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documentation.suse.com / High Performance Computing Guide / Spack package management tool
Applies to SUSE Linux Enterprise Server 15 SP6

9 Spack package management tool

Spack is a configurable Python-based package manager, automating the installation and fine-tuning of simulations and libraries. Spack can install many variants of the same build using different compilers, options, and MPI implementations. For more information, see the Spack Documentation.

9.1 Installing Spack

Use this procedure to install Spack on any node in the cluster.

Procedure 9.1: Installing and configuring Spack
  1. Install Spack:

    # zypper in spack
  2. Set up your environment with the appropriate script for your shell:

    • For bash/zsh/sh:

      # . /usr/share/spack/setup-env.sh
    • For tcsh/csh:

      # source /usr/share/spack/setup-env.csh
    • For fish:

      # . /usr/share/spack/setup-env.fish
  3. It is recommended to install bash-completion so you can use TAB key auto-completion for Spack commands:

    # zypper in bash-completion
    # spack TAB
    activate      clone         dependencies  fetch         list          providers     solve         url
    add           commands      dependents    find          load          pydoc         spec          verify
    arch          compiler      deprecate     flake9        location      python        stage         versions
    blame         compilers     dev-build     gc            log-parse     reindex       test          view
    buildcache    concretize    develop       gpg           maintainers   remove        test-env
    build-env     config        docs          graph         mark          repo          tutorial
    cd            containerize  edit          help          mirror        resource      undevelop
    checksum      create        env           info          module        restage       uninstall
    ci            deactivate    extensions    install       patch         rm            unit-test
    clean         debug         external      license       pkg           setup         unload

9.2 Using Spack: simple example with netcdf-cxx4

This example procedure shows you different ways to build netcdf-cxx4 with Spack.

Procedure 9.2: Building netcdf-cxx4 with Spack
  1. Show detailed information on netcdf-cxx4:

    # spack info netcdf-cxx4
    AutotoolsPackage:   netcdf-cxx4
    
    Description:
        NetCDF (network Common Data Form) is a set of software libraries and
        machine-independent data formats that support the creation, access, and
        sharing of array-oriented scientific data. This is the C++ distribution.
    
    Homepage: https://www.unidata.ucar.edu/software/netcdf
    
    Maintainers: @WardF
    
    Tags:
        None
    
    Preferred version: 1
        4.3.1    ftp://ftp.unidata.ucar.edu/pub/netcdf/netcdf-cxx4-4.3.1.tar.gz
    
    Safe versions:
        4.3.1    ftp://ftp.unidata.ucar.edu/pub/netcdf/netcdf-cxx4-4.3.1.tar.gz
        4.3.0    ftp://ftp.unidata.ucar.edu/pub/netcdf/netcdf-cxx4-4.3.0.tar.gz
    
    Variants: 2
        Name [Default]    Allowed values    Description
        ==============    ==============    ===================================================
    
        doxygen [on]      on, off           Enable doxygen docs
        pic [on]          on, off           Produce position-independent code (for shared libs)
        shared [on]       on, off           Enable shared library
        static [on]       on, off           Enable building static libraries
    
    Installation Phases:
        autoreconf    configure    build    install
    
    Build Dependencies: 3
        autoconf  automake  doxygen  libtool  m4  netcdf-c
    
    Link Dependencies:
        netcdf-c
    
    Run Dependencies:
        None
    
    Virtual Packages:
        None

    1

    Spack uses the latest version by default, unless you specify otherwise with @VERSION.

    2

    You can disable the variant options using -VARIANT or enable them using +VARIANT.

    3

    The packages required by netcdf-cxx4 must already be built.

