This CL address clippy warning about finding the zero
length of something using `is_empty()` instead of `len() == 0`.
Change-Id: I2b36c7c7b65b733609fc0dcd33be06f9d772bc9b
Signed-off-by: Aaqa Ishtyaq <aaqaishtyaq@gmail.com>
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8029
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
This reduces the size of `Builtin` from 88 (!) bytes to 8, and as the
largest variant of `Value`, the size of that type from 96 to 64.
The next largest type is NixList, clocking in at 64 bytes.
This has noticeable performance impact. In an implementation without
disk I/O, evaluating nixpkgs.stdenv looks like this:
Benchmark 1: tvix -E '(import <nixpkgs> {}).stdenv.drvPath'
Time (mean ± σ): 1.151 s ± 0.003 s [User: 1.041 s, System: 0.109 s]
Range (min … max): 1.147 s … 1.155 s 10 runs
After this change, it looks like this:
Benchmark 1: tvix -E '(import <nixpkgs> {}).stdenv.drvPath'
Time (mean ± σ): 1.046 s ± 0.004 s [User: 0.954 s, System: 0.092 s]
Range (min … max): 1.041 s … 1.053 s 10 runs
Change-Id: I5ab7cc02a9a450c0227daf1f1f72966358311ebb
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8027
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
This fixes a very complicated bug (b/246). Evaluation
progresses *much* further after this, leading to several less
complicated bugs likely being uncovered by this
What was the problem?
=====================
Previously, when evaluating a thunk, we had a code path that looked
like this:
match *thunk {
ThunkRepr::Evaluated(Value::Thunk(ref inner_thunk)) => {
let inner_repr = inner_thunk.0.borrow().clone();
drop(thunk);
self.0.replace(inner_repr);
}
/* ... */
}
This code path created a copy of the inner `ThunkRepr` of a nested
thunk, and moved that copy into the `ThunkRepr` of the parent.
The effect of this was that the original `ThunkRepr` (unforced!) lived
on in the original thunk, without the memoization of the subsequent
forcing applying to it.
This had the result that Tvix would repeatedly evaluate these thunks
without ever memoizing them, if they occured repeatedly as shared
inner thunks. Most notably, this would *always* occur when
builtins.import was used.
What's the solution?
====================
I have completely rewritten `Thunk::force_trampoline_self` to make all
flows that can occur in it explicit. I have also removed the outer
loop inside of that function, and resorted to more use of trampolining
instead.
The function is now well-commented and it should be possible to read
it from top-to-bottom and get a general sense of what is going on,
though the trampolining itself (which is implemented in the VM) needs
to be at least partially understood for this.
What's the new problem(s)?
==========================
One new (known) problem is that we have to construct `Error` instances
in all error types here, but we do not have spans available in some
thunk-related situations. Due to b/238 we cannot ask the VM for an
arbitrary span from the callsite leading to the force. This means that
there are now code paths where, under certain conditions, causing an
evaluation error during thunk forcing will panic.
To fix this we will need to investigate and fix b/238, and/or add a
span tracking mechanism to thunks themselves.
What other impacts does this have?
==================================
With this commit, eval of nixpkgs mostly succeeds (things like stdenv
evaluate to the same hashes for us and C++ Nix, meaning we now
construct identical derivations without eval breaking).
Due to this we progress much further into nixpkgs, which lets us
uncover more additional bugs. For example, after this commit we can
quickly see that cl/7949 introduces some kind of behavioural issue and
should not be merged as-is (this was not apparent before).
Additionally, tvix-eval is now seemingly very fast. When doing
performance analysis of a nixpkgs eval, we now mostly see the code
path for shelling out to C++ Nix to add things to the store in there.
We still need those code paths, so we can not (yet) do a performance
analysis beyond that.
Change-Id: I738525bad8bc5ede5d8c737f023b14b8f4160612
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8012
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
This keeps the actual TotalDisplay implementation readable, as this
float formatting code suddenly made up the majority of its implementation.
Change-Id: I2c0d00e4a691e0b8ffbc72680f680e16feef4bee
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7925
Reviewed-by: flokli <flokli@flokli.de>
Autosubmit: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
Apparently our naive implementation of float formatting, which simply
used {:.5}, and trimmed trailing "0" strings not sufficient.
