Benchmarks

Here are some simple benchmarks. Take them with a grain of salt since they run on virtual machines in the cloud to generate the documentation automatically.

First-derivative operators

Periodic domains

Let's set up some benchmark code.

using BenchmarkTools
using LinearAlgebra, SparseArrays
using SummationByPartsOperators

BLAS.set_num_threads(1) # make sure that BLAS is serial to be fair

T = Float64
xmin, xmax = T(0), T(1)

D_SBP = periodic_derivative_operator(derivative_order=1, accuracy_order=2,
                                     xmin=xmin, xmax=xmax, N=100)
x = grid(D_SBP)

D_sparse = sparse(D_SBP)

u = randn(eltype(D_SBP), length(x)); du = similar(u);
@show D_SBP * u ≈ D_sparse * u

function doit(D, text, du, u)
  println(text)
  sleep(0.1)
  show(stdout, MIME"text/plain"(), @benchmark mul!($du, $D, $u))
  println()
end
doit (generic function with 1 method)

First, we benchmark the implementation from SummationByPartsOperators.jl.

doit(D_SBP, "D_SBP:", du, u)
D_SBP:
BenchmarkTools.Trial: 10000 samples with 995 evaluations per sample.
 Range (minmax):  27.478 ns52.723 ns   GC (min … max): 0.00% … 0.00%
 Time  (median):     28.354 ns               GC (median):    0.00%
 Time  (mean ± σ):   28.709 ns ±  1.673 ns   GC (mean ± σ):  0.00% ± 0.00%

   ▃▄▅█▂                                                   
  ▅█████▃▄▅▄▃▂▂▃▃▂▂▂▁▂▂▁▂▂▁▂▂▂▁▁▁▁▂▁▁▁▁▂▂▂▁▁▁▂▂▂▂▂▂▂▂▂▂▂▂▂ ▃
  27.5 ns         Histogram: frequency by time        37.3 ns <

 Memory estimate: 0 bytes, allocs estimate: 0.

Next, we compare this to the runtime obtained using a sparse matrix representation of the derivative operator. Depending on the hardware etc., this can be an order of magnitude slower than the optimized implementation from SummationByPartsOperators.jl.

doit(D_sparse, "D_sparse:", du, u)
D_sparse:
BenchmarkTools.Trial: 10000 samples with 482 evaluations per sample.
 Range (minmax):  223.033 ns386.494 ns   GC (min … max): 0.00% … 0.00%
 Time  (median):     228.060 ns                GC (median):    0.00%
 Time  (mean ± σ):   231.004 ns ±   9.021 ns   GC (mean ± σ):  0.00% ± 0.00%

     ▆█▅▂▂▂                                                     
  ▁▃███████▇▅▆▆▄▄▃▃▂▂▂▂▂▁▂▂▂▁▁▂▂▃▂▂▂▂▂▂▂▂▂▁▂▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁ ▂
  223 ns           Histogram: frequency by time          258 ns <

 Memory estimate: 0 bytes, allocs estimate: 0.

These results were obtained using the following versions.

using InteractiveUtils
versioninfo()

using Pkg
Pkg.status(["SummationByPartsOperators"],
           mode=PKGMODE_MANIFEST)
Julia Version 1.10.11
Commit a2b11907d7b (2026-03-09 14:59 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 4 × AMD EPYC 9V74 80-Core Processor
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, znver3)
Threads: 2 default, 0 interactive, 1 GC (on 4 virtual cores)
Environment:
  JULIA_PKG_SERVER_REGISTRY_PREFERENCE = eager
Status `~/work/SummationByPartsOperators.jl/SummationByPartsOperators.jl/docs/Manifest.toml`
  [9f78cca6] SummationByPartsOperators v0.5.96 `~/work/SummationByPartsOperators.jl/SummationByPartsOperators.jl`

Bounded domains

We start again by setting up some benchmark code.

using BenchmarkTools
using LinearAlgebra, SparseArrays
using SummationByPartsOperators, BandedMatrices

BLAS.set_num_threads(1) # make sure that BLAS is serial to be fair

T = Float64
xmin, xmax = T(0), T(1)