  2. Build netcdf-cxx4 with the variants static and doxygen disabled:

    # spack install netcdf-cxx4 -static -doxygen
    ==> netcdf-c: Executing phase: 'autoreconf'
    ==> netcdf-c: Executing phase: 'configure'
    ==> netcdf-c: Executing phase: 'build'
    ==> netcdf-c: Executing phase: 'install'
    [+] /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/netcdf-c-4.7.4-vry3tfp6kpq364gyxrj6fali4kqhirx7
    ==> Installing netcdf-cxx4-4.3.1-msiysdrdua3vv6izluhaeos4nyo5gslq
    ==> No binary for netcdf-cxx4-4.3.1-msiysdrdua3vv6izluhaeos4nyo5gslq found: installing from source
    ==> Fetching https://spack-llnl-mirror.s3-us-west-2.amazonaws.com/_source-cache/archive/6a/6a1189a181eed043b5859e15d5c080c30d0e107406fbb212c8fb9814e90f3445.tar.gz
    #################################################################################################################### 100.0%
    ==> netcdf-cxx4: Executing phase: 'autoreconf'
    ==> netcdf-cxx4: Executing phase: 'configure'
    ==> netcdf-cxx4: Executing phase: 'build'
    ==> netcdf-cxx4: Executing phase: 'install'
    [+] /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/netcdf-cxx4-4.3.1-msiysdrdua3vv6izluhaeos4nyo5gslq
  3. Rebuild netcdf-cxx4 with the default variants, and specify the version:

    # spack install netcdf-cxx4@4.3.1
    ==> Warning: Missing a source id for python@3.6.13
    ==> Warning: Missing a source id for pkgconf@1.5.3
    [+] /usr (external autoconf-2.69-tatq2aqbhboxbyjt2fsraoapgqwf3y5x)
    [+] /usr (external automake-1.15.1-3d7wkh42v52c6n77t4p7l2i7nguryisl)
    [+] /usr (external bison-3.0.4-y6ckc7e7mqnnkgmkbgcfbw5vgqzg5b6m)
    [+] /usr (external cmake-3.17.0-jr4evnjsgd7uh5stt33woclti37743kg)
    [+] /usr (external flex-2.6.4-vea2lhgajmeyjm6ei5d2bqvpss4ipors)
    [+] /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/libiconv-1.16-itovpc5jssshcgpeejrro6l7jn4ynaq7
    [+] /usr (external python-3.6.13-rpf47wa6wfn7h3rnydpxijoczc6opno2)
    [+] /usr (external libtool-2.4.6-ddch2qlie7t4ypbqg6kmf3uswqg2uylp)
    [+] /usr (external m4-1.4.18-tloh56qj47ahddst5g2xqsawffuz5ew6)
    [+] /usr (external pkgconf-1.5.3-gmxadsjg6q3xqwjwws5a4v4b4ugvi6p4)
    [+] /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/util-macros-1.19.1-rpnlbst6v3oqjm7tfoxasmn7wlilpqut
    [+] /usr (external xz-5.2.3-x3glm5yp2ixldbe7n557evglhygvlkqh)
    [+] /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/zlib-1.2.11-z6y74kgd73yc23kr5252slbydmk4posh
    [+] /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/doxygen-1.8.20-3griwieblqgb6ykc5avzkzrxmtaw4s2g
    [+] /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/numactl-2.0.14-tcuvjjtkhnyf5ijrazenjra5h5dbj4in
    [+] /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/libpciaccess-0.16-y3w7dlktz22lmdj6fei4aj2f4t2rqu6l
    [+] /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/libxml2-2.9.10-d4c7cskvhn7qwzzb2wiq7rl67vbl44je
    [+] /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/hwloc-1.11.11-rjdqchtk6i27lqxxwi4cvfyvrxxgwq7k
    [+] /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/openmpi-3.1.6-ks5elgg25bbnzwa7fmv7lewbkrcp2qsx
    [+] /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/hdf5-1.10.7-3cyidn4yvikyyuxehak7ftey2l57ku37
    [+] /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/netcdf-c-4.7.4-vry3tfp6kpq364gyxrj6fali4kqhirx7
    ==> Installing netcdf-cxx4-4.3.1-tiyqyxb3eqpptrlcll6rlf27aisekluy
    ==> No binary for netcdf-cxx4-4.3.1-tiyqyxb3eqpptrlcll6rlf27aisekluy found: installing from source
    ==> Using cached archive: /var/spack/cache/_source-cache/archive/6a/6a1189a181eed043b5859e15d5c080c30d0e107406fbb212c8fb9814e90f3445.tar.gz
    ==> netcdf-cxx4: Executing phase: 'autoreconf'
    ==> netcdf-cxx4: Executing phase: 'configure'
    ==> netcdf-cxx4: Executing phase: 'build'
    ==> netcdf-cxx4: Executing phase: 'install'
    [+] /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/netcdf-cxx4-4.3.1-tiyqyxb3eqpptrlcll6rlf27aisekluy
  4. Check which packages are now available with Spack:

