Add the 'exciting' package. (#20060)

* Add the 'exciting' package.
Version 14 (latest available) is defined.
An as-of-yet unpublished patch (dfgather.patch) from the developers is also
included.

* fixed flake8 errors (I *thought* I had already gotten them!  OOPS!)

* Update var/spack/repos/builtin/packages/exciting/package.py

Co-authored-by: Adam J. Stewart <ajstewart426@gmail.com>

* fixed install method to just do the install, and no build method is needed.

* *Actually* added the lapack dependency!

* removed variant from blas dependency

Co-authored-by: Adam J. Stewart <ajstewart426@gmail.com>

var/spack/repos/builtin/packages/exciting/dfgather.patch

@@ -0,0 +1,27 @@
+--- dfgather.F90_old	2020-09-16 17:19:18.000000000 -0600
++++ dfgather.F90	2020-09-16 17:19:21.000000000 -0600
+@@ -27,6 +27,11 @@
+   ! loop over q-points
+       Do iq = 1, nqpt
+          tq0 = tqgamma (iq)
++
++        call genfilname(basename='X0', bzsampl=bzsampl,&
++         & acont=input%xs%tddft%acont, nar= .not. input%xs%tddft%aresdf,&
++         & tord=input%xs%tddft%torddf, markfxcbse=tfxcbse, iqmt=iq, filnam=fnchi0)
++     
+      ! calculate k+q and G+k+q related variables
+          Call init1offs (qvkloff(1, iq))
+      ! size of local field effects
+@@ -54,6 +59,12 @@
+                call mpi_bcast(chi0hd,3*3,MPI_DOUBLE_COMPLEX,iproc,mpi_comm_world,ierr)
+ #endif
+                if(rank.eq.0.or.(firstinnode.and. .not.input%sharedfs))then
++                 if (iw == wpari) then
++                   print *, 'procs=', procs
++                   print *, 'rank=', rank
++                   print *, 'iq=', iq, '/', nqpt
++                   print *, 'fnchi0=',trim(fnchi0)
++                 end if
+                Call putx0 (tq0, iq, iw, trim(fnchi0), '', chi0, chi0wg, &
+               & chi0hd)
+               endif