D_SBP = derivative_operator(MattssonNordström2004(), derivative_order=1,
                            accuracy_order=6, xmin=xmin, xmax=xmax, N=10^3)
D_sparse = sparse(D_SBP)
D_banded = BandedMatrix(D_SBP)

u = randn(eltype(D_SBP), size(D_SBP, 1)); du = similar(u);
@show D_SBP * u ≈ D_sparse * u ≈ D_banded * u

function doit(D, text, du, u)
  println(text)
  sleep(0.1)
  show(stdout, MIME"text/plain"(), @benchmark mul!($du, $D, $u))
  println()
end
doit (generic function with 1 method)

First, we benchmark the implementation from SummationByPartsOperators.jl.

doit(D_SBP, "D_SBP:", du, u)
D_SBP:
BenchmarkTools.Trial: 10000 samples with 199 evaluations per sample.
 Range (minmax):  424.809 ns 1.116 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     429.392 ns               GC (median):    0.00%
 Time  (mean ± σ):   433.730 ns ± 15.480 ns   GC (mean ± σ):  0.00% ± 0.00%

  ▂▅▇██▇▆▅▃▃▂ ▁  ▁▁                         ▂▂▃▃▂▂▂▁▁        ▃
  ███████████▆█████▇▆▄▄▅▄▃▃▁▁▁▁▁▁▄▃▃▃▁▁▁▁▄▆████████████▇▇▆▇▇ █
  425 ns        Histogram: log(frequency) by time       481 ns <

 Memory estimate: 0 bytes, allocs estimate: 0.

Again, we compare this to a representation of the derivative operator as a sparse matrix. No surprise - it is again much slower, as in periodic domains.

doit(D_sparse, "D_sparse:", du, u)
D_sparse:
BenchmarkTools.Trial: 10000 samples with 6 evaluations per sample.
 Range (minmax):  5.189 μs 10.968 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     5.395 μs                GC (median):    0.00%
 Time  (mean ± σ):   5.445 μs ± 282.155 ns   GC (mean ± σ):  0.00% ± 0.00%

       ▃▇                                                   
  ▂▂▂▃▆██▄▃▂▂▂▂▂▂▂▂▂▂▂▂▁▂▂▂▁▁▂▂▂▂▁▁▁▁▁▁▁▂▁▁▁▁▂▂▂▂▂▂▂▂▂▂▂▂▂ ▃
  5.19 μs         Histogram: frequency by time        6.85 μs <

 Memory estimate: 0 bytes, allocs estimate: 0.

Finally, we compare it to a representation as a banded matrix. Disappointingly, this is still much slower than the optimized implementation from SummationByPartsOperators.jl.

doit(D_banded, "D_banded:", du, u)
D_banded:
BenchmarkTools.Trial: 10000 samples with 1 evaluation per sample.
 Range (minmax):   9.995 μs 37.426 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     10.025 μs                GC (median):    0.00%
 Time  (mean ± σ):   10.133 μs ± 983.450 ns   GC (mean ± σ):  0.00% ± 0.00%

   ▅▄▁▃▃▄▄▁▁▁▁▁▃▁▁▄▄▃▄▄▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▃▁▁▁▁▁▃▁▁▃▁▁▁▁▁▁▁▃▄▅ █
  10 μs         Histogram: log(frequency) by time        18 μs <

 Memory estimate: 0 bytes, allocs estimate: 0.

These results were obtained using the following versions.

using InteractiveUtils
versioninfo()

using Pkg
Pkg.status(["SummationByPartsOperators", "BandedMatrices"],
           mode=PKGMODE_MANIFEST)
Julia Version 1.10.11
Commit a2b11907d7b (2026-03-09 14:59 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 4 × AMD EPYC 9V74 80-Core Processor
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, znver3)
Threads: 2 default, 0 interactive, 1 GC (on 4 virtual cores)
Environment:
  JULIA_PKG_SERVER_REGISTRY_PREFERENCE = eager
Status `~/work/SummationByPartsOperators.jl/SummationByPartsOperators.jl/docs/Manifest.toml`
  [aae01518] BandedMatrices v1.11.0
  [9f78cca6] SummationByPartsOperators v0.5.96 `~/work/SummationByPartsOperators.jl/SummationByPartsOperators.jl`

