From 27506f77a0ebc8db048ded210c7c350dcd59d405 Mon Sep 17 00:00:00 2001
From: SauersML <123714540+SauersML@users.noreply.github.com>
Date: Wed, 24 Sep 2025 00:51:15 -0500
Subject: [PATCH] Align PCA test with sample scaling and silence backend
 warnings

---
 src/linalg_backends.rs | 34 +++++++++++++++++++++-------------
 tests/pca_tests.rs     | 15 ++++++++++++---
 2 files changed, 33 insertions(+), 16 deletions(-)

diff --git a/src/linalg_backends.rs b/src/linalg_backends.rs
index d3f6d56..36344fe 100644
--- a/src/linalg_backends.rs
+++ b/src/linalg_backends.rs
@@ -22,15 +22,18 @@ impl<F: 'static + Copy + Send + Sync> LinAlgBackendProvider<F> {
     feature = "faer_links_ndarray_static_openblas"
 ))]
 use ndarray::s;
-#[cfg(any(
-    feature = "backend_openblas",
-    feature = "backend_openblas_system",
-    feature = "backend_mkl",
-    feature = "backend_mkl_system",
-    feature = "faer_links_ndarray_static_openblas"
+use ndarray::{Array1, Array2};
+#[cfg(all(
+    not(feature = "backend_faer"),
+    any(
+        feature = "backend_openblas",
+        feature = "backend_openblas_system",
+        feature = "backend_mkl",
+        feature = "backend_mkl_system",
+        feature = "faer_links_ndarray_static_openblas"
+    )
 ))]
 use ndarray_linalg::Lapack;
-use ndarray::{Array1, Array2};
 // use num_traits::Float; // No longer needed directly by provider
 use std::error::Error;
 use std::marker::PhantomData;
@@ -90,9 +93,11 @@ mod ndarray_backend_impl {
     use ndarray_linalg::{Eigh, Lapack, SVDInto, QR, UPLO};
     use std::error::Error;
 
+    #[cfg_attr(feature = "backend_faer", allow(dead_code))]
     #[derive(Debug, Default, Copy, Clone)]
     pub struct NdarrayLinAlgBackend;
 
+    #[cfg_attr(feature = "backend_faer", allow(dead_code))]
     fn to_dyn_error<E: Error + Send + Sync + 'static>(e: E) -> Box<dyn Error + Send + Sync> {
         Box::new(e)
     }
@@ -185,12 +190,15 @@ mod ndarray_backend_impl {
     pub use NdarrayLinAlgBackend as Backend;
 }
 
-#[cfg(any(
-    feature = "backend_openblas",
-    feature = "backend_openblas_system",
-    feature = "backend_mkl",
-    feature = "backend_mkl_system",
-    feature = "faer_links_ndarray_static_openblas"
+#[cfg(all(
+    not(feature = "backend_faer"),
+    any(
+        feature = "backend_openblas",
+        feature = "backend_openblas_system",
+        feature = "backend_mkl",
+        feature = "backend_mkl_system",
+        feature = "faer_links_ndarray_static_openblas"
+    )
 ))]
 use ndarray_backend_impl::Backend as NdarrayLinAlgBackend;
 
diff --git a/tests/pca_tests.rs b/tests/pca_tests.rs
index 61e03d4..78c2f5e 100644
--- a/tests/pca_tests.rs
+++ b/tests/pca_tests.rs
@@ -91,7 +91,7 @@ fn eigenvalues_descending(matrix: &Array2<f64>) -> Vec<f64> {
 fn eigenvalues_descending(matrix: &Array2<f64>) -> Vec<f64> {
     use ndarray_linalg::{Eigh, UPLO};
 
-    let (mut eigenvalues, _) = matrix.eigh(UPLO::Upper).expect("eigendecomposition failed");
+    let (eigenvalues, _) = matrix.eigh(UPLO::Upper).expect("eigendecomposition failed");
     let mut values = eigenvalues.to_vec();
     values.sort_by(|a, b| b.partial_cmp(a).expect("eigenvalues must be comparable"));
     values
@@ -1953,8 +1953,17 @@ mod pca_tests {
         }
 
         if explained_variance_fit_eff_v161.len() > 0 {
-            if !approx::abs_diff_eq!(explained_variance_fit_eff_v161[0], 4.0, epsilon = TOLERANCE) {
-                panic!("Efficient PCA (fit) first explained variance for hardcoded data should be approx 4.0. Got: {}", explained_variance_fit_eff_v161[0]);
+            let expected_first_ev = n_features as f64;
+            if !approx::abs_diff_eq!(
+                explained_variance_fit_eff_v161[0],
+                expected_first_ev,
+                epsilon = TOLERANCE
+            ) {
+                panic!(
+                    "Efficient PCA (fit) first explained variance for hardcoded data should reflect sample-variance scaling (~{}). Got: {}",
+                    expected_first_ev,
+                    explained_variance_fit_eff_v161[0]
+                );
             }
         }