This is a problem on big-endian CPUs because you end up with nimvm
computing something different than Nim proper, so e.g. a const table
won't work.
I also took the liberty to replace a redundant implementation of load4
in murmurHash.
(Thanks to barracuda156 for helping debug this.)
refs #6978, refs #6752, refs #21613, refs #24234
The `jsNoInt64`, `whenHasBigInt64`, `whenJsNoBigInt64` templates are
replaced with bool constants to use with `when`. Weird that I didn't do
this in the first place.
The `whenJsNoBigInt64` template was also slightly misleading. The first
branch was compiled for both no bigint64 on JS as well as on C/C++. It
seems only `trandom` depended on this by mistake.
The workaround for #6752 added in #6978 to `times` is also removed with
`--jsbigint64:on`, but #24233 was also encountered with this, so this PR
depends on #24234.
makes new hash the default, with an opt-out (& js-no-big-int) define.
Also update changelog (& fix one typo).
Only really expect the chronos hash-order sensitive test to fail until
they merge that PR and tag a new release.
Unlike present Nim this actually fills `Hash` for `string` & related.
For the curious, note that `hashData` remains the aboriginal Nim string
hasher & `import hashes {.all.}` allows simultaneous test/time of {orig,
murmur, farm} on your favorite CPU & back end compiler.
Update tests also conditioned upon `nimPreviewHashFarm` so they should
pass either with or without that `define` on.
In `--jsbigint=on` mode, only the lower 32-bits of `Hash` match nimvm &
run-time values because `type Hash = int` and on JS int=int32, not int64
as for 64-bit Nim platforms. Due to the matching, `const` Table should
match run-time `Table` on all platforms.
To operate in `--jsbigint=off` mode is feasible but needs much "double
precision mul/xor/ror/shr-arithmetic"-style work. That is distracting &
also of questionable value since JS added BigInt in 2018, ringabout
added Nim support for it in 2021 & `nimPreviewHashFarm` is unlikely to
swap from an opt-in to an opt-out default before 2025..2026 which will
have given a backward looking time window of 7..8 years for deployment
platforms - reasonably generous.
Add a changelog entry for 2.2.
why ?
- We already have an emit that does the same thing
- The name asm itself is a bit confusing, you might think it's an alias
for asm.js or something else.
- The asm keyword is used differently on different compiler targets (it
makes it inexpressive).
- Does anyone (other than some compiler libraries) use asm instead of
emit ? If yes, it's a bit strange to use asm somewhere and emit
somewhere. By making the asm keyword for js target deprecated, there
would be even less use of the asm keyword for js target, reducing the
amount of confusion.
- New users might accidentally use a non-universal approach via the asm
keyword instead of emit, and then when they learn about asm, try to
figure out what the differences are.
see https://forum.nim-lang.org/t/10821
---------
Co-authored-by: Andreas Rumpf <rumpf_a@web.de>
* test fix#16546#16548 + another issue
* please don't tell me other packages do this
* fix CI + test typeclass callconv pragma
* better logic in parser
* docs and changelog
* add example of hashing an object by all of its fields with `fields`
* Update lib/pure/hashes.nim
* Update lib/pure/hashes.nim
* Update lib/pure/hashes.nim
Co-authored-by: flywind <43030857+xflywind@users.noreply.github.com>
Co-authored-by: Timothee Cour <timothee.cour2@gmail.com>
* Unwind just the "pseudorandom probing" (whole hash-code-keyed variable
stride double hashing) part of recent sets & tables changes (which has
still been causing bugs over a month later (e.g., two days ago
https://github.com/nim-lang/Nim/issues/13794) as well as still having
several "figure this out" implementation question comments in them (see
just diffs of this PR).
This topic has been discussed in many places:
https://github.com/nim-lang/Nim/issues/13393https://github.com/nim-lang/Nim/pull/13418https://github.com/nim-lang/Nim/pull/13440https://github.com/nim-lang/Nim/issues/13794
Alternative/non-mandatory stronger integer hashes (or vice-versa opt-in
identity hashes) are a better solution that is more general (no illusion
of one hard-coded sequence solving all problems) while retaining the
virtues of linear probing such as cache obliviousness and age-less tables
under delete-heavy workloads (still untested after a month of this change).
The only real solution for truly adversarial keys is a hash keyed off of
data unobservable to attackers. That all fits better with a few families
of user-pluggable/define-switchable hashes which can be provided in a
separate PR more about `hashes.nim`.
This PR carefully preserves the better (but still hard coded!) probing
of the `intsets` and other recent fixes like `move` annotations, hash
order invariant tests, `intsets.missingOrExcl` fixing, and the move of
`rightSize` into `hashcommon.nim`.