Dissipation operators

We follow the same structure as before. At first, we set up some benchmark code.

using BenchmarkTools
using LinearAlgebra, SparseArrays
using SummationByPartsOperators, BandedMatrices

BLAS.set_num_threads(1) # make sure that BLAS is serial to be fair

T = Float64
xmin, xmax = T(0), T(1)

D_SBP = derivative_operator(MattssonNordström2004(), derivative_order=1,
                            accuracy_order=6, xmin=xmin, xmax=xmax, N=10^3)
Di_SBP  = dissipation_operator(MattssonSvärdNordström2004(), D_SBP)
Di_sparse = sparse(Di_SBP)
Di_banded = BandedMatrix(Di_SBP)
Di_full   = Matrix(Di_SBP)

u = randn(eltype(D_SBP), size(D_SBP, 1)); du = similar(u);
@show Di_SBP * u ≈ Di_sparse * u ≈ Di_banded * u ≈ Di_full * u

function doit(D, text, du, u)
  println(text)
  sleep(0.1)
  show(stdout, MIME"text/plain"(), @benchmark mul!($du, $D, $u))
  println()
end
doit (generic function with 1 method)

At first, let us benchmark the derivative and dissipation operators implemented in SummationByPartsOperators.jl.

doit(D_SBP, "D_SBP:", du, u)
doit(Di_SBP, "Di_SBP:", du, u)
D_SBP:
BenchmarkTools.Trial: 10000 samples with 199 evaluations per sample.
 Range (minmax):  421.588 ns678.658 ns   GC (min … max): 0.00% … 0.00%
 Time  (median):     426.523 ns                GC (median):    0.00%
 Time  (mean ± σ):   430.492 ns ±  13.823 ns   GC (mean ± σ):  0.00% ± 0.00%

   ▃▇█▅▆▂                                                      
  ▄██████▆▅▃▃▂▂▂▂▂▂▂▂▂▂▂▂▂▂▁▂▁▂▁▂▁▁▁▂▁▁▁▂▂▂▂▃▃▃▃▃▃▃▂▂▂▂▂▂▂▂▂▂ ▃
  422 ns           Histogram: frequency by time          479 ns <

 Memory estimate: 0 bytes, allocs estimate: 0.
Di_SBP:
BenchmarkTools.Trial: 10000 samples with 17 evaluations per sample.
 Range (minmax):  975.588 ns 2.017 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     985.000 ns               GC (median):    0.00%
 Time  (mean ± σ):   994.447 ns ± 67.611 ns   GC (mean ± σ):  0.00% ± 0.00%

  ▇                                                          ▁
  █▆▅▅▅▃▄▅▃▃▃▁▁▃▃▅▄▁▃▄▄▃▃▄▃▁▄▁▁▁▃▃▁▁▁▁▃▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▃▁▄▇▇▇ █
  976 ns        Histogram: log(frequency) by time      1.45 μs <

 Memory estimate: 0 bytes, allocs estimate: 0.

Next, we compare the results to sparse matrix representations. It will not come as a surprise that these are again much (around an order of magnitude) slower.

doit(Di_sparse, "Di_sparse:", du, u)
doit(Di_banded, "Di_banded:", du, u)
Di_sparse:
BenchmarkTools.Trial: 10000 samples with 5 evaluations per sample.
 Range (minmax):  6.313 μs 13.438 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     6.456 μs                GC (median):    0.00%
 Time  (mean ± σ):   6.515 μs ± 331.596 ns   GC (mean ± σ):  0.00% ± 0.00%

   ▃▆█▃                                                    ▂
  ▇████▇▆▅▄▃▃▁▃▄▄▅▆▄▅▅▄▃▁▃▁▁▃▃▁▃▃▃▃▃▁▃▁▄▄▁▁▃▁▃▁▁▅▇█████▇▇▇ █
  6.31 μs      Histogram: log(frequency) by time      8.21 μs <

 Memory estimate: 0 bytes, allocs estimate: 0.
Di_banded:
BenchmarkTools.Trial: 10000 samples with 4 evaluations per sample.
 Range (minmax):  7.296 μs 14.812 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     7.373 μs                GC (median):    0.00%
 Time  (mean ± σ):   7.453 μs ± 415.913 ns   GC (mean ± σ):  0.00% ± 0.00%

  ▄█▃                                                      ▂
  ████▅▅▁▃▃▄▄▃▄▅▄▅▄▁▅▁▄▄▁▃▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▃▁▁▁▁▅▇███▇▇▇ █
  7.3 μs       Histogram: log(frequency) by time       9.6 μs <

 Memory estimate: 0 bytes, allocs estimate: 0.