    # spack find
    ==> 14 installed packages
    -- linux-sle_hpc15-skylake / gcc@7.5.0 --------------------------
    doxygen@1.8.20  hwloc@1.11.11  libpciaccess@0.16  netcdf-c@4.7.4     netcdf-cxx4@4.3.1  openmpi@3.1.6       xz@5.2.3
    hdf5@1.10.7     libiconv@1.16  libxml2@2.9.10     netcdf-cxx4@4.3.1  numactl@2.0.14     util-macros@1.19.1  zlib@1.2.11

    In this example, there are now two versions of netcdf-cxx4. All of the build requirements for netcdf-cxx4 are also present. If you want to show dependency hashes as well as versions, use the -l option:

    # spack find -l
    ==> 14 installed packages
    -- linux-sle_hpc15-skylake / gcc@7.5.0 --------------------------
    3griwie doxygen@1.8.20  y3w7dlk libpciaccess@0.16  tiyqyxb netcdf-cxx4@4.3.1   x3glm5y xz@5.2.3
    3cyidn4 hdf5@1.10.7     d4c7csk libxml2@2.9.10     tcuvjjt numactl@2.0.14      z6y74kg zlib@1.2.11
    rjdqcht hwloc@1.11.11   vry3tfp netcdf-c@4.7.4     ks5elgg openmpi@3.1.6
    itovpc5 libiconv@1.16   msiysdr netcdf-cxx4@4.3.1  rpnlbst util-macros@1.19.1
  5. Show the differences between the two versions of netcdf-cxx4:

    1. Find the paths to the netcdf-cxx4 packages:

      # spack find --paths
      ==> 15 installed packages
      -- linux-sle_hpc15-skylake / gcc@7.5.0 --------------------------
      doxygen@1.8.20      /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/doxygen-1.8.20-3griwieblqgb6ykc5avzkzrxmtaw4s2g
      hdf5@1.10.7         /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/hdf5-1.10.7-3cyidn4yvikyyuxehak7ftey2l57ku37
      hwloc@1.11.11       /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/hwloc-1.11.11-rjdqchtk6i27lqxxwi4cvfyvrxxgwq7k
      hwloc@2.2.0         /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/hwloc-2.2.0-4lxxw65tzjeqhyxelowclnwqfb3m3rmk
      libiconv@1.16       /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/libiconv-1.16-itovpc5jssshcgpeejrro6l7jn4ynaq7
      libpciaccess@0.16   /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/libpciaccess-0.16-y3w7dlktz22lmdj6fei4aj2f4t2rqu6l
      libxml2@2.9.10      /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/libxml2-2.9.10-d4c7cskvhn7qwzzb2wiq7rl67vbl44je
      netcdf-c@4.7.4      /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/netcdf-c-4.7.4-vry3tfp6kpq364gyxrj6fali4kqhirx7
      netcdf-cxx4@4.3.1   /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/netcdf-cxx4-4.3.1-msiysdrdua3vv6izluhaeos4nyo5gslq
      netcdf-cxx4@4.3.1   /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/netcdf-cxx4-4.3.1-tiyqyxb3eqpptrlcll6rlf27aisekluy
      numactl@2.0.14      /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/numactl-2.0.14-tcuvjjtkhnyf5ijrazenjra5h5dbj4in
      openmpi@3.1.6       /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/openmpi-3.1.6-ks5elgg25bbnzwa7fmv7lewbkrcp2qsx
      util-macros@1.19.1  /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/util-macros-1.19.1-rpnlbst6v3oqjm7tfoxasmn7wlilpqut
      xz@5.2.3            /usr
      zlib@1.2.11         /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/zlib-1.2.11-z6y74kgd73yc23kr5252slbydmk4posh
    2. Move into the parent directory:

