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devel / comp.lang.python / CPython / Decimal and bit length of value.

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* CPython / Decimal and bit length of value.Nacnud Nac
`- Re: CPython / Decimal and bit length of value.jak

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CPython / Decimal and bit length of value.

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 by: Nacnud Nac - Fri, 3 Sep 2021 20:09 UTC

Hi,
Is there a quick way to get the number of bits required to store the value in a Decimal class? 
What obvious thing am I missing? I'm working with really large integers, say, in the order of 5_000_000 of ASCII base 10 digits. 
It seems the function mpd_sizeinbase would be a nice thing to be able to call.....
It'd be nice to just be able to tell the "size of data", or something like that, that was stored in the *data? I note there is len "field" in the structure mpd_t
Sorry for the dumb question....
Thanks,Duncan

Re: CPython / Decimal and bit length of value.

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From: nospam@please.ty (jak)
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Subject: Re: CPython / Decimal and bit length of value.
Date: Sun, 5 Sep 2021 13:41:01 +0200
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 by: jak - Sun, 5 Sep 2021 11:41 UTC

Il 03/09/2021 22:09, Nacnud Nac ha scritto:
> Hi,
> Is there a quick way to get the number of bits required to store the value in a Decimal class?
> What obvious thing am I missing? I'm working with really large integers, say, in the order of 5_000_000 of ASCII base 10 digits.
> It seems the function mpd_sizeinbase would be a nice thing to be able to call.....
> It'd be nice to just be able to tell the "size of data", or something like that, that was stored in the *data? I note there is len "field" in the structure mpd_t
> Sorry for the dumb question....
> Thanks,Duncan
>
to semplfy the example I'll use the value 1000000:

value="1000000"

exponent in base 10 is len(value) - 1 # (1 * 10^6)

now need change from base 10 to base 2: newexp = 6 / log(2) # 19 (more
or less)

you will need newexp + 1 bits to represent the number: 2^20 = 1.048.576

hope helps

devel / comp.lang.python / CPython / Decimal and bit length of value.

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