From 885187818f3b92f69573cdc82e7cb623c856885b Mon Sep 17 00:00:00 2001
From: Alexis Montoison <35051714+amontoison@users.noreply.github.com>
Date: Tue, 5 Nov 2024 16:46:58 -0600
Subject: [PATCH] Remove broadcast in MINRES-QLP (#929)

---
 src/minres_qlp.jl | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/minres_qlp.jl b/src/minres_qlp.jl
index 2538a1802..cd0dc20c2 100644
--- a/src/minres_qlp.jl
+++ b/src/minres_qlp.jl
@@ -353,7 +353,10 @@ kwargs_minres_qlp = (:M, :ldiv, :λ, :atol, :rtol, :Artol, :itmax, :timemax, :ve
         # [w̅ₖ₋₁ vₖ] [cpₖ  spₖ] = [ẘₖ₋₁ w̅ₖ] ⟷ ẘₖ₋₁ = cpₖ * w̅ₖ₋₁ + spₖ * vₖ
         #           [spₖ -cpₖ]             ⟷ w̅ₖ   = spₖ * w̅ₖ₋₁ - cpₖ * vₖ
         @kswap!(wₖ₋₁, wₖ)
-        wₖ .= spₖ .* wₖ₋₁ .- cpₖ .* vₖ
+        # Compute w̅ₖ
+        kcopy!(n, wₖ, wₖ₋₁)
+        kaxpby!(n, -cpₖ, vₖ, spₖ, wₖ)
+        # Compute ẘₖ₋₁
         kaxpby!(n, spₖ, vₖ, cpₖ, wₖ₋₁)
       else
         # [ẘₖ₋₂ w̄ₖ₋₁ vₖ] [cpₖ  0   spₖ] [1   0    0 ] = [wₖ₋₂ ẘₖ₋₁ w̄ₖ] ⟷ wₖ₋₂ = cpₖ * ẘₖ₋₂ + spₖ * vₖ