Finally, let's benchmark the same computation if a full (dense) matrix is used to represent the derivative operator. This is obviously a bad idea but 🤷

doit(Di_full, "Di_full:", du, u)
Di_full:
BenchmarkTools.Trial: 10000 samples with 1 evaluation per sample.
 Range (minmax):  128.253 μs428.004 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     132.719 μs                GC (median):    0.00%
 Time  (mean ± σ):   136.124 μs ±  10.805 μs   GC (mean ± σ):  0.00% ± 0.00%

     ▁▇█▅▃▃▃      ▃▄▄▃▂▁                                      ▂
  ▆▇▆████████▇▆▇▅▇████████████▇▇▇▇▆▅▆▆▆▆▆▆▆▅▆▄▅▄▅▅▄▅▄▅▅▅▅▂▄▄▄ █
  128 μs        Histogram: log(frequency) by time        173 μs <

 Memory estimate: 0 bytes, allocs estimate: 0.

These results were obtained using the following versions.

using InteractiveUtils
versioninfo()

using Pkg
Pkg.status(["SummationByPartsOperators", "BandedMatrices"],
           mode=PKGMODE_MANIFEST)
Julia Version 1.10.11
Commit a2b11907d7b (2026-03-09 14:59 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 4 × AMD EPYC 9V74 80-Core Processor
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, znver3)
Threads: 2 default, 0 interactive, 1 GC (on 4 virtual cores)
Environment:
  JULIA_PKG_SERVER_REGISTRY_PREFERENCE = eager
Status `~/work/SummationByPartsOperators.jl/SummationByPartsOperators.jl/docs/Manifest.toml`
  [aae01518] BandedMatrices v1.11.0
  [9f78cca6] SummationByPartsOperators v0.5.96 `~/work/SummationByPartsOperators.jl/SummationByPartsOperators.jl`

Structure-of-Arrays (SoA) and Array-of-Structures (AoS)

SummationByPartsOperators.jl tries to provide efficient support of

To demonstrate this, let us set up some benchmark code.

using BenchmarkTools
using StaticArrays, StructArrays
using LinearAlgebra, SparseArrays
using SummationByPartsOperators

BLAS.set_num_threads(1) # make sure that BLAS is serial to be fair

struct Vec5{T} <: FieldVector{5,T}
  x1::T
  x2::T
  x3::T
  x4::T
  x5::T
end

# Apply `mul!` to each component of a plain array of structures one after another
function mul_aos!(du, D, u, args...)
  for i in 1:size(du, 1)
    mul!(view(du, i, :), D, view(u, i, :), args...)
  end
end

T = Float64
xmin, xmax = T(0), T(1)

D_SBP = derivative_operator(MattssonNordström2004(), derivative_order=1,
                            accuracy_order=4, xmin=xmin, xmax=xmax, N=101)
D_sparse = sparse(D_SBP)
D_full   = Matrix(D_SBP)
101×101 Matrix{Float64}:
 -141.176    173.529   -23.5294   …    0.0         0.0       0.0
  -50.0        0.0      50.0           0.0         0.0       0.0
    9.30233  -68.6047    0.0           0.0         0.0       0.0
    3.06122    0.0     -60.2041        0.0         0.0       0.0
    0.0        0.0       8.33333       0.0         0.0       0.0
    0.0        0.0       0.0      …    0.0         0.0       0.0
    0.0        0.0       0.0           0.0         0.0       0.0
    0.0        0.0       0.0           0.0         0.0       0.0
    0.0        0.0       0.0           0.0         0.0       0.0
    0.0        0.0       0.0           0.0         0.0       0.0
    ⋮                             ⋱                          ⋮
    0.0        0.0       0.0           0.0         0.0       0.0
    0.0        0.0       0.0           0.0         0.0       0.0
    0.0        0.0       0.0           0.0         0.0       0.0
    0.0        0.0       0.0      …    0.0         0.0       0.0
    0.0        0.0       0.0          -8.33333     0.0       0.0
    0.0        0.0       0.0          60.2041      0.0      -3.06122
    0.0        0.0       0.0           0.0        68.6047   -9.30233
    0.0        0.0       0.0         -50.0         0.0      50.0
    0.0        0.0       0.0      …   23.5294   -173.529   141.176

