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2023-03-13 r/5979 fix(tvix/eval): implement cppnix JSON-serialisation semanticsVincent Ambo1-2/+2
This drops the usage of serde::Serialize, as the trait can not be used to implement the correct semantics (function colouring!). Instead, a manual JSON serialisation function is written which correctly handles toString, outPath and other similar weirdnesses. Unexpectedly, the eval-okay-tojson test from the C++ Nix test suite now passes, too. This fixes an issue where serialising data structures containing derivations to JSON would fail. Change-Id: I5c39e3d8356ee93a07eda481410f88610f6dd9f8 Reviewed-on: https://cl.tvl.fyi/c/depot/+/8209 Reviewed-by: raitobezarius <tvl@lahfa.xyz> Tested-by: BuildkiteCI
2023-03-13 r/5966 refactor(tvix/eval): wrap NixList in RcVincent Ambo1-11/+13
The size of a `Vector<Value>` is 64 *bytes*, which is quite large, and it bloated the entire Value type to this size. This change adds an indirection for the inner vector through Rc. Initially I tried to use a Box, but this breaks pointer equality guarantees for the Vector when it is small enough to be inlined. This reduces the size of Value from 64 to 32 bytes. Change-Id: Ic3211e861b1966c78b2c3d536ba291fea92647fd Reviewed-on: https://cl.tvl.fyi/c/depot/+/8150 Reviewed-by: raitobezarius <tvl@lahfa.xyz> Tested-by: BuildkiteCI
2023-03-13 r/5964 refactor(tvix/eval): flatten call stack of VM using generatorsVincent Ambo1-28/+4
Warning: This is probably the biggest refactor in tvix-eval history, so far. This replaces all instances of trampolines and recursion during evaluation of the VM loop with generators. A generator is an asynchronous function that can be suspended to yield a message (in our case, vm::generators::GeneratorRequest) and receive a response (vm::generators::GeneratorResponsee). The `genawaiter` crate provides an interpreter for generators that can drive their execution and lets us move control flow between the VM and suspended generators. To do this, massive changes have occured basically everywhere in the code. On a high-level: 1. The VM is now organised around a frame stack. A frame is either a call frame (execution of Tvix bytecode) or a generator frame (a running or suspended generator). The VM has an outer loop that pops a frame off the frame stack, and then enters an inner loop either driving the execution of the bytecode or the execution of a generator. Both types of frames have several branches that can result in the frame re-enqueuing itself, and enqueuing some other work (in the form of a different frame) on top of itself. The VM will eventually resume the frame when everything "above" it has been suspended. In this way, the VM's new frame stack takes over much of the work that was previously achieved by recursion. 2. All methods previously taking a VM have been refactored into async functions that instead emit/receive generator messages for communication with the VM. Notably, this includes *all* builtins. This has had some other effects: - Some test have been removed or commented out, either because they tested code that was mostly already dead (nix_eq) or because they now require generator scaffolding which we do not have in place for tests (yet). - Because generator functions are technically async (though no async IO is involved), we lose the ability to use much of the Rust standard library e.g. in builtins. This has led to many algorithms being unrolled into iterative versions instead of iterator combinations, and things like sorting had to be implemented from scratch. - Many call sites that previously saw a `Result<..., ErrorKind>` bubble up now only see the result value, as the error handling is encapsulated within the generator loop. This reduces number of places inside of