[Numpy-discussion] Large numbers into float128

Matthew Brett matthew.brett@gmail....
Sat Oct 29 17:55:21 CDT 2011


Hi,

Can anyone think of a good way to set a float128 value to an
arbitrarily large number?

As in

v = int_to_float128(some_value)

?

I'm trying things like

v = np.float128(2**64+2)

but, because (in other threads) the float128 seems to be going through
float64 on assignment, this loses precision, so although 2**64+2 is
representable in float128, in fact I get:

In [35]: np.float128(2**64+2)
Out[35]: 18446744073709551616.0

In [36]: 2**64+2
Out[36]: 18446744073709551618L

So - can anyone think of another way to assign values to float128 that
will keep the precision?

Thanks a lot,

Matthew


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