void testSVD()
{
  const Int_t nrVar  = 2;
  const Int_t nrPnts = 4;

  Double_t ay[] = {2,0,2,0};
  TVectorD y; y.Use(nrPnts,ay);

  TMatrixD A(nrPnts,nrVar);
  A(0,0)=1;   A(0,1)=1;
  A(1,0)=1;   A(1,1)=1;
  A(2,0)=1;   A(2,1)=1;
  A(3,0)=1;   A(3,1)=1;

  TDecompSVD svd(A);
  svd.Print();

  Bool_t ok;
  const TVectorD c_svd = svd.Solve(y,ok);
  c_svd.Print();

  cout << "decomposed   " << svd.kDecomposed << endl;
  cout << "condition nb " << svd.GetCondition() << endl;
  cout << "tolerance    " << svd.GetTol() << endl;
  cout << "singular     " << svd.kSingular << endl;
}