mpi: use mpi attribute consistently as the default MPI implementations

Use the attribute mpi to provide a system wide default MPI
implementation. The default is openmpi (as before).
This now allows for overriding the MPI implentation by using
the overlay mechanism. Build all packages with mpich instead
of the default openmpi can now be achived like this:
self: super:
 {
   mpi = super.mpich;
 }

All derivations that have been using "mpi ? null" to provide optional
building with MPI have been change in the following way to allow for
optional builds with MPI:
{ ...
, mpi
, useMpi ? false
}

pkgs/applications/graphics/paraview/default.nix

@@ -1,6 +1,6 @@
 { boost, cmake, fetchFromGitHub, ffmpeg, qtbase, qtx11extras,
   qttools, qtxmlpatterns, qtsvg, gdal, gfortran, libXt, makeWrapper,
-  mkDerivation, ninja, openmpi, python3, lib, stdenv, tbb, libGLU, libGL }:
+  mkDerivation, ninja, mpi, python3, lib, stdenv, tbb, libGLU, libGL }:
 
 mkDerivation rec {
   pname = "paraview";
@@ -65,7 +65,7 @@ mkDerivation rec {
   buildInputs = [
     libGLU libGL
     libXt
-    openmpi
+    mpi
     tbb
     boost
     ffmpeg

pkgs/applications/science/biology/migrate/default.nix

@@ -1,4 +1,4 @@
-{ gccStdenv, fetchurl, zlib, openmpi }:
+{ gccStdenv, fetchurl, zlib, mpi }:
 
 gccStdenv.mkDerivation rec {
   version = "3.7.2";
@@ -9,7 +9,7 @@ gccStdenv.mkDerivation rec {
     sha256 = "1p2364ffjc56i82snzvjpy6pkf6wvqwvlvlqxliscx2c303fxs8v";
   };
 
-  buildInputs = [ zlib openmpi ];
+  buildInputs = [ zlib mpi ];
   setSourceRoot = ''sourceRoot=$(echo */src)'';
   buildFlags = [ "thread" "mpis" ];
   preInstall = "mkdir -p $out/man/man1";

pkgs/applications/science/biology/neuron/default.nix

@@ -8,7 +8,8 @@
 , readline
 , which
 , python ? null
-, mpi ? null
+, useMpi ? false
+, mpi
 , iv
 }:
 
@@ -17,7 +18,8 @@ stdenv.mkDerivation rec {
   version = "7.5";
 
   nativeBuildInputs = [ which pkg-config automake autoconf libtool ];
-  buildInputs = [ ncurses readline python mpi iv ];
+  buildInputs = [ ncurses readline python iv ]
+    ++ lib.optional useMpi mpi;
 
   src = fetchurl {
     url = "https://www.neuron.yale.edu/ftp/neuron/versions/v${version}/nrn-${version}.tar.gz";
@@ -54,7 +56,7 @@ stdenv.mkDerivation rec {
   configureFlags = with lib;
                     [ "--with-readline=${readline}" "--with-iv=${iv}" ]
                     ++  optionals (python != null)  [ "--with-nrnpython=${python.interpreter}" ]
-                    ++ (if mpi != null then ["--with-mpi" "--with-paranrn"]
+                    ++ (if useMpi then ["--with-mpi" "--with-paranrn"]
                         else ["--without-mpi"]);
 
 
@@ -84,4 +86,3 @@ stdenv.mkDerivation rec {
     platforms   = platforms.x86_64 ++ platforms.i686;
   };
 }
-

pkgs/applications/science/biology/raxml/default.nix

@@ -1,7 +1,7 @@
 { lib, stdenv
 , fetchFromGitHub
-, pkgs
-, mpi ? false
+, useMpi ? false
+, mpi
 }:
 
 stdenv.mkDerivation rec {
@@ -15,16 +15,16 @@ stdenv.mkDerivation rec {
     sha256 = "1jqjzhch0rips0vp04prvb8vmc20c5pdmsqn8knadcf91yy859fh";
   };
 
-  buildInputs = lib.optionals mpi [ pkgs.openmpi ];
+  buildInputs = lib.optionals useMpi [ mpi ];
 
