refactor(Scalar)!: replace PIMPL virtual dispatch with std::variant (#847, fixes #935)#1011
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This pull request replaces the Scalar class's PIMPL and virtual-dispatch hierarchy with a std::variant-backed value type, centralizing type promotion and enforcing strict rules against lossy in-place operations. Callers like UniTensor and Norm are updated to align with these rules, and comprehensive tests are added. The review feedback highlights critical C++ compilation and compatibility issues: binary_cmp must use forbid_complex as a template parameter with if constexpr to avoid compilation failures with complex types, a custom type_identity helper is needed to maintain C++17 compatibility instead of using C++20's std::type_identity, and an explicit static_cast should be added in isqrt to prevent implicit narrowing warnings.
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| template <typename CmpOp> | ||
| bool binary_cmp(const Scalar &lhs, const Scalar &rhs, CmpOp &&op, const char *opname, | ||
| bool forbid_complex) { |
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The forbid_complex parameter is currently a runtime bool variable. Because of this, both branches of if (forbid_complex) must be compiled by the compiler. When binary_cmp is instantiated for ordering comparisons (like < or <=) with CmpOp as [](auto &&a, auto &&b) { return a < b; }, the compiler attempts to compile lv < rv for std::complex types, which fails to compile because std::complex does not define operator<.
To fix this, forbid_complex should be made a template parameter so that if constexpr (forbid_complex) can be used to discard the invalid comparison branch at compile time.
template <bool forbid_complex, typename CmpOp>
bool binary_cmp(const Scalar &lhs, const Scalar &rhs, CmpOp &&op, const char *opname) {There was a problem hiding this comment.
Applied in 2f09a7d. binary_cmp now takes forbid_complex as a template parameter and branches with if constexpr, and the four ordering callers use binary_cmp<true> / equality uses binary_cmp<false>.
Worth recording why this was latent rather than an outright build break: with the runtime bool, the op(complex, complex) in the ordering branch did compile — but only because complex128 < complex128 silently resolves to operator<(const Scalar&, const Scalar&) via the implicit Scalar converting constructors, i.e. it recursed back into Scalar::less. So CI was green, but the intended "complex has no ordering" contract was expressed only at runtime and rode on an accidental conversion. if constexpr discards the branch for the ordering lambdas, so op(complex,complex) is never instantiated for them and the recursion path is gone. Verified with a standalone probe (fails to compile without Scalar.hpp in scope; the accidental operator<(Scalar,Scalar) is what made it compile with it).
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oh - conversions to scalar should be explicit!
| if (forbid_complex) { | ||
| cytnx_error_msg(Type.is_complex(lhs.dtype()) || Type.is_complex(rhs.dtype()), | ||
| "[ERROR] Scalar %s: comparison not supported for complex type%s", opname, | ||
| "\n"); | ||
| } |
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Use if constexpr with the template parameter forbid_complex to perform compile-time branching.
| if (forbid_complex) { | |
| cytnx_error_msg(Type.is_complex(lhs.dtype()) || Type.is_complex(rhs.dtype()), | |
| "[ERROR] Scalar %s: comparison not supported for complex type%s", opname, | |
| "\n"); | |
| } | |
| if constexpr (forbid_complex) { | |
| cytnx_error_msg(Type.is_complex(lhs.dtype()) || Type.is_complex(rhs.dtype()), | |
| "[ERROR] Scalar %s: comparison not supported for complex type%s", opname, | |
| "\n"); | |
| } |
| if (forbid_complex) { | ||
| cytnx_error_msg(true, | ||
| "[ERROR] Scalar %s: comparison not supported for complex type%s", | ||
| opname, "\n"); | ||
| } else { | ||
| result = op(lv, rv); | ||
| } |
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Use if constexpr with the template parameter forbid_complex to discard the invalid comparison branch at compile-time for complex types.
| if (forbid_complex) { | |
| cytnx_error_msg(true, | |
| "[ERROR] Scalar %s: comparison not supported for complex type%s", | |
| opname, "\n"); | |
| } else { | |
| result = op(lv, rv); | |
| } | |
| if constexpr (forbid_complex) { | |
| cytnx_error_msg(true, | |
| "[ERROR] Scalar %s: comparison not supported for complex type%s", | |
| opname, "\n"); | |
| } else { | |
| result = op(lv, rv); | |
| } |
| bool Scalar::less(const Scalar &rhs) const { | ||
| return binary_cmp( | ||
| *this, rhs, [](auto &&a, auto &&b) { return a < b; }, "less-than (<)", true); | ||
| } | ||
| bool Scalar::leq(const Scalar &rhs) const { | ||
| return binary_cmp( | ||
| *this, rhs, [](auto &&a, auto &&b) { return a <= b; }, "less-equal (<=)", true); | ||
| } | ||
| bool Scalar::greater(const Scalar &rhs) const { | ||
| return binary_cmp( | ||
| *this, rhs, [](auto &&a, auto &&b) { return a > b; }, "greater-than (>)", true); | ||
| } | ||
| bool Scalar::geq(const Scalar &rhs) const { | ||
| return binary_cmp( | ||
| *this, rhs, [](auto &&a, auto &&b) { return a >= b; }, "greater-equal (>=)", true); | ||
| } | ||
| bool Scalar::eq(const Scalar &rhs) const { | ||
| return binary_cmp( | ||
| *this, rhs, [](auto &&a, auto &&b) { return a == b; }, "equal (==)", false); | ||
| } |
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Update the calls to binary_cmp to pass forbid_complex as a template argument.
