Make better decision on PartialPivLU vs inverse(): We have specialized inverse() only for FIXED matrices.

2 files changed, 4 insertions, 2 deletions

diff --git a/unsupported/Eigen/src/MatrixFunctions/MatrixPower.h b/unsupported/Eigen/src/MatrixFunctions/MatrixPower.h
index 2cb1d95d9..520f23bff 100644
--- a/unsupported/Eigen/src/MatrixFunctions/MatrixPower.h
+++ b/unsupported/Eigen/src/MatrixFunctions/MatrixPower.h
@@ -194,7 +194,7 @@ void MatrixPowerTriangular<MatrixType>::computeIntPower(const Derived& b, Result
     else if (p>0) {
       m_tmp1 = m_T;
     }
-    else if (m_A.cols() > 2 && b.cols()*(pp-applyings) <= m_A.cols()*squarings) {
+    else if (m_OKforLU && b.cols()*(pp-applyings) <= m_A.cols()*squarings) {
       res = m_T.solve(b);
       for (--pp; pp >= 1; --pp)
 	res = m_T.solve(res);
@@ -424,7 +424,7 @@ void MatrixPower<MatrixType>::computeIntPower(const Derived& b, ResultType& res,
     else if (p>0) {
       m_tmp1 = m_A;
     }
-    else if (m_A.cols() > 2 && b.cols()*(pp-applyings) <= m_A.cols()*squarings) {
+    else if (m_OKforLU && b.cols()*(pp-applyings) <= m_A.cols()*squarings) {
       PartialPivLU<MatrixType> A(m_A);
       res = A.solve(b);
       for (--pp; pp >= 1; --pp)
diff --git a/unsupported/Eigen/src/MatrixFunctions/MatrixPowerBase.h b/unsupported/Eigen/src/MatrixFunctions/MatrixPowerBase.h
index aa28b821b..96846cb93 100644
--- a/unsupported/Eigen/src/MatrixFunctions/MatrixPowerBase.h
+++ b/unsupported/Eigen/src/MatrixFunctions/MatrixPowerBase.h
@@ -24,6 +24,7 @@ namespace Eigen {
   typedef typename Base::RealArray  RealArray;
 
 #define EIGEN_MATRIX_POWER_PROTECTED_MEMBERS(Derived) \
+  using Base::m_OKforLU; \
   using Base::m_A; \
   using Base::m_Id; \
   using Base::m_tmp1; \
@@ -98,6 +99,7 @@ class MatrixPowerBase
 
   protected:
     typedef Array<RealScalar,RowsAtCompileTime,1,ColMajor,MaxRowsAtCompileTime> RealArray;
+    static const bool m_OKforLU = RowsAtCompileTime == Dynamic || RowsAtCompileTime > 4;
 
     const MatrixType& m_A;
     const MatrixType m_Id;