      # cd /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0
    3. Run a diff between each version's spec.yaml file. This file describes how the package was built.

      # diff -ru netcdf-cxx4-4.3.1-msiysdrdua3vv6izluhaeos4nyo5gslq/.spack/spec.yaml netcdf-cxx4-4.3.1-tiyqyxb3eqpptrlcll6rlf27aisekluy/.spack/spec.yaml
      --- netcdf-cxx4-4.3.1-msiysdrdua3vv6izluhaeos4nyo5gslq/.spack/spec.yaml 2021-10-04 11:42:23.444000000 +0200
      +++ netcdf-cxx4-4.3.1-tiyqyxb3eqpptrlcll6rlf27aisekluy/.spack/spec.yaml 2021-10-04 11:51:49.880000000 +0200
      @@ -38,10 +38,10 @@
             version: 7.5.0
           namespace: builtin
           parameters:
      -      doxygen: false
      +      doxygen: true
             pic: true
             shared: true
      -      static: false
      +      static: true
             cflags: []
             cppflags: []
             cxxflags: []
      @@ -54,8 +54,8 @@
               type:
               - build
               - link
      -    hash: msiysdrdua3vv6izluhaeos4nyo5gslq
      -    full_hash: oeylqzvergh3ckviaqyhy3idn7vyk3hi
      +    hash: tiyqyxb3eqpptrlcll6rlf27aisekluy
      +    full_hash: i6btamzuyoo343n63f3rqopkz7ymkapq
       - netcdf-c:
           version: 4.7.4
      arch:

      This example shows that one version of netcdf-cxx4 was built with doxygen and static enabled, and the other version of netcdf-cxx4 was built with doxygen and static disabled.

9.3 Using Spack: complex example with mpich

This example procedure shows you different ways to build mpich with Spack.

Procedure 9.3: Building mpich with Spack
  1. List the available versions of mpich:

    # spack versions mpich
    ==> Safe versions (already checksummed):
      develop  3.3.2  3.3.1  3.3  3.2.1  3.2  3.1.4  3.1.3  3.1.2  3.1.1  3.1  3.0.4
    ==> Remote versions (not yet checksummed):
    ==> Warning: Found no unchecksummed versions for mpich
  2. Show detailed information on mpich:

    # spack info mpich
    AutotoolsPackage:   mpich
    
    Description:
        MPICH is a high performance and widely portable implementation of the
        Message Passing Interface (MPI) standard.
    
    Homepage: http://www.mpich.org
    
    Maintainers: @raffenet @yfguo
    
    Tags:
        None
    
    Preferred version:
        3.3.2      http://www.mpich.org/static/downloads/3.3.2/mpich-3.3.2.tar.gz
    
    Safe versions:
        develop    [git] https://github.com/pmodels/mpich.git
        3.3.2      http://www.mpich.org/static/downloads/3.3.2/mpich-3.3.2.tar.gz
        3.3.1      http://www.mpich.org/static/downloads/3.3.1/mpich-3.3.1.tar.gz
        3.3        http://www.mpich.org/static/downloads/3.3/mpich-3.3.tar.gz
        3.2.1      http://www.mpich.org/static/downloads/3.2.1/mpich-3.2.1.tar.gz
        3.2        http://www.mpich.org/static/downloads/3.2/mpich-3.2.tar.gz
        3.1.4      http://www.mpich.org/static/downloads/3.1.4/mpich-3.1.4.tar.gz
        3.1.3      http://www.mpich.org/static/downloads/3.1.3/mpich-3.1.3.tar.gz
        3.1.2      http://www.mpich.org/static/downloads/3.1.2/mpich-3.1.2.tar.gz
        3.1.1      http://www.mpich.org/static/downloads/3.1.1/mpich-3.1.1.tar.gz
        3.1        http://www.mpich.org/static/downloads/3.1/mpich-3.1.tar.gz
        3.0.4      http://www.mpich.org/static/downloads/3.0.4/mpich-3.0.4.tar.gz
    
