Manifest.toml

# This file is machine-generated - editing it directly is not advised

[[AbstractFFTs]]
deps = ["LinearAlgebra"]
git-tree-sha1 = "051c95d6836228d120f5f4b984dd5aba1624f716"
uuid = "621f4979-c628-5d54-868e-fcf4e3e8185c"
version = "0.5.0"

[[Adapt]]
deps = ["LinearAlgebra"]
git-tree-sha1 = "42c42f2221906892ceb765dbcb1a51deeffd86d7"
uuid = "79e6a3ab-5dfb-504d-930d-738a2a938a0e"
version = "2.3.0"

[[ArgCheck]]
git-tree-sha1 = "dedbbb2ddb876f899585c4ec4433265e3017215a"
uuid = "dce04be8-c92d-5529-be00-80e4d2c0e197"
version = "2.1.0"

[[BFloat16s]]
deps = ["LinearAlgebra", "Test"]
git-tree-sha1 = "4af69e205efc343068dc8722b8dfec1ade89254a"
uuid = "ab4f0b2a-ad5b-11e8-123f-65d77653426b"
version = "0.1.0"

[[BangBang]]
deps = ["Compat", "ConstructionBase", "Future", "InitialValues", "LinearAlgebra", "Requires", "Setfield", "Tables", "ZygoteRules"]
git-tree-sha1 = "f42321255afc37da855b6cd9f2a1fc36c017ceee"
uuid = "198e06fe-97b7-11e9-32a5-e1d131e6ad66"
version = "0.3.29"

[[Base64]]
uuid = "2a0f44e3-6c83-55bd-87e4-b1978d98bd5f"

[[Baselet]]
git-tree-sha1 = "aebf55e6d7795e02ca500a689d326ac979aaf89e"
uuid = "9718e550-a3fa-408a-8086-8db961cd8217"
version = "0.1.1"

[[CEnum]]
git-tree-sha1 = "215a9aa4a1f23fbd05b92769fdd62559488d70e9"
uuid = "fa961155-64e5-5f13-b03f-caf6b980ea82"
version = "0.4.1"

[[CUDA]]
deps = ["AbstractFFTs", "Adapt", "BFloat16s", "CEnum", "DataStructures", "ExprTools", "GPUArrays", "GPUCompiler", "LLVM", "Libdl", "LinearAlgebra", "Logging", "MacroTools", "NNlib", "Pkg", "Printf", "Random", "Reexport", "Requires", "SparseArrays", "Statistics", "TimerOutputs"]
git-tree-sha1 = "7663b61782b569b03fba91d330a5ed2f86cd4cb8"
uuid = "052768ef-5323-5732-b1bb-66c8b64840ba"
version = "2.3.0"

[[Compat]]
deps = ["Base64", "Dates", "DelimitedFiles", "Distributed", "InteractiveUtils", "LibGit2", "Libdl", "LinearAlgebra", "Markdown", "Mmap", "Pkg", "Printf", "REPL", "Random", "SHA", "Serialization", "SharedArrays", "Sockets", "SparseArrays", "Statistics", "Test", "UUIDs", "Unicode"]
git-tree-sha1 = "919c7f3151e79ff196add81d7f4e45d91bbf420b"
uuid = "34da2185-b29b-5c13-b0c7-acf172513d20"
version = "3.25.0"

[[CompositionsBase]]
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uuid = "a33af91c-f02d-484b-be07-31d278c5ca2b"
version = "0.1.0"

[[ConstructionBase]]
git-tree-sha1 = "a2a6a5fea4d6f730ec4c18a76d27ec10e8ec1c50"
uuid = "187b0558-2788-49d3-abe0-74a17ed4e7c9"
version = "1.0.0"

[[ContextVariablesX]]
deps = ["Compat", "Logging", "UUIDs"]
git-tree-sha1 = "fc81d9dd4ffdafb56680f01e6d9db464a6b3689d"
uuid = "6add18c4-b38d-439d-96f6-d6bc489c04c5"
version = "0.1.1"

[[DataAPI]]
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uuid = "9a962f9c-6df0-11e9-0e5d-c546b8b5ee8a"
version = "1.4.0"

[[DataStructures]]
deps = ["Compat", "InteractiveUtils", "OrderedCollections"]
git-tree-sha1 = "fb0aa371da91c1ff9dc7fbed6122d3e411420b9c"
uuid = "864edb3b-99cc-5e75-8d2d-829cb0a9cfe8"
version = "0.18.8"

[[DataValueInterfaces]]
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uuid = "e2d170a0-9d28-54be-80f0-106bbe20a464"
version = "1.0.0"

[[Dates]]
deps = ["Printf"]
uuid = "ade2ca70-3891-5945-98fb-dc099432e06a"

