Fixed: Correctly filters checksum files in CI

Replaces `grep -F` with `awk` to reliably filter checksum files
in CI workflows by matching the last field against the target
filename. This ensures that the correct checksum is selected,
even when the filename contains spaces or special characters.

Also, updates the `yaml-fix` recipe in the justfile to use
`prettier` if available, falling back to `npx` if not. This
resolves an issue where YAML formatting would fail if `prettier`
was not globally installed.

Adds more terms to the spellcheck dictionary and a reference file.
Refs: feat/ldlt

Author: acgetchell

.github/workflows/ci.yml

@@ -136,7 +136,7 @@ jobs:
 
           orig_dir="$PWD"
           cd "$tmpdir"
-          grep -F "  $TARBALL" "$CHECKSUMS_FILE" > checksum.txt
+          awk -v f="$TARBALL" '$NF==f {print; found=1} END {exit found?0:1}' "$CHECKSUMS_FILE" > checksum.txt
           verify_sha256 checksum.txt
           cd "$orig_dir"
 
@@ -177,7 +177,7 @@ jobs:
 
           (
             cd "$tmpdir"
-            grep -F "  ${SHFMT_ASSET}" sha256sums.txt > checksum.txt
+            awk -v f="${SHFMT_ASSET}" '$NF==f {print; found=1} END {exit found?0:1}' sha256sums.txt > checksum.txt
             sha256sum -c checksum.txt
           )
 
@@ -210,7 +210,7 @@ jobs:
 
           (
             cd "$tmpdir"
-            grep -F "  ${SHFMT_ASSET}" sha256sums.txt > checksum.txt
+            awk -v f="${SHFMT_ASSET}" '$NF==f {print; found=1} END {exit found?0:1}' sha256sums.txt > checksum.txt
             shasum -a 256 -c checksum.txt
           )
 

.github/workflows/codecov.yml

@@ -48,7 +48,7 @@ jobs:
           fi
 
       - name: Install just
-        uses: taiki-e/install-action@bfc291e1e39400b67eda124e4a7b4380e93b3390  # v2.65.0
+        uses: taiki-e/install-action@bfc291e1e39400b67eda124e4a7b4380e93b3390 # v2.65.0
         with:
           tool: just
 
@@ -76,7 +76,7 @@ jobs:
 
       - name: Upload coverage to Codecov
         if: ${{ success() && hashFiles('coverage/cobertura.xml') != '' }}
-        uses: codecov/codecov-action@671740ac38dd9b0130fbe1cec585b89eea48d3de  # v5.5.2
+        uses: codecov/codecov-action@671740ac38dd9b0130fbe1cec585b89eea48d3de # v5.5.2
         with:
           files: coverage/cobertura.xml
           flags: unittests

.gitignore

@@ -15,6 +15,4 @@ venv/
 .mypy_cache/
 uv.lock
 /node_modules/
-/.package-lock.json
 /package-lock.json
-/package.json

README.md

@@ -81,14 +81,25 @@ for (x_i, e_i) in x.iter().zip(expected.iter()) {
 }
 ```
 
-Compute a determinant for a symmetric SPD matrix via LDLT (no pivoting):
+Compute a determinant for a symmetric SPD matrix via LDLT (no pivoting).
+
+For symmetric positive-definite matrices, `LDL^T` is essentially a square-root-free form of the Cholesky decomposition
+(you can recover a Cholesky factor by absorbing `sqrt(D)` into `L`):
 
 ```rust
 use la_stack::prelude::*;
 
