old_contents: ##############################################################################
  # Copyright (c) 2013-2016, Lawrence Livermore National Security, LLC.
  # Produced at the Lawrence Livermore National Laboratory.
  #
  # This file is part of Spack.
  # Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
  # LLNL-CODE-647188
  #
  # For details, see https://github.com/llnl/spack
  # Please also see the LICENSE file for our notice and the LGPL.
  #
  # This program is free software; you can redistribute it and/or modify
  # it under the terms of the GNU Lesser General Public License (as
  # published by the Free Software Foundation) version 2.1, February 1999.
  #
  # This program is distributed in the hope that it will be useful, but
  # WITHOUT ANY WARRANTY; without even the IMPLIED WARRANTY OF
  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the terms and
  # conditions of the GNU Lesser General Public License for more details.
  #
  # You should have received a copy of the GNU Lesser General Public
  # License along with this program; if not, write to the Free Software
  # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  ##############################################################################
  from spack import *
  
  
  class Nccl(MakefilePackage):
      """Optimized primitives for collective multi-GPU communication."""
  
      homepage = "https://github.com/NVIDIA/nccl"
      url      = "https://github.com/NVIDIA/nccl/archive/v1.3.4-1.tar.gz"
  
      version('1.3.4-1', '5b9ce7fbdce0fde68e0f66318e6ff422')
      version('1.3.0-1', 'f6fb1d56913a7d212ca0c300e76f01fb')
  
      depends_on('cuda')
  
      @property
      def install_targets(self):
          return ['PREFIX={0}'.format(self.prefix), 'install']
  
new_contents: ##############################################################################
  # Copyright (c) 2013-2016, Lawrence Livermore National Security, LLC.
  # Produced at the Lawrence Livermore National Laboratory.
  #
  # This file is part of Spack.
  # Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
  # LLNL-CODE-647188
  #
  # For details, see https://github.com/llnl/spack
  # Please also see the LICENSE file for our notice and the LGPL.
  #
  # This program is free software; you can redistribute it and/or modify
  # it under the terms of the GNU Lesser General Public License (as
  # published by the Free Software Foundation) version 2.1, February 1999.
  #
  # This program is distributed in the hope that it will be useful, but
  # WITHOUT ANY WARRANTY; without even the IMPLIED WARRANTY OF
  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the terms and
  # conditions of the GNU Lesser General Public License for more details.
  #
  # You should have received a copy of the GNU Lesser General Public
  # License along with this program; if not, write to the Free Software
  # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  ##############################################################################
  from spack import *
  
  
  class Nccl(MakefilePackage):
      """Optimized primitives for collective multi-GPU communication."""
  
      homepage = "https://github.com/NVIDIA/nccl"
      url      = "https://github.com/NVIDIA/nccl/archive/v1.3.4-1.tar.gz"
  
      version('1.3.4-1', '5b9ce7fbdce0fde68e0f66318e6ff422')
      version('1.3.0-1', 'f6fb1d56913a7d212ca0c300e76f01fb')
  
      depends_on('cuda')
  
      @property
      def build_targets(self):
          return ['CUDA_HOME={0}'.format(self.spec['cuda'].prefix)]
  
      @property
      def install_targets(self):
          return ['PREFIX={0}'.format(self.prefix), 'install']
  
subject: add CUDA_HOME arg to nccl makefile (#3666)