   # TODO darwin, AVX and AVX2 makefile targets
-  buildPhase = if mpi then ''
+  buildPhase = if useMpi then ''
       make -f Makefile.MPI.gcc
     '' else ''
       make -f Makefile.SSE3.PTHREADS.gcc
     '';
 
-  installPhase = if mpi then ''
+  installPhase = if useMpi then ''
     mkdir -p $out/bin && cp raxmlHPC-MPI $out/bin
   '' else ''
     mkdir -p $out/bin && cp raxmlHPC-PTHREADS-SSE3 $out/bin

pkgs/applications/science/chemistry/openmolcas/default.nix

@@ -1,6 +1,6 @@
 { lib, stdenv, fetchFromGitLab, cmake, gfortran, perl
 , openblas, hdf5-cpp, python3, texlive
-, armadillo, openmpi, globalarrays, openssh
+, armadillo, mpi, globalarrays, openssh
 , makeWrapper, fetchpatch
 } :
 
@@ -33,7 +33,7 @@ in stdenv.mkDerivation {
     hdf5-cpp
     python
     armadillo
-    openmpi
+    mpi
     globalarrays
     openssh
   ];

pkgs/applications/science/chemistry/quantum-espresso/default.nix

@@ -1,6 +1,7 @@
 { lib, stdenv, fetchurl
 , gfortran, fftw, blas, lapack
-, mpi ? null
+, useMpi ? false
+, mpi
 }:
 
 stdenv.mkDerivation rec {
@@ -21,9 +22,9 @@ stdenv.mkDerivation rec {
   '';
 
   buildInputs = [ fftw blas lapack gfortran ]
-    ++ (lib.optionals (mpi != null) [ mpi ]);
+    ++ (lib.optionals useMpi [ mpi ]);
 
-configureFlags = if (mpi != null) then [ "LD=${mpi}/bin/mpif90" ] else [ "LD=${gfortran}/bin/gfortran" ];
+configureFlags = if useMpi then [ "LD=${mpi}/bin/mpif90" ] else [ "LD=${gfortran}/bin/gfortran" ];
 
   makeFlags = [ "all" ];
 

pkgs/applications/science/chemistry/siesta/default.nix

@@ -1,6 +1,7 @@
 { lib, stdenv, fetchurl
-, gfortran, blas, lapack
-, mpi ? null, scalapack
+, gfortran, blas, lapack, scalapack
+, useMpi ? false
+, mpi
 }:
 
 stdenv.mkDerivation {
@@ -17,7 +18,7 @@ stdenv.mkDerivation {
   };
 
   buildInputs = [ blas lapack gfortran ]
-    ++ (lib.optionals (mpi != null) [ mpi scalapack ]);
+    ++ lib.optionals useMpi [ mpi scalapack ];
 
   enableParallelBuilding = true;
 
@@ -29,7 +30,7 @@ stdenv.mkDerivation {
     cp gfortran.make arch.make
   '';
 
-  preBuild = if (mpi != null) then ''
+  preBuild = if useMpi then ''
     makeFlagsArray=(
         CC="mpicc" FC="mpifort"
         FPPFLAGS="-DMPI" MPI_INTERFACE="libmpi_f90.a" MPI_INCLUDE="."

pkgs/applications/science/electronics/openems/default.nix

@@ -11,16 +11,15 @@
 , cmake
 , octave
 , gl2ps
+, mpi
 , withQcsxcad ? true
 , withMPI ? false
 , withHyp2mat ? true
 , qcsxcad ? null
-, openmpi ? null
 , hyp2mat ? null
 }:
 
 assert withQcsxcad -> qcsxcad != null;
-assert withMPI -> openmpi != null;
 assert withHyp2mat -> hyp2mat != null;
 
 stdenv.mkDerivation {
@@ -50,7 +49,7 @@ stdenv.mkDerivation {
     csxcad
     (octave.override { inherit hdf5; }) ]
     ++ lib.optionals withQcsxcad [ qcsxcad ]
-    ++ lib.optionals withMPI [ openmpi ]
+    ++ lib.optionals withMPI [ mpi ]
     ++ lib.optionals withHyp2mat [ hyp2mat ];
 
