From 3e99566dd39f8ab70aa366c542a3bb192020e9cb Mon Sep 17 00:00:00 2001
From: Carles Fernandez <carles.fernandez@gmail.com>
Date: Fri, 1 Aug 2014 12:27:11 +0200
Subject: [PATCH] Use OpenBLAS instead of BLAS if available. OpenBLAS is an
 optimized BLAS library.

---
 CMakeLists.txt                   | 23 +++++++++++++++++------
 cmake/Modules/FindOpenBLAS.cmake | 25 +++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 6 deletions(-)
 create mode 100644 cmake/Modules/FindOpenBLAS.cmake

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1e6750c33..d2941e964 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -562,9 +562,10 @@ endif(DOXYGEN_FOUND)
 ################################################################################
 
 if(OS_IS_LINUX)
-    #############################################
+    #############################################################################
     # Check that LAPACK is found in the system 
-    #############################################
+    # LAPACK is required for matrix decompositions (eg. SVD) and matrix inverse.
+    #############################################################################
     find_library(LAPACK lapack)
     if(NOT LAPACK)
         message(" The LAPACK library has not been found.")
@@ -578,9 +579,11 @@ if(OS_IS_LINUX)
         endif(${LINUX_DISTRIBUTION} MATCHES "Fedora" OR ${LINUX_DISTRIBUTION} MATCHES "Red Hat")
         message(FATAL_ERROR "LAPACK is required to build gnss-sdr")
     endif(NOT LAPACK)
-    #############################################
+    #############################################################################
     # Check that BLAS is found in the system
-    #############################################
+    # BLAS is used for matrix multiplication.
+    #ÊWithout BLAS, matrix multiplication will still work, but might be slower.
+    #############################################################################
     find_library(BLAS blas)
     if(NOT BLAS)
         message(" The BLAS library has not been found.")
@@ -668,7 +671,11 @@ if(NOT ARMADILLO_FOUND)
 "12c12
 < // #define ARMA_USE_LAPACK
 ---
->    #define ARMA_USE_LAPACK 
+>    #define ARMA_USE_LAPACK
+19c19
+< // #define ARMA_USE_BLAS
+---
+>    #define ARMA_USE_BLAS
 ") 
      endif(EXISTS ${CMAKE_CURRENT_BINARY_DIR}/download/armadillo-${armadillo_RELEASE}/armadillo-${armadillo_RELEASE}.tar.gz)
      ExternalProject_Add(
@@ -689,7 +696,11 @@ if(NOT ARMADILLO_FOUND)
      ExternalProject_Get_Property(armadillo-${armadillo_RELEASE} binary_dir)
      set(ARMADILLO_INCLUDE_DIRS ${binary_dir}/include )     
      find_library(LAPACK NAMES lapack HINTS /usr/lib /usr/local/lib /usr/lib64)
-     set(ARMADILLO_LIBRARIES ${LAPACK} ${GFORTRAN} ${binary_dir}/${CMAKE_FIND_LIBRARY_PREFIXES}armadillo.a)
+     find_package(OpenBLAS)
+     if(OPENBLAS_FOUND)
+         set(BLAS OPENBLAS)
+     endif(OPENBLAS_FOUND)
+     set(ARMADILLO_LIBRARIES ${BLAS} ${LAPACK} ${GFORTRAN} ${binary_dir}/${CMAKE_FIND_LIBRARY_PREFIXES}armadillo.a)
      set(LOCAL_ARMADILLO true CACHE STRING "Armadillo downloaded and built automatically" FORCE)
      # Save a copy at the thirdparty folder
      file(COPY ${CMAKE_CURRENT_BINARY_DIR}/armadillo-${armadillo_RELEASE}
diff --git a/cmake/Modules/FindOpenBLAS.cmake b/cmake/Modules/FindOpenBLAS.cmake
new file mode 100644
index 000000000..d8751b216
--- /dev/null
+++ b/cmake/Modules/FindOpenBLAS.cmake
@@ -0,0 +1,25 @@
+# - Try to find OpenBLAS library (not headers!)
+#
+# The following environment variable is optionally searched 
+# OPENBLAS_HOME: Base directory where all OpenBlas components are found
+
+SET(OPEN_BLAS_SEARCH_PATHS  /lib/ 
+                            /lib64/  
+                            /usr/lib 
+                            /usr/lib64 
+                            /usr/local/lib 
+                            /usr/local/lib64 
+                            /opt/OpenBLAS/lib 
+                            /opt/local/lib 
+                            /usr/lib/openblas-base 
+                            $ENV{OPENBLAS_HOME}/lib 
+                            )
+                            
+FIND_LIBRARY(OPENBLAS NAMES openblas PATHS ${OPEN_BLAS_SEARCH_PATHS})
+
+IF (OPENBLAS)
+    SET(OPENBLAS_FOUND ON)
+    MESSAGE(STATUS "Found OpenBLAS")
+ENDIF (OPENBLAS)
+
+MARK_AS_ADVANCED(OPENBLAS)