builtin implementations where error context can be attached to calls that can fail. Currently what we gain in this tradeoff is significantly more detailed span information (which we still need to bubble up, this commit does not change the error display). We'll need to do some analysis later of how useful the errors turn out to be and potentially introduce some methods for attaching context to a generator frame again. This change is very difficult to do in stages, as it is very much an "all or nothing" change that affects huge parts of the codebase. I've tried to isolate changes that can be isolated into the parent CLs of this one, but this change is still quite difficult to wrap one's mind and I'm available to discuss it and explain things to any reviewer. Fixes: b/238, b/237, b/251 and potentially others. Change-Id: I39244163ff5bbecd169fe7b274df19262b515699 Reviewed-on: https://cl.tvl.fyi/c/depot/+/8104 Reviewed-by: raitobezarius <tvl@lahfa.xyz> Reviewed-by: Adam Joseph <adam@westernsemico.com> Tested-by: BuildkiteCI
2023-03-13 r/5961 feat(tvix/eval): implement asynchronous list sorting algorithmVincent Ambo1-0/+47
In order to implement an asynchronous builtins.sort (required for moving builtins to generators), we need an `async` sorting algorithm as our comparators involve invoking a Nix function. This commit implements a fairly simple, optimised bubble sort as the sorting algorithm used in our `async fn sort_by`. There don't seem to be any crates providing async versions of things like this, and they might actually be pretty hard to implement generically due to some constraints about how `async` works. Note that this algorithm is less efficient than the hybrid "timsort/mergesort/insert sort" used in the Rust standard library. I tried to write a merge sort implementation, but ran into isuses with the sort becoming unstable because our comparators can not yield equality. This is the simplest implementation which I know to be correct. Note that as of this commit this is *not* covered by the Tvix test suite, but it will be as soon as the rest of the generator code lands. Change-Id: Ia9a604f7dd941d6acc9212c902e0e637ed75bebc Reviewed-on: https://cl.tvl.fyi/c/depot/+/8239 Reviewed-by: Adam Joseph <adam@westernsemico.com> Tested-by: BuildkiteCI
2023-01-17 r/5670 refactor(tvix/value): use proptest strategies from imbl crateVincent Ambo1-23/+0
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>
2023-01-12 r/5654 fix(tvix/eval): len_without_is_empty clippy warnAaqa Ishtyaq1-0/+4
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
2023-01-12 r/5652 feat(tvix/eval): implement builtins.toJSONVincent Ambo1-2/+2
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>
2023-01-10 r/5640 feat(tvix/eval): implement serde::Deserialize for ValueRyan Lahfa1-1/+3
Co-Authored-By: Vincent Ambo <tazjin@tvl.su> Change-Id: Ib6f7d1f4f4faac36b44f5f75cccc57bf912cf606 Reviewed-on: https://cl.tvl.fyi/c/depot/+/7626 Reviewed-by: tazjin <tazjin@tvl.su> Tested-by: BuildkiteCI
2022-12-29 r/5541 refactor(tvix/eval): persistent, memory-sharing OrdMap for NixAttrsVincent Ambo1-3/+3
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
2022-12-29 r/5540 refactor(tvix/eval): use im::Vector directly where possibleVincent Ambo1-10/+9
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
2022-12-29 r/5534 refactor(tvix/eval): use im::Vector for NixList representationVincent Ambo1-29/+29
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>
2022-11-30 r/5354 feat(tvix/eval): From<Rc<Vec<Value>>> for NixListAdam Joseph1-0/+6
Change-Id: I2ab53453ed7370b520bb929ef7285e4f23eec65b Reviewed-on: https://cl.tvl.fyi/c/depot/+/7453 Reviewed-by: tazjin <tazjin@tvl.su> Tested-by: BuildkiteCI Autosubmit: Adam Joseph <adam@westernsemico.com>
