gh-111389: Add PyHASH_MULTIPLIER constant

[vstinner]

• Issue: Consider restoring _PyHASH_INF/BITS/MODULUS/IMAG as public #111389

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📚 Documentation preview 📚: https://cpython-previews--119214.org.readthedocs.build/

[vstinner]

The private _PyHASH_MULTIPLIER constant was removed in Python 3.13 alpha 1, but had to be reverted since it broke too many projects.

A code search on PyPI top 7,500 projects (2024-03-16) finds 4 projects using it:

• asyncpg (0.29.0)
• numba (0.59.0)
• orjson (3.9.15)
• recordclass (0.21.1)

[gpshead]

This makes sense, no harm in this being public even if I think it is odd that anyone uses it.

[vstinner]

This makes sense, no harm in this being public even if I think it is odd that anyone uses it.

It's a good prime number to increase to implement good hash function. Using a random number can lead to more collision.

cc @mdickinson

[mdickinson]

cc @mdickinson

Change seems reasonable to me; the value is potentially useful to have available if you're implementing something complex-like in a C extension and need equality to behave well with respect to Python's complex. (I'll confess that I've never seen this need in practice, but I've seen the equivalent for float hashing, so it doesn't seem like a huge stretch.)

[vstinner]

(I'll confess that I've never seen this need in practice

I don't know about the specific case of floating point objects, but the constant is used by at least 4 projects: #119214 (comment)

[miss-islington-app]

Thanks @vstinner for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖 I'm not a witch! I'm not a witch!

[bedevere-app]

GH-119334 is a backport of this pull request to the 3.13 branch.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot wasm32-wasi 3.13 has failed when building commit 1177897.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/1502/builds/133) and take a look at the build logs.
4. Check if the failure is related to this commit (1177897) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/1502/builds/133

Failed tests:

• test_math
• test_statistics

Summary of the results of the build (if available):