At first, we benchmark the application of the operators implemented in SummationByPartsOperators.jl and their representations as sparse and dense matrices in the scalar case. As before, the sparse matrix representation is around an order of magnitude slower and the dense matrix representation is far off.

println("Scalar case")
u = randn(T, size(D_SBP, 1)); du = similar(u)
println("D_SBP")
show(stdout, MIME"text/plain"(), @benchmark mul!($du, $D_SBP, $u))
println("\nD_sparse")
show(stdout, MIME"text/plain"(), @benchmark mul!($du, $D_sparse, $u))
println("\nD_full")
show(stdout, MIME"text/plain"(), @benchmark mul!($du, $D_full, $u))
Scalar case
D_SBP
BenchmarkTools.Trial: 10000 samples with 987 evaluations per sample.
 Range (minmax):  49.832 ns92.733 ns   GC (min … max): 0.00% … 0.00%
 Time  (median):     51.922 ns               GC (median):    0.00%
 Time  (mean ± σ):   52.588 ns ±  2.709 ns   GC (mean ± σ):  0.00% ± 0.00%

   ▂▄▄▆█▇▆▅▅▄▄                                              
  ▂███████████▇▇▅▅▅▅▆▅▄▄▃▃▃▂▃▃▂▂▂▁▂▂▂▂▂▃▃▂▃▃▃▃▃▃▃▂▂▂▂▂▂▂▂▂▂ ▄
  49.8 ns         Histogram: frequency by time        62.7 ns <

 Memory estimate: 0 bytes, allocs estimate: 0.
D_sparse
BenchmarkTools.Trial: 10000 samples with 204 evaluations per sample.
 Range (minmax):  389.358 ns 1.043 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     428.044 ns               GC (median):    0.00%
 Time  (mean ± σ):   432.504 ns ± 22.702 ns   GC (mean ± σ):  0.00% ± 0.00%

                    ▃▄▆██▇▅▁                                 
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  389 ns          Histogram: frequency by time          488 ns <

 Memory estimate: 0 bytes, allocs estimate: 0.
D_full
BenchmarkTools.Trial: 10000 samples with 10 evaluations per sample.
 Range (minmax):  1.222 μs 10.087 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     1.236 μs                GC (median):    0.00%
 Time  (mean ± σ):   1.253 μs ± 162.241 ns   GC (mean ± σ):  0.00% ± 0.00%

  █                                                         ▂
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  1.22 μs      Histogram: log(frequency) by time      2.05 μs <

 Memory estimate: 0 bytes, allocs estimate: 0.

Next, we use a plain array of structures (AoS) in the form of a two-dimensional array and our custom mul_aos! implementation that loops over each component, using mul! on views. Here, the differences between the timings are less pronounced.

println("Plain Array of Structures")
u_aos_plain = randn(T, 5, size(D_SBP, 1)); du_aos_plain = similar(u_aos_plain)
println("D_SBP")
show(stdout, MIME"text/plain"(), @benchmark mul_aos!($du_aos_plain, $D_SBP, $u_aos_plain))
println("\nD_sparse")
show(stdout, MIME"text/plain"(), @benchmark mul_aos!($du_aos_plain, $D_sparse, $u_aos_plain))
println("\nD_full")
show(stdout, MIME"text/plain"(), @benchmark mul_aos!($du_aos_plain, $D_full, $u_aos_plain))
Plain Array of Structures
D_SBP
BenchmarkTools.Trial: 10000 samples with 10 evaluations per sample.
 Range (minmax):  1.305 μs  4.137 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     1.315 μs                GC (median):    0.00%
 Time  (mean ± σ):   1.329 μs ± 108.091 ns   GC (mean ± σ):  0.00% ± 0.00%

