On Tue, Feb 8, 2022 at 12:19 AM Brett Cannon <brett@python.org> 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.