| bool Scalar::less(const Scalar &rhs) const { | |
| return binary_cmp( | |
| *this, rhs, [](auto &&a, auto &&b) { return a < b; }, "less-than (<)", true); | |
| } | |
| bool Scalar::leq(const Scalar &rhs) const { | |
| return binary_cmp( | |
| *this, rhs, [](auto &&a, auto &&b) { return a <= b; }, "less-equal (<=)", true); | |
| } | |
| bool Scalar::greater(const Scalar &rhs) const { | |
| return binary_cmp( | |
| *this, rhs, [](auto &&a, auto &&b) { return a > b; }, "greater-than (>)", true); | |
| } | |
| bool Scalar::geq(const Scalar &rhs) const { | |
| return binary_cmp( | |
| *this, rhs, [](auto &&a, auto &&b) { return a >= b; }, "greater-equal (>=)", true); | |
| } | |
| bool Scalar::eq(const Scalar &rhs) const { | |
| return binary_cmp( | |
| *this, rhs, [](auto &&a, auto &&b) { return a == b; }, "equal (==)", false); | |
| } | |
| bool Scalar::less(const Scalar &rhs) const { | |
| return binary_cmp<true>( | |
| *this, rhs, [](auto &&a, auto &&b) { return a < b; }, "less-than (<)"); | |
| } | |
| bool Scalar::leq(const Scalar &rhs) const { | |
| return binary_cmp<true>( | |
| *this, rhs, [](auto &&a, auto &&b) { return a <= b; }, "less-equal (<=)"); | |
| } | |
| bool Scalar::greater(const Scalar &rhs) const { | |
| return binary_cmp<true>( | |
| *this, rhs, [](auto &&a, auto &&b) { return a > b; }, "greater-than (>)"); | |
| } | |
| bool Scalar::geq(const Scalar &rhs) const { | |
| return binary_cmp<true>( | |
| *this, rhs, [](auto &&a, auto &&b) { return a >= b; }, "greater-equal (>=)"); | |
| } | |
| bool Scalar::eq(const Scalar &rhs) const { | |
| return binary_cmp<false>( | |
| *this, rhs, [](auto &&a, auto &&b) { return a == b; }, "equal (==)"); | |
| } |
| namespace cytnx { | ||
|
|
||
| cytnx_complex128 complex128(const Scalar& in) { return in._impl->to_cytnx_complex128(); } | ||
| namespace { |
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To ensure compatibility with C++17 (since std::type_identity is a C++20 feature), we can define a simple type_identity helper struct in the anonymous namespace.
| namespace { | |
| namespace { | |
| template <typename T> | |
| struct type_identity { | |
| using type = T; | |
| }; | |
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The project targets C++20 (CMAKE_CXX_STANDARD 20), so std::type_identity was never a compatibility problem here. But per maintainer direction we removed the hand-written switch dispatch entirely rather than keep tagging types: astype() now dispatches by visiting the variant — it materializes a value-initialized prototype ScalarVariant at the target index and std::visits the (source, destination) pair to recover both compile-time types. That drops std::type_identity/VisitByDtype altogether (2f09a7d), and the dtype→type mapping is now the variant’s own index↔alternative correspondence, already pinned by the static_asserts in Scalar.hpp, so it can’t drift from Type_list.
| fn(std::type_identity<cytnx_complex128>{}); | ||
| return; | ||
| case Type.ComplexFloat: | ||
| fn(std::type_identity<cytnx_complex64>{}); | ||
| return; | ||
| case Type.Double: | ||
| fn(std::type_identity<cytnx_double>{}); | ||
| return; | ||
| case Type.Float: | ||
| fn(std::type_identity<cytnx_float>{}); | ||
| return; | ||
| case Type.Int64: | ||
| fn(std::type_identity<cytnx_int64>{}); | ||
| return; | ||
| case Type.Uint64: | ||
| fn(std::type_identity<cytnx_uint64>{}); | ||
| return; | ||
| case Type.Int32: | ||
| fn(std::type_identity<cytnx_int32>{}); | ||
| return; | ||
| case Type.Uint32: | ||
| fn(std::type_identity<cytnx_uint32>{}); | ||
| return; | ||
| case Type.Int16: | ||
| fn(std::type_identity<cytnx_int16>{}); | ||
| return; | ||
| case Type.Uint16: | ||
| fn(std::type_identity<cytnx_uint16>{}); | ||
| return; | ||
| case Type.Bool: | ||
| fn(std::type_identity<cytnx_bool>{}); |
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Use the custom type_identity helper instead of std::type_identity to maintain C++17 compatibility.