  █  ▂▂▂▁▁▂▂▂▂▁▁▂▁▂▂▂▁▂▂▂▁▂▂▂▂▂▂▂▂▂▂▂▁▂▂▁▂▂▁▁▁▁▂▁▂▁▂▁▁▁▁▁▁▂▂▂ ▂
  1.3 μs          Histogram: frequency by time         2.1 μs <

 Memory estimate: 0 bytes, allocs estimate: 0.
D_sparse
BenchmarkTools.Trial: 10000 samples with 9 evaluations per sample.
 Range (minmax):  2.822 μs  5.831 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     2.903 μs                GC (median):    0.00%
 Time  (mean ± σ):   2.934 μs ± 167.216 ns   GC (mean ± σ):  0.00% ± 0.00%

  ▁▄▆██▅▄▃▁                                                 ▂
  █████████▆▄▅▄▄▄▁▄▅▄▄▅▅▅▄▃▃▅▃▁▁▃▃▁▃▁▃▁▃▃▃▃▁▁▁▃▁▁▁▄▄▆██████ █
  2.82 μs      Histogram: log(frequency) by time      3.85 μs <

 Memory estimate: 240 bytes, allocs estimate: 5.
D_full
BenchmarkTools.Trial: 10000 samples with 4 evaluations per sample.
 Range (minmax):  6.905 μs 14.011 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     6.953 μs                GC (median):    0.00%
 Time  (mean ± σ):   7.026 μs ± 403.387 ns   GC (mean ± σ):  0.00% ± 0.00%

  ▇                                                         ▁
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  6.91 μs      Histogram: log(frequency) by time      9.16 μs <

 Memory estimate: 0 bytes, allocs estimate: 0.

Now, we use an array of structures (AoS) based on reinterpret and standard mul!. This is much more efficient for the implementation in SummationByPartsOperators.jl. In Julia v1.6, this is also more efficient for sparse matrices but less efficient for dense matrices (compared to the plain AoS approach with mul_aos! above).

println("Array of Structures (reinterpreted array)")
u_aos_r = reinterpret(reshape, Vec5{T}, u_aos_plain); du_aos_r = similar(u_aos_r)
@show D_SBP * u_aos_r ≈ D_sparse * u_aos_r ≈ D_full * u_aos_r
mul!(du_aos_r, D_SBP, u_aos_r)
@show reinterpret(reshape, T, du_aos_r) ≈ du_aos_plain
println("D_SBP")
show(stdout, MIME"text/plain"(), @benchmark mul!($du_aos_r, $D_SBP, $u_aos_r))
println("\nD_sparse")
show(stdout, MIME"text/plain"(), @benchmark mul!($du_aos_r, $D_sparse, $u_aos_r))
println("\nD_full")
show(stdout, MIME"text/plain"(), @benchmark mul!($du_aos_r, $D_full, $u_aos_r))
Array of Structures (reinterpreted array)
D_SBP * u_aos_r ≈ D_sparse * u_aos_r ≈ D_full * u_aos_r = true
reinterpret(reshape, T, du_aos_r) ≈ du_aos_plain = true
D_SBP
BenchmarkTools.Trial: 10000 samples with 409 evaluations per sample.
 Range (minmax):  232.868 ns362.037 ns   GC (min … max): 0.00% … 0.00%
 Time  (median):     234.411 ns                GC (median):    0.00%
 Time  (mean ± σ):   236.634 ns ±   6.800 ns   GC (mean ± σ):  0.00% ± 0.00%

   ▁▇█▄▂                                      ▂▃▃▂▁▁           ▂
  ▃██████▇▄▄▄▅▆▇▇▇▆▆▄▄▃▃▃▁▁▁▁▁▁▃▁▁▄▁▁▁▃▁▁▃▃▅██████████▇▇▇▇▇▆▆ █
  233 ns        Histogram: log(frequency) by time        259 ns <