    Variants:
        Name [Default]       Allowed values          Description
        =================    ====================    ========================================================================
    
        argobots [off]       on, off                 Enable Argobots support
        device [ch3]         ch3, ch4                Abstract Device Interface (ADI) implementation. The ch4 device is
                                                     currently in experimental state
        fortran [on]         on, off                 Enable Fortran support
        hwloc [on]           on, off                 Use external hwloc package
        hydra [on]1        on, off                 Build the hydra process manager
        libxml2 [on]         on, off                 Use libxml2 for XML support instead of the custom minimalistic
                                                     implementation
        netmod [tcp]2     tcp, mxm, ofi, ucx      Network module. Only single netmod builds are supported. For ch3 device
                                                     configurations, this presumes the ch3:nemesis communication channel.
                                                     ch3:sock is not supported by this spack package at this time.
        pci [on]             on, off                 Support analyzing devices on PCI bus
        pmi [pmi]            off, pmi, pmi2, pmix    PMI interface.
        romio [on]           on, off                 Enable ROMIO MPI I/O implementation
        slurm [off]          on, off                 Enable SLURM support
        verbs [off]          on, off                 Build support for OpenFabrics verbs.
        wrapperrpath [on]    on, off                 Enable wrapper rpath
    
    Installation Phases:
        autoreconf    configure    build    install
    
    Build Dependencies:
        argobots  automake   hwloc      libpciaccess  libxml2  pkgconfig  python  ucx
        autoconf  findutils  libfabric  libtool       m4       pmix       slurm
    
    Link Dependencies:
        argobots  hwloc  libfabric  libpciaccess  libxml2  pmix  slurm  ucx
    
    Run Dependencies:
        None
    
    Virtual Packages:
        mpich@3: provides mpi@:3.0
        mpich@1: provides mpi@:1.3
        mpich provides mpi

    1

    NAME [on] is a boolean variant.

    2

    NAME=VALUE is a non-boolean variant.

  3. Build mpich with some variants disabled:

    # spack install mpich@3.3.2 -romio -libxml2 -hydra -fortran
    ==> mpich: Executing phase: 'autoreconf'
    ==> mpich: Executing phase: 'configure'
    ==> mpich: Executing phase: 'build'
    ==> mpich: Executing phase: 'install'
    [+] /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/mpich-3.3.2-3nexqqx2r4m7p2y7lmovuwvvobi2bygw
  4. Rebuild mpich with the default variants:

    # spack install mpich@3.3.2
    .....
    [+] /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/mpich-3.3.2-sahjm2uhsoc3bi2cljtypwuqaflhamnx
  5. Rebuild mpich with the compiler flag cppflags, a specific libxml version of 2.9.4, an x86_64 target, and a non-boolean netmod option:

    # spack install mpich@3.3.21 -static2 cppflags="-O3 -fPIC"3 target=x86_644 ^libxml2@2.9.45 netmod=tcp6

    1

    @ is an optional version specifier.

    2

    + or - specifies the boolean variant (on or off).

    3

    cflags, cxxflags, fflags, cppflags, ldflags, and ldlibs are variants for the compiler flag.

    4

    target=value and os=value specify the architecture and the operating system. You can list all of the available targets by running the command spack arch --known-targets.

    5

    ^ specifies a dependency.

