From 7e0dd173120434e7c7cbb45b018e98d477baaa33 Mon Sep 17 00:00:00 2001
From: Desire NUENTSA <desire.nuentsa_wakam@inria.fr>
Date: Wed, 19 Sep 2012 18:32:02 +0200
Subject: [PATCH] Improve BiCGSTAB : With exact preconditioner, the solution
 should be found in one iteration

---
 Eigen/src/IterativeLinearSolvers/BiCGSTAB.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/Eigen/src/IterativeLinearSolvers/BiCGSTAB.h b/Eigen/src/IterativeLinearSolvers/BiCGSTAB.h
index 126341be8..5a822e0ea 100644
--- a/Eigen/src/IterativeLinearSolvers/BiCGSTAB.h
+++ b/Eigen/src/IterativeLinearSolvers/BiCGSTAB.h
@@ -39,10 +39,11 @@ bool bicgstab(const MatrixType& mat, const Rhs& rhs, Dest& x,
   int maxIters = iters;
 
   int n = mat.cols();
+  x = precond.solve(x);
   VectorType r  = rhs - mat * x;
   VectorType r0 = r;
   
-  RealScalar r0_sqnorm = r0.squaredNorm();
+  RealScalar r0_sqnorm = rhs.squaredNorm();
   Scalar rho    = 1;
   Scalar alpha  = 1;
   Scalar w      = 1;
@@ -223,7 +224,8 @@ public:
   template<typename Rhs,typename Dest>
   void _solve(const Rhs& b, Dest& x) const
   {
-    x.setZero();
+//     x.setZero();
+  x = b;
     _solveWithGuess(b,x);
   }