From 48169a81011fbfef2a97c3df90a9b7b446d264db Mon Sep 17 00:00:00 2001
From: Jishnu Bhattacharya <jishnub.github@gmail.com>
Date: Mon, 14 Apr 2025 22:42:26 +0530
Subject: [PATCH 1/2] Fix `lmul!`/`rmul!` for 0-sized matrices

---
 src/bidiag.jl  | 2 ++
 test/bidiag.jl | 9 +++++++++
 2 files changed, 11 insertions(+)

diff --git a/src/bidiag.jl b/src/bidiag.jl
index d2f9e624..60fbc7e5 100644
--- a/src/bidiag.jl
+++ b/src/bidiag.jl
@@ -538,6 +538,7 @@ function lmul!(D::Diagonal, B::Bidiagonal)
     matmul_size_check(size(D), size(B))
     (; dv, ev) = B
     isL = B.uplo == 'L'
+    iszero(size(D,1)) && return B
     dv[1] = D.diag[1] * dv[1]
     for i in axes(ev,1)
         ev[i] = D.diag[i + isL] * ev[i]
@@ -575,6 +576,7 @@ function rmul!(B::Bidiagonal, D::Diagonal)
     matmul_size_check(size(B), size(D))
     (; dv, ev) = B
     isU = B.uplo == 'U'
+    iszero(size(D,1)) && return B
     dv[1] *= D.diag[1]
     for i in axes(ev,1)
         ev[i] *= D.diag[i + isU]
diff --git a/test/bidiag.jl b/test/bidiag.jl
index 6fa851dd..e111433d 100644
--- a/test/bidiag.jl
+++ b/test/bidiag.jl
@@ -1192,4 +1192,13 @@ end
     @test_throws msg ldiv!(C, B, zeros(2,1))
 end
 
+@testset "l/rmul with 0-sized matrices" begin
+    n = 0
+    B = Bidiagonal(ones(n), ones(max(n-1,0)), :U)
+    B2 = copy(B)
+    D = Diagonal(ones(n))
+    @test lmul!(D, B) == B2
+    @test rmul!(B, D) == B2
+end
+
 end # module TestBidiagonal

From 4aca27487e9ece7afe11a1922d7f086fe55f8f4f Mon Sep 17 00:00:00 2001
From: Jishnu Bhattacharya <jishnub.github@gmail.com>
Date: Mon, 14 Apr 2025 23:05:25 +0530
Subject: [PATCH 2/2] Add `@inbounds` annotation

---
 src/bidiag.jl | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/bidiag.jl b/src/bidiag.jl
index 60fbc7e5..05c1371c 100644
--- a/src/bidiag.jl
+++ b/src/bidiag.jl
@@ -539,8 +539,8 @@ function lmul!(D::Diagonal, B::Bidiagonal)
     (; dv, ev) = B
     isL = B.uplo == 'L'
     iszero(size(D,1)) && return B
-    dv[1] = D.diag[1] * dv[1]
-    for i in axes(ev,1)
+    @inbounds dv[1] = D.diag[1] * dv[1]
+    @inbounds for i in axes(ev,1)
         ev[i] = D.diag[i + isL] * ev[i]
         dv[i+1] = D.diag[i+1] * dv[i+1]
     end
@@ -577,8 +577,8 @@ function rmul!(B::Bidiagonal, D::Diagonal)
     (; dv, ev) = B
     isU = B.uplo == 'U'
     iszero(size(D,1)) && return B
-    dv[1] *= D.diag[1]
-    for i in axes(ev,1)
+    @inbounds dv[1] *= D.diag[1]
+    @inbounds for i in axes(ev,1)
         ev[i] *= D.diag[i + isU]
         dv[i+1] *= D.diag[i+1]
     end