Why do I get zero?

Running 7.10.0 (R2010a) under Windows 7 on an Intel i5 (Lenovo laptop):

K>> TAhi

TAhi = -8.6578e+009

K>> TAlo

TAlo = -8.6578e+009

K>> TAhi/2.0 - TAlo/2.0

ans = 9.5367e-007

K>> (TAhi+TAlo)/2.0 - TAlo

ans = 0

Why do I get 0 when I should get 9.5367e-007 ? I wouldn't image e-007 is anywhere near machine tolerance.

Any help is appreciated!

Answer 1

[Nirmal Gunaseelan]

The next highest floating point number representable relative to the current number is probably the issue here. Please read further at EPS documentation page.

Answer 2

[Fangjun Jiang]

Maybe you can type in the following command and then do your calculation again to see the difference

format long

Answer 3

[David Young]

(TAhi-TAlo)/TAhi is close to machine precision, and it's this relative size that matters when comparing two almost equal numbers.