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 BenchmarkToolsusing LinearAlgebra, SparseArraysusing SummationByPartsOperatorsBLAS.set_num_threads(1) # make sure that BLAS is serial to be fairT = Float64xmin, 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 * ufunction 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 997 evaluations per sample.
 Range (minmax):  18.008 ns72.853 ns   GC (min … max): 0.00% … 0.00%
 Time  (median):     18.176 ns               GC (median):    0.00%
 Time  (mean ± σ):   18.447 ns ±  1.548 ns   GC (mean ± σ):  0.00% ± 0.00%

  ▇                                                         ▁
  █▅▄▆▄▃▅▄▅▆▆▆▅▅▄▃▆▅▅▄▄▅▇▄▅▃▄▄▄▅▅▆▁▁▁▃▄▁▁▃▁▄▁▃▁▁█▇▁▁▁▃▅▇▇▇ █
  18 ns        Histogram: log(frequency) by time      26.9 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 800 evaluations per sample.
 Range (minmax):  157.064 ns300.830 ns   GC (min … max): 0.00% … 0.00%
 Time  (median):     162.683 ns                GC (median):    0.00%
 Time  (mean ± σ):   164.046 ns ±   3.820 ns   GC (mean ± σ):  0.00% ± 0.00%

               ▁   ▁▆█▂▁ ▁▁▁▂▄▃▁ ▂▂▁▁▁▁▃▂▁                    ▁
  ▆▅▄▅▇▆▇▇▇▆▇▇███████████████████████████████▇▇█▇▇▇▆▆▅▆▅▅▅▅▅▅ █
  157 ns        Histogram: log(frequency) by time        175 ns <

 Memory estimate: 0 bytes, allocs estimate: 0.

These results were obtained using the following versions.

using InteractiveUtilsversioninfo()using PkgPkg.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 × Intel(R) Xeon(R) 6973P-C
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, icelake-client)
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 v0.5.97-DEV `~/work/SummationByPartsOperators.jl/SummationByPartsOperators.jl`

Bounded domains

We start again by setting up some benchmark code.

using BenchmarkToolsusing LinearAlgebra, SparseArraysusing SummationByPartsOperators, BandedMatricesBLAS.set_num_threads(1) # make sure that BLAS is serial to be fairT = Float64xmin, 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 * ufunction 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 287 evaluations per sample.
 Range (minmax):  282.373 ns408.237 ns   GC (min … max): 0.00% … 0.00%
 Time  (median):     283.955 ns                GC (median):    0.00%
 Time  (mean ± σ):   287.713 ns ±  10.808 ns   GC (mean ± σ):  0.00% ± 0.00%

  ▂█                                ▁    ▂▂▁▁▁▁                ▁
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  282 ns        Histogram: log(frequency) by time        329 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 8 evaluations per sample.
 Range (minmax):  3.141 μs  6.322 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     3.193 μs                GC (median):    0.00%
 Time  (mean ± σ):   3.227 μs ± 166.245 ns   GC (mean ± σ):  0.00% ± 0.00%

   ▄▇█▃▂▂                                     ▁            ▂
  ▇███████▇▄▅▁▁▆▆▆▄▄▃▃▁▁▁▄▁▃▁▃▃▃▄▁▁▄▄▃▃▄▃▁▃▅▇████▇█▇▇▆▆▆▆▆ █
  3.14 μs      Histogram: log(frequency) by time      3.94 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 4 evaluations per sample.
 Range (minmax):  7.058 μs 11.945 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     7.126 μs                GC (median):    0.00%
 Time  (mean ± σ):   7.174 μs ± 279.070 ns   GC (mean ± σ):  0.00% ± 0.00%

  █▂█▃▂▄ ▄▁                                                 ▂
  █████████▄▄▄▅▄▄▄▄▄▅▄▅▃▅▃▄▃▃▁▁▁▁▁▃▃▁▃▁▁▁▁▃▄▄▁▅▅▅▆▇▆▇█▇█▇▇▇ █
  7.06 μs      Histogram: log(frequency) by time      8.63 μs <

 Memory estimate: 0 bytes, allocs estimate: 0.