   postFixup = ''

pkgs/applications/science/math/cntk/default.nix

@@ -1,5 +1,5 @@
 { lib, stdenv, fetchgit, fetchFromGitHub, cmake
-, openblas, blas, lapack, opencv3, libzip, boost, protobuf, openmpi
+, openblas, blas, lapack, opencv3, libzip, boost, protobuf, mpi
 , onebitSGDSupport ? false
 , cudaSupport ? false, addOpenGLRunpath, cudatoolkit, nvidia_x11
 , cudnnSupport ? cudaSupport, cudnn
@@ -33,7 +33,7 @@ in stdenv.mkDerivation rec {
   # Force OpenMPI to use g++ in PATH.
   OMPI_CXX = "g++";
 
-  buildInputs = [ openblas opencv3 libzip boost protobuf openmpi ]
+  buildInputs = [ openblas opencv3 libzip boost protobuf mpi ]
              ++ lib.optional cudaSupport cudatoolkit
              ++ lib.optional cudnnSupport cudnn;
 
@@ -43,7 +43,7 @@ in stdenv.mkDerivation rec {
     "--with-openblas=${openblas}"
     "--with-boost=${boost.dev}"
     "--with-protobuf=${protobuf}"
-    "--with-mpi=${openmpi}"
+    "--with-mpi=${mpi}"
     "--cuda=${if cudaSupport then "yes" else "no"}"
     # FIXME
     "--asgd=no"

pkgs/applications/science/math/getdp/default.nix

@@ -1,4 +1,4 @@
-{ lib, stdenv, fetchurl, cmake, gfortran, blas, lapack, openmpi, petsc, python3 }:
+{ lib, stdenv, fetchurl, cmake, gfortran, blas, lapack, mpi, petsc, python3 }:
 
 stdenv.mkDerivation rec {
   name = "getdp-${version}";
@@ -9,7 +9,7 @@ stdenv.mkDerivation rec {
   };
 
   nativeBuildInputs = [ cmake gfortran ];
-  buildInputs = [ blas lapack openmpi petsc python3 ];
+  buildInputs = [ blas lapack mpi petsc python3 ];
 
   meta = with lib; {
     description = "A General Environment for the Treatment of Discrete Problems";

pkgs/applications/science/math/scotch/default.nix

@@ -1,11 +1,11 @@
-{ lib, stdenv, fetchurl, bison, openmpi, flex, zlib}:
+{ lib, stdenv, fetchurl, bison, mpi, flex, zlib}:
 
 stdenv.mkDerivation rec {
   version = "6.0.4";
   pname = "scotch";
   src_name = "scotch_${version}";
 
-  buildInputs = [ bison openmpi flex zlib ];
+  buildInputs = [ bison mpi flex zlib ];
 
   src = fetchurl {
     url = "https://gforge.inria.fr/frs/download.php/file/34618/${src_name}.tar.gz";

pkgs/applications/science/molecular-dynamics/gromacs/default.nix

@@ -3,10 +3,10 @@
 , cmake
 , hwloc
 , fftw
-, openmpi
 , perl
 , singlePrec ? true
 , mpiEnabled ? false
+, mpi
 , cpuAcceleration ? null
 }:
 
@@ -33,7 +33,7 @@ in stdenv.mkDerivation rec {
 
   nativeBuildInputs = [ cmake ];
   buildInputs = [ fftw perl hwloc ]
-  ++ (lib.optionals mpiEnabled [ openmpi ]);
+  ++ (lib.optionals mpiEnabled [ mpi ]);
 
   cmakeFlags = [
     "-DGMX_SIMD:STRING=${SIMD cpuAcceleration}"

pkgs/applications/science/molecular-dynamics/lammps/default.nix

@@ -1,6 +1,7 @@
 { lib, stdenv, fetchFromGitHub
 , libpng, gzip, fftw, blas, lapack
-, mpi ? null
+, withMPI ? false
+, mpi
 }:
 let packages = [
      "asphere" "body" "class2" "colloid" "compress" "coreshell"
@@ -8,7 +9,6 @@ let packages = [
      "opt" "peri" "qeq" "replica" "rigid" "shock" "snap" "srd" "user-reaxc"
     ];
     lammps_includes = "-DLAMMPS_EXCEPTIONS -DLAMMPS_GZIP -DLAMMPS_MEMALIGN=64";
-    withMPI = (mpi != null);
 in
 stdenv.mkDerivation rec {
   # LAMMPS has weird versioning converted to ISO 8601 format