 Memory estimate: 0 bytes, allocs estimate: 0.
D_sparse
BenchmarkTools.Trial: 10000 samples with 179 evaluations per sample.
 Range (minmax):  588.318 ns 16.667 μs   GC (min … max): 0.00% … 93.82%
 Time  (median):     652.209 ns                GC (median):    0.00%
 Time  (mean ± σ):   662.461 ns ± 169.358 ns   GC (mean ± σ):  0.24% ±  0.94%

            ▁▁▄▆█                                            
  ▁▂▃▂▂▂▃▅▇███████▇▆▅▄▄▅▄▃▃▂▂▂▂▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁ ▃
  588 ns           Histogram: frequency by time          849 ns <

 Memory estimate: 32 bytes, allocs estimate: 1.
D_full
BenchmarkTools.Trial: 10000 samples with 1 evaluation per sample.
 Range (minmax):  13.300 μs31.858 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     13.370 μs               GC (median):    0.00%
 Time  (mean ± σ):   13.511 μs ±  1.059 μs   GC (mean ± σ):  0.00% ± 0.00%

  █                                                          ▁
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  13.3 μs      Histogram: log(frequency) by time      21.2 μs <

 Memory estimate: 0 bytes, allocs estimate: 0.

Next, we still use an array of structures (AoS), but copy the data into a plain Array instead of using the reinterpreted versions. There is no significant difference to the previous version in this case.

println("Array of Structures")
u_aos = Array(u_aos_r); du_aos = similar(u_aos)
@show D_SBP * u_aos ≈ D_sparse * u_aos ≈ D_full * u_aos
mul!(du_aos, D_SBP, u_aos)
@show du_aos ≈ du_aos_r
println("D_SBP")
show(stdout, MIME"text/plain"(), @benchmark mul!($du_aos, $D_SBP, $u_aos))
println("\nD_sparse")
show(stdout, MIME"text/plain"(), @benchmark mul!($du_aos, $D_sparse, $u_aos))
println("\nD_full")
show(stdout, MIME"text/plain"(), @benchmark mul!($du_aos, $D_full, $u_aos))
Array of Structures
D_SBP * u_aos ≈ D_sparse * u_aos ≈ D_full * u_aos = true
du_aos ≈ du_aos_r = true
D_SBP
BenchmarkTools.Trial: 10000 samples with 413 evaluations per sample.
 Range (minmax):  232.869 ns334.329 ns   GC (min … max): 0.00% … 0.00%
 Time  (median):     238.421 ns                GC (median):    0.00%
 Time  (mean ± σ):   241.363 ns ±   7.675 ns   GC (mean ± σ):  0.00% ± 0.00%

       ▄▇█▄▃                                                   
  ▁▁▁▂▇██████▇▆▅▄▃▃▃▃▂▂▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▂▂▂▂▂▂▂▂▂▂▁▂▂▁▁▁▁▁▁▁▁▁▁ ▂
  233 ns           Histogram: frequency by time          267 ns <

 Memory estimate: 0 bytes, allocs estimate: 0.
D_sparse
BenchmarkTools.Trial: 10000 samples with 171 evaluations per sample.
 Range (minmax):  617.655 ns 1.314 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     690.222 ns               GC (median):    0.00%
 Time  (mean ± σ):   693.249 ns ± 30.397 ns   GC (mean ± σ):  0.00% ± 0.00%

                      ▁▂▂▄▄▇▇▇▃▃▃▁ ▁▁                        
  ▁▁▂▂▂▃▂▂▂▂▃▃▃▄▄▆▆▇█▇███████████████▇▅▅▆▅▄▄▄▄▃▄▄▃▃▃▃▃▂▂▂▂▂▁ ▄
  618 ns          Histogram: frequency by time          772 ns <

 Memory estimate: 0 bytes, allocs estimate: 0.
D_full
BenchmarkTools.Trial: 10000 samples with 1 evaluation per sample.
 Range (minmax):  13.320 μs38.347 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     13.390 μs               GC (median):    0.00%
 Time  (mean ± σ):   13.524 μs ±  1.072 μs   GC (mean ± σ):  0.00% ± 0.00%

  █                                                           ▁
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  13.3 μs      Histogram: log(frequency) by time      21.2 μs <

 Memory estimate: 0 bytes, allocs estimate: 0.

