Add safe uninitialized GEMM overwrite paths

Cargo.toml

@@ -31,7 +31,7 @@ mdarray-opteinsum = { version = "0.3.0", path = "mdarray-opteinsum", default-fea
 ndarray-opteinsum = { version = "0.3.0", path = "ndarray-opteinsum", default-features = false }
 
 approx = "0.5"
-cblas-inject = "0.1"
+cblas-inject = "0.1.2"
 cblas-sys = "0.2"
 criterion = "0.5"
 faer = { version = "0.24", default-features = false, features = ["std", "rayon"] }

docs/2026-07-31-issue-188-worklog.md

@@ -0,0 +1,73 @@
+# Issue 188 worklog
+
+## Scope
+
+Add overwrite-only contraction entry points whose destination is borrowed as
+`MaybeUninit<T>`. The initialized beta APIs remain unchanged.
+
+## 2026-07-31
+
+- Raised the workspace `cblas-inject` minimum to `0.1.2`.
+- Added explicit-context `einsum2_into_uninit`,
+  `einsum2_into_owned_uninit`, `dot_general_into_uninit`, and
+  `bgemm_raw_strided_into_uninit`.
+- Added checked output injectivity, checked offset traversal, conservative
+  input/output overlap rejection, empty-output no-write behavior, trace-axis
+  reduction, and tests for matrix output and pre-write validation failure.
+- Migrated `strided-opteinsum` intermediate pool acquisition to
+  `MaybeUninit` and finalize only after a successful overwrite call.
+- Kept the default Faer-only `strided-opteinsum` path on initialized storage
+  until Faer provides a typed overwrite API; direct Faer uninitialized entry
+  points now return a typed `Unsupported` error instead of silently routing to
+  the naive provider.
+- Added a shared raw-GEMM preflight before label construction, temporary
+  allocation, or provider dispatch; it checks full dimension agreement,
+  injectivity, conservative aliasing, checked products, and BLAS sizes.
+- Made column-major uninitialized allocation and opteinsum pool sizing
+  propagate checked overflow errors instead of using unchecked products.
+
+## Verification
+
+- `cargo fmt --all`
+- Added coverage tests for the Faer-gated validation/naive fallback, the
+  `dot_general_into_uninit` forwarding boundary, and both direct and
+  temporary raw-output finalize paths.
+- `CARGO_BUILD_JOBS=4 RUSTFLAGS='-C link-arg=-Wl,--threads=1' cargo llvm-cov --workspace --json --output-path /tmp/coverage-188.json`
+- `python3 scripts/check-coverage.py /tmp/coverage-188.json` (54/54 files;
+  `contiguous.rs` 86.98%, `dot_general.rs` 86.53%, `uninit.rs` 82.17%)
+- `cargo test -p strided-einsum2 --lib`
+- `cargo test -p strided-opteinsum --lib`
+- `cargo test -p strided-einsum2 --no-default-features`
+- `cargo test -p strided-einsum2 --no-default-features --features faer`
+- `cargo test -p strided-einsum2 --no-default-features --features blas`
+- `cargo test -p strided-einsum2 --no-default-features --features blas-inject`
+- `cargo test -p strided-opteinsum --no-default-features --features faer`
+- `cargo test -p strided-opteinsum --no-default-features --features blas`
+- `cargo test -p strided-opteinsum --no-default-features --features blas-inject`
+- `cargo check -p strided-einsum2 --no-default-features`
+- `cargo check -p strided-einsum2 --no-default-features --features faer`
+- `cargo check -p strided-einsum2 --no-default-features --features blas-inject`
+- `cargo check -p strided-einsum2 --no-default-features --features blas`
+- `cargo test -p strided-einsum2 --no-default-features --features blas-inject --test blas_inject_fallback -- --test-threads=1`
+- `cargo fmt --all -- --check`
+- `git diff --check`
+- `CARGO_BUILD_JOBS=4 RUSTFLAGS='-C link-arg=-Wl,--threads=1' cargo test --workspace`
+
+The first unrestricted workspace run reached the doctest linker but hit a
+Rust 1.97 `rust-lld` bus error under the full local parallel load. The same
+workspace command passed after limiting Cargo jobs and linker threads. The
+repository has no configured rules-review script; package clippy remains
+non-clean on the current Rust 1.97 toolchain because of pre-existing lints in
+the workspace, so it is not used as the PR gate.
+
+## Remaining work
+
+- Faer uninitialized output remains blocked by #195: the current Faer
+  `MatMut::from_raw_parts_mut` contract does not permit forming `MatMut<T>` over
+  `MaybeUninit<T>`, including for `Accum::Replace`. No cast or zero-fill
+  workaround is allowed.
+- The naive, system BLAS, and injected BLAS overwrite paths are wired through
+  the public uninitialized APIs. Their feature-specific tests cover direct and
+  non-contiguous temporary/writeback execution, including a poisoned-C
+  zgemm regression. Faer remains explicitly blocked on strided-rs#195; its
+  initialized compatibility path is tested separately.

strided-einsum2/src/backend.rs

@@ -4,6 +4,7 @@
 //! and the `ActiveBackend` type alias that serves as the single point of
 //! backend selection based on Cargo features.
 
+use strided_kernel::ExecContext;
 use strided_view::ElementOp;
 
 /// Trait for backends that can execute batched GEMM on contiguous operands.
@@ -47,6 +48,23 @@ pub trait Backend<T: crate::ScalarBase> {
     ) -> strided_view::Result<()>;
 }
 
+/// Private overwrite-only backend contract. The initialized `Backend` trait
+/// remains unchanged for beta-bearing callers.
+#[allow(dead_code)]
+pub(crate) trait OverwriteBackend<T: crate::ScalarBase> {
+    fn bgemm_contiguous_overwrite(
+        c: &mut crate::contiguous::UninitContiguousOperand<'_, '_, T>,
+        a: &crate::contiguous::ContiguousOperand<T>,
+        b: &crate::contiguous::ContiguousOperand<T>,
+        batch_dims: &[usize],
+        m: usize,
+        n: usize,
+        k: usize,
+        alpha: T,
+        ctx: &ExecContext,
+    ) -> strided_view::Result<()>;
+}
+
 // ---------------------------------------------------------------------------
 // Marker structs
 // ---------------------------------------------------------------------------
@@ -139,6 +157,26 @@ where
     }
 }
 
+#[cfg(not(any(feature = "blas", feature = "blas-inject")))]
+impl<T> OverwriteBackend<T> for NaiveBackend
+where
+    T: crate::ScalarBase + strided_view::ElementOpApply,
+{
+    fn bgemm_contiguous_overwrite(
+        c: &mut crate::contiguous::UninitContiguousOperand<'_, '_, T>,
+        a: &crate::contiguous::ContiguousOperand<T>,
+        b: &crate::contiguous::ContiguousOperand<T>,
+        batch_dims: &[usize],
+        m: usize,
+        n: usize,
+        k: usize,
+        alpha: T,
+        ctx: &ExecContext,
+    ) -> strided_view::Result<()> {
+        crate::uninit::bgemm_contiguous_naive(c, a, b, batch_dims, m, n, k, alpha, ctx)
+    }
+}
+
 // ---------------------------------------------------------------------------
 // ActiveBackend type alias -- the SINGLE point of backend selection
 // ---------------------------------------------------------------------------