pkgs/applications/science/physics/elmerfem/default.nix

@@ -1,4 +1,4 @@
-{ lib, stdenv, fetchFromGitHub, cmake, git, gfortran, openmpi, blas, liblapack, qt4, qwt6_qt4, pkg-config }:
+{ lib, stdenv, fetchFromGitHub, cmake, git, gfortran, mpi, blas, liblapack, qt4, qwt6_qt4, pkg-config }:
 
 stdenv.mkDerivation rec {
   pname = "elmerfem";
@@ -14,7 +14,7 @@ stdenv.mkDerivation rec {
   hardeningDisable = [ "format" ];
 
   nativeBuildInputs = [ cmake pkg-config git ];
-  buildInputs = [ gfortran openmpi blas liblapack qt4 qwt6_qt4 ];
+  buildInputs = [ gfortran mpi blas liblapack qt4 qwt6_qt4 ];
 
   preConfigure = ''
     patchShebangs ./

pkgs/development/libraries/boost/generic.nix

@@ -14,7 +14,8 @@
 , enableNumpy ? false
 , taggedLayout ? ((enableRelease && enableDebug) || (enableSingleThreaded && enableMultiThreaded) || (enableShared && enableStatic))
 , patches ? []
-, mpi ? null
+, useMpi ? false
+, mpi
 , extraB2Args ? []
 
 # Attributes inherit from specific versions
@@ -94,7 +95,7 @@ let
     ++ optional (variant == "release") "debug-symbols=off"
     ++ optional (toolset != null) "toolset=${toolset}"
     ++ optional (!enablePython) "--without-python"
-    ++ optional (mpi != null || stdenv.hostPlatform != stdenv.buildPlatform) "--user-config=user-config.jam"
+    ++ optional (useMpi || stdenv.hostPlatform != stdenv.buildPlatform) "--user-config=user-config.jam"
     ++ optionals (stdenv.hostPlatform.libc == "msvcrt") [
     "threadapi=win32"
   ] ++ extraB2Args
@@ -140,7 +141,7 @@ stdenv.mkDerivation {
         substituteInPlace tools/build/src/tools/clang-darwin.jam \
           --replace '@rpath/$(<[1]:D=)' "$out/lib/\$(<[1]:D=)";
     fi;
-  '' + optionalString (mpi != null) ''
+  '' + optionalString useMpi ''
     cat << EOF >> user-config.jam
     using mpi : ${mpi}/bin/mpiCC ;
     EOF

pkgs/development/libraries/globalarrays/default.nix

@@ -1,5 +1,5 @@
 { lib, stdenv, fetchpatch, fetchFromGitHub, autoreconfHook
-, blas, gfortran, openssh, openmpi
+, blas, gfortran, openssh, mpi
 } :
 
 let
@@ -17,7 +17,7 @@ in stdenv.mkDerivation {
   };
 
   nativeBuildInputs = [ autoreconfHook ];
-  buildInputs = [ openmpi blas gfortran openssh ];
+  buildInputs = [ mpi blas gfortran openssh ];
 
   preConfigure = ''
     configureFlagsArray+=( "--enable-i8" \

pkgs/development/libraries/precice/default.nix

@@ -1,4 +1,4 @@
-{ lib, stdenv, fetchFromGitHub, cmake, gcc, boost, eigen, libxml2, openmpi, python3, petsc }:
+{ lib, stdenv, fetchFromGitHub, cmake, gcc, boost, eigen, libxml2, mpi, python3, petsc }:
 
 stdenv.mkDerivation rec {
   pname = "precice";
@@ -21,7 +21,7 @@ stdenv.mkDerivation rec {
   NIX_CFLAGS_COMPILE = lib.optional stdenv.isDarwin [ "-D_GNU_SOURCE" ];
 