-let a = Matrix::<2>::from_rows([[4.0, 2.0], [2.0, 3.0]]);
+// This matrix is symmetric positive-definite (A = L*L^T) so LDLT works without pivoting.
+let a = Matrix::<5>::from_rows([
+    [1.0, 1.0, 0.0, 0.0, 0.0],
+    [1.0, 2.0, 1.0, 0.0, 0.0],
+    [0.0, 1.0, 2.0, 1.0, 0.0],
+    [0.0, 0.0, 1.0, 2.0, 1.0],
+    [0.0, 0.0, 0.0, 1.0, 2.0],
+]);
+
 let det = a.ldlt(DEFAULT_SINGULAR_TOL).unwrap().det();
-assert!((det - 8.0).abs() <= 1e-12);
+assert!((det - 1.0).abs() <= 1e-12);
 ```
 
 ## 🧩 API at a glance

REFERENCES.md

@@ -15,16 +15,41 @@ A Zenodo DOI will be added for tagged releases.
 The LU implementation in `la-stack` follows the standard Gaussian elimination / LU factorization
 approach with partial pivoting for numerical stability.
 
-- Golub, Gene H., and Charles F. Van Loan. *Matrix Computations* (4th ed.). Johns Hopkins University Press, 2013.
-- Higham, Nicholas J. *Accuracy and Stability of Numerical Algorithms* (2nd ed.). SIAM, 2002.
-- Trefethen, Lloyd N., and David Bau III. *Numerical Linear Algebra*. SIAM, 1997.
+See references [1-3] below.
 
 ### LDL^T factorization (symmetric SPD/PSD)
 
 The LDL^T (often abbreviated "LDLT") implementation in `la-stack` is intended for symmetric positive
-definite (SPD) and positive semi-definite (PSD) matrices (e.g. Gram matrices), and does not perform
+ definite (SPD) and positive semi-definite (PSD) matrices (e.g. Gram matrices), and does not perform
 pivoting.
 
-- Golub, Gene H., and Charles F. Van Loan. *Matrix Computations* (4th ed.). Johns Hopkins University Press, 2013.
-- Higham, Nicholas J. *Accuracy and Stability of Numerical Algorithms* (2nd ed.). SIAM, 2002.
-- Trefethen, Lloyd N., and David Bau III. *Numerical Linear Algebra*. SIAM, 1997.
+For background on the SPD/PSD setting, see [4-5]. For pivoted variants used for symmetric *indefinite*
+matrices, see [6].
+
+## References
+
+### LU / Gaussian elimination
+
+1. Trefethen, Lloyd N., and Robert S. Schreiber. "Average-case stability of Gaussian elimination."
+   *SIAM Journal on Matrix Analysis and Applications* 11.3 (1990): 335–360.
+   [PDF](https://people.maths.ox.ac.uk/trefethen/publication/PDF/1990_44.pdf)
+2. Businger, P. A. "Monitoring the Numerical Stability of Gaussian Elimination."
+   *Numerische Mathematik* 16 (1970/71): 360–361.
+   [Full text](https://eudml.org/doc/132040)
+3. Huang, Han, and K. Tikhomirov. "Average-case analysis of the Gaussian elimination with partial pivoting."
+   *Probability Theory and Related Fields* 189 (2024): 501–567.
+   [Open-access PDF](https://link.springer.com/article/10.1007/s00440-024-01276-2) (also: [arXiv:2206.01726](https://arxiv.org/abs/2206.01726))
+
+### LDL^T / Cholesky (symmetric SPD/PSD)
+
+4. Cholesky, Andre-Louis. "On the numerical solution of systems of linear equations"
+   (manuscript dated 2 Dec 1910; published 2005).
+   Scan + English analysis: [BibNum](https://www.bibnum.education.fr/mathematiques/algebre/sur-la-resolution-numerique-des-systemes-d-equations-lineaires)
+5. Brezinski, Claude. "La methode de Cholesky." (2005).
+   [PDF](https://eudml.org/doc/252115)
+
+### Pivoted LDL^T (symmetric indefinite)
+
+6. Bunch, J. R., L. Kaufman, and B. N. Parlett. "Decomposition of a Symmetric Matrix."
+   *Numerische Mathematik* 27 (1976/1977): 95–110.
+   [Full text](https://eudml.org/doc/132435)

cspell.json

@@ -6,6 +6,8 @@
     "acgetchell",
     "addopts",
     "blas",
+    "Brezinski",
+    "Businger",
     "capsys",
     "Clippy",
     "clippy",
@@ -39,6 +41,8 @@
     "logscale",
     "lu",