These results were obtained using the following versions.

using InteractiveUtilsversioninfo()using PkgPkg.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 × Intel(R) Xeon(R) 6973P-C
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, icelake-client)
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 v0.5.97-DEV `~/work/SummationByPartsOperators.jl/SummationByPartsOperators.jl`

Dissipation operators

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

using BenchmarkToolsusing LinearAlgebra, SparseArraysusing SummationByPartsOperators, BandedMatricesBLAS.set_num_threads(1) # make sure that BLAS is serial to be fairT = Float64xmin, 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 * ufunction 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 262 evaluations per sample.
 Range (minmax):  296.756 ns657.302 ns   GC (min … max): 0.00% … 0.00%
 Time  (median):     298.214 ns                GC (median):    0.00%
 Time  (mean ± σ):   301.963 ns ±  11.800 ns   GC (mean ± σ):  0.00% ± 0.00%

  ▁█                                       ▂▂▁▁            ▁
  ███▅▄▄▅▅▆▇▇▆▅▄▃▄▅▅▆▄▄▄▄▄▅▆▇▇▆▅▅▄▄▅▆▅▄▄█▇▆▅▅███████▇▇▆▅▄▅▃▃▃ █
  297 ns        Histogram: log(frequency) by time        340 ns <

 Memory estimate: 0 bytes, allocs estimate: 0.
Di_SBP:
BenchmarkTools.Trial: 10000 samples with 129 evaluations per sample.
 Range (minmax):  733.450 ns 1.659 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     756.818 ns               GC (median):    0.00%
 Time  (mean ± σ):   768.888 ns ± 46.227 ns   GC (mean ± σ):  0.00% ± 0.00%

  █▆▅▆▆▅▅█▃▁  ▁ ▃▃▃▃▂▂▂▂▁▁                                   ▂
  █████████████████████████▇▆▇▇▇▇▇▇▇▅▆▅▅▅▅▅▅▃▅▄▁▄▅▅▅▄▆▅▇▇▇▇▆ █
  733 ns        Histogram: log(frequency) by time       995 ns <

 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 8 evaluations per sample.
 Range (minmax):  3.636 μs  5.569 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     3.712 μs                GC (median):    0.00%
 Time  (mean ± σ):   3.745 μs ± 155.958 ns   GC (mean ± σ):  0.00% ± 0.00%

   ▃▆▇█▇▆▄▃▂▁                                               ▃
  ▇██████████▇▆▃▅▁▅▅▆▅▅▅▆▃▅▅▅▃▁▄▁▃▁▄▃▄▅▆▆█▇▇▇▆▆▇▇███████▇▇▇ █
  3.64 μs      Histogram: log(frequency) by time      4.47 μs <

 Memory estimate: 0 bytes, allocs estimate: 0.
Di_banded:
BenchmarkTools.Trial: 10000 samples with 6 evaluations per sample.
 Range (minmax):  5.147 μs  7.361 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     5.192 μs                GC (median):    0.00%
 Time  (mean ± σ):   5.235 μs ± 218.510 ns   GC (mean ± σ):  0.00% ± 0.00%

  █▃▃▄▂▁ ▂ ▁ ▂                            ▁ ▁               ▂
  ████████▇█▇█▇▁▃▃▄▃▁▄▃▄▅▃▅▅▃▃▄▃▄▃▁▃▃▁▁▁▁▆█▆█▅▆▆▅▆▇▇▆▇▇██▇█ █
  5.15 μs      Histogram: log(frequency) by time      6.24 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):  260.518 μs367.391 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     267.664 μs                GC (median):    0.00%
 Time  (mean ± σ):   271.064 μs ±   6.384 μs   GC (mean ± σ):  0.00% ± 0.00%

         ▁▂▂▂▂▂▆██▄▁        ▁▁        ▃▅▅▅▄▄▃▃▂▂▁▁             ▂
  ▃▁▅▅▅▄▆███████████▆▅▄▃▅█▇████▇▆▇▆▆███████████████▇▆▆▇▇▇▇▇▇▆ █
  261 μs        Histogram: log(frequency) by time        288 μs <

 Memory estimate: 0 bytes, allocs estimate: 0.