==

Click to see traceback logs

remote: Enumerating objects: 19, done. remote: Counting objects: 5% (1/18) remote: Counting objects: 11% (2/18) remote: Counting objects: 16% (3/18) remote: Counting objects: 22% (4/18) remote: Counting objects: 27% (5/18) remote: Counting objects: 33% (6/18) remote: Counting objects: 38% (7/18) remote: Counting objects: 44% (8/18) remote: Counting objects: 50% (9/18) remote: Counting objects: 55% (10/18) remote: Counting objects: 61% (11/18) remote: Counting objects: 66% (12/18) remote: Counting objects: 72% (13/18) remote: Counting objects: 77% (14/18) remote: Counting objects: 83% (15/18) remote: Counting objects: 88% (16/18) remote: Counting objects: 94% (17/18) remote: Counting objects: 100% (18/18) remote: Counting objects: 100% (18/18), done. remote: Compressing objects: 8% (1/12) remote: Compressing objects: 16% (2/12) remote: Compressing objects: 25% (3/12) remote: Compressing objects: 33% (4/12) remote: Compressing objects: 41% (5/12) remote: Compressing objects: 50% (6/12) remote: Compressing objects: 58% (7/12) remote: Compressing objects: 66% (8/12) remote: Compressing objects: 75% (9/12) remote: Compressing objects: 83% (10/12) remote: Compressing objects: 91% (11/12) remote: Compressing objects: 100% (12/12) remote: Compressing objects: 100% (12/12), done. remote: Total 19 (delta 6), reused 9 (delta 6), pack-reused 1  From https://github.com/python/cpython * branch 3.13 -> FETCH_HEAD Note: switching to '1177897551066c1e8c394809152614a6483f9ce7'. You are in 'detached HEAD' state. You can look around, make experimental changes and commit them, and you can discard any commits you make in this state without impacting any branches by switching back to a branch. If you want to create a new branch to retain commits you create, you may do so (now or later) by using -c with the switch command. Example: git switch -c <new-branch-name> Or undo this operation with: git switch - Turn off this advice by setting config variable advice.detachedHead to false HEAD is now at 1177897551 [3.13] gh-111389: Add PyHASH_MULTIPLIER constant (GH-119214) (#119334) Switched to and reset branch '3.13' configure: WARNING: no system libmpdecimal found; falling back to bundled libmpdecimal (deprecated and scheduled for removal in Python 3.15)configure: WARNING: using cross tools not prefixed with host tripletconfigure: WARNING: no system libmpdecimal found; falling back to bundled libmpdecimal (deprecated and scheduled for removal in Python 3.15) In file included from ../../Modules/md5module.c:46: In file included from ../../Modules/_hacl/Hacl_Hash_MD5.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:130:11: warning: 'htole32' macro redefined [-Wmacro-redefined] 130 | # define htole32(x) (x) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:43:9: note: previous definition is here 43 | #define htole32(x) (uint32_t)(x) |^ In file included from ../../Modules/md5module.c:46: In file included from ../../Modules/_hacl/Hacl_Hash_MD5.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:131:11: warning: 'le32toh' macro redefined [-Wmacro-redefined] 131 | # define le32toh(x) (x) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:44:9: note: previous definition is here 44 | #define le32toh(x) (uint32_t)(x) |^ In file included from ../../Modules/md5module.c:46: In file included from ../../Modules/_hacl/Hacl_Hash_MD5.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:132:11: warning: 'htobe32' macro redefined [-Wmacro-redefined] 132 | # define htobe32(x) \ |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:37:9: note: previous definition is here 37 | #define htobe32(x) __bswap32(x) |^ In file included from ../../Modules/md5module.c:46: In file included from ../../Modules/_hacl/Hacl_Hash_MD5.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:138:11: warning: 'be32toh' macro redefined [-Wmacro-redefined] 138 | # define be32toh(x) (htobe32((x))) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:38:9: note: previous definition is here 38 | #define be32toh(x) __bswap32(x) |^ In file included from ../../Modules/md5module.c:46: In file included from ../../Modules/_hacl/Hacl_Hash_MD5.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:140:11: warning: 'htole64' macro redefined [-Wmacro-redefined] 140 | # define htole64(x) (x) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:45:9: note: previous definition is here 45 | #define htole64(x) (uint64_t)(x) |^ In file included from ../../Modules/md5module.c:46: In file included from ../../Modules/_hacl/Hacl_Hash_MD5.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:141:11: warning: 'le64toh' macro redefined [-Wmacro-redefined] 141 | # define le64toh(x) (x) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:46:9: note: previous definition is here 46 | #define le64toh(x) (uint64_t)(x) |^ In file included from ../../Modules/md5module.c:46: In file included from ../../Modules/_hacl/Hacl_Hash_MD5.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:142:11: warning: 'htobe64' macro redefined [-Wmacro-redefined] 142 | # define htobe64(x) \ |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:39:9: note: previous definition is here 39 | #define htobe64(x) __bswap64(x) |^ In file included from ../../Modules/md5module.c:46: In file included from ../../Modules/_hacl/Hacl_Hash_MD5.