   nativeBuildInputs = [ cmake gcc ];
-  buildInputs = [ boost eigen libxml2 openmpi python3 python3.pkgs.numpy ];
+  buildInputs = [ boost eigen libxml2 mpi python3 python3.pkgs.numpy ];
 
   meta = {
     description = "preCICE stands for Precise Code Interaction Coupling Environment";

pkgs/development/python-modules/cntk/default.nix

@@ -3,7 +3,7 @@
 , pkgs
 , numpy
 , scipy
-, openmpi
+, mpi
 , enum34
 , protobuf
 , pip
@@ -17,8 +17,8 @@ in
 buildPythonPackage {
   inherit (cntk) name version src;
 
-  nativeBuildInputs = [ swig openmpi ];
-  buildInputs = [ cntk openmpi ];
+  nativeBuildInputs = [ swig mpi ];
+  buildInputs = [ cntk mpi ];
   propagatedBuildInputs = [ numpy scipy enum34 protobuf pip ];
 
   CNTK_LIB_PATH = "${cntk}/lib";
@@ -28,7 +28,7 @@ buildPythonPackage {
 
   postPatch = ''
     cd bindings/python
-    sed -i 's,"libmpi.so.12","${openmpi}/lib/libmpi.so",g' cntk/train/distributed.py
+    sed -i 's,"libmpi.so.12","${mpi}/lib/libmpi.so",g' cntk/train/distributed.py
 
     # Remove distro and libs checks; they aren't compatible with NixOS and besides we guarantee
     # compatibility by providing a package.

pkgs/development/python-modules/pytorch/default.nix

@@ -1,7 +1,7 @@
 { stdenv, lib, fetchFromGitHub, fetchpatch, buildPythonPackage, python,
   cudaSupport ? false, cudatoolkit ? null, cudnn ? null, nccl ? null, magma ? null,
   mklDnnSupport ? true, useSystemNccl ? true,
-  openMPISupport ? false, openmpi ? null,
+  MPISupport ? false, mpi,
   buildDocs ? false,
   cudaArchList ? null,
 
@@ -29,8 +29,6 @@
 
   isPy3k, pythonOlder }:
 
-assert !openMPISupport || openmpi != null;
-
 # assert that everything needed for cuda is present and that the correct cuda versions are used
 assert !cudaSupport || cudatoolkit != null;
 assert cudnn == null || cudatoolkit != null;
@@ -38,7 +36,7 @@ assert !cudaSupport || (let majorIs = lib.versions.major cudatoolkit.version;
                         in majorIs == "9" || majorIs == "10" || majorIs == "11");
 
 # confirm that cudatoolkits are sync'd across dependencies
-assert !(openMPISupport && cudaSupport) || openmpi.cudatoolkit == cudatoolkit;
+assert !(MPISupport && cudaSupport) || mpi.cudatoolkit == cudatoolkit;
 assert !cudaSupport || magma.cudatoolkit == cudatoolkit;
 
 let
@@ -224,7 +222,7 @@ in buildPythonPackage rec {
     typing-extensions
     # the following are required for tensorboard support
     pillow six future tensorflow-tensorboard protobuf
-  ] ++ lib.optionals openMPISupport [ openmpi ]
+  ] ++ lib.optionals MPISupport [ mpi ]
     ++ lib.optionals (pythonOlder "3.7") [ dataclasses ];
 
   checkInputs = [ hypothesis ninja psutil ];

pkgs/development/python-modules/tensorflow/default.nix

@@ -11,7 +11,7 @@
 # Common deps
 , git, pybind11, which, binutils, glibcLocales, cython, perl
 # Common libraries
-, jemalloc, openmpi, gast, grpc, sqlite, boringssl, jsoncpp
+, jemalloc, mpi, gast, grpc, sqlite, boringssl, jsoncpp
 , curl, snappy, flatbuffers-core, lmdb-core, icu, double-conversion, libpng, libjpeg_turbo, giflib
 # Upsteam by default includes cuda support since tensorflow 1.15. We could do
 # that in nix as well. It would make some things easier and less confusing, but
@@ -129,7 +129,7 @@ let
 
