diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index f34260e..f77f517 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -13,6 +13,7 @@ jobs:
       matrix:
         version:
           - '1' # automatically expands to the latest stable 1.x release of Julia
+          - 'lts'
           - 'nightly'
         os:
           - ubuntu-latest
@@ -26,7 +27,7 @@ jobs:
             arch: x86
     steps:
       - uses: actions/checkout@v2
-      - uses: julia-actions/setup-julia@v1
+      - uses: julia-actions/setup-julia@v2
         with:
           version: ${{ matrix.version }}
           arch: ${{ matrix.arch }}
diff --git a/src/SweepOperator.jl b/src/SweepOperator.jl
index 1a0e2b7..8f6014d 100644
--- a/src/SweepOperator.jl
+++ b/src/SweepOperator.jl
@@ -7,6 +7,7 @@ import LinearAlgebra: BlasFloat, checksquare
 const AMat = AbstractMatrix
 const AVec = AbstractVector
 
+#-----------------------------------------------------------------------------# sweep!
 """
     sweep!(A, k ; inv=false)
     sweep!(A, ks; inv=false)
@@ -22,10 +23,11 @@ Perform the sweep operation (or inverse sweep if `inv=true`) on matrix `A` on el
     sweep!(xtx, 1, true)
 """
 function sweep!(A::AMat, k::Integer, inv::Bool = false)
-    sweep_with_buffer!(Vector{eltype(A)}(undef, size(A, 2)), A, k, inv)
+    akk = Vector{eltype(A)}(undef, size(A, 2))
+    sweep_with_buffer!(akk, A, k, inv)
 end
 
-function sweep!(A::AMat{T}, ks::AVec{I}, inv::Bool = false) where {T<:BlasFloat, I<:Integer}
+function sweep!(A::AMat{T}, ks::AVec{I}, inv::Bool = false) where {T <: BlasFloat, I <: Integer}
     akk = Vector{T}(undef, size(A,1))
     for k in ks
         sweep_with_buffer!(akk, A, k, inv)
@@ -33,6 +35,7 @@ function sweep!(A::AMat{T}, ks::AVec{I}, inv::Bool = false) where {T<:BlasFloat,
     A
 end
 
+#-----------------------------------------------------------------------------# sweep_with_buffer!
 function sweep_with_buffer!(akk::AVec{T}, A::AMat{T}, k::Integer, inv::Bool = false) where {T}
     # ensure @inbounds is safe
     p = checksquare(A)
@@ -49,6 +52,14 @@ function sweep_with_buffer!(akk::AVec{T}, A::AMat{T}, k::Integer, inv::Bool = fa
     return A
 end
 
+# This is slower than unbuffered version??
+function sweep_with_buffer!(akk::AVec{T}, A::AMat{T}, ks::AVec{I}, inv::Bool = false) where {T, I <: Integer}
+    for k in ks
+        sweep_with_buffer!(akk, A, k, inv)
+    end
+    A
+end
+
 #-----------------------------------------------------------------------------# setrowcol!
 # Set upper triangle of: (A[k, :] = x; A[:, k] = x)
 function setrowcol!(A::StridedArray, k, x)
@@ -62,24 +73,23 @@ setrowcol!(A::Union{Hermitian,Symmetric,UpperTriangular}, k, x) = setrowcol!(A.d
 const BlasNumber = Union{LinearAlgebra.BlasFloat, LinearAlgebra.BlasComplex}
 
 # In-place update of (the upper triangle of) A + α * x * x'
-function syrk!(A::StridedMatrix{T}, α::T, x::AbstractArray{<:T}) where {T<:BlasNumber}
+function syrk!(A::StridedMatrix{T}, α::T, x::AbstractArray{<:T}) where {T <: BlasNumber}
     BLAS.syrk!('U', 'N', α, x, one(T), A)
 end
 
-function syrk!(A::Hermitian{T, S}, α::T, x::AbstractArray{<:T}) where {T<:BlasNumber, S<:StridedMatrix{T}}
+function syrk!(A::Hermitian{T, S}, α::T, x::AbstractArray{<:T}) where {T <: BlasNumber, S <: StridedMatrix{T}}
     Hermitian(BLAS.syrk!('U', 'N', α, x, one(T), A.data))
 end
 
-function syrk!(A::Symmetric{T, S}, α::T, x::AbstractArray{<:T}) where {T<:BlasNumber, S<:StridedMatrix{T}}
+function syrk!(A::Symmetric{T, S}, α::T, x::AbstractArray{<:T}) where {T <: BlasNumber, S <: StridedMatrix{T}}
     Symmetric(BLAS.syrk!('U', 'N', α, x, one(T), A.data))
 end
 
 function syrk!(A, α, x)  # fallback
     p = checksquare(A)
     for i in 1:p, j in i:p
-        @inbounds A[i,j] += α * x[i] * x[j]
+        @inbounds A[i, j] += α * x[i] * x[j]
     end
 end
 