Finally, let's look at a structure of arrays (SoA). Interestingly, this is slower than the array of structures we used above. On Julia v1.6, the sparse matrix representation performs particularly bad in this case.

println("Structure of Arrays")
u_soa = StructArray(u_aos); du_soa = similar(u_soa)
@show D_SBP * u_soa ≈ D_sparse * u_soa ≈ D_full * u_soa
mul!(du_soa, D_SBP, u_soa)
@show du_soa ≈ du_aos
println("D_SBP")
show(stdout, MIME"text/plain"(), @benchmark mul!($du_soa, $D_SBP, $u_soa))
println("\nD_sparse")
show(stdout, MIME"text/plain"(), @benchmark mul!($du_soa, $D_sparse, $u_soa))
println("\nD_full")
show(stdout, MIME"text/plain"(), @benchmark mul!($du_soa, $D_full, $u_soa))
Structure of Arrays
D_SBP * u_soa ≈ D_sparse * u_soa ≈ D_full * u_soa = true
du_soa ≈ du_aos = true
D_SBP
BenchmarkTools.Trial: 10000 samples with 376 evaluations per sample.
 Range (minmax):  248.085 ns391.439 ns   GC (min … max): 0.00% … 0.00%
 Time  (median):     253.149 ns                GC (median):    0.00%
 Time  (mean ± σ):   255.352 ns ±   7.835 ns   GC (mean ± σ):  0.00% ± 0.00%

      ▁▅▇▅▆▅▂▁                                                 
  ▃▄▅▆████████▅▄▃▂▃▂▂▂▂▂▂▂▂▂▂▂▂▁▁▁▁▂▁▁▂▂▂▂▃▂▃▃▃▃▃▃▃▃▂▂▂▂▂▂▂▂▂ ▃
  248 ns           Histogram: frequency by time          282 ns <

 Memory estimate: 0 bytes, allocs estimate: 0.
D_sparse
BenchmarkTools.Trial: 10000 samples with 1 evaluation per sample.
 Range (minmax):  51.087 μs110.767 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     51.377 μs                GC (median):    0.00%
 Time  (mean ± σ):   51.911 μs ±   2.241 μs   GC (mean ± σ):  0.00% ± 0.00%

  ▅█▅▂                                            ▁▁▁         ▂
  ████▆▆▆▅▆▄▅▄▅▇▆▆▅▅▁▄▄▃▁▃▃▁▁▁▁▃▁▃▁▁▁▁▁▁▁▁▁▁▁▁▁▆▇██████▇▇▇▆▆ █
  51.1 μs       Histogram: log(frequency) by time      60.9 μs <

 Memory estimate: 0 bytes, allocs estimate: 0.
D_full
BenchmarkTools.Trial: 10000 samples with 6 evaluations per sample.
 Range (minmax):  5.627 μs 10.628 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     5.654 μs                GC (median):    0.00%
 Time  (mean ± σ):   5.711 μs ± 285.667 ns   GC (mean ± σ):  0.00% ± 0.00%

  ▇                                                   ▁     ▂
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  5.63 μs      Histogram: log(frequency) by time      7.08 μs <

 Memory estimate: 0 bytes, allocs estimate: 0.

These results were obtained using the following versions.

using InteractiveUtils
versioninfo()

using Pkg
Pkg.status(["SummationByPartsOperators", "StaticArrays", "StructArrays"],
           mode=PKGMODE_MANIFEST)
Julia Version 1.10.11
Commit a2b11907d7b (2026-03-09 14:59 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 4 × AMD EPYC 9V74 80-Core Processor
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, znver3)
Threads: 2 default, 0 interactive, 1 GC (on 4 virtual cores)
Environment:
  JULIA_PKG_SERVER_REGISTRY_PREFERENCE = eager
Status `~/work/SummationByPartsOperators.jl/SummationByPartsOperators.jl/docs/Manifest.toml`
  [90137ffa] StaticArrays v1.9.18
  [09ab397b] StructArrays v0.7.3
  [9f78cca6] SummationByPartsOperators v0.5.96 `~/work/SummationByPartsOperators.jl/SummationByPartsOperators.jl`