[ROOT] TMatrix Invert Mult

From: sdean (sdean@fnal.gov)
Date: Thu May 01 2003 - 14:27:30 MEST 

Hi there,

Please inspect the following piece of code which attempts to perform one
of the most basic matrix operations, that of multiplying a matrix by its
inverse to obtain the unit matrix:

root [0] TMatrix a(2,2)
root [1] a(0,0)=1.0;
root [2] a(1,0)=2.0;
root [3] a(0,1)=3.0;
root [4] a(1,1)=4.0;
root [5] TMatrix b(2,2)
root [6] b=a.Invert();
root [7] TMatrix c(2,2)
root [8] c.Mult(b,a)
root [9] c(0,0)
(Real_t)5.50000000000000000e+00
root [10] c(1,0)
(Real_t)(-2.50000000000000000e+00)
root [11] c(0,1)
(Real_t)(-3.75000000000000000e+00)
root [12] c(1,1)
(Real_t)1.75000000000000000e+00

The results look much too precise for this to be a conversion error. Can
anyone see where I'm going wrong?

cheers,

Simon

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