From da6219b19dd92231cd0afe380ae4880b62bfe88d Mon Sep 17 00:00:00 2001
From: Desire NUENTSA <desire.nuentsa_wakam@inria.fr>
Date: Wed, 20 Mar 2013 16:15:18 +0100
Subject: Bug567 : Fix iterative solvers to immediately return when the initial
 guess is the true solution and for trivial solution

---
 Eigen/src/IterativeLinearSolvers/BiCGSTAB.h | 5 +++++
 1 file changed, 5 insertions(+)

(limited to 'Eigen/src/IterativeLinearSolvers/BiCGSTAB.h')

diff --git a/Eigen/src/IterativeLinearSolvers/BiCGSTAB.h b/Eigen/src/IterativeLinearSolvers/BiCGSTAB.h
index 5a822e0ea..fbefb696f 100644
--- a/Eigen/src/IterativeLinearSolvers/BiCGSTAB.h
+++ b/Eigen/src/IterativeLinearSolvers/BiCGSTAB.h
@@ -44,6 +44,11 @@ bool bicgstab(const MatrixType& mat, const Rhs& rhs, Dest& x,
   VectorType r0 = r;
   
   RealScalar r0_sqnorm = rhs.squaredNorm();
+  if(r0_sqnorm == 0)
+  {
+    x.setZero();
+    return true;
+  }
   Scalar rho    = 1;
   Scalar alpha  = 1;
   Scalar w      = 1;
-- 
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