case Type.ComplexDouble:
fn(type_identity<cytnx_complex128>{});
return;
case Type.ComplexFloat:
fn(type_identity<cytnx_complex64>{});
return;
case Type.Double:
fn(type_identity<cytnx_double>{});
return;
case Type.Float:
fn(type_identity<cytnx_float>{});
return;
case Type.Int64:
fn(type_identity<cytnx_int64>{});
return;
case Type.Uint64:
fn(type_identity<cytnx_uint64>{});
return;
case Type.Int32:
fn(type_identity<cytnx_int32>{});
return;
case Type.Uint32:
fn(type_identity<cytnx_uint32>{});
return;
case Type.Int16:
fn(type_identity<cytnx_int16>{});
return;
case Type.Uint16:
fn(type_identity<cytnx_uint16>{});
return;
case Type.Bool:
fn(type_identity<cytnx_bool>{});
return;| } else if constexpr (std::is_same_v<T, cytnx_bool>) { | ||
| cytnx_error_msg(true, "[ERROR] isqrt not supported for Bool type%s", "\n"); | ||
| } else { | ||
| v = std::sqrt(v); |
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When T is an integer type, std::sqrt(v) returns a double. Assigning it directly to v causes an implicit narrowing conversion. Adding an explicit static_cast<T> avoids compiler warnings.
| v = std::sqrt(v); | |
| v = static_cast<T>(std::sqrt(v)); |
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Applied in 2f09a7d — v = static_cast<T>(std::sqrt(v));. isqrt() is a unary in-place transform and stays dtype-preserving, so the narrow-back is the intended behavior (now explicit).
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I'm not understanding why #937 diabled a bunch of Python behavior allows in-place arithmetic to change type, and in principle it is fine here too, it just changes the type held in the There almost certainly are bugs still in As a check, #937 includes a few tests that are of the pattern
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Code ReviewReplaces Core design — verified
API surface & caller migrations — verified item-by-itemAll 11 dtype ctors + assignments, the 9 explicit cast operators, Findings (none blocking)
VerdictStructurally eliminates the #935 bug class (self-assignment UB, double-alloc copy — gone by Posted by Claude Code on behalf of @pcchen |
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It would be interesting to see some benchmarks. Scalar arithmetic is probably 100-1000x faster now... |
… instead of throw Addresses review on #1011. Dispatch (@gemini-code-assist): replace the hand-written dtype->type switch (which used std::type_identity tags) in astype() with a std::visit over a value-initialized "prototype" variant materialized at the target index. The dtype<->type mapping is now the variant's own index<->alternative correspondence (already pinned by the static_asserts in Scalar.hpp), so it can't drift from Type_list. This also removes std::type_identity entirely (the project is C++20, so it was never a compatibility problem -- the switch is simply gone). In-place ops (@ianmccul): +=/-=/*=//= no longer throw on a mixed dtype. #937 disabled those paths only because the old PIMPL implementation gave wrong answers; the variant rewrite fixes that, so in-place arithmetic now follows Python value-type semantics -- `a op= b` == `a = a op b`, promoting the destination via Type.type_promote (maintainer ruling 2026-07-08). Delegates to radd/rsub/rmul/rdiv, keeping in-place and out-of-place bit-for-bit consistent; the fresh out-of-place result makes `a += a` alias-safe. binary_cmp (@gemini-code-assist): make forbid_complex a template parameter so the complex-ordering branch is discarded with `if constexpr`. Previously the runtime bool forced the compiler to type-check `op(complex, complex)` for the ordering lambdas, which only compiled by accidentally routing through operator<(Scalar, Scalar) via the implicit Scalar ctors -- a latent infinite-recursion hazard, now removed. isqrt narrows via explicit static_cast. iabs()/isqrt() stay dtype-preserving: they are unary in-place value transforms with no second operand to promote against; the abs()/iabs() consistency (#935) remains by value. Tests: convert the in-place throw pins (4 named + the 121-pair matrix in Scalar_test.cpp; 5 in scalar_variant_test.py) to assert promotion, matching out-of-place. Migrated UniTensor callers keep their out-of-place computation; stale "in-place throws" comments updated. Full C++ suite: 1606 passed, 0 failed, 11 pre-existing skips; 537 Scalar gtests green. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Pushed 2f09a7d in response to the review. In-place arithmetic no longer throws (@ianmccul)You're right — "in-place ops must preserve the LHS dtype" was never the actual goal. #937 only disabled those paths because the old PIMPL gave wrong answers; the variant rewrite fixes that, so there's no reason to throw. In-place arithmetic now follows Python value-type semantics: Concretely:
I re-checked against your Ruling recorded in-code (maintainer, 2026-07-08). The removed guard's
