speed up power iterations

JuliaImageRecon · Nov 25, 2023 · da8483c · da8483c
1 parent f7e70e0
commit da8483c
Showing 1 changed file with 6 additions and 1 deletion.
diff --git a/src/Utils.jl b/src/Utils.jl
@@ -298,7 +298,12 @@ function power_iterations(AᴴA; rtol=1e-2, maxiter=30, verbose=false)
 
   for i = 1:maxiter
     b ./= norm(b)
-    copy!(bᵒˡᵈ, b)
+
+    # swap b and bᵒˡᵈ (pointers only, no data is moved or allocated)
+    bᵗᵐᵖ = bᵒˡᵈ
+    bᵒˡᵈ = b
+    b = bᵗᵐᵖ
+
     mul!(b, AᴴA, bᵒˡᵈ)
 
     λᵒˡᵈ = λ