-
 end # module
diff --git a/test/benchmarks.jl b/test/benchmarks.jl
new file mode 100644
index 0000000..cd575bd
--- /dev/null
+++ b/test/benchmarks.jl
@@ -0,0 +1,83 @@
+using Test, LinearAlgebra, Random, BenchmarkTools, SweepOperator
+
+versioninfo()
+
+
+#-----------------------------------------------------------------------------# 1) Matrix Inverse
+# Code from https://github.com/joshday/SweepOperator.jl/issues/9
+
+
+"""
+    inv_by_chol!(A)
+
+Invert a pd matrix `A` in-place by Cholesky decomposition.
+"""
+function inv_by_chol!(A::Matrix{T}) where T <: LinearAlgebra.BlasReal
+    LAPACK.potrf!('U', A)
+    LAPACK.potri!('U', A)
+    A
+end
+
+"""
+    sweep_block_kernel!(A, krange, invsw)
+
+Perform the block form of sweep on a contiguous range of indices `krange`.
+
+[ Ak̲k̲ Ak̲k Ak̲k̅ ]          [ Ak̲k̲-Ak̲k*Akk⁻¹*Akk̲  Ak̲k*Akk⁻¹ Ak̲k̅-Ak̲k*Akk⁻¹*Akk̅ ]
+[  -  Akk Akk̅ ] -sweep-> [        -            -Akk⁻¹       Akk⁻¹*Akk̅     ]
+[  -   -  Ak̅k̅ ]          [        -              -      Ak̅k̅-Ak̅k*Akk⁻¹*Akk̅ ]
+"""
+function sweep_block_kernel!(
+        A      :: AbstractMatrix{T},
+        krange :: AbstractUnitRange{<:Integer},
+        invsw  :: Bool = false
+        ) where {T <: LinearAlgebra.BlasReal}
+    k̲range = 1:(krange[1] - 1)
+    k̅range = (krange[end]+1):size(A, 2)
+    Akk = view(A, krange, krange)
+    Ak̲k = view(A, k̲range, krange)
+    Ak̲k̲ = view(A, k̲range, k̲range)
+    Akk̅ = view(A, krange, k̅range)
+    Ak̅k̅ = view(A, k̅range, k̅range)
+    Ak̲k̅ = view(A, k̲range, k̅range)
+    # U = cholesky(Akk).U
+    U, _ = LAPACK.potrf!('U', Akk)
+    # Ak̲k = Ak̲k * U⁻¹
+    BLAS.trsm!('R', 'U', 'N', 'N', one(T), U, Ak̲k)
+    # Ak̲k̲ = Ak̲k̲ - Ak̲k * U⁻¹ * U⁻ᵀ * Akk̲
+    BLAS.syrk!('U', 'N', -one(T), Ak̲k, one(T), Ak̲k̲)
+    # Akk̅ = U⁻ᵀ * Akk̅
+    BLAS.trsm!('L', 'U', 'T', 'N', one(T), U, Akk̅)
+    # Ak̲k̅ = Ak̲k̅ - Ak̲k * U⁻¹ * U⁻ᵀ * Akk̅
+    BLAS.gemm!('N', 'N', -one(T), Ak̲k, Akk̅, one(T), Ak̲k̅)
+    # Ak̅k̅ = Ak̅k̅ - Ak̅k * U⁻¹ * U⁻ᵀ * Akk̅
+    BLAS.syrk!('U', 'T', -one(T), Akk̅, one(T), Ak̅k̅)
+    # Ak̲k = Ak̲k * Akk⁻¹ = Ak̲k * U⁻¹ * U⁻ᵀ
+    s = ifelse(invsw, -one(T), one(T))
+    BLAS.trsm!('R', 'U', 'T', 'N', s, Akk, Ak̲k)
+    # Akk̅ = Akk⁻¹ * Akk̅ = U⁻¹ * U⁻ᵀ * Akk̅
+    BLAS.trsm!('L', 'U', 'N', 'N', s, Akk, Akk̅)
+    # Akk = Akk⁻¹ = U⁻ᵀ U⁻¹
+    LAPACK.potri!('U', U)
+    UpperTriangular(Akk) .*= -1
+    A
+end
+
+# create an nxn pos-def test matrix
+function run_benchmark(n::Int, seed::Int = 123)
+    Random.seed!(seed)
+    A = randn(n, n)
+    A = A'A + I
+    Ainv = UpperTriangular(inv(A))
+    @test UpperTriangular(inv_by_chol!(copy(A)))        ≈ Ainv
+    @test -UpperTriangular(sweep!(copy(A), 1:n))        ≈ Ainv
+    @test -UpperTriangular(sweep_block!(copy(A), 1:n))  ≈ Ainv
+
+    out = Dict()
+
+    out["Cholesky"]     = @benchmark inv_by_chol!(copy(A))
+    out["Sweep"]        = @benchmark sweep!(copy(A), 1:n)
+    out["Block Sweep"]  = @benchmark sweep_block!(copy(A), 1:n)
+
+    return out
+end