    6

    name=value specifies a non-boolean variant.

  6. List all of the available packages and their dependency hashes:

    # spack find -l
    ==> 33 installed packages
    -- linux-sle_hpc15-skylake / gcc@7.5.0 --------------------------
    3griwie doxygen@1.8.20  y3w7dlk libpciaccess@0.16  vry3tfp netcdf-c@4.7.4      x3glm5y xz@5.2.3
    3cyidn4 hdf5@1.10.7     to2atk6 libpciaccess@0.16  msiysdr netcdf-cxx4@4.3.1   bzeebyp xz@5.2.3
    rjdqcht hwloc@1.11.11   4cyoxau libxml2@2.9.4      tiyqyxb netcdf-cxx4@4.3.1   z6y74kg zlib@1.2.11
    4lxxw65 hwloc@2.2.0     d4c7csk libxml2@2.9.10     tcuvjjt numactl@2.0.14      m4zmub6 zlib@1.2.11
    yof3lps hwloc@2.2.0     3nexqqx mpich@3.3.2        ks5elgg openmpi@3.1.6
    itovpc5 libiconv@1.16   sahjm2u mpich@3.3.2        rpnlbst util-macros@1.19.1
    5mvdlgl libiconv@1.16   jxbspwk mpich@3.3.2        boclx6a util-macros@1.19.1
    
    -- linux-sle_hpc15-x86_64 / gcc@7.5.0 ---------------------------
    yzxibyd hwloc@2.2.0    7wmqik2 libpciaccess@0.16  6xjiutf mpich@3.3.2         zmfrpzf xz@5.2.3
    mm7at5h libiconv@1.16  jrtvvdj libxml2@2.9.4      jjxbukq util-macros@1.19.1  jxqtsne zlib@1.2.11
  7. Show the specifications and output dependencies of /6xjiutf (mpich):

    # spack find --deps /6xjiutf
    ==> 1 installed package
    -- linux-sle_hpc15-x86_64 / gcc@7.5.0 ---------------------------
    mpich@3.3.2
        hwloc@2.2.0
            libpciaccess@0.16
            libxml2@2.9.4
                libiconv@1.16
                xz@5.2.3
                zlib@1.2.11

9.4 Using a specific compiler

In this example procedure, the goal is to build mpich with gcc-10.2.0.

Procedure 9.4: Using a specific compiler with Spack
  1. Install gcc-10.2.0:

    # spack install gcc@10.2.0
    .....
    [+] /usr/opt/spack/linux-sle_hpc15-skylake/gcc-7.5.0/gcc-10.2.0-tkcq6d6xnyfgyqsnpzq36dlk2etylgp7
  2. Test whether gcc is usable by loading it and attempting to build mpich, using the % option to specify that you want to use gcc-10.2.0:

    # module load gcc-10.2.0-gcc-7.5.0-tkcq6d6 1
    # gcc --version
    gcc (Spack GCC) 10.2.0
    # spack install mpich@3.2.1 %gcc@10.2.0
    ==> Error: No compilers with spec gcc@10.2.0 found for operating system sle_hpc15 and target skylake.
    Run 'spack compiler find' to add compilers or 'spack compilers' to see which compilers are already recognized by spack.

    1

    module load gcc-10.2.0 also works if you have only one version of gcc-10.2.0 available in Spack.

    In this example, the compiler cannot be found yet.

  3. Update the list of available compilers:

    # spack compiler find
    ==> Added 1 new compiler to /home/tux/.spack/linux/compilers.yaml
        gcc@10.2.0
    ==> Compilers are defined in the following files:
        /home/tux/.spack/linux/compilers.yaml
  4. Rerun the command to build mpich with gcc-10.2.0:

    # spack install mpich@3.2.1 %gcc@10.2.0
    .....
    [+] /usr/opt/spack/linux-sle_hpc15-skylake/gcc-10.2.0/mpich-3.2.1-e56rcwtqofh2xytep5pjgq6wrxwmsy25