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…847, fixes #935) Replace Scalar's Scalar_base* PIMPL (11 derived classes, 108 virtuals, ~2900 LOC, one heap allocation per Scalar) with a std::variant held by value, per #847's proposed layout: std::variant<std::monostate, cytnx_complex128, cytnx_complex64, cytnx_double, cytnx_float, cytnx_int64, cytnx_uint64, cytnx_int32, cytnx_uint32, cytnx_int16, cytnx_uint16, cytnx_bool> std::monostate represents the Void/uninitialized state (dtype() returns Type.Void). ScalarVariant is index-aligned with Type_list -- pinned by static_asserts in the header -- so dtype() is simply the active alternative's index. All public signatures are preserved: the 11 typed ctors, Scalar(T, dtype), explicit conversion operators, astype/conj/abs/sqrt (+ in-place forms), real()/imag(), dtype(), maxval/minval(dtype), print/ostream, all arithmetic and comparison operators, and Scalar::Sproxy. sizeof(Scalar) goes from 8 B (pointer) + a heap object to 24 B fully inline with true value semantics (copy/move/assign are `= default`, trivially correct). - self-assignment UB in operator=: eliminated by `= default`. - double-allocation copy ctor: eliminated by `= default`. - broken in-place promotion (Int64 /= Double silently doing integer division, RHS converted to destination dtype): in-place ops now throw instead of silently truncating (Ruling 1 below). - mixed-precision in-place float loss (Float += Double): now throws. - minval(Type.Double/Float) returned numeric_limits::min() (smallest positive normal); now returns ::lowest() (most negative finite). - abs()/iabs() dtype inconsistency on complex: abs() always returns the real dtype magnitude (Double/Float). iabs() keeps the complex dtype (no in-place op changes dtype) and stores the magnitude with zero imaginary part; its value now provably matches abs()'s. Documented in the header and pinned by tests. - hand-rolled enum-order promotion everywhere: every promotion decision (binary ops, comparisons, in-place guard) now routes through the single constexpr Type.type_promote() via std::visit; this also makes ComplexFloat + Double correctly yield ComplexDouble. Ruling 1 (maintainer decision 2026-07-07; BREAKING, also visible from Python where it raises RuntimeError): the in-place operators += -= *= /= throw cytnx::error when the RHS dtype does not convert into the LHS dtype, i.e. when Type.type_promote(lhs, rhs) != lhs.dtype(). Throwing classes: unsigned-LHS mixed with signed ints, int-LHS with float RHS, real-LHS with complex RHS, Bool-LHS with non-Bool. Conversions that are value-preserving per the sanctioned type_promote table (see include/Type.hpp type_promote; maintainer sign-off 2026-07-07) remain valid: same dtype; Int64 += Int32; Double += Float; ComplexDouble += Double; signed-LHS with a same-or-narrower unsigned RHS. Same-width signed/unsigned in-place mixes follow the type_promote table by explicit maintainer ruling (2026-07-07): in-place and out-of-place stay consistent, and any future tightening happens in the table. The thrown message carries only the actionable core (both dtype names, the would-be result dtype, the out-of-place/astype() remedy); the provenance lives in the guard's comment block. PR #937 (credit: @ianmccul for the guard semantics and the original tests/Scalar_test.cpp) is superseded by this commit; its test suite is absorbed and extended here. Deliberate divergences from #937's broader guard, following the ruling and the Phase-3 plan: out-of-place binary arithmetic and comparisons never throw for real dtypes (they promote via type_promote; #937 disabled mixed signed/unsigned and Bool cases outright); in-place ops whose RHS-to-LHS conversion follows the type_promote table (e.g. Int64 += Int32) are allowed because the ruling's throw categories exclude them -- #937 had disabled any differing integer dtype; and integer abs()/sqrt() remain functional (#937 disabled them). Ordering comparisons on complex still throw; complex equality is allowed (as before). A known consequence of the table -- Scalar(Int64(-1)) == Scalar(Uint64 max) evaluating true via the Int64 promotion -- is pinned by test with maintainer sign-off. Storage_base::set_item(idx, const Scalar&) is re-implemented via std::visit on the Scalar's active alternative, forwarding the concrete value into the existing typed SetItem<T> (monostate throws instead of writing garbage). get_item already constructed the Scalar from the typed at<T>() and is unchanged. Migrated in-tree callers that relied on lossy in-place mixes (none were covered by existing tests; test tally is baseline + new, nothing removed): - BlockUniTensor::normalize_() and BlockFermionicUniTensor:: normalize_(): the norm^2 accumulator is now seeded with the floating dtype linalg::Norm() actually produces instead of this->dtype(), which for an integer-dtype UniTensor was an Int += Double lossy mix. The Norm output-dtype policy is centralized in a new constexpr Type_class::norm_result_dtype() (include/Type.hpp), used by both normalize_ sites and by src/linalg/Norm.cpp itself (replacing its hand-rolled enum-order dtype checks). - DenseUniTensor::Add_/Sub_ (dense += diagonal element loop): switched to out-of-place `v = v +/- rhs` since the two UniTensors' dtypes may legitimately differ (per #937's own migration guidance). - linalg_internal_cpu/{Add,Sub,Mul,Cpr}_internal.hpp: replaced the incidental Scalar_init_interface::type_promote_t alias (inherited from Type_class by the deleted PIMPL factory class) with Type_class::type_promote_t directly. - linalg_internal_cpu/Gemm_Batch_internal.hpp: replaced direct x._impl->to_cytnx_complex128()/64() with the public complex128()/ complex64() accessors. Tests: absorbs tests/Scalar_test.cpp (based on #937's, adjusted to the ruling's matrix) and extends it with a programmatic 11x11 dtype matrix over + - * / and comparisons (asserting result dtype == Type.type_promote(a,b) and value correctness), an 11x11 in-place throw matrix (throws iff type_promote(lhs,rhs) != lhs), and a pinned mixed-signedness equality quirk test. Adds pytests/scalar_variant_test.py covering Python arithmetic across dtypes, the new in-place RuntimeError behavior, Storage indexed assignment from Scalar, and numpy-scalar constructor paths (pinning a pre-existing pybind quirk where non-int64 integer numpy scalars resolve to the Int64 ctor overload). pybind/scalar_py.cpp is unchanged: none of its 84 bindings touched Scalar internals. Gates: C++ 1617 ran / 1602 passed (1086 baseline + 516 new) / 11 skipped / same 4 known linalg_Test.BkUt_* failures (#977). pytest 100 passed (57 baseline + 43 new). grep Scalar_base in include/ src/ pybind/ -> zero hits. build_py warning-clean. BREAKING CHANGE: mixed-dtype in-place Scalar arithmetic that would change or truncate the LHS dtype now throws cytnx::error (Python: RuntimeError) instead of silently truncating. Use out-of-place arithmetic or astype(). Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
… instead of throw Addresses review on #1011. Dispatch (@gemini-code-assist): replace the hand-written dtype->type switch (which used std::type_identity tags) in astype() with a std::visit over a value-initialized "prototype" variant materialized at the target index. The dtype<->type mapping is now the variant's own index<->alternative correspondence (already pinned by the static_asserts in Scalar.hpp), so it can't drift from Type_list. This also removes std::type_identity entirely (the project is C++20, so it was never a compatibility problem -- the switch is simply gone). In-place ops (@ianmccul): +=/-=/*=//= no longer throw on a mixed dtype. #937 disabled those paths only because the old PIMPL implementation gave wrong answers; the variant rewrite fixes that, so in-place arithmetic now follows Python value-type semantics -- `a op= b` == `a = a op b`, promoting the destination via Type.type_promote (maintainer ruling 2026-07-08). Delegates to radd/rsub/rmul/rdiv, keeping in-place and out-of-place bit-for-bit consistent; the fresh out-of-place result makes `a += a` alias-safe. binary_cmp (@gemini-code-assist): make forbid_complex a template parameter so the complex-ordering branch is discarded with `if constexpr`. Previously the runtime bool forced the compiler to type-check `op(complex, complex)` for the ordering lambdas, which only compiled by accidentally routing through operator<(Scalar, Scalar) via the implicit Scalar ctors -- a latent infinite-recursion hazard, now removed. isqrt narrows via explicit static_cast. iabs()/isqrt() stay dtype-preserving: they are unary in-place value transforms with no second operand to promote against; the abs()/iabs() consistency (#935) remains by value. Tests: convert the in-place throw pins (4 named + the 121-pair matrix in Scalar_test.cpp; 5 in scalar_variant_test.py) to assert promotion, matching out-of-place. Migrated UniTensor callers keep their out-of-place computation; stale "in-place throws" comments updated. Full C++ suite: 1606 passed, 0 failed, 11 pre-existing skips; 537 Scalar gtests green. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Review follow-up — delta re-review of
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| // init!! | ||
| /// @brief init a Scalar with a cytnx::cytnx_complex128 | ||
| Scalar(const cytnx_complex128 &in) : _impl(new Scalar_base()) { this->Init_by_number(in); } | ||
| Scalar(const cytnx_complex128 &in) : _val(in) {} |
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All of these scalar value constructors should be explicit and can be replaced with one constrained constructor:
template <CytnxType T>
explicit Scalar(T x) : _val(x) {}
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Agree on the consolidation — one constrained constructor is strictly better than the 11 spelled-out value ctors (less code, and a single crisp "no matching constructor" for non-cytnx types instead of an 11-way ambiguity). Two mechanical notes: a CytnxType concept doesn't exist on this branch yet (one lives in unmerged #979, so it needs a local definition here or coordination), and the two-arg Scalar(v, dtype), Sproxy, default, and copy constructors stay as they are.