It wrongly trimmed numbers with zeroes but no decimal point, like
`10000` got trimmed to `1`.
Nix uses `std::to_string` on the double, which according to
https://en.cppreference.com/w/cpp/string/basic_string/to_string
is equivalent to `std::sprintf(buf, "%f", value)`.
https://en.cppreference.com/w/cpp/io/c/fprintf mentions this is treated
like this:
> Precision specifies the exact number of digits to appear after
> the decimal point character. The default precision is 6. In the
> alternative implementation decimal point character is written even if
> no digits follow it. For infinity and not-a-number conversion style
> see notes.
This doesn't seem to be the case though, and Nix uses scientific
notation in some cases.
There's a whole bunch of strategies to determine which is a more compact
notation, and which notation should be used for a given number.
https://github.com/rust-lang/rust/issues/24556 provides some pointers
into various rabbit holes for those interested.
This gist seems to be that currently a different formatting is not
exposed in rust directly, at least not for public consumption.
There is the
[lexical-core](https://github.com/Alexhuszagh/rust-lexical) crate
though, which provides a way to format floats with various strategies
and formats.
Change our implementation of `TotalDisplay` for the `Value::Float` case
to use that. We still need to do some post-processing, because Nix
always adds the sign in scientific notation (and there's no way to
configure lexical-core to do that), and lexical-core in some cases keeps
the trailing zeros.
Even with all that in place, there as a difference in `eval-okay-
fromjson.nix` (from tvix-tests), which I couldn't get to work. I updated
the fixture to a less problematic number.
With this, the testsuite passes again, and does for the upcoming CL
introducing builtins.fromTOML, and enabling the nix testsuite bits for
it, too.
Change-Id: Ie6fba5619e1d9fd7ce669a51594658b029057acc
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7922
Tested-by: BuildkiteCI
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: tazjin <tazjin@tvl.su>
This forces users to pass the fully constructed set of globals to the
VM, making it harder to accidentally "lose" the set while weak
references to it still exist.
This doesn't modify any functionality, but is laying the foundation
for simplifying some of the builtins behaviour that has grown more
complex again.
Change-Id: I5120f97861c65dc46d90b8a4e2c92ad32cc53e03
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7877
Autosubmit: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
This makes it possible for users to add additional context to an
error, which will then be rendered as an additional secondary span in
the formatted error output.
We should strive to do this basically anywhere errors are raised that
can occur multiple times, *especially* during type casts. This was
triggered by me debugging a type cast error attached to a fairly
large-ish span (a builtin invocation).
Change-Id: I51be41fabee00cf04de973935daf34fe6424e76f
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7849
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
Instead of having a representation of suspended native thunks that
involves constructing a fake code chunk, make these thunks a
first-class part of the internal thunk representation.
The previous code was not that simple to understand, and actually
contained a critical bug which could lead to Tvix crashes. This
version fixes the particular instance of that bug, but instead
uncovers another (b/238) which can still lead to Tvix crashes.
Fixes: b/237.
Change-Id: I771d03864084d63953bdbb518fec94487481f839
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7750
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
This is unnecessary, Rc already provides all the boxing we need.
Change-Id: I08cf0939c48da43f04c847526c7e5dae5336d528
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7749
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>
Reviewed-by: sterni <sternenseemann@systemli.org>
Instead of going through Vec/BTreeMap for generating our internal
types, use the proptest strategies from imbl.
The one thing I couldn't figure out in the previous implementation is
where the ranges/sizes of generated collections came from. The
strategies in proptest use different types (Range, with an unknown
default value, and SizeRange with 0..100). I've opted to specify
0..100 directly, but we can probably make it configurable.
Change-Id: I749bc4c703fe424099240cab822b1642e5216361
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7791
Autosubmit: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
External implementors of builtins must be able to force values, which
necessitates publishing a bunch more items from the crate.
Change-Id: I8f6b8ae88156aae417dbe630a698d123d0c1c8d4
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7830
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
This CL addresses clippy warning len_without_is_empty
which expects `.is_empty()` method to be present when
implementing `.len()` method for an item.
Change-Id: I8878db630b9ef5853649a906b764a33299bb5dc8
Signed-off-by: Aaqa Ishtyaq <aaqaishtyaq@gmail.com>
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7806
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Implements `Serialize` for `tvix_eval::Value`. Special care is taken
with serialisation of attribute sets, and forcing of thunks.
