# Thought about big numbers

**URL:** https://forum.duniter.org/t/thought-about-big-numbers/691
**Category:** R&D
**Tags:** base
**Created:** [14 February 2016 14:03 UTC](https://forum.duniter.org/t/thought-about-big-numbers/691 "2016-02-14T14:03:40Z")
**Posts on this page:** 1
**Showing post:** 4

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### Author: ![cgeek](https://forum.duniter.org/user_avatar/forum.duniter.org/cgeek/32/279_2.png) [@cgeek](https://forum.duniter.org/u/cgeek)
#### Post date: [15 February 2016 13:16 UTC](https://forum.duniter.org/t/thought-about-big-numbers/691/4 "2016-02-15T13:16:44Z")

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We do remove old money: the outputs of 160 years old transactions is purely and simply non-usable. So in the nodes database, the sources of this age are removed.

Now, how do we identify the sources to remove? The `UnitBase` could be very helpful.

Indeed, the UnitBase increments every 23 years approximately (the monetary mass $M$ grows by 10 times every 23 years with c = 10% as you know). We deduce from this that, passed exactly 160 years, $M$ has grown by $10^{160 / 23} = 10^{6,95}$ times.

So we can consider $7$ incrementations of `UnitBase` allow us to destroy some money.

For example, let’s say that current UnitBase is 7 and call it `CurrentBase`. Then any source with `UnitBase <= CurrentBase - 7` can be destroyed: the sources refering to UnitBase = 0.

Other example: if CurrentBase is 28, then any source with `UnitBase <= 21` can be destroyed.

As a conclusion, we could say that we only keep the last $7$ UnitBase sources, as they are equivalent to money between now and 160 years old.

And a second conclusion, we see that:

- UD is has a max “value” of 999.999 = 10^6
- We have a max number of members around 1 million = 10^6
- We handle at max 7 UnitBase = 10^(7 - 1) (because base 10^0 = 1, so we don’t count it as a power of 10)

So in the end, we have a window of total monetary mass maxed at $10^{3 \times 6} = 10^{18}$. And that’s super cool, because an unsigned integer today can handle a value up to $9 \times 10^{18}$. We are all good 🙂

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