Poor accuracy in true division of integers

[skirpichev]

For example:

>>> x, y = 15649, 2024092432744435552
>>> x/y
7.73136628883186e-15
>>> import mpmath
>>> float(mpmath.mpf(x)/mpmath.mpf(y))  # as in CPython
7.731366288831862e-15

The result expected to be correctly rounded with the round-half-to-even rule.

[skirpichev]

@msimacek is this included in the 25.0.1 or in 25.0.0?

In CI I get following failure (building gp312_250-manylinux_x86_64 wheel):

E           assert (mpz(2305843008955759739) / mpz(784637716923335094969050127462454050937374032249308213819)) == 2.9387358767269886e-39

CPython's result (which is same for mpz):

Python 3.14.0 (tags/v3.14.0:ebf955df7a8, Oct 15 2025, 06:24:48) [GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> 2305843008955759739 / 784637716923335094969050127462454050937374032249308213819
2.9387358767269883e-39

I don't think this is fixed.

[skirpichev]

@msimacek can this be reopened or should I open a new issue?

I downloaded latest stable and run. It seems the fix was applied, but in my new example it's not enough:

Python 3.12.8 (Thu Oct 09 17:26:36 UTC 2025)
[Graal, Oracle GraalVM, Java 25.0.1 (amd64)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> x, y = 15649, 2024092432744435552  # now ok
>>> x/y
7.731366288831862e-15
>>> 2305843008955759739 / 784637716923335094969050127462454050937374032249308213819  # this is wrong
2.9387358767269886e-39
>>> _.hex()  # one bit off, correct answer is '0x1.ffffffff0a03cp-129'
'0x1.ffffffff0a03dp-129'

[msimacek]

Hi, sorry, let's reopen this