[[DefineSingletons]]
git-tree-sha1 = "1a356f194281dff9ef1119faa9125a0d4e210729"
uuid = "244e2a9f-e319-4986-a169-4d1fe445cd52"
version = "0.1.0"

[[DelimitedFiles]]
deps = ["Mmap"]
uuid = "8bb1440f-4735-579b-a4ab-409b98df4dab"

[[Distributed]]
deps = ["Random", "Serialization", "Sockets"]
uuid = "8ba89e20-285c-5b6f-9357-94700520ee1b"

[[ExprTools]]
git-tree-sha1 = "10407a39b87f29d47ebaca8edbc75d7c302ff93e"
uuid = "e2ba6199-217a-4e67-a87a-7c52f15ade04"
version = "0.1.3"

[[FLoops]]
deps = ["Compat", "FLoopsBase", "JuliaVariables", "MLStyle", "Setfield", "Transducers"]
git-tree-sha1 = "6d0830bffc733b3e4d4d1a7e7109d0a51d68495d"
uuid = "cc61a311-1640-44b5-9fba-1b764f453329"
version = "0.1.4"

[[FLoopsBase]]
deps = ["ContextVariablesX"]
git-tree-sha1 = "cf3d8b2527be12d204d06aba922b30339a9653dd"
uuid = "b9860ae5-e623-471e-878b-f6a53c775ea6"
version = "0.1.0"

[[FoldsCUDA]]
deps = ["CUDA", "FLoops", "GPUArrays", "InitialValues", "SplittablesBase", "Transducers"]
git-tree-sha1 = "0508070d60a5ba2dcf6ecd6567888275c0288fe6"
uuid = "6cd66ae4-5932-4b96-926d-e73e578e42cc"
version = "0.1.1"

[[Future]]
deps = ["Random"]
uuid = "9fa8497b-333b-5362-9e8d-4d0656e87820"

[[GPUArrays]]
deps = ["AbstractFFTs", "Adapt", "LinearAlgebra", "Printf", "Random", "Serialization"]
git-tree-sha1 = "2c1dd57bca7ba0b3b4bf81d9332aeb81b154ef4c"
uuid = "0c68f7d7-f131-5f86-a1c3-88cf8149b2d7"
version = "6.1.2"

[[GPUCompiler]]
deps = ["DataStructures", "InteractiveUtils", "LLVM", "Libdl", "Scratch", "Serialization", "TimerOutputs", "UUIDs"]
git-tree-sha1 = "c853c810b52a80f9aad79ab109207889e57f41ef"
uuid = "61eb1bfa-7361-4325-ad38-22787b887f55"
version = "0.8.3"

[[InitialValues]]
git-tree-sha1 = "26c8832afd63ac558b98a823265856670d898b6c"
uuid = "22cec73e-a1b8-11e9-2c92-598750a2cf9c"
version = "0.2.10"

[[InteractiveUtils]]
deps = ["Markdown"]
uuid = "b77e0a4c-d291-57a0-90e8-8db25a27a240"

[[IteratorInterfaceExtensions]]
git-tree-sha1 = "a3f24677c21f5bbe9d2a714f95dcd58337fb2856"
uuid = "82899510-4779-5014-852e-03e436cf321d"
version = "1.0.0"

[[JuliaVariables]]
deps = ["MLStyle", "NameResolution"]
git-tree-sha1 = "e0fcfa0a2f6122fbe13603764c5310dde00c5593"
uuid = "b14d175d-62b4-44ba-8fb7-3064adc8c3ec"
version = "0.2.3"

[[LLVM]]
deps = ["CEnum", "Libdl", "Printf", "Unicode"]
git-tree-sha1 = "a2101830a761d592b113129887fda626387f68d4"
uuid = "929cbde3-209d-540e-8aea-75f648917ca0"
version = "3.5.1"

[[LibGit2]]
deps = ["Printf"]
uuid = "76f85450-5226-5b5a-8eaa-529ad045b433"

[[Libdl]]
uuid = "8f399da3-3557-5675-b5ff-fb832c97cbdb"

[[LinearAlgebra]]
deps = ["Libdl"]
uuid = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"

[[Logging]]
uuid = "56ddb016-857b-54e1-b83d-db4d58db5568"

[[MLStyle]]
git-tree-sha1 = "937eda9ce36fcce082a42edd7181c8d23f4eb550"
uuid = "d8e11817-5142-5d16-987a-aa16d5891078"
version = "0.4.6"

[[MacroTools]]
deps = ["Markdown", "Random"]
git-tree-sha1 = "6a8a2a625ab0dea913aba95c11370589e0239ff0"
uuid = "1914dd2f-81c6-5fcd-8719-6d5c9610ff09"
version = "0.5.6"

[[Markdown]]
deps = ["Base64"]
uuid = "d6f4376e-aef5-505a-96c1-9c027394607a"

