From f51c0f32e62748cd5b1c9a63bcbcf6c21d79256c Mon Sep 17 00:00:00 2001
From: Nuwan Yapa <yapanuwan@gmail.com>
Date: Mon, 30 Dec 2024 18:21:45 -0500
Subject: [PATCH] Function for calculating rank

---
 helper.jl | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/helper.jl b/helper.jl
index 6f52421..da9f150 100644
--- a/helper.jl
+++ b/helper.jl
@@ -71,3 +71,11 @@ function gram_schmidt(vecs, ws, precision=1e-10, verbose=false)
     end
     return vecs[mask]
 end
+
+"Rank of a basis set (pre-normalized) under c-product"
+function c_rank(vecs, ws, threshold=1e-8)
+    basis = hcat(vecs...)
+    N = transpose(basis) * spdiagm(ws) * basis
+    abs_singular_values = eigvals(N) .|> abs .|> sqrt
+    return count(abs_singular_values .> threshold)
+end
\ No newline at end of file