anchor.diff: -{ stdenv
  -, fetchurl
  -, blas
  -, gfortran
  -, liblapack
  -, python }:
  +{ stdenv , fetchurl , blas , gfortran , liblapack , python }:
   
   stdenv.mkDerivation rec {
     pname = "petsc";
  -  version = "3.8.4";
  +  version = "3.12.4";
   
     src = fetchurl {
       url = "http://ftp.mcs.anl.gov/pub/petsc/release-snapshots/petsc-${version}.tar.gz";
  -    sha256 = "1iy49gagxncx09d88kxnwkj876p35683mpfk33x37165si6xqy4z";
  +    sha256 = "1hw4f12v2xwrs37gjh83dbixhg0yxandqx7s7k5vlfx91l9l3aan";
     };
   
     nativeBuildInputs = [ blas gfortran.cc.lib liblapack python ];
  
positive.code:     configureFlagsArray=(
        $configureFlagsArray
        "--CC=$CC"
        "--with-cxx=0"
        "--with-fc=0"
        "--with-mpi=0"
        "--with-blas-lib=[${blas}/lib/libblas.a,${gfortran.cc.lib}/lib/libgfortran.a]"
  
negative.code:     )
    '';
  
    meta = with stdenv.lib; {
      description = ''
        Library of linear algebra algorithms for solving partial differential
        equations
      '';
      homepage = "https://www.mcs.anl.gov/petsc/index.html";
      license = licenses.bsd2;
      maintainers = with maintainers; [ wucke13 ];
      platforms = platforms.all;
    };
  }
  