The tests should cover both cases well.
Change-Id: I9bb135bacf6f87bc6bd0bd88cef0a42308e6c335
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7803
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Autosubmit: tazjin <tazjin@tvl.su>
With this is_valid_nix_identifier should line up with the upstream lexer
definition:
ID [a-zA-Z\_][a-zA-Z0-9\_\'\-]*
While we're working on this, add a simple test checking the various
formatting rules. Interestingly, it would not be suitable as an identity
test, since you have to write
{ "assert" = null; }
in order to avoid an evaluation error, but C++ Nix is happy to print
this as
{ assert = null; }
– maybe should be considered to be a bug.
Change-Id: I0a4e1ccb5033a80f3767fb8d1c4bba08d303c5d8
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7744
Autosubmit: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
The `im::OrdMap` is already small and cheap to copy while sharing
memory, so this is not required anymore.
Only the `KV` variant may have slightly larger content, but in
practice this doesn't seem to make a difference when comparing the two
variants and this one is less complicated.
Change-Id: I64a563b209a2444125653777551373cb2989ca7d
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7677
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
This uses the `im::OrdMap` for `NixAttrs` to enable sharing of memory
between different iterations of a map.
This slightly speeds up eval, but not significantly. Future work might
include benchmarking whether using a `HashMap` and only ordering in
cases where order is actually required would help.
This switches to a fork of `im` that fixes some bugs with its OrdMap
implementation.
Change-Id: I2f6a5ff471b6d508c1e8a98b13f889f49c0d9537
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7676
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
The conversion from im::Vector -> Vec is cheaper for NixList
construction (of course), so where possible we should make use of
that.
This updates most builtins dealing with lists to use Vector directly,
and marks the function constructing NixList from Vec as deprecated so
that we get appropriate warnings in places where it's still in use.
These places are currently inside of JSON serialisation logic which is
in flux right now, so lets leave them as-is until it's stabilised.
Change-Id: I037f12a2800f2576db4d9526bd935efd079163f0
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7671
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
This is a persistent, structurally sharing data structure which is
more efficient in some of our use-cases. I have verified the
efficiency improvement using `hyperfine` repeatedly over expressions
on nixpkgs.
Lists are not the most performance-critical structure in Nix (that
would be attribute sets), but we can already see a small (~5-10%)
improvement.
Note that there are a handful of cases where we still go via `Vec`
that need to be fixed, most notable for `builtins.sort` which can not
currently be implemented directly using `im::Vector` because of a
restrictive type bound.
Change-Id: I237cc50cbd7629a046e5a5e4601fbb40355e551d
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7670
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
It's been a while since the last time, so quite a lot of stuff has
accumulated here.
Change-Id: I0762827c197b30a917ff470fd8ae8f220f6ba247
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7597
Reviewed-by: grfn <grfn@gws.fyi>
Autosubmit: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
Introduces continuation-passing-based trampolining of thunk forcing to
avoid recursing when forcing deeply nested expressions.
This is required for evaluating large expressions.
This change was extracted out of cl/7362.
Co-authored-by: Vincent Ambo <tazjin@tvl.su>
Co-authored-by: Griffin Smith <grfn@gws.fyi>
Change-Id: Ifc1747e712663684b2fff53095de62b8459a47f3
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7551
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
... if they are known. We currently do not propagate names correctly
for curried functions.
Change-Id: I19d57fb30a5c0000ccdf690b91076f6b2191de23
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7596
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>
This value creates a human-readable explanation of a value. This can
be used to implement documentation related functionality.
For some values, the amount of information displayed can be expanded
quite a bit.
Change-Id: Ie8c400feae909e7680af163596f99060262e4241
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7592
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI
This "ties the knot" of importing files into a store when referring
to them through path literals, e.g. inside of strings.
I'm not yet sure if this interface is sufficient for
builtins.path (which we haven't implemented at all yet), but it's
enough to wire up eval & store initially.
In the default implementations nothing interesting happens in this
function at all.
Change-Id: Ie01ff4161617d1e743a68dbd1a5e54c1b40c0990
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7582
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI
This lets users set the `io_handle` field on an `Evaluation`, which is
then propagated to the VM.
