Deal with patched/un-patched version of householder_qr_inplace_blocked

CMakeLists.txt

@@ -205,6 +205,11 @@ if(GTSAM_USE_SYSTEM_EIGEN)
 
 	find_package(Eigen3 REQUIRED)
 	include_directories(AFTER "${EIGEN3_INCLUDE_DIR}")
+	
+	# check if MKL is also enabled - can have one or the other, but not both!
+	if(EIGEN_USE_MKL_ALL)
+	  message(FATAL_ERROR "MKL cannot be used together with system-installed Eigen, as MKL support relies on patches which are not yet in the system-installed Eigen. Disable either GTSAM_USE_SYSTEM_EIGEN or GTSAM_WITH_EIGEN_MKL")
+	endif()
 else()
 	# Use bundled Eigen include path. 
 	set(GTSAM_EIGEN_INCLUDE_PREFIX "gtsam/3rdparty/Eigen/")

gtsam/base/Matrix.cpp

@@ -706,6 +706,7 @@ std::string formatMatrixIndented(const std::string& label, const Matrix& matrix,
   return ss.str();
 }
 
+/* ************************************************************************* */
 void inplace_QR(Matrix& A){
   size_t rows = A.rows();
   size_t cols = A.cols();
@@ -716,7 +717,13 @@ void inplace_QR(Matrix& A){
   HCoeffsType hCoeffs(size);
   RowVectorType temp(cols);
 
+#ifdef GTSAM_USE_SYSTEM_EIGEN
+  // System-Eigen is used, and MKL is off
+  Eigen::internal::householder_qr_inplace_blocked<Matrix, HCoeffsType>(A, hCoeffs, 48, temp.data());
+#else
+  // Patched Eigen is used, and MKL is either on or off
   Eigen::internal::householder_qr_inplace_blocked<Matrix, HCoeffsType>::run(A, hCoeffs, 48, temp.data());
+#endif
 
   zeroBelowDiagonal(A);
 }

gtsam/config.h.in

@@ -42,6 +42,9 @@
 // Whether we are using TBB (if TBB was found and GTSAM_WITH_TBB is enabled in CMake)
 #cmakedefine GTSAM_USE_TBB
 
+// Whether we are using system-Eigen or our own patched version
+#cmakedefine GTSAM_USE_SYSTEM_EIGEN
+
 // Whether Eigen will use MKL (if MKL was found and GTSAM_WITH_EIGEN_MKL is enabled in CMake)
 #cmakedefine GTSAM_USE_EIGEN_MKL
 #cmakedefine EIGEN_USE_MKL_ALL // This is also defined in gtsam_eigen_includes.h