anchor.diff:  
   stdenv.mkDerivation rec {
     name = "simgrid-${version}";
  -  version = "3.19.1";
  +  version = "3.20";
   
     src = fetchFromGitHub {
       owner = "simgrid";
       repo = "simgrid";
       rev = "v${version}";
  -    sha256 = "0vpgcp40xv20hcpslx5wz2mf2phaq41f7x8yr0bm7mknqd3zwxih";
  +    sha256 = "0xb20qhvsah2dz2hvn850i3w9a5ghsbcx8vka2ap6xsdkxf593gy";
     };
   
  -  nativeBuildInputs = [ cmake perl elfutils python3 boost valgrind ]
  +  nativeBuildInputs = [ cmake perl python3 boost valgrind ]
         ++ optionals fortranSupport [ gfortran ]
         ++ optionals buildJavaBindings [ openjdk ]
         ++ optionals buildDocumentation [ transfig ghostscript doxygen ]
  -      ++ optionals modelCheckingSupport [ libunwind libevent ];
  +      ++ optionals modelCheckingSupport [ libunwind libevent elfutils ];
   
     #buildInputs = optional luaSupport lua5;
   
  
positive.code: { stdenv, fetchFromGitHub, cmake, elfutils, perl, python3, boost, valgrind
  # Optional requirements
  # Lua 5.3 needed and not available now
  #, luaSupport ? false, lua5
  , fortranSupport ? false, gfortran
  , buildDocumentation ? false, transfig, ghostscript, doxygen
  , buildJavaBindings ? false, openjdk
  , modelCheckingSupport ? false, libunwind, libevent # Inside elfutils - , libelf, libevent, libdw
  , debug ? false
  , moreTests ? false
  }:
  
negative.code:   '';
  
    doCheck = true;
  
    checkPhase = ''
      runHook preCheck
  
      ctest -j $NIX_BUILD_CORES --output-on-failure -E smpi-replay-multiple
  
      runHook postCheck
    '';
  
    enableParallelBuilding = true;
  
    meta = {
  