[[MicroCollections]]
deps = ["BangBang", "Setfield"]
git-tree-sha1 = "e991b6a9d38091c4a0d7cd051fcb57c05f98ac03"
uuid = "128add7d-3638-4c79-886c-908ea0c25c34"
version = "0.1.0"

[[Mmap]]
uuid = "a63ad114-7e13-5084-954f-fe012c677804"

[[NNlib]]
deps = ["Compat", "Libdl", "LinearAlgebra", "Pkg", "Requires", "Statistics"]
git-tree-sha1 = "2b7c3213ed4f2eed686f9f531f85d3ea2f75286f"
uuid = "872c559c-99b0-510c-b3b7-b6c96a88d5cd"
version = "0.7.9"

[[NameResolution]]
deps = ["PrettyPrint"]
git-tree-sha1 = "1a0fa0e9613f46c9b8c11eee38ebb4f590013c5e"
uuid = "71a1bf82-56d0-4bbc-8a3c-48b961074391"
version = "0.1.5"

[[OrderedCollections]]
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uuid = "bac558e1-5e72-5ebc-8fee-abe8a469f55d"
version = "1.3.2"

[[Pkg]]
deps = ["Dates", "LibGit2", "Libdl", "Logging", "Markdown", "Printf", "REPL", "Random", "SHA", "UUIDs"]
uuid = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"

[[PrettyPrint]]
git-tree-sha1 = "632eb4abab3449ab30c5e1afaa874f0b98b586e4"
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version = "0.2.0"

[[Printf]]
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uuid = "de0858da-6303-5e67-8744-51eddeeeb8d7"

[[REPL]]
deps = ["InteractiveUtils", "Markdown", "Sockets"]
uuid = "3fa0cd96-eef1-5676-8a61-b3b8758bbffb"

[[Random]]
deps = ["Serialization"]
uuid = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"

[[Reexport]]
deps = ["Pkg"]
git-tree-sha1 = "7b1d07f411bc8ddb7977ec7f377b97b158514fe0"
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[[Requires]]
deps = ["UUIDs"]
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uuid = "ae029012-a4dd-5104-9daa-d747884805df"
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[[SHA]]
uuid = "ea8e919c-243c-51af-8825-aaa63cd721ce"

[[Scratch]]
deps = ["Dates"]
git-tree-sha1 = "ad4b278adb62d185bbcb6864dc24959ab0627bf6"
uuid = "6c6a2e73-6563-6170-7368-637461726353"
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[[Serialization]]
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[[Setfield]]
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[[SharedArrays]]
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[[Sockets]]
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[[SparseArrays]]
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[[SplittablesBase]]
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[[Statistics]]
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[[TableTraits]]
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[[Test]]
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[[TimerOutputs]]
deps = ["Printf"]
git-tree-sha1 = "3318281dd4121ecf9713ce1383b9ace7d7476fdd"
uuid = "a759f4b9-e2f1-59dc-863e-4aeb61b1ea8f"
version = "0.5.7"

[[Transducers]]
deps = ["ArgCheck", "BangBang", "CompositionsBase", "DefineSingletons", "Distributed", "InitialValues", "Logging", "Markdown", "MicroCollections", "Requires", "Setfield", "SplittablesBase", "Tables"]
git-tree-sha1 = "80f9fad2026c304f391198d391a0c698b666b201"
uuid = "28d57a85-8fef-5791-bfe6-a80928e7c999"
version = "0.4.53"

[[UUIDs]]
deps = ["Random", "SHA"]
uuid = "cf7118a7-6976-5b1a-9a39-7adc72f591a4"

[[Unicode]]
uuid = "4ec0a83e-493e-50e2-b9ac-8f72acf5a8f5"

[[ZygoteRules]]
deps = ["MacroTools"]
git-tree-sha1 = "9e7a1e8ca60b742e508a315c17eef5211e7fbfd7"
uuid = "700de1a5-db45-46bc-99cf-38207098b444"
version = "0.2.1"

mwe.jl

using Baselet
using CUDA
using FLoops
using FoldsCUDA

function findmax2_floop(xs; ex = CUDAEx())
    init0 = (firstindex(xs) - 1 => typemin(eltype(xs)))
    init = (init0, init0)
    @floop ex for (x, i) in zip(xs, eachindex(xs))
        b = tuple(i => x)
        @reduce() do (a = init; b)
            x, y = Baselet.sort((a..., b...); by = last, rev = true)
            a = (x, y)
        end
    end
    return a
end

function merge_max2(a, b)
    x, y = Baselet.sort((a..., b...); by = last, rev = true)
    return (x, y)
end

singleton_max2(x, i) = ((i => x),)

function findmax2_cuda(xs)
    init0 = (firstindