Seperate MKL FFT and MKL BLAS configurations.

MKL FFT bindings had assumed that MKL was also being used to provide the
BLAS implementation, however the build system allows these 2 things to
be configured independantly.

dlib/CMakeLists.txt

@@ -451,8 +451,8 @@ if (NOT TARGET dlib)
       endif()
 
 
-      if (DLIB_USE_BLAS OR DLIB_USE_LAPACK)
-         # Try to find BLAS and LAPACK 
+      if (DLIB_USE_BLAS OR DLIB_USE_LAPACK OR DLIB_USE_MKL_FFT)
+          # Try to find BLAS, LAPACK and MKL
          include(cmake_utils/cmake_find_blas.txt)
 
          if (DLIB_USE_BLAS)
@@ -472,14 +472,17 @@ if (NOT TARGET dlib)
                toggle_preprocessor_switch(DLIB_USE_LAPACK)
             endif()
          endif()
-      endif()
 
+         if (DLIB_USE_MKL_FFT)
             if (found_intel_mkl)
+               set (dlib_needed_libraries ${dlib_needed_libraries} ${mkl_libraries})
                include_directories(${mkl_include_dir})
             else()
                set(DLIB_USE_MKL_FFT OFF CACHE STRING ${DLIB_USE_MKL_FFT_STR} FORCE )
                toggle_preprocessor_switch(DLIB_USE_MKL_FFT)
             endif()
+         endif()
+      endif()
 
 
       if (DLIB_USE_CUDA)

dlib/cmake_utils/cmake_find_blas.txt

@@ -10,14 +10,18 @@
 #
 #  blas_found        - True if BLAS is available
 #  lapack_found      - True if LAPACK is available
+#  found_intel_mkl   - True is the the Intel MKL library is available
 #  blas_libraries    - link against these to use BLAS library 
 #  lapack_libraries  - link against these to use LAPACK library 
+#  mkl_libraries     - link against these to use the MKL library
+#  mkl_include_dir   - add to the include path to use the MKL library
 
 # setting this makes CMake allow normal looking if else statements
 SET(CMAKE_ALLOW_LOOSE_LOOP_CONSTRUCTS true)
 
 SET(blas_found 0)
 SET(lapack_found 0)
+SET(found_intel_mkl 0)
 
 
 if (UNIX)
@@ -79,13 +83,20 @@ if (UNIX)
 
    include(CheckLibraryExists)
 
+    # Get mkl_include_dir
+    set(mkl_include_search_path
+        /opt/intel/mkl/include
+        /opt/intel/include
+    )
+    find_path(mkl_include_dir mkl_version.h ${mkl_include_search_path})
 
     # Search for the needed libraries from the MKL.  We will try to link against the mkl_rt
     # file first since this way avoids linking bugs in some cases.
     find_library(mkl_rt mkl_rt ${mkl_search_path})
     mark_as_advanced(  mkl_rt )
     # if we found the MKL 
-    if ( mkl_rt)
+    if (mkl_include_dir AND mkl_rt)
+        set(mkl_libraries  ${mkl_rt} )
         set(blas_libraries  ${mkl_rt} )
         set(lapack_libraries  ${mkl_rt} )
         set(blas_found 1)
@@ -104,7 +115,8 @@ if (UNIX)
 
         mark_as_advanced( mkl_intel mkl_core mkl_thread mkl_iomp mkl_pthread)
         # If we found the MKL 
-        if (mkl_intel AND mkl_core AND mkl_thread AND mkl_iomp AND mkl_pthread)
+        if (mkl_include_dir AND mkl_intel AND mkl_core AND mkl_thread AND mkl_iomp AND mkl_pthread)
+            set(mkl_libraries ${mkl_intel} ${mkl_core} ${mkl_thread} ${mkl_iomp} ${mkl_pthread})
             set(blas_libraries ${mkl_intel} ${mkl_core} ${mkl_thread} ${mkl_iomp} ${mkl_pthread})
             set(lapack_libraries ${mkl_intel} ${mkl_core} ${mkl_thread} ${mkl_iomp} ${mkl_pthread})
             set(blas_found 1)
@@ -114,15 +126,6 @@ if (UNIX)
         endif()
     endif()
 
-    # Get mkl_include_dir
-    if (found_intel_mkl)
-        set(mkl_include_search_path
-            /opt/intel/mkl/include
-            /opt/intel/include
-        )
-        find_path(mkl_include_dir mkl_version.h ${mkl_include_search_path})
-    endif()
-
    # try to find some other LAPACK libraries if we didn't find the MKL
    set(extra_paths
         /usr/lib64