These results were obtained using the following versions.

using InteractiveUtilsversioninfo()using PkgPkg.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 × Intel(R) Xeon(R) 6973P-C
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, icelake-client)
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 v0.5.97-DEV `~/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 BenchmarkToolsusing StaticArrays, StructArraysusing LinearAlgebra, SparseArraysusing SummationByPartsOperatorsBLAS.set_num_threads(1) # make sure that BLAS is serial to be fairstruct Vec5{T} <: FieldVector{5,T}  x1::T  x2::T  x3::T  x4::T  x5::Tend# Apply `mul!` to each component of a plain array of structures one after anotherfunction mul_aos!(du, D, u, args...)  for i in 1:size(du, 1)    mul!(view(du, i, :), D, view(u, i, :), args...)  endendT = Float64xmin, 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 994 evaluations per sample.
 Range (minmax):  31.694 ns93.209 ns   GC (min … max): 0.00% … 0.00%
 Time  (median):     33.089 ns               GC (median):    0.00%
 Time  (mean ± σ):   33.413 ns ±  1.971 ns   GC (mean ± σ):  0.00% ± 0.00%

  ▂  ▃▃  █                                                   ▁
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  31.7 ns      Histogram: log(frequency) by time      42.4 ns <

 Memory estimate: 0 bytes, allocs estimate: 0.
D_sparse
BenchmarkTools.Trial: 10000 samples with 401 evaluations per sample.
 Range (minmax):  241.411 ns313.015 ns   GC (min … max): 0.00% … 0.00%
 Time  (median):     243.439 ns                GC (median):    0.00%
 Time  (mean ± σ):   244.694 ns ±   4.666 ns   GC (mean ± σ):  0.00% ± 0.00%

  ▃▆▅▄▃▅█▄▁                                 ▂▃▂▂▁▁▁▁           ▂
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  241 ns        Histogram: log(frequency) by time        260 ns <

 Memory estimate: 0 bytes, allocs estimate: 0.
D_full
BenchmarkTools.Trial: 10000 samples with 10 evaluations per sample.
 Range (minmax):  1.104 μs 5.497 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     1.114 μs               GC (median):    0.00%
 Time  (mean ± σ):   1.125 μs ± 96.926 ns   GC (mean ± σ):  0.00% ± 0.00%

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  1.1 μs         Histogram: frequency by time        1.82 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 194 evaluations per sample.
 Range (minmax):  493.108 ns891.361 ns   GC (min … max): 0.00% … 0.00%
 Time  (median):     498.613 ns                GC (median):    0.00%
 Time  (mean ± σ):   504.074 ns ±  16.368 ns   GC (mean ± σ):  0.00% ± 0.00%

   ▂▅▇██▆▅▅▄▃▂                                 ▂▂▂▃▂▃▂▂▂▁     ▃
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  493 ns        Histogram: log(frequency) by time        554 ns <

 Memory estimate: 0 bytes, allocs estimate: 0.
D_sparse
BenchmarkTools.Trial: 10000 samples with 10 evaluations per sample.
 Range (minmax):  1.603 μs 6.062 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     1.626 μs               GC (median):    0.00%
 Time  (mean ± σ):   1.648 μs ± 96.836 ns   GC (mean ± σ):  0.00% ± 0.00%

   █                                                        
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  1.6 μs         Histogram: frequency by time        2.16 μs <

 Memory estimate: 240 bytes, allocs estimate: 5.
D_full
BenchmarkTools.Trial: 10000 samples with 5 evaluations per sample.
 Range (minmax):  6.355 μs 10.674 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     6.410 μs                GC (median):    0.00%
 Time  (mean ± σ):   6.466 μs ± 297.511 ns   GC (mean ± σ):  0.00% ± 0.00%

  ▃█                                                   ▁    ▂
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  6.36 μs      Histogram: log(frequency) by time      7.99 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_rmul!(du_aos_r, D_SBP, u_aos_r)@show reinterpret(reshape, T, du_aos_r)  du_aos_plainprintln("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 907 evaluations per sample.
 Range (minmax):  119.821 ns886.234 ns   GC (min … max): 0.00% … 0.00%
 Time  (median):     120.393 ns                GC (median):    0.00%
 Time  (mean ± σ):   122.170 ns ±  10.743 ns   GC (mean ± σ):  0.00% ± 0.00%

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  120 ns        Histogram: log(frequency) by time        138 ns <

