improve truncation

Author: lkdvos

src/implementations/truncation.jl

@@ -28,11 +28,13 @@ end
 
 # special case `NoTruncation` for null: should keep exact zeros due to rectangularity
 function truncate(::typeof(left_null!), (U, S), strategy::NoTruncation)
-    ind = (1:max(0, size(S, 1) - size(S, 2))) .+ length(diagview(S))
+    m, n = size(S)
+    ind = (n + 1):m
     return U[:, ind], ind
 end
 function truncate(::typeof(right_null!), (S, Vᴴ), strategy::NoTruncation)
-    ind = (1:max(0, size(S, 2) - size(S, 1))) .+ length(diagview(S))
+    m, n = size(S)
+    ind = (m + 1):n
     return Vᴴ[ind, :], ind
 end