From 942a58b1dc842a57a955b71391401d5f57a7ea11 Mon Sep 17 00:00:00 2001
From: Cory <cory@balaton.dev>
Date: Sun, 17 Sep 2023 16:23:16 +0200
Subject: [PATCH] Create test for creating symmetric tridiagonals

---
 src/test_suite.cpp | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/src/test_suite.cpp b/src/test_suite.cpp
index e92af50..dc13845 100644
--- a/src/test_suite.cpp
+++ b/src/test_suite.cpp
@@ -1,6 +1,8 @@
 #include <cassert>
 #include <cmath>
+#include <iostream>
 
+#include "utils.hpp"
 #include "matrix.hpp"
 
 void test_create_symmetric_tridiagonal() {
@@ -21,6 +23,28 @@ void test_create_symmetric_tridiagonal() {
         diff = eigval(i) - (d + 2.*a*std::cos(((i+1.)*M_PI)/(N+1.)));
         assert(std::abs(diff) < tol); 
     }
+
+    arma::vec v, res, analytic_vec = arma::vec(N);
+    for (int i=0; i < N; i++) {
+        v = eigvec.col(i);
+
+        // Build the analytic vector
+        for (int j=0; j < N; j++) {
+            analytic_vec(j) = std::sin(((j+1.)*(i+1.)*M_PI) / (N+1.));
+        }
+
+        analytic_vec = arma::normalise(analytic_vec);
+
+        // flip the sign of the analytic vector if they are different
+        if (analytic_vec(0)*v(0) < 0.) {
+            analytic_vec *= -1;
+        }
+
+        res = v - analytic_vec;
+        for (int j=0; j < N; j++) {
+            assert(std::abs(res(j)) < tol);
+        }
+    }
 }
 
 void test_max_off_diag_symmetric() {