     buildInputs = [
       jemalloc
-      openmpi
+      mpi
       glibcLocales
       git
 

pkgs/development/r-modules/default.nix

@@ -237,7 +237,7 @@ let
     BayesSAE = [ pkgs.gsl_1 ];
     BayesVarSel = [ pkgs.gsl_1 ];
     BayesXsrc = [ pkgs.readline.dev pkgs.ncurses ];
-    bigGP = [ pkgs.openmpi ];
+    bigGP = [ pkgs.mpi ];
     bio3d = [ pkgs.zlib ];
     BiocCheck = [ pkgs.which ];
     Biostrings = [ pkgs.zlib ];
@@ -284,8 +284,8 @@ let
     n1qn1 = [ pkgs.gfortran ];
     odbc = [ pkgs.unixODBC ];
     pander = [ pkgs.pandoc pkgs.which ];
-    pbdMPI = [ pkgs.openmpi ];
-    pbdPROF = [ pkgs.openmpi ];
+    pbdMPI = [ pkgs.mpi ];
+    pbdPROF = [ pkgs.mpi ];
     pbdZMQ = lib.optionals stdenv.isDarwin [ pkgs.which ];
     pdftools = [ pkgs.poppler.dev ];
     phytools = [ pkgs.which ];
@@ -309,14 +309,14 @@ let
     RGtk2 = [ pkgs.gtk2.dev ];
     rhdf5 = [ pkgs.zlib ];
     Rhdf5lib = [ pkgs.zlib ];
-    Rhpc = [ pkgs.zlib pkgs.bzip2.dev pkgs.icu pkgs.lzma.dev pkgs.openmpi pkgs.pcre.dev ];
+    Rhpc = [ pkgs.zlib pkgs.bzip2.dev pkgs.icu pkgs.lzma.dev pkgs.mpi pkgs.pcre.dev ];
     Rhtslib = [ pkgs.zlib.dev pkgs.automake pkgs.autoconf pkgs.bzip2.dev pkgs.lzma.dev pkgs.curl.dev ];
     rjags = [ pkgs.jags ];
     rJava = [ pkgs.zlib pkgs.bzip2.dev pkgs.icu pkgs.lzma.dev pkgs.pcre.dev pkgs.jdk pkgs.libzip ];
     Rlibeemd = [ pkgs.gsl_1 ];
     rmatio = [ pkgs.zlib.dev ];
     Rmpfr = [ pkgs.gmp pkgs.mpfr.dev ];
-    Rmpi = [ pkgs.openmpi ];
+    Rmpi = [ pkgs.mpi ];
     RMySQL = [ pkgs.zlib pkgs.libmysqlclient pkgs.openssl.dev ];
     RNetCDF = [ pkgs.netcdf pkgs.udunits ];
     RODBC = [ pkgs.libiodbc ];

pkgs/development/tools/poetry2nix/poetry2nix/overrides.nix

@@ -245,7 +245,7 @@ self: super:
 
   horovod = super.horovod.overridePythonAttrs (
     old: {
-      propagatedBuildInputs = old.propagatedBuildInputs ++ [ pkgs.openmpi ];
+      propagatedBuildInputs = old.propagatedBuildInputs ++ [ pkgs.mpi ];
     }
   );
 
@@ -528,14 +528,14 @@ self: super:
             { }
             {
               mpi = {
-                mpicc = "${pkgs.openmpi.outPath}/bin/mpicc";
+                mpicc = "${pkgs.mpi.outPath}/bin/mpicc";
               };
             }
         );
       };
     in
     {
-      propagatedBuildInputs = old.propagatedBuildInputs ++ [ pkgs.openmpi ];
+      propagatedBuildInputs = old.propagatedBuildInputs ++ [ pkgs.mpi ];
       enableParallelBuilding = true;
       preBuild = ''
         ln -sf ${cfg} mpi.cfg

pkgs/tools/misc/hdf5/default.nix

@@ -5,13 +5,14 @@
 , gfortran ? null
 , zlib ? null
 , szip ? null
-, mpi ? null
+, mpiSupport ? false
+, mpi
 , enableShared ? !stdenv.hostPlatform.isStatic
 }:
 
