Zero or not?

[Matthias Brennwald]

Dear all

I expected the below code to yield only zeros, but it does not:

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u = [ 0 , 1e-3 , 1e-4 ; 1e-3 , 0 , 0 ; 0 , 1e-4 , 0 ];
d = u - diag(sum(u));
sum(d)
----------------------------

The output is:
  0.0000e+00  -4.0658e-20   0.0000e+00

Why is this? Is there something I can do to 'fix' this?

Matthias


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Matthias Brennwald
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