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:149:11: warning: 'be64toh' macro redefined [-Wmacro-redefined] 149 | # define be64toh(x) (htobe64((x))) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:40:9: note: previous definition is here 40 | #define be64toh(x) __bswap64(x) |^ 8 warnings generated. In file included from ../../Modules/sha1module.c:47: In file included from ../../Modules/_hacl/Hacl_Hash_SHA1.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:130:11: warning: 'htole32' macro redefined [-Wmacro-redefined] 130 | # define htole32(x) (x) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:43:9: note: previous definition is here 43 | #define htole32(x) (uint32_t)(x) |^ In file included from ../../Modules/sha1module.c:47: In file included from ../../Modules/_hacl/Hacl_Hash_SHA1.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:131:11: warning: 'le32toh' macro redefined [-Wmacro-redefined] 131 | # define le32toh(x) (x) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:44:9: note: previous definition is here 44 | #define le32toh(x) (uint32_t)(x) |^ In file included from ../../Modules/sha1module.c:47: In file included from ../../Modules/_hacl/Hacl_Hash_SHA1.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:132:11: warning: 'htobe32' macro redefined [-Wmacro-redefined] 132 | # define htobe32(x) \ |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:37:9: note: previous definition is here 37 | #define htobe32(x) __bswap32(x) |^ In file included from ../../Modules/sha1module.c:47: In file included from ../../Modules/_hacl/Hacl_Hash_SHA1.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:138:11: warning: 'be32toh' macro redefined [-Wmacro-redefined] 138 | # define be32toh(x) (htobe32((x))) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:38:9: note: previous definition is here 38 | #define be32toh(x) __bswap32(x) |^ In file included from ../../Modules/sha1module.c:47: In file included from ../../Modules/_hacl/Hacl_Hash_SHA1.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:140:11: warning: 'htole64' macro redefined [-Wmacro-redefined] 140 | # define htole64(x) (x) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:45:9: note: previous definition is here 45 | #define htole64(x) (uint64_t)(x) |^ In file included from ../../Modules/sha1module.c:47: In file included from ../../Modules/_hacl/Hacl_Hash_SHA1.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:141:11: warning: 'le64toh' macro redefined [-Wmacro-redefined] 141 | # define le64toh(x) (x) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:46:9: note: previous definition is here 46 | #define le64toh(x) (uint64_t)(x) |^ In file included from ../../Modules/sha1module.c:47: In file included from ../../Modules/_hacl/Hacl_Hash_SHA1.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:142:11: warning: 'htobe64' macro redefined [-Wmacro-redefined] 142 | # define htobe64(x) \ |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:39:9: note: previous definition is here 39 | #define htobe64(x) __bswap64(x) |^ In file included from ../../Modules/sha1module.c:47: In file included from ../../Modules/_hacl/Hacl_Hash_SHA1.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:149:11: warning: 'be64toh' macro redefined [-Wmacro-redefined] 149 | # define be64toh(x) (htobe64((x))) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:40:9: note: previous definition is here 40 | #define be64toh(x) __bswap64(x) |^ 8 warnings generated. In file included from ../../Modules/sha3module.c:59: In file included from ../../Modules/_hacl/Hacl_Hash_SHA3.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:130:11: warning: 'htole32' macro redefined [-Wmacro-redefined] 130 | # define htole32(x) (x) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:43:9: note: previous definition is here 43 | #define htole32(x) (uint32_t)(x) |^ In file included from ../../Modules/sha3module.c:59: In file included from ../../Modules/_hacl/Hacl_Hash_SHA3.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:131:11: warning: 'le32toh' macro redefined [-Wmacro-redefined] 131 | # define le32toh(x) (x) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:44:9: note: previous definition is here 44 | #define le32toh(x) (uint32_t)(x) |^ In file included from ../../Modules/sha3module.c:59: In file included from ../../Modules/_hacl/Hacl_Hash_SHA3.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:132:11: warning: 'htobe32' macro redefined [-Wmacro-redefined] 132 | # define htobe32(x) \ |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:37:9: note: previous definition is here 37 | #define htobe32(x) __bswap32(x) |^ In file included from ../../Modules/sha3module.c:59: In file included from ../../Modules/_hacl/Hacl_Hash_SHA3.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:138:11: warning: 'be32toh' macro redefined [-Wmacro-redefined] 138 | # define be32toh(x) (htobe32((x))) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:38:9: note: previous definition is here 38 | #define be32toh(x) __bswap32(x) |^ In file included from ../../Modules/sha3module.c:59: In file included from ../../Modules/_hacl/Hacl_Hash_SHA3.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:140:11: warning: 'htole64' macro redefined [-Wmacro-redefined] 140 | # define htole64(x) (x) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:45:9: note: previous definition is here 45 | #define htole64(x) (uint64_t)(x) |^ In file included from ../../Modules/sha3module.c:59: In file included from ../../Modules/_hacl/Hacl_Hash_SHA3.