* Fix `data.len` -> `dataLen` problem.
* This is an alternate resolution to https://github.com/nim-lang/Nim/issues/13393
(which arguably could be resolved outside the stdlib).
Add version1 of Wang Yi's hash specialized to 8 byte integers. This gives
simple help to users having trouble with overly colliding hash(key)s. I.e.,
A) `import hashes; proc hash(x: myInt): Hash = hashWangYi1(int(x))`
in the instantiation context of a `HashSet` or `Table`
or
B) more globally, compile with `nim c -d:hashWangYi1`.
No hash can be all things to all use cases, but this one is A) vetted to
scramble well by the SMHasher test suite (a necessarily limited but far
more thorough test than prior proposals here), B) only a few ALU ops on
many common CPUs, and C) possesses an easy via "grade school multi-digit
multiplication" fall back for weaker deployment contexts.
Some people might want to stampede ahead unbridled, but my view is that a
good plan is to
A) include this in the stdlib for a release or three to let people try it
on various key sets nim-core could realistically never access/test
(maybe mentioning it in the changelog so people actually try it out),
B) have them report problems (if any),
C) if all seems good, make the stdlib more novice friendly by adding
`hashIdentity(x)=x` and changing the default `hash() = hashWangYi1`
with some `when defined` rearranging so users can `-d:hashIdentity`
if they want the old behavior back.
This plan is compatible with any number of competing integer hashes if
people want to add them. I would strongly recommend they all *at least*
pass the SMHasher suite since the idea here is to become more friendly to
novices who do not generally understand hashing failure modes.
* Re-organize to work around `when nimvm` limitations; Add some tests; Add
a changelog.md entry.
* Add less than 64-bit CPU when fork.
* Fix decl instead of call typo.
* First attempt at fixing range error on 32-bit platforms; Still do the
arithmetic in doubled up 64-bit, but truncate the hash to the lower
32-bits, but then still return `uint64` to be the same. So, type
correct but truncated hash value. Update `thashes.nim` as well.
* A second try at making 32-bit mode CI work.
* Use a more systematic identifier convention than Wang Yi's code.
* Fix test that was wrong for as long as `toHashSet` used `rightSize` (a
very long time, I think). `$a`/`$b` depend on iteration order which
varies with table range reduced hash order which varies with range for
some `hash()`. With 3 elements, 3!=6 is small and we've just gotten
lucky with past experimental `hash()` changes. An alternate fix here
would be to not stringify but use the HashSet operators, but it is not
clear that doesn't alter the "spirit" of the test.
* Fix another stringified test depending upon hash order.
* Oops - revert the string-keyed test.
* Fix another stringify test depending on hash order.
* Add a better than always zero `defined(js)` branch.
* It turns out to be easy to just work all in `BigInt` inside JS and thus
guarantee the same low order bits of output hashes (for `isSafeInteger`
input numbers). Since `hashWangYi1` output bits are equally random in
all their bits, this means that tables will be safely scrambled for table
sizes up to 2**32 or 4 gigaentries which is probably fine, as long as the
integer keys are all < 2**53 (also likely fine). (I'm unsure why the
infidelity with C/C++ back ends cut off is 32, not 53 bits.)
Since HashSet & Table only use the low order bits, a quick corollary of
this is that `$` on most int-keyed sets/tables will be the same in all
the various back ends which seems a nice-to-have trait.
* These string hash tests fail for me locally. Maybe this is what causes
the CI hang for testament pcat collections?
* Oops. That failure was from me manually patching string hash in hashes. Revert.
* Import more test improvements from https://github.com/nim-lang/Nim/pull/13410
* Fix bug where I swapped order when reverting the test. Ack.
* Oh, just accept either order like more and more hash tests.
* Iterate in the same order.
* `return` inside `emit` made us skip `popFrame` causing weird troubles.
* Oops - do Windows branch also.
* `nimV1hash` -> multiply-mnemonic, type-scoped `nimIntHash1` (mnemonic
resolutions are "1 == identity", 1 for Nim Version 1, 1 for
first/simplest/fastest in a series of possibilities. Should be very
easy to remember.)
* Re-organize `when nimvm` logic to be a strict `when`-`else`.
* Merge other changes.
* Lift constants to a common area.
* Fall back to identity hash when `BigInt` is unavailable.
* Increase timeout slightly (probably just real-time perturbation of CI
system performance).
* hashes: implement murmur3
* refactoring; there is only one murmurHash and it works at compile-time via VM hooks
* fixes JS tests
* makes toOpenArrayByte work with C++
* make it bootstrap in C++ mode for 0.20