2022-11-23 r/5301 feat(tvix/eval): make NixList::clone() cheapAdam Joseph1-24/+20
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
2022-11-04 r/5236 fix(tvix/eval): remove impl PartialEq for ValueAdam Joseph1-1/+1
It isn't possible to implement PartialEq properly for Value, because any sensible implementation needs to force() thunks, which cannot be done without a `&mut VM`. The existing derive(PartialEq) has false negatives, which caused the bug which cl/7142 fixed. Fortunately that bug was easy to find, but a silent false negative deep within the bowels of nixpkgs could be a real nightmare to hunt down. Let's just remove the PartialEq impl for Value, and the other derive(PartialEq)'s that depend on it. Signed-off-by: Adam Joseph <adam@westernsemico.com> Change-Id: Iacd3726fefc7fc1edadcd7e9b586e04cf8466775 Reviewed-on: https://cl.tvl.fyi/c/depot/+/7144 Reviewed-by: kanepyork <rikingcoding@gmail.com> Reviewed-by: tazjin <tazjin@tvl.su> Tested-by: BuildkiteCI
2022-10-29 r/5222 feat(tvix/eval): Implement builtins.sortGriffin Smith1-1/+7
This is a bit tricky because the comparator can throw errors, so we need to propagate them out if they exist and try to avoid sorting forever by returning a reasonable ordering in this case (as short-circuiting is not available). Co-Authored-By: Vincent Ambo <tazjin@tvl.su> Change-Id: Icae1d30f43ec1ae64b2ba51e73ee467605686792 Reviewed-on: https://cl.tvl.fyi/c/depot/+/7072 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org>
2022-10-29 r/5221 feat(tvix/eval): Implement comparison for listsGriffin Smith1-0/+10
Lists are compared lexicographically in C++ nix as of [0], and our updated nix test suites depend on this. This implements comparison of list values in `Value::nix_cmp` using a very similar algorithm to what C++ does - similarly to there, this requires passing in the VM so we can force thunks in the list elements as we go. [0]: https://github.com/NixOS/nix/commit/09471d2680292af48b2788108de56a8da755d661# Change-Id: I5d8bb07f90647a1fec83f775243e21af856afbb1 Reviewed-on: https://cl.tvl.fyi/c/depot/+/7070 Autosubmit: grfn <grfn@gws.fyi> Reviewed-by: sterni <sternenseemann@systemli.org> Tested-by: BuildkiteCI
2022-10-26 r/5200 feat(tvix/eval): add NixList::force_elements()Adam Joseph1-0/+5
This adds a function NixList::force_elements() which forces each element of the list shallowly. This behavior is needed for `builtins.replaceStrings`, and probably a few other builtins as well. Signed-off-by: Adam Joseph <adam@westernsemico.com> Change-Id: I3f0681acbbfe50e781b5f07b6a441647f5e6f8da Reviewed-on: https://cl.tvl.fyi/c/depot/+/7094 Tested-by: BuildkiteCI Reviewed-by: tazjin <tazjin@tvl.su>
2022-10-24 r/5189 feat(nix/eval): Implement builtins.groupByGriffin Smith1-0/+8
Change-Id: I3e0aa017a7100cbeb86d2e5747471b36affcc102 Reviewed-on: https://cl.tvl.fyi/c/depot/+/7038 Autosubmit: grfn <grfn@gws.fyi> Reviewed-by: tazjin <tazjin@tvl.su> Tested-by: BuildkiteCI
2022-10-23 r/5178 fix(tvix/eval): detect cycles when printing infinite valuesVincent Ambo1-5/+5
Using the same method as in Thunk::deep_force, detect cycles when printing values by maintaining a set of already seen thunks. With this, display of infinite values matches that of Nix: > nix-instantiate --eval --strict -E 'let as = { x = 123; y = as; }; in as' { x = 123; y = { x = 123; y = <CYCLE>; }; } > tvix-eval -E 'let as = { x = 123; y = as; }; in as' => { x = 123; y = { x = 123; y = <CYCLE>; }; } :: set Change-Id: I007b918d5131d82c28884e46e46ff365ef691aa8 Reviewed-on: https://cl.tvl.fyi/c/depot/+/7056 Tested-by: BuildkiteCI Reviewed-by: grfn <grfn@gws.fyi>
2022-10-22 r/5175 feat(tvix/eval): Implement builtins.deepSeqGriffin Smith1-0/+10
