Fix indexing columns

Author: jishnub

src/bidiag.jl

@@ -955,7 +955,7 @@ function _mul!(C::AbstractVecOrMat, A::BiTriSym, B::AbstractVecOrMat, _add::MulA
     iszero(_add.alpha) && return _rmul_or_fill!(C, _add.beta)
     if nA == 1
         A11 = @inbounds A[1,1]
-        for i in 1:nB
+        for i in axes(B, 2)
             @inbounds _modify!(_add, A11 * B[1,i], C, (1,i))
         end
         return C

test/bidiag.jl

@@ -1192,4 +1192,12 @@ end
     @test_throws msg ldiv!(C, B, zeros(2,1))
 end
 
+@testset "1-row mul" begin
+    B = Bidiagonal(2:2, 1:0, :U)
+    for v in ([3], fill(3, 1, 4))
+        @test mul!(zero(v), B, v) == 2v
+        @test mul!(2v, B, v, 2, 2) == 8v
+    end
+end
+
 end # module TestBidiagonal

test/tridiag.jl

@@ -1184,4 +1184,14 @@ end
     @test convert(SymTridiagonal, S) == S
 end
 
+@testset "1-row mul" begin
+    for T in (Tridiagonal(1:0, 2:2, 1:0),
+                SymTridiagonal(2:2, 1:0))
+        for v in ([3], fill(3, 1, 4))
+            @test mul!(zero(v), T, v) == 2v
+            @test mul!(2v, T, v, 2, 2) == 8v
+        end
+    end
+end
+
 end # module TestTridiagonal