Add official MKL cmake finder. (#147)

FindMKL.cmake

@@ -0,0 +1,142 @@
+# ===============================================================================
+# Copyright 2021-2022 Intel Corporation.
+#
+# This software and the related documents are Intel copyrighted  materials,  and
+# your use of  them is  governed by the  express license  under which  they were
+# provided to you (License).  Unless the License provides otherwise, you may not
+# use, modify, copy, publish, distribute,  disclose or transmit this software or
+# the related documents without Intel's prior written permission.
+#
+# This software and the related documents  are provided as  is,  with no express
+# or implied  warranties,  other  than those  that are  expressly stated  in the
+# License.
+# ===============================================================================
+
+# ===================================================================
+# CMake Config file for Intel(R) oneAPI Math Kernel Library (oneMKL)
+# ===================================================================
+
+# ===============================================================================
+# Input parameters
+# =================
+# MKL_ROOT: oneMKL root directory (May be required for non-standard install
+#           locations. Optional otherwise.)
+#    Default: use location from MKLROOT environment variable
+#             or "/opt/intel/oneapi/mkl/latest" if MKLROOT is not defined
+# ==================
+# Output parameters
+# ==================
+# MKL_ROOT oneMKL root directory. MKL::MKL Link line for C API
+# ===============================================================================
+
+if(TARGET MKL::MKL)
+  message(STATUS "MKL::MKL target has already been loaded.")
+  set(MKL_FOUND TRUE)
+  return()
+endif()
+
+if(${CMAKE_VERSION} VERSION_LESS "3.13")
+  message(FATAL_ERROR "The minimum supported CMake version is 3.13. You are running version ${CMAKE_VERSION}")
+endif()
+
+include(FindPackageHandleStandardArgs)
+
+if(NOT MKL_LIBRARIES)
+
+  # Set CMake policies for well-defined behavior across CMake versions
+  cmake_policy(SET CMP0011 NEW)
+
+  # ================
+  # Compiler checks
+  # ================
+
+  include(CMakeDetermineCCompiler)
+  if(CMAKE_C_COMPILER)
+    get_filename_component(C_COMPILER_NAME ${CMAKE_C_COMPILER} NAME)
+  endif()
+  if(CMAKE_CXX_COMPILER)
+    get_filename_component(CXX_COMPILER_NAME ${CMAKE_CXX_COMPILER} NAME)
+  endif()
+
+  if(NOT
+     ((C_COMPILER_NAME MATCHES "^clang")
+      OR (CMAKE_C_COMPILER_ID STREQUAL "GNU")
+      OR (CXX_COMPILER_NAME MATCHES "^clang")
+      OR (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")))
+    message(FATAL_ERROR "Only clang or gnu compilers supported. Name=${C_COMPILER_NAME} - Id=${CMAKE_C_COMPILER_ID}")
+  endif()
+
+  # ================
+  # System-specific
+  # ================
+
+  # Extensions
+  if(UNIX AND NOT APPLE)
+    set(LIB_PREFIX "lib")
+    set(LIB_EXT ".a")
+  else()
+    message(FATAL_ERROR "MKL support not available for architectures other than linux.")
+  endif()
+
+  # ==========
+  # Setup MKL
+  # ==========
+
+  # Set MKL_ROOT directory
+  set(MKLROOT_DEFAULT "/opt/intel/oneapi/mkl/latest")
+  if(NOT DEFINED MKL_ROOT)
+    if(DEFINED ENV{MKLROOT})
+      set(MKL_ROOT $ENV{MKLROOT})
+    elseif(EXISTS ${MKLROOT_DEFAULT})
+      set(MKL_ROOT ${MKLROOT_DEFAULT})
+    else()
+      message(FATAL_ERROR "MKLROOT environment variable is not defined.")
+    endif()
+  endif()
+
+  set(MKL_INCLUDE "${MKL_ROOT}/include")
+
+  # Define MKL headers
+  find_path(
+    MKL_H mkl.h
+    HINTS ${MKL_ROOT}
+    PATH_SUFFIXES include)
+  list(APPEND MKL_INCLUDE ${MKL_H})
+
+  # Checkpoint - Verify if required options are defined
+  find_package_handle_standard_args(MKL REQUIRED_VARS MKL_ROOT MKL_INCLUDE)
+
+  # Create a list of requested libraries, based on input options (MKL_LIBRARIES) Create full link-line in MKL_LINK_LINE
+  set(MKL_LINK_LINE "")
+  set(MKL_LIBRARIES "")
+  set(MKL_SUPP_LINK "")
+  list(APPEND MKL_LINK_LINE "-Wl,--start-group" MKL::mkl_intel_lp64 MKL::mkl_gnu_thread MKL::mkl_core "-Wl,--end-group")
+  list(APPEND MKL_LIBRARIES mkl_intel_lp64 mkl_gnu_thread mkl_core)
+  list(APPEND MKL_SUPP_LINK -lgomp -fopenmp -lm -ldl -lpthread)
+
+  set(MKL_IMPORTED_TARGETS "")
+
+  # Find all requested libraries
+  foreach(lib ${MKL_LIBRARIES})
+    unset(${lib}_file CACHE)
+    find_library(
+      ${lib}_file ${LIB_PREFIX}${lib}${LIB_EXT}
+      PATHS ${MKL_ROOT}
+      PATH_SUFFIXES "lib" "lib/intel64")
+    add_library(MKL::${lib} STATIC IMPORTED)
+    find_package_handle_standard_args(MKL REQUIRED_VARS ${lib}_file)
+    # CMP0111, implemented in CMake 3.20+ requires a shared library target on Windows to be defined with IMPLIB and
+    # LOCATION property. It also requires a static library target to be defined with LOCATION property. Setting
+    # the policy to OLD usage, using cmake_policy() does not work as of 3.20.0, hence the if-else below.
+    set_target_properties(MKL::${lib} PROPERTIES IMPORTED_LOCATION "${${lib}_file}")
+    list(APPEND MKL_IMPORTED_TARGETS MKL::${lib})
+  endforeach()
+
+  # Single target for all C, Fortran link-lines
+  add_library(MKL::MKL INTERFACE IMPORTED GLOBAL)
+  target_compile_options(MKL::MKL INTERFACE -m64)
+  target_compile_definitions(MKL::MKL INTERFACE EIGEN_USE_MKL_ALL)
+  target_link_libraries(MKL::MKL INTERFACE ${MKL_LINK_LINE} ${MKL_SUPP_LINK})
+  target_include_directories(MKL::MKL BEFORE INTERFACE ${MKL_INCLUDE})
+  list(APPEND MKL_IMPORTED_TARGETS MKL::MKL)
+endif() # MKL_LIBRARIES