On explicit, though, there's a collision with two things already in this PR that needs a deliberate choice rather than a drive-by:
- This PR dropped the member template operators (
s + 3,s < 3, …) — those expressions currently compile only via the implicitScalar(3)conversion into the freeoperator+(const Scalar&, const Scalar&). Making the ctorsexplicitas-is breaks everyscalar ⊙ numbercall site (and every raw number passed to aconst Scalar¶meter). - Conversely, the implicit ctors are exactly what caused the
operator<infinite-recursion hazard thatea426983just fixed — which is a genuine argument forexplicit.
So the two coherent end-states are:
- (a)
explicit+ constrained mixed-mode operators: the singleexplicit Scalar(T)ctor plustemplate <CytnxType T>free operators (+ - * / < > <= >= ==against raw values), sos + 3keeps working by design instead of by implicit conversion. This is the cleanest end-state — no accidental conversion routes anywhere — and effectively reinstates (constrained, intentionally) the operator surface the PR dropped. - (b) one implicit constrained ctor: variant-style converting behavior — the consolidation win with zero other changes, deferring the
explicitquestion.
Not viable: explicit alone — it silently breaks the arithmetic surface.
Timing-wise, if explicit is wanted at all, this PR is the moment (it's already !-breaking; doing it later is a second break). My lean is (a) as one more commit here.
Posted by Claude Code on behalf of @pcchen
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C++20 operator <=> makes (a) a bit easier,
#include <compare>
// only these two need to be written:
std::partial_ordering operator<=>(const Scalar& lhs, const Scalar& rhs);
bool operator==(const Scalar& lhs, const Scalar& rhs);
// the rest are easy:
template <CytnxType T>
std::partial_ordering operator<=>(const Scalar& lhs, T rhs) {
return lhs <=> Scalar(rhs);
}
template <CytnxType T>
std::partial_ordering operator<=>(T lhs, const Scalar& rhs) {
return Scalar(lhs) <=> rhs;
}
template <CytnxType T>
bool operator==(const Scalar& lhs, T rhs) {
return lhs == Scalar(rhs);
}
template <CytnxType T>
bool operator==(T lhs, const Scalar& rhs) {
return Scalar(lhs) == rhs;
}
| void Init_by_number(const cytnx_complex128 &in) { this->_val = in; } | ||
| void Init_by_number(const cytnx_complex64 &in) { this->_val = in; } | ||
| void Init_by_number(const cytnx_double &in) { this->_val = in; } | ||
| void Init_by_number(const cytnx_float &in) { this->_val = in; } | ||
| void Init_by_number(const cytnx_int64 &in) { this->_val = in; } | ||
| void Init_by_number(const cytnx_uint64 &in) { this->_val = in; } | ||
| void Init_by_number(const cytnx_int32 &in) { this->_val = in; } | ||
| void Init_by_number(const cytnx_uint32 &in) { this->_val = in; } | ||
| void Init_by_number(const cytnx_int16 &in) { this->_val = in; } | ||
| void Init_by_number(const cytnx_uint16 &in) { this->_val = in; } | ||
| void Init_by_number(const cytnx_bool &in) { this->_val = in; } |
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These are not needed. Remove.
| this->_impl->assign_selftype(in); | ||
| }; | ||
| Scalar(const T &in, const unsigned int &dtype) { | ||
| this->Init_by_number(in); |
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replace all of these with
template <CytnxType T>
Scalar &operator=(T x) {
this->_val = x;
return *this;
}There was a problem hiding this comment.
The analogous Sproxy consolidation (11 → 1 constrained template) is done in bfc105c. The Scalar assignment operators here are deferred to the item-A follow-up PR together with the explicit-ctor work, since they share the same overload-resolution surface — see the plan in the PR comment.