Change-Id: I616d7140724fb2b4db47c2ebf95451d5303a487a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7566
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI
This type carries the information required for calculating a
span (i.e. the chunk and offset), instead of the span itself. The span
is then only calculated in cases where it is required (when throwing
errors).
This reduces the eval time for
`builtins.length (builtins.attrNames (import <nixpkgs> {}))` by *one
third*!
The data structure in chunks that carries span information reduces
in-memory size by trading off the speed of retrieving span
information. This is because the span information is only actually
required when throwing errors (or emitting warnings).
However, somewhere along the way we grew a dependency on carrying span
information in thunks (for correctly reporting error chains). Hitting
the code paths for span retrieval was expensive, and carrying the
spans in a different way would still be less cache-efficient. This
change is the best tradeoff I could come up with.
Refs: b/229.
Change-Id: I27d4c4b5c5f9be90ac47f2db61941e123a78a77b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7558
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI
Having thunks which, when forced, execute native Rust code rather
than interpreted opcodes lets us avoid having to bundle
`src/libexpr/primops/derivation.nix` like cppnix does by implementing
it in Rust instead.
Change-Id: If91d77a6736234321eee87ba4b4777eed5a3fe1c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7450
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI
Fixes b/212. Based on feedback in https://cl.tvl.fyi/c/depot/+/7492, all
uses of `NixAttrs::from_map` have been removed. Only `from_iter` and
`from_kv` remain.
Change-Id: I52e25f73018c2aa1843197427516b7a852503e2c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7500
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
Autosubmit: IslandUsurper <lyle@menteeth.us>
Allows for the removal of some BTreeMap usage when constructing NixAttrs
by allowing any iterator over 2-tuples to build a NixAttrs. Some
instances of BTreeMap didn't have anything to do with making NixAttrs,
and some were just the best tool for the job, so they are left using the
old `from_map` interface.
Change-Id: I668ea600b0d93eae700a6b1861ac84502c968d78
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7492
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
With this change, the test introduced by cl/7370 passes.
Change-Id: Ie7d2f02a59d61151f14ebd328e6cfa5892cacfb0
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7375
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
Autosubmit: Adam Joseph <adam@westernsemico.com>
This passes all the function/thunk-pointer-equality tests in
cl/7369.
Change-Id: Ib47535ba2fc77a4f1c2cc2fd23d3a879e21d8b4c
Signed-off-by: Adam Joseph <adam@westernsemico.com>
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7358
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
See cl/7368
Change-Id: I97630994c3d65f4d16414a0da236ce000a5b6d33
Signed-off-by: Adam Joseph <adam@westernsemico.com>
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7374
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
See cl/7372; Nix equality semantics require the ability to track
pointer equality of upvalue-sets.
Signed-off-by: Adam Joseph <adam@westernsemico.com>
Change-Id: I82ba517499cf370189a80355e4e46a5caaab7153
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7373
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
When we start unrecursivifying (sp?) things, Rust's borrow checker
is going to be a headache; its magic only works when you use the CPU
stack as your call stack.
Fixing the borrow checker issues usually involves adding lots of
`clone()`s. Right now `NixList` is the only variant of `Value` that
isn't cheap to clone() -- all the others are either a wrapper around
Rc or else are of bounded size.
Note that this requires dropping the `DerefMut for NixList` instance
and using `Vec<Value>` instead in those situations.
Change-Id: I5a47df66855342aa2064f8f3cb7934ff422d26bd
Signed-off-by: Adam Joseph <adam@westernsemico.com>
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7359
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
When comparing Nix values for equality, an issue can occur where
recursive values contain thunks to themselves which causes borrow
errors when forcing them for comparison later down the line.
To work around this we clone the values for now. There might be some
optimisations possible like checking for thunk equality directly and
short-circuiting on that (we have to check what Nix does).
Change-Id: I7e75c992ea68f100058f52b4b46168da7d671994
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7314
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
When passing multiple arguments, every intermediate callable needs to
be forced as this is expected by the VM's call_value function.
Also adds a debug assertion for this which makes it easier to spot
exactly what went wrong.
Change-Id: I3aa519cb6cdaab713bd18282bef901c4cd77c535
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7312
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
