From 750af063629cd366f6d01985b37a21ebc37a5af3 Mon Sep 17 00:00:00 2001
From: Christoph Hertzberg <chtz@informatik.uni-bremen.de>
Date: Tue, 22 May 2018 21:04:32 +0200
Subject: Add an option to test with external BLAS library

---
 cmake/EigenTesting.cmake | 4 ++++
 test/CMakeLists.txt      | 9 +++++++++
 2 files changed, 13 insertions(+)

diff --git a/cmake/EigenTesting.cmake b/cmake/EigenTesting.cmake
index 16d6d279f..7d2d63722 100644
--- a/cmake/EigenTesting.cmake
+++ b/cmake/EigenTesting.cmake
@@ -679,6 +679,10 @@ macro(ei_set_build_string)
     set(TMP_BUILD_STRING ${TMP_BUILD_STRING}-${LOCAL_COMPILER_FLAGS})
   endif()
 
+  if(EIGEN_TEST_EXTERNAL_BLAS)
+    set(TMP_BUILD_STRING ${TMP_BUILD_STRING}-external_blas)
+  endif()
+
   ei_is_64bit_env(IS_64BIT_ENV)
   if(NOT IS_64BIT_ENV)
     set(TMP_BUILD_STRING ${TMP_BUILD_STRING}-32bit)
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index f8deafc07..073effd81 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -30,6 +30,15 @@ if(NOT EIGEN_Fortran_COMPILER_WORKS)
   find_package(LAPACK QUIET)
 endif()
 
+# TODO do the same for EXTERNAL_LAPACK
+option(EIGEN_TEST_EXTERNAL_BLAS "Use external BLAS library for testsuite" OFF)
+if(EIGEN_TEST_EXTERNAL_BLAS)
+  find_package(BLAS REQUIRED)
+  message(STATUS "BLAS_COMPILER_FLAGS: ${BLAS_COMPILER_FLAGS}")
+  add_definitions("-DEIGEN_USE_BLAS") # is adding  ${BLAS_COMPILER_FLAGS} necessary?
+  list(APPEND EXTERNAL_LIBS "${BLAS_LIBRARIES}")
+endif(EIGEN_TEST_EXTERNAL_BLAS)
+
 # configure blas/lapack (use Eigen's ones)
 set(EIGEN_BLAS_LIBRARIES eigen_blas)
 set(EIGEN_LAPACK_LIBRARIES eigen_lapack)
-- 
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