Posted by Claude Code on behalf of @pcchen
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||
| // casting | ||
| /// @brief The explicit casting operator of the Scalar class to cytnx::cytnx_double. | ||
| explicit operator cytnx_double() const { return this->_impl->to_cytnx_double(); } | ||
| explicit operator cytnx_double() const; |
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Replace these with
template <CytnxType To>
explicit operator To() const {
return std::visit(
[]<typename U>(const U &from) -> To {
if constexpr (requires { static_cast<To>(from); }) {
return static_cast<To>(from);
} else {
cytnx_error_msg(true,
"[ERROR] Cannot convert Scalar from dtype [%s] to dtype [%s].%s",
Type_enum_name<U>, Type_enum_name<To>, "\n");
return To{};
}
},
_val);
}This also requires extending Type_enum_name<std::monostate>, which is a good idea anyway.
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Done in bfc105c — implemented exactly per this blueprint (one constrained explicit operator To() with requires { static_cast<To>(from); }, Type_enum_name-based error text, and Type_enum_name<std::monostate> added). complex→real keeps the real()/imag() hint in its error branch.
Posted by Claude Code on behalf of @pcchen
| // Void source stays Void regardless of target: astype() of an | ||
| // uninitialized Scalar is a no-op (matches the pre-refactor behavior). |
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This seems like a missed opportunity for a cleanup. I can't imagine why we want an explicit converion of a Scalar to some particular type to be a no-operation if it represents void.
| template <typename TDst, typename TSrc> | ||
| TDst convert_value(const TSrc &src) { | ||
| if constexpr (is_complex_v<TDst> || !is_complex_v<TSrc>) { | ||
| return static_cast<TDst>(src); | ||
| } else { | ||
| cytnx_error_msg(true, | ||
| "[ERROR] Cannot convert a complex Scalar to a real dtype. Use real() or " | ||
| "imag() to extract a component first.%s", | ||
| "\n"); | ||
| return TDst{}; | ||
| } | ||
| } |
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I think this isn't used after my suggested refactor of the explicit conversion operators
| namespace { | ||
| template <typename TDst> | ||
| TDst explicit_cast(const Scalar &s) { | ||
| TDst out{}; | ||
| std::visit( | ||
| [&](auto &&v) { | ||
| using T = std::decay_t<decltype(v)>; | ||
| if constexpr (std::is_same_v<T, std::monostate>) { | ||
| cytnx_error_msg( | ||
| true, "[ERROR] Cannot cast a Void (uninitialized) Scalar to any type.%s", "\n"); | ||
| } else { | ||
| out = convert_value<TDst>(v); | ||
| } | ||
| }, | ||
| s._val); | ||
| return out; | ||
| } | ||
| } // namespace |
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I think this isn't used after my suggested refactor of the explicit conversion operators?
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Some of the comments above depend on One of them also requires extending Something to look at after this, is whether it makes sense to replace the Some things spotted by codex:
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Consolidated checklist to land this PRGathered from the review threads (@ianmccul's ruling + codex findings + CI). Nothing else is outstanding. A. Constructor/operator surface — option (a), per @ianmccul's ruling
B. Conversion-operator refactor (@ianmccul)
C. Codex-spotted correctness items
D. CI (currently 1 pytest red)
Follow-ups (not this PR)
Posted by Claude Code on behalf of @pcchen |
I think that is not correct. The reason for |
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Sequencing note: #1015 stacks its Storage work on a snapshot of this PR (its commit Posted by Claude Code on behalf of @pcchen |
…oid guards, Sproxy consolidation Implements items B, C and D of the consolidated review checklist (A -- explicit constrained ctor + operator<=> -- is split into a follow-up PR, since it changes overload resolution codebase-wide and carries an unresolved complex-ordering semantic decision): B. Conversion surface (review threads on Scalar.hpp:354, Scalar.cpp:227/60/322): - One constrained template replaces the 9 per-type cast operators; conversions the language cannot perform error with Type_enum_name-based text (complex->real adds the real()/imag() hint). to_complex128()/to_complex64() delegate to it. - Type_enum_name<std::monostate> added (displays as "Void"). - astype() on a Void source now errors instead of silently staying Void; the dead convert_value/explicit_cast helpers are removed. C. Correctness items (codex findings): - conj() on a Void Scalar throws (old PIMPL contract) instead of silently returning Void. - Sproxy's 11 per-type assignment overloads collapse to one CytnxType-constrained template delegating through Scalar. - Type_class::norm_result_dtype(Void) rejects instead of mapping to Double. The CytnxType concept is the documented one-liner from #979. - Stale "lossy in-place combinations throw" comment updated to the promote semantics. D. pytest: test_inplace_same_dtype_keeps_dtype pins Int32 operands via astype() to sidestep the preexisting pybind ctor-collapse quirk that #1014 fixes (workaround documented for removal). Verified: C++ suite 1676 ran / 1665 passed / 11 skipped / 0 failed (4 new Void-guard tests); pytests/scalar_variant_test.py 43/43 against the freshly built extension; clang-format 14.0.6. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Checklist items B+C+D implemented — pushed as