 # cpp and mpi options are mutually exclusive
 # (--enable-unsupported could be used to force the build)
-assert !cpp || mpi == null;
+assert !cpp || !mpiSupport;
 
 let inherit (lib) optional optionals; in
 
@@ -24,7 +25,7 @@ stdenv.mkDerivation rec {
   };
 
   passthru = {
-    mpiSupport = (mpi != null);
+    inherit mpiSupport;
     inherit mpi;
   };
 
@@ -38,13 +39,13 @@ stdenv.mkDerivation rec {
 
   propagatedBuildInputs = []
     ++ optional (zlib != null) zlib
-    ++ optional (mpi != null) mpi;
+    ++ optional mpiSupport mpi;
 
   configureFlags = []
     ++ optional cpp "--enable-cxx"
     ++ optional (gfortran != null) "--enable-fortran"
     ++ optional (szip != null) "--with-szlib=${szip}"
-    ++ optionals (mpi != null) ["--enable-parallel" "CC=${mpi}/bin/mpicc"]
+    ++ optionals mpiSupport ["--enable-parallel" "CC=${mpi}/bin/mpicc"]
     ++ optional enableShared "--enable-shared";
 
   patches = [

pkgs/tools/misc/hpcg/default.nix

@@ -1,4 +1,4 @@
-{ lib, stdenv, fetchurl, openmpi } :
+{ lib, stdenv, fetchurl, mpi } :
 
 stdenv.mkDerivation rec {
   pname = "hpcg";
@@ -13,7 +13,7 @@ stdenv.mkDerivation rec {
 
   enableParallelBuilding = true;
 
-  buildInputs = [ openmpi ];
+  buildInputs = [ mpi ];
 
   makeFlags = [ "arch=Linux_MPI" ];
 

pkgs/tools/system/ior/default.nix

@@ -1,4 +1,4 @@
-{ lib, stdenv, fetchFromGitHub, openmpi, perl, autoreconfHook }:
+{ lib, stdenv, fetchFromGitHub, mpi, perl, autoreconfHook }:
 
 stdenv.mkDerivation rec {
   pname = "ior";
@@ -12,7 +12,7 @@ stdenv.mkDerivation rec {
   };
 
   nativeBuildInputs = [ autoreconfHook ];
-  buildInputs = [ openmpi perl ];
+  buildInputs = [ mpi perl ];
 
   enableParallelBuilding = true;
 

pkgs/top-level/all-packages.nix

@@ -4975,12 +4975,11 @@ in
   hdf5 = callPackage ../tools/misc/hdf5 {
     gfortran = null;
     szip = null;
-    mpi = null;
   };
 
   hdf5-mpi = appendToName "mpi" (hdf5.override {
     szip = null;
-    mpi = pkgs.openmpi;
+    mpiSupport = true;
   });
 
   hdf5-cpp = appendToName "cpp" (hdf5.override {
@@ -7216,6 +7215,8 @@ in
 
   openmpi = callPackage ../development/libraries/openmpi { };
 
+  mpi = openmpi; # this attribute should used to build MPI applications
+
   ucx = callPackage ../development/libraries/ucx {};
 
   openmodelica = callPackage ../applications/science/misc/openmodelica {
@@ -22092,9 +22093,7 @@ in
 
   fractal = callPackage ../applications/networking/instant-messengers/fractal { };
 
-  freecad = libsForQt5.callPackage ../applications/graphics/freecad {
-    mpi = openmpi;
-  };
+  freecad = libsForQt5.callPackage ../applications/graphics/freecad { };
 
   freemind = callPackage ../applications/misc/freemind {
     jdk = jdk8; # TODO: remove override https://github.com/NixOS/nixpkgs/pull/89731
@@ -22480,7 +22479,7 @@ in
 
   hpcg = callPackage ../tools/misc/hpcg/default.nix { };
 
-  hpl = callPackage ../tools/misc/hpl { mpi = openmpi; };
+  hpl = callPackage ../tools/misc/hpl { };
 
   hpmyroom = libsForQt5.callPackage ../applications/networking/hpmyroom { };
 
