On Tue, Feb 8, 2022 at 12:19 AM Brett Cannon <[email protected]> wrote:
> Do we have a buildbot that has a CPU or OS that can't handle IEEE-754? What
> are the chances we will get one? If the answers are "none" and "slim", then
> it seems reasonable to require NaN and IEEE-754.
All CPU architectures of current buildbot workers use IEEE 754 (little
or big endian).
I looked at the following CPU architectures:
* x86 (Intel 32-bit)
* x86-64 (Intel 64-bit)
* armv7l (ARM 32-bit)
* aarch64 (ARM 64-bit)
* ppc64, ppc64le (PowerPC 64-bit)
* s390x (IBM)
There is also a "SPARCv9 Oracle Solaris 11.4" worker, but sadly it
seems to be disconnected for 3 months. The SPARCv9 architecture uses
IEEE 754.
On buildbots, I checked float.__getformat__("double"). It is logged as
"builtins.float.double_format" in the "pythoninfo" step of buidbots.
Little-endian examples:
* x86-64 (AMD64 Arch Linux Asan Debug 3.x): IEEE, little-endian
* x86 (Gentoo Non-Debug with X 3.x): IEEE, little-endian
* aarch64 (CentOS9 LTO + PGO 3.10): IEEE, little-endian
* aarch64 (Fedora Rawhide Clang 3.x): IEEE, little-endian
* aarch64: MacOS M1 (ARM64 macOS 3.x): IEEE, little-endian
* aarch64 (ARM64 Windows 3.x): IEEE, little-endian
* PPC64LE (CentOS9 3.10): IEEE, little-endian
* armv7l (ARM Raspbian 3.x): IEEE, little-endian
Big-endian examples:
* PPC64 (AIX 3.x): IEEE, big-endian
* s390x (Debian 3.x): IEEE, big-endian
float.__getformat__("double") is initialized by _PyFloat_InitState()
at Python startup with this code:
---
#if SIZEOF_DOUBLE == 8
{
double x = 9006104071832581.0;
if (memcmp(&x, "\x43\x3f\xff\x01\x02\x03\x04\x05", 8) == 0)
detected_double_format = ieee_big_endian_format;
else if (memcmp(&x, "\x05\x04\x03\x02\x01\xff\x3f\x43", 8) == 0)
detected_double_format = ieee_little_endian_format;
else
detected_double_format = unknown_format;
}
#else
detected_double_format = unknown_format;
#endif
---
Victor
--
Night gathers, and now my watch begins. It shall not end until my death.
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