var/spack/repos/builtin/packages/exciting/package.py

@@ -0,0 +1,117 @@
+# Copyright 2013-2020 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+from spack import *
+
+
+class Exciting(MakefilePackage):
+    """
+    exciting is a full-potential all-electron density-functional-theory package
+    implementing the families of linearized augmented planewave methods. It can
+    be applied to all kinds of materials, irrespective of the atomic species in
+    volved, and also allows for exploring the physics of core electrons. A
+    particular focus are excited states within many-body perturbation theory.
+    """
+
+    homepage = "http://exciting-code.org/"
+    url      = "http://exciting.wdfiles.com/local--files/nitrogen-14/exciting.nitrogen-14.tar.gz"
+
+    version('14', sha256='a7feaffdc23881d6c0737d2f79f94d9bf073e85ea358a57196d7f7618a0a3eff')
+
+    # as-of-yet unpublished fix to version 14
+    patch('dfgather.patch', when='@14', working_dir='src/src_xs', level=0)
+    variant('mpi', default=False, description='Use MPI')
+    variant('mkl', default=False, description='Use MKL')
+    variant('omp', default=True, description='Use OpenMP')
+    variant('scalapack', default=False, description='Use ScaLAPACK')
+    depends_on('blas')
+    depends_on('lapack')
+    depends_on('fftw', when='~mkl')
+    depends_on('mkl', when='+mkl')
+    depends_on('mpi', when='+mpi')
+    depends_on('scalapack', when='+scalapack')
+    conflicts('%gcc@10:', msg='exciting cannot be built with GCC 10')
+
+    for __compiler in spack.compilers.supported_compilers():
+        if __compiler != 'intel':
+            conflicts('%{0}'.format(__compiler), when='^mkl',
+                      msg='MKL only works with the Intel compiler')
+
+    def edit(self, spec, prefix):
+        opts = {}
+        opts['BUILDSMP'] = 'true'
+        opts['F90_OPTS'] = '-cpp '
+        opts['F77_OPTS'] = '-cpp -O3 '
+        opts['CPP_ON_OPTS'] = '-cpp -DXS -DISO -DLIBXC'
+        opts['LIB_ARP'] = 'libarpack.a'
+        opts['F90'] = spack_fc
+        opts['F77'] = spack_f77
+        if '+omp' in spec:
+            opts['LDFLAGS'] = self.compiler.openmp_flag + ' -DUSEOMP'
+            opts['F90_OPTS'] += self.compiler.openmp_flag + ' -DUSEOMP'
+            opts['F77_OPTS'] += self.compiler.openmp_flag + ' -DUSEOMP'
+        if '%intel' in spec:
+            opts['F90_OPTS'] += ' -O3 -cpp -ip -unroll -scalar_rep '
+            opts['CPP_ON_OPTS'] += ' -DIFORT -DFFTW'
+        if '%gcc' in spec:
+            opts['F90_OPTS'] += '-O3 -march=native -ffree-line-length-0'
+        filter_file('FCFLAGS = @FCFLAGS@',
+                    ' '.join(['FCFLAGS = @FCFLAGS@', '-cpp',
+                              self.compiler.openmp_flag]),
+                    'src/libXC/src/Makefile.in')
+        if '+mkl' in spec:
+            if '%intel' in spec:
+                opts['LIB_LPK'] = '-mkl=parallel'
+            opts['INC_MKL'] = spec['mkl'].headers.include_flags
+            opts['LIB_MKL'] = spec['mkl'].libs.ld_flags
+        else:
+            opts['LIB_LPK'] = ' '.join([spec['lapack'].libs.ld_flags,
+                                        spec['blas'].libs.ld_flags,
+                                        self.compiler.openmp_flag])
+        if '+mpi' in spec:
+            opts['BUILDMPI'] = 'true'
+            opts['MPIF90'] = spec['mpi'].mpifc
+            opts['MPIF90_CPP_OPTS'] = self.compiler.openmp_flag
+            opts['MPIF90_CPP_OPTS'] += ' -DMPI -DMPIRHO -DMPISEC '
+            opts['MPIF90_OPTS'] = ' '.join(['$(F90_OPTS)', '$(CPP_ON_OPTS) '
+                                            '$(MPIF90_CPP_OPTS)'])
+            opts['MPIF90MT'] = '$(MPIF90)'
+        else:
+            opts['BUILDMPI'] = 'false'
+
+        if '+scalapack' in spec:
+            opts['LIB_SCLPK'] = spec['scalapack'].libs.ld_flags
+            opts['LIB_SCLPK'] += ' ' + self.compiler.openmp_flag
+            opts['CPP_SCLPK'] = ' -DSCAL '
+            opts['LIBS_MPI'] = '$(LIB_SCLPK)'
+            opts['MPIF90_CPP_OPTS'] += ' $(CPP_SCLPK) '
+
+        opts['USE_SYS_LAPACK'] = 'true'
+        opts['LIB_FFT'] = 'fftlib.a'
+        opts['LIB_BZINT'] = 'libbzint.a'
+        opts['LIBS'] = '$(LIB_ARP) $(LIB_LPK) $(LIB_FFT) $(LIB_BZINT)'
+        with open('build/make.inc', 'a') as inc:
+            for key in opts:
+                inc.write('{0} = {1}\n'.format(key, opts[key]))
+
+    def install(self, spec, prefix):
+        install_tree('bin', prefix)
+        install_tree('species', prefix.species)
+        install_tree('tools', prefix.tools)
+
+    def setup_run_environment(self, env):
+        env.set('WNHOME', self.prefix)
+        env.set('EXCITINGROOT', self.prefix)
+        env.set('EXCITINGBIN', self.prefix.bin)
+        env.set('EXCITINGTOOLS', self.prefix.tools)
+        env.set('EXCITINGSTM', self.prefix.tools.stm)
+        env.set('EXCITINGVISUAL', self.prefix.xml.visualizationtemplates)
+        env.set('EXCITINGCONVERT', self.prefix.xml.inputfileconverter)
+        env.set('TIMEFORMAT', ' Elapsed time = %0lR')
+        env.set('WRITEMINMAX', '1')
+        env.append_path('PYTHONPATH', self.prefix.tools.stm)
+        env.append_path('PATH', self.prefix.tools)
+        env.append_path('PATH', self.prefix)
+        env.append_path('PATH', self.prefix.tools.stm)