
  this->pydat1().parj(55) =-0.006; // fragemention parameter f 

***** To Default setting (Manual 6.2, hep-ph/0108264)
"pysubs msel 1",
"pydat2 pmas 6 1 175.",
"pypars mstp 2 1",
"pypars mstp 33 0",
"pypars mstp 128 0",
"pypars mstp 82 1",
"pydat1 mstj 11 4",
"pydat1 parj 55 -0.005",

[Sample]
Pythia = Algorithm( "Pythia" )
Pythia.PythiaCommand = [ "pyinit pylisti 12",
                         "pyinit pylistf 1",
                         "pyinit dumpr 1 5",
                         "pystat 1 3 4 5",
                         "pypars mstp 128 0",
                         "pypars mstp 51 7", // CTEQ5L
                         "pypars mstp 52 1", // CTEQ5L
                         "pysubs ckin 1 2.", // allowed m^hat=sqrt(s)
                         "pysubs ckin 3 0.", // allowed pt
                         "pydat3 mdcy 15 1 0", --> for Tauola
                         "pydat1 mstj 41 1" ]  --> for Photos
Tauola = Algorithm( "Tauola" )
Tauola.TauolaCommand = [ "tauola polar 1",
                         "tauola radcor 1",
                         "tauola phox 0.01",
                         "tauola dmode 0",
                         "tauola jak1 0",
                         "tauola jak2 0" ]
Photos = Algorithm( "Photos" )
Photos.PhotosCommand = [ "photos pmode 1", --> this is "1"
                         "photos xphcut 0.01",
                         "photos alpha -1.",
                         "photos interf 1",
                         "photos isec 1",
                         "photos iftop 0" ]

[photos pmode]
photos pmode 1 - enable radiation of photons for leptons and hadrons
photos pmode 2 - enable radiation of photons for tau-leptons only
photos pmode 3 - enable radiation of photons for leptons only
(http://phyweb.lbl.gov/%7Eianh/monte/Generators/Photos/node5.html)

[note]
By setting "pydat1 mstj 22 2", Ks does not decay.