Attempt to fix ql (#154)

* attempt to fix ql

* add basic test for periodic schro

* fix typo

Author: MasonProtter

src/infql.jl

@@ -192,7 +192,7 @@ function _blocktripert_ql(A, d, e)
     B = BlockBandedMatrix(A,(2,1))
 
 
-    BB = _BlockBandedMatrix(B.data.args[1], (fill(2,N+2), fill(2,N)), (2,1))
+    BB = _BlockBandedMatrix(B.data.args[1], fill(2,N+2), fill(2,N), (2,1))
     BB[Block(N),Block.(N-1:N)] .= P[Block(1), Block.(1:2)]
     F = ql!(view(BB, Block.(1:N), Block.(1:N)))
     BB[Block(N+1),Block.(N-1:N)] .= P[Block(2), Block.(1:2)]
@@ -518,4 +518,4 @@ function materialize!(M::Lmul{<:AdjQLPackedQLayout{<:LazyLayout},<:PaddedLayout}
         end
     end
     B
-end
+end

test/test_infql.jl

@@ -267,4 +267,15 @@ using ArrayLayouts: TriangularLayout, UnknownLayout
             @test (Q * B)[1:10,:] ≈ Q[1:10,1:10]*B[1:10,:]
         end
     end
-end
+    @testset "Periodic Schrödinger" begin
+
+        A = BlockTridiagonal(Vcat([[0. 1.; 0. 0.]],Fill([0. 1.; 0. 0.], ∞)),
+                             Vcat([[-1. 1.; 1. 1.]], Fill([-1. 1.; 1. 1.], ∞)),
+                             Vcat([[0. 0.; 1. 0.]], Fill([0. 0.; 1. 0.], ∞)))
+
+        A[1,1] = 2 
+
+        x = -0.95
+        @test ql(A-x*I).L[1,1] isa Float64
+    end
+end