faster

src/principal_eigenvalue.jl

@@ -18,10 +18,11 @@ In other words, all eigenvalues of 𝕋 have real part <= 0. This means that 
 """
 function principal_eigenvalue(𝕋; r0 = ones(size(𝕋, 1)))
     a, η, r = 0.0, 0.0, r0
-    # faster in certain cases. Check that all sum up to zero
     try
+        # faster in certain cases. Check that all sum up to zero
         @assert maximum(abs.(sum(𝕋, dims = 1))) < 1e-9
-        vals, vecs = Arpack.eigs(𝕋; v0 = collect(r0), nev = 1, which = :SM)
+        # standard way of solving Ax = 0 is to do inverse iteration https://stackoverflow.com/questions/33563401/lapack-routines-for-solving-a-x-0
+        vals, vecs = Arpack.eigs(𝕋; v0 = collect(r0), nev = 1, which = :LM, sigma = 0.0)
         η = vals[1]
         r = vecs[:, 1]
     catch