This is done via a new `deepForce` function on Value. Since values can be cyclical (for example, see the test-case), we need to do some extra work to avoid RefCell borrow errors if we ever hit a graph cycle: While deep-forcing values, we keep a set of thunks that we have already seen and avoid doing any work on the same thunk twice. The set is encapsulated in a separate type to stop potentially invalid pointers from leaking out. Finally, since deep_force is conceptually similar to `VM::force_for_output` (but more suited to usage in eval since it doesn't clone the values) this removes the latter, replacing it with the former. Co-Authored-By: Vincent Ambo <tazjin@tvl.su> Change-Id: Iefddefcf09fae3b6a4d161a5873febcff54b9157 Reviewed-on: https://cl.tvl.fyi/c/depot/+/7000 Tested-by: BuildkiteCI Reviewed-by: grfn <grfn@gws.fyi> Reviewed-by: tazjin <tazjin@tvl.su>
2022-10-19 r/5158 feat(tvix/eval): NixList::concat(): avoid an unnecessary moveAdam Joseph1-4/+3
In `a++b`, the previous implementation would move `b` (i.e. memcpy its elements) twice. Let's do that only once. We sure do call NixList.clone() a whole lot. At some point in the future we probably want to do a SmolStr-type split for NixList into a two-variant enum where one side is an Rc<Vec<Value>> for lists longer than a certain length. Signed-off-by: Adam Joseph <adam@westernsemico.com> Change-Id: I32154d18785a1f663454a8b9d4afd3e78bffdf9c Reviewed-on: https://cl.tvl.fyi/c/depot/+/7040 Tested-by: BuildkiteCI Reviewed-by: tazjin <tazjin@tvl.su>
2022-10-03 r/5021 refactor(tvix/eval): implement IntoIterator for NixListVincent Ambo1-4/+9
This is the same code as before, just moved into a trait impl to gain access to stuff that needs IntoIterator Change-Id: Iff9375cd05593dd2681fa85ccc7f4554bf944a02 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6842 Autosubmit: tazjin <tazjin@tvl.su> Reviewed-by: sterni <sternenseemann@systemli.org> Tested-by: BuildkiteCI
2022-09-18 r/4909 chore(tvix/eval): Pass in VM to nix_eqGriffin Smith1-2/+3
Pass in, but ignore, a mutable reference to the VM to the `nix_eq` functions, in preparation for using that VM to force thunks during comparison. Change-Id: I565435d8dfb33768f930fdb5a6b0fb1365d7e161 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6651 Autosubmit: grfn <grfn@gws.fyi> Tested-by: BuildkiteCI Reviewed-by: tazjin <tazjin@tvl.su>
2022-09-18 r/4908 refactor(tvix/eval): Don't (ab)use PartialEq for Nix equalityGriffin Smith1-0/+23
Using rust's PartialEq trait to implement Nix equality semantics is reasonably fraught with peril, both because the actual laws are different than what nix expects, and (more importantly) because certain things actually require extra context to compare for equality (for example, thunks need to be forced). This converts the manual PartialEq impl for Value (and all its descendants) to a *derived* PartialEq impl (which requires a lot of extra PartialEq derives on miscellanious other types within the codebase), and converts the previous nix-semantics equality comparison into a new `nix_eq` method. This returns an EvalResult, even though it can't currently return an error, to allow it to fail when eg forcing thunks (which it will do soon). Since the PartialEq impls for Value and NixAttrs are now quite boring, this converts the generated proptests for those into handwritten ones that cover `nix_eq` instead Change-Id: If3da7171f88c22eda5b7a60030d8b00c3b76f672 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6650 Autosubmit: grfn <grfn@gws.fyi> Tested-by: BuildkiteCI Reviewed-by: tazjin <tazjin@tvl.su>
2022-09-18 r/4902 test(tvix/eval): impl Arbitrary for ValueGriffin Smith1-0/+19