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Note that I never said anything about Please make sure Claude reads the comments! |
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For the third time, I never said anything about changing the comparison behavior of complex. Returning
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Is it possible to talk to a human here? |
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yes. |
…iant # Conflicts: # src/DenseUniTensor.cpp # src/linalg/Norm.cpp
… master master's #979 landed `concept CytnxType` in include/Type.hpp, while this branch had added its own equivalent one-liner in include/backend/Scalar.hpp (checklist item C). Merging master in left both definitions present, so every TU that pulls in Scalar.hpp (via Storage.hpp) failed to compile with "redefinition of template<class T> concept cytnx::CytnxType" -- the DownstreamFindPackage CI failure. The two definitions are semantically identical (Type.hpp's `variant_contains_v<T, Type_list> && !is_void_v<T>` == the 11 concrete types this branch enumerated). Scalar.hpp already includes Type.hpp, so drop the local copy and rely on the canonical one, exactly the "the other rebases" resolution flagged in the #1011 review when #979 lands first. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
master advanced past the previous merge when PR #1011 (refactor/scalar-variant: Scalar PIMPL -> std::variant) landed. Re-merge to keep #1000 mergeable. Conflict resolution: - src/linalg/Norm.cpp: #1000 computed the rank-0 norm output dtype with an explicit if/else (ComplexDouble->Double, ComplexFloat->Float, else input-or- Double); #1011 introduced Type_class::norm_result_dtype() encapsulating the identical policy (is_float ? to_real : Double) and made it the single home of that rule, shared with the UniTensor normalize_ accumulators. Adopted the helper (Void is already guarded upstream at norm_impl's is_void check). Verified byte-for-byte equivalent dtype for every input type. Follow-through (keep the suite clean under -W error::DeprecationWarning): migrated the two remaining .Norm().item() callers the PR's own migration had missed -- pytests/unitensor_test.py and pytests/binding_inplace_test.py -- to .norm() (a native float in Python; same value). Surfaced because the rebuilt module shifted the DeprecationWarning-registry dedup order; harmless on CI (plain pytest) but now deterministically clean under -W error. Verification (CI-matching openblas-cpu, non-ASan): - C++ test_main: 1768 tests, 1757 passed / 11 skipped / 0 failed. - pybind rebuilds clean; full pytests/ suite passes under plain pytest; the merge-relevant files pass under -W error::DeprecationWarning. - clang-format v14 clean. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
3 participants
Problem
Fixes #847 and #935.
Scalarwas a raw-pointer PIMPL over 11 virtual subclasses (108 virtuals, ~2,900 LOC) with hand-rolled enum-order promotion everywhere. #935 (@ianmccul) cataloged the consequences: self-assignment UB, a double-allocating copy constructor, in-place promotion inconsistent withtype_promote,minvalreturning the wrong value for floats,abs/iabsdtype inconsistency.What changed
Scalarnow holds a by-valuestd::variant(monostate = Void). 61% code reduction (3,669 → 1,415 lines), heavy instantiation confined to one TU,sizeof(Scalar)8 B + heap → 24 B flat. Copy/move/assign are= default(the UB and double-alloc are structurally gone). All promotion routes throughType.type_promote—static_asserts pin the variant layout toType_listindex-for-index, sodtype()is literally the variant index and adding a dtype fails compilation until handled.Type_class::norm_result_dtypecentralizes the Norm output-dtype policy (previously derived by hand in three files).Behavior changes (BREAKING)
Int64 += Uint64) follow thetype_promotetable and remain allowed by explicit maintainer ruling, keepinga += b≡a = a + b; the resultingScalar(int64(-1)) == Scalar(uint64_max)quirk is test-pinned and inherent to the sanctioned table.minvalfor floating dtypes now returnslowest();abs()on complex returns the real dtype;iabs()keeps the dtype (in-place ops never change dtype) — each documented and pinned.Testing
516 new gtests (two 121-pair programmatic promotion/throw matrices + named behavior pins) and 43 pytests. Full suite: 1602 passed / 11 skipped / only the 4 pre-existing failures addressed by #977; pytest 100. Four in-tree callers migrated (normalize_ seeding, diag-loop accumulation, linalg header aliases), each with a why-comment. The pybind surface is untouched; two pre-existing binding quirks (numpy-int ctor collapse — value-corrupting for large uint64 — and missing
Scalar.__bool__) are pinned as known quirks and tracked separately.🤖 Generated with Claude Code