@@ -27254,15 +27253,11 @@ in
 
   quantum-espresso = callPackage ../applications/science/chemistry/quantum-espresso { };
 
-  quantum-espresso-mpi = callPackage ../applications/science/chemistry/quantum-espresso {
-     mpi = openmpi;
-  };
+  quantum-espresso-mpi = callPackage ../applications/science/chemistry/quantum-espresso { useMpi = true; };
 
   siesta = callPackage ../applications/science/chemistry/siesta { };
 
-  siesta-mpi = callPackage ../applications/science/chemistry/siesta {
-     mpi = openmpi;
-  };
+  siesta-mpi = callPackage ../applications/science/chemistry/siesta { useMpi = true; };
 
   ### SCIENCE/GEOMETRY
 
@@ -27393,7 +27388,7 @@ in
   };
 
   neuron-mpi = appendToName "mpi" (neuron.override {
-    mpi = pkgs.openmpi;
+    useMpi = true;
   });
 
   neuron-full = neuron-mpi.override { inherit python; };
@@ -27445,7 +27440,7 @@ in
   raxml = callPackage ../applications/science/biology/raxml { };
 
   raxml-mpi = appendToName "mpi" (raxml.override {
-    mpi = true;
+    useMpi = true;
   });
 
   sambamba = callPackage ../applications/science/biology/sambamba { };
@@ -27567,9 +27562,7 @@ in
 
   planarity = callPackage ../development/libraries/science/math/planarity { };
 
-  scalapack = callPackage ../development/libraries/science/math/scalapack {
-    mpi = openmpi;
-  };
+  scalapack = callPackage ../development/libraries/science/math/scalapack { };
 
   rankwidth = callPackage ../development/libraries/science/math/rankwidth { };
 
@@ -27599,9 +27592,7 @@ in
 
   petsc = callPackage ../development/libraries/science/math/petsc { };
 
-  parmetis = callPackage ../development/libraries/science/math/parmetis {
-    mpi = openmpi;
-  };
+  parmetis = callPackage ../development/libraries/science/math/parmetis { };
 
   QuadProgpp = callPackage ../development/libraries/science/math/QuadProgpp { };
 
@@ -27631,17 +27622,13 @@ in
 
   ### SCIENCE/MOLECULAR-DYNAMICS
 
-  dl-poly-classic-mpi = callPackage ../applications/science/molecular-dynamics/dl-poly-classic {
-    mpi = openmpi;
-  };
+  dl-poly-classic-mpi = callPackage ../applications/science/molecular-dynamics/dl-poly-classic { };
 
   lammps = callPackage ../applications/science/molecular-dynamics/lammps {
     fftw = fftw;
   };
 
-  lammps-mpi = lowPrio (lammps.override {
-    mpi = openmpi;
-  });
+  lammps-mpi = lowPrio (lammps.override { withMPI = true; });
 
   gromacs = callPackage ../applications/science/molecular-dynamics/gromacs {
     singlePrec = true;

pkgs/top-level/python-packages.nix

@@ -2184,7 +2184,6 @@ in {
 
   fenics = callPackage ../development/libraries/science/math/fenics {
     inherit (pkgs) pkg-config;
-    mpi = pkgs.openmpi;
     pytest = self.pytest_4;
   };
 
@@ -3486,7 +3485,7 @@ in {
 
   labelbox = callPackage ../development/python-modules/labelbox { };
 
-  lammps-cython = callPackage ../development/python-modules/lammps-cython { mpi = pkgs.openmpi; };
+  lammps-cython = callPackage ../development/python-modules/lammps-cython { mpi = pkgs.mpi; };
 
   langcodes = callPackage ../development/python-modules/langcodes { };
 
@@ -4120,7 +4119,7 @@ in {
 
   mpd = callPackage ../development/python-modules/mpd { };
 
-  mpi4py = callPackage ../development/python-modules/mpi4py { mpi = pkgs.openmpi; };
+  mpi4py = callPackage ../development/python-modules/mpi4py { mpi = pkgs.mpi; };
 
   mplleaflet = callPackage ../development/python-modules/mplleaflet { };