Impl Arbitrary for Value (and NixAttrs and NixList) in the same way we did for NixString. Value currently only generates non-"internal" values (no thunks, AttrNotFound, etc.) and can't generate functions (builtins or closures), because those'd require full generation of tvix bytecode, which is a bit more work than I'd like to do now - there's a `todo!` left in the code for a place where we could allow opting-in to internal values and functions later. Change-Id: I07a59e2b1d89cfaa912d4ecebd642caf4ddb040a Reviewed-on: https://cl.tvl.fyi/c/depot/+/6627 Autosubmit: grfn <grfn@gws.fyi> Tested-by: BuildkiteCI Reviewed-by: tazjin <tazjin@tvl.su>
2022-09-15 r/4862 feat(tvix/eval): Support builtins.headWilliam Carroll1-0/+4
TL;DR: - support `builtins.head` - define `ErrorKind::IndexOutOfBounds` and canonical error code - support basic unit tests Change-Id: I859107ffb4e220cba1be8c2ac41d1913dcca37ff Reviewed-on: https://cl.tvl.fyi/c/depot/+/6544 Reviewed-by: wpcarro <wpcarro@gmail.com> Autosubmit: wpcarro <wpcarro@gmail.com> Reviewed-by: sterni <sternenseemann@systemli.org> Reviewed-by: tazjin <tazjin@tvl.su> Tested-by: BuildkiteCI
2022-09-07 r/4740 feat(tvix/eval): Support builtins.lengthWilliam Carroll1-0/+4
Get the length of a list Change-Id: I41d91e96d833269541a1b3c23b7cc879f96d1e5a Reviewed-on: https://cl.tvl.fyi/c/depot/+/6407 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org>
2022-09-07 r/4704 feat(tvix/eval): implement NixList::iterVincent Ambo1-0/+4
This does not require a custom iterator type (for now?) Change-Id: I5beb194bd8629571bd4040c69c977c27149807fa Reviewed-on: https://cl.tvl.fyi/c/depot/+/6371 Reviewed-by: sterni <sternenseemann@systemli.org> Tested-by: BuildkiteCI
2022-09-02 r/4596 feat(tvix/eval): implement builtins.catAttrsVincent Ambo1-0/+4
Change-Id: Idf92ac82438fbfcf7b2f6e058830e4744637d8c6 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6262 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org>
2022-08-30 r/4540 docs(tvix/eval): Use correct syntax for module doc commentsVincent Ambo1-1/+1
Change-Id: I35741856f34b86a538f226a8eaf8806edede60ec Reviewed-on: https://cl.tvl.fyi/c/depot/+/6207 Reviewed-by: grfn <grfn@gws.fyi> Tested-by: BuildkiteCI
2022-08-27 r/4512 chore(tvix/eval): explicitly set #[repr(transparent)] on wrappersVincent Ambo1-0/+1
For representation wrappers that are used to control the visibility of type internals, this ensures that the wrapper does not increase the size of the type. In practice, the optimiser likely does this anyways but it is good to guarantee it. Change-Id: Ic6df7d668fe6006dfbd5b6cfcfc2088afa95b810 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6178 Tested-by: BuildkiteCI Reviewed-by: grfn <grfn@gws.fyi>
2022-08-25 r/4480 refactor(tvix/eval): encapsulate list construction in value::listVincent Ambo1-1/+12
Ensuring that the implementation is not leaking out of the module lets us keep things open for optimisations (e.g. empty list or pairs through tuples). Change-Id: I18fd9b7740f28c55736471e16c6b4095a05dd6d0 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6145 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org>
2022-08-25 r/4479 feat(tvix/eval): implement list concatenationVincent Ambo1-0/+9
Change-Id: Icdf715d116371a9f139bdf95266410bf967bef25 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6144 Reviewed-by: sterni <sternenseemann@systemli.org> Tested-by: BuildkiteCI
2022-08-13 r/4436 feat(tvix/value): implement Display properly for listsVincent Ambo1-2/+8
Change-Id: I991d235cf52fbd42eb839b384f9c55ee64fa86c4 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6100 Tested-by: BuildkiteCI Reviewed-by: grfn <grfn@gws.fyi>
2022-08-13 r/4429 feat(tvix/value): add runtime representation of simple listsVincent Ambo1-0/+14
There might be more logic in the future to encapsulate different backing implementations of lists as well. Change-Id: Ib7064fab48bf88b0c8913b0ecfa2108177c7c9fd Reviewed-on: https://cl.tvl.fyi/c/depot/+/6093 Tested-by: BuildkiteCI Reviewed-by: grfn <grfn@gws.fyi> Autosubmit: tazjin <tazjin@tvl.su>