 Memory estimate: 0 bytes, allocs estimate: 0.
D_sparse
BenchmarkTools.Trial: 10000 samples with 207 evaluations per sample.
 Range (minmax):  364.812 ns 17.290 μs   GC (min … max): 0.00% … 96.26%
 Time  (median):     373.932 ns                GC (median):    0.00%
 Time  (mean ± σ):   378.837 ns ± 169.496 ns   GC (mean ± σ):  0.44% ±  0.96%

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  365 ns        Histogram: log(frequency) by time        415 ns <

 Memory estimate: 32 bytes, allocs estimate: 1.
D_full
BenchmarkTools.Trial: 10000 samples with 1 evaluation per sample.
 Range (minmax):  9.312 μs 25.455 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     9.354 μs                GC (median):    0.00%
 Time  (mean ± σ):   9.430 μs ± 641.586 ns   GC (mean ± σ):  0.00% ± 0.00%

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  9.31 μs      Histogram: log(frequency) by time      13.4 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_aosmul!(du_aos, D_SBP, u_aos)@show du_aos  du_aos_rprintln("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 907 evaluations per sample.
 Range (minmax):  120.180 ns173.050 ns   GC (min … max): 0.00% … 0.00%
 Time  (median):     120.465 ns                GC (median):    0.00%
 Time  (mean ± σ):   121.945 ns ±   3.904 ns   GC (mean ± σ):  0.00% ± 0.00%

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  120 ns        Histogram: log(frequency) by time        135 ns <

 Memory estimate: 0 bytes, allocs estimate: 0.
D_sparse
BenchmarkTools.Trial: 10000 samples with 211 evaluations per sample.
 Range (minmax):  351.815 ns727.137 ns   GC (min … max): 0.00% … 0.00%
 Time  (median):     421.777 ns                GC (median):    0.00%
 Time  (mean ± σ):   419.500 ns ±  35.132 ns   GC (mean ± σ):  0.00% ± 0.00%

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  352 ns        Histogram: log(frequency) by time        510 ns <

 Memory estimate: 0 bytes, allocs estimate: 0.
D_full
BenchmarkTools.Trial: 10000 samples with 1 evaluation per sample.
 Range (minmax):   9.762 μs 34.654 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     10.310 μs                GC (median):    0.00%
 Time  (mean ± σ):   10.283 μs ± 807.419 ns   GC (mean ± σ):  0.00% ± 0.00%

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  9.76 μs       Histogram: log(frequency) by time      15.3 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_soamul!(du_soa, D_SBP, u_soa)@show du_soa  du_aosprintln("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 676 evaluations per sample.
 Range (minmax):  177.975 ns274.596 ns   GC (min … max): 0.00% … 0.00%
 Time  (median):     185.938 ns                GC (median):    0.00%
 Time  (mean ± σ):   188.001 ns ±   6.090 ns   GC (mean ± σ):  0.00% ± 0.00%

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  178 ns        Histogram: log(frequency) by time        209 ns <

 Memory estimate: 0 bytes, allocs estimate: 0.
D_sparse
BenchmarkTools.Trial: 10000 samples with 1 evaluation per sample.
 Range (minmax):  34.229 μs91.749 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     34.643 μs               GC (median):    0.00%
 Time  (mean ± σ):   36.554 μs ±  3.092 μs   GC (mean ± σ):  0.00% ± 0.00%

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  34.2 μs      Histogram: log(frequency) by time      46.2 μs <

 Memory estimate: 0 bytes, allocs estimate: 0.
D_full
BenchmarkTools.Trial: 10000 samples with 7 evaluations per sample.
 Range (minmax):  4.666 μs 11.230 μs   GC (min … max): 0.00% … 0.00%
 Time  (median):     4.911 μs                GC (median):    0.00%
 Time  (mean ± σ):   5.077 μs ± 548.969 ns   GC (mean ± σ):  0.00% ± 0.00%

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  4.67 μs      Histogram: log(frequency) by time      7.02 μs <

 Memory estimate: 0 bytes, allocs estimate: 0.

These results were obtained using the following versions.

using InteractiveUtilsversioninfo()using PkgPkg.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 × Intel(R) Xeon(R) 6973P-C
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, icelake-client)
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 v0.5.97-DEV `~/work/SummationByPartsOperators.jl/SummationByPartsOperators.jl`