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:141:11: warning: 'le64toh' macro redefined [-Wmacro-redefined] 141 | # define le64toh(x) (x) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:46:9: note: previous definition is here 46 | #define le64toh(x) (uint64_t)(x) |^ In file included from ../../Modules/sha3module.c:59: In file included from ../../Modules/_hacl/Hacl_Hash_SHA3.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:142:11: warning: 'htobe64' macro redefined [-Wmacro-redefined] 142 | # define htobe64(x) \ |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:39:9: note: previous definition is here 39 | #define htobe64(x) __bswap64(x) |^ In file included from ../../Modules/sha3module.c:59: In file included from ../../Modules/_hacl/Hacl_Hash_SHA3.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:149:11: warning: 'be64toh' macro redefined [-Wmacro-redefined] 149 | # define be64toh(x) (htobe64((x))) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:40:9: note: previous definition is here 40 | #define be64toh(x) __bswap64(x) |^ 8 warnings generated. ../../Modules/expat/xmlparse.c:7839:11: warning: format specifies type 'int' but the argument has type 'ptrdiff_t' (aka 'long') [-Wformat] 7838 | " (+" EXPAT_FMT_PTRDIFF_T("6") " bytes %s|%d, xmlparse.c:%d) %*s\"", |~~~~~~~~~~~~~~~~~~~~~~~~ 7839 | bytesMore, (account == XML_ACCOUNT_DIRECT) ? "DIR" : "EXP", |^~~~~~~~~ 1 warning generated. ../../Modules/_testinternalcapi/test_critical_sections.c:142:1: warning: unused function 'thread_critical_sections' [-Wunused-function] 142 | thread_critical_sections(void *arg) |^~~~~~~~~~~~~~~~~~~~~~~~ 1 warning generated. ../../Modules/posixmodule.c:7859:1: warning: unused function 'warn_about_fork_with_threads' [-Wunused-function] 7859 | warn_about_fork_with_threads(const char* name) |^~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1 warning generated. In file included from ../../Modules/sha2module.c:48: In file included from ../../Modules/_hacl/Hacl_Hash_SHA2.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:130:11: warning: 'htole32' macro redefined [-Wmacro-redefined] 130 | # define htole32(x) (x) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:43:9: note: previous definition is here 43 | #define htole32(x) (uint32_t)(x) |^ In file included from ../../Modules/sha2module.c:48: In file included from ../../Modules/_hacl/Hacl_Hash_SHA2.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:131:11: warning: 'le32toh' macro redefined [-Wmacro-redefined] 131 | # define le32toh(x) (x) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:44:9: note: previous definition is here 44 | #define le32toh(x) (uint32_t)(x) |^ In file included from ../../Modules/sha2module.c:48: In file included from ../../Modules/_hacl/Hacl_Hash_SHA2.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:132:11: warning: 'htobe32' macro redefined [-Wmacro-redefined] 132 | # define htobe32(x) \ |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:37:9: note: previous definition is here 37 | #define htobe32(x) __bswap32(x) |^ In file included from ../../Modules/sha2module.c:48: In file included from ../../Modules/_hacl/Hacl_Hash_SHA2.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:138:11: warning: 'be32toh' macro redefined [-Wmacro-redefined] 138 | # define be32toh(x) (htobe32((x))) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:38:9: note: previous definition is here 38 | #define be32toh(x) __bswap32(x) |^ In file included from ../../Modules/sha2module.c:48: In file included from ../../Modules/_hacl/Hacl_Hash_SHA2.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:140:11: warning: 'htole64' macro redefined [-Wmacro-redefined] 140 | # define htole64(x) (x) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:45:9: note: previous definition is here 45 | #define htole64(x) (uint64_t)(x) |^ In file included from ../../Modules/sha2module.c:48: In file included from ../../Modules/_hacl/Hacl_Hash_SHA2.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:141:11: warning: 'le64toh' macro redefined [-Wmacro-redefined] 141 | # define le64toh(x) (x) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:46:9: note: previous definition is here 46 | #define le64toh(x) (uint64_t)(x) |^ In file included from ../../Modules/sha2module.c:48: In file included from ../../Modules/_hacl/Hacl_Hash_SHA2.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:142:11: warning: 'htobe64' macro redefined [-Wmacro-redefined] 142 | # define htobe64(x) \ |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:39:9: note: previous definition is here 39 | #define htobe64(x) __bswap64(x) |^ In file included from ../../Modules/sha2module.c:48: In file included from ../../Modules/_hacl/Hacl_Hash_SHA2.h:35: In file included from ../../Modules/_hacl/include/krml/types.h:12: ../../Modules/_hacl/include/krml/lowstar_endianness.h:149:11: warning: 'be64toh' macro redefined [-Wmacro-redefined] 149 | # define be64toh(x) (htobe64((x))) |^ /opt/wasi-sdk-21.0/bin/../share/wasi-sysroot/include/endian.h:40:9: note: previous definition is here 40 | #define be64toh(x) __bswap64(x) |^ 8 warnings generated. Kill <WorkerThread #1 running test=test_math pid=2536312 time=25 min> process group Kill <WorkerThread #1 running test=test_statistics pid=2552347 time=25 min> process group make: *** [Makefile:2210: buildbottest] Error 2 Cannot open file '/home/buildbot/buildarea/3.13.bcannon-wasi.wasi.debug/build/build/cross-build/wasm32-wasi/test-results.xml' for upload