     "markdownlint",
+    "Mathematik",
+    "methode",
     "minversion",
     "MSRV",
     "msvc",
@@ -51,8 +55,10 @@
     "noplot",
     "nrhs",
     "nrows",
+    "Numerische",
     "openblas",
     "orcid",
+    "Parlett",
     "pastey",
     "patchlevel",
     "pipefail",
@@ -68,6 +74,7 @@
     "rustup",
     "samply",
     "sarif",
+    "Schreiber",
     "semgrep",
     "setuptools",
     "shellcheck",
@@ -78,6 +85,7 @@
     "Taplo",
     "taplo",
     "testpaths",
+    "Tikhomirov",
     "Trefethen",
     "tridiagonal",
     "unittests",

justfile

@@ -340,14 +340,14 @@ setup-tools:
         install_with_brew node
         echo ""
     else
-        echo "❌ 'brew' not found."
+        echo "⚠️  'brew' not found; skipping automatic tool installation."
         if [[ "$os" == "Darwin" ]]; then
-            echo "Install Homebrew from https://brew.sh and re-run: just setup-tools"
-            exit 1
+            echo "Install Homebrew from https://brew.sh (recommended), or install the following tools manually:"
+        else
+            echo "Install the following tools via your system package manager:"
         fi
-        echo "Install the following tools via your system package manager, then re-run: just setup-tools"
         echo "  uv, jq, taplo, yamllint, shfmt, shellcheck, actionlint, node+npx"
-        exit 1
+        echo ""
     fi
 
     echo "Ensuring Rust toolchain + components..."
@@ -517,7 +517,7 @@ validate-json: _ensure-jq
     fi
 
 # YAML
-yaml-fix: _ensure-npx
+yaml-fix:
     #!/usr/bin/env bash
     set -euo pipefail
     files=()
@@ -526,8 +526,26 @@ yaml-fix: _ensure-npx
     done < <(git ls-files -z '*.yml' '*.yaml')
     if [ "${#files[@]}" -gt 0 ]; then
         echo "📝 prettier --write (YAML, ${#files[@]} files)"
+
+        cmd=()
+        if command -v prettier >/dev/null; then
+            cmd=(prettier --write --print-width 120)
+        elif command -v npx >/dev/null; then
+            # Prefer non-interactive installs when supported (newer npm/npx).
+            # NOTE: With `set -u`, expanding an empty array like "${arr[@]}" can error on older bash.
+            cmd=(npx)
+            if npx --help 2>&1 | grep -q -- '--yes'; then
+                cmd+=(--yes)
+            fi
+            cmd+=(prettier --write --print-width 120)
+        else
+            echo "❌ 'prettier' not found. Install via npm (recommended): npm i -g prettier"
+            echo "   Or install Node.js (for npx): https://nodejs.org"
+            exit 1
+        fi
+
         # Use CLI flags instead of a repo-wide prettier config: keeps the scope to YAML only.
-        printf '%s\0' "${files[@]}" | xargs -0 -n100 npx prettier --write --print-width 120
+        printf '%s\0' "${files[@]}" | xargs -0 -n100 "${cmd[@]}"
     else
         echo "No YAML files found to format."
     fi

src/lib.rs

@@ -29,6 +29,23 @@ mod readme_doctests {
     /// }
     /// ```
     fn solve_5x5_example() {}
+
+    /// ```rust
+    /// use la_stack::prelude::*;
+    ///
+    /// // This matrix is symmetric positive-definite (A = L*L^T) so LDLT works without pivoting.
+    /// let a = Matrix::<5>::from_rows([
+    ///     [1.0, 1.0, 0.0, 0.0, 0.0],
+    ///     [1.0, 2.0, 1.0, 0.0, 0.0],
+    ///     [0.0, 1.0, 2.0, 1.0, 0.0],
+    ///     [0.0, 0.0, 1.0, 2.0, 1.0],
+    ///     [0.0, 0.0, 0.0, 1.0, 2.0],
+    /// ]);
+    ///
+    /// let det = a.ldlt(DEFAULT_SINGULAR_TOL).unwrap().det();
+    /// assert!((det - 1.0).abs() <= 1e-12);
+    /// ```
+    fn det_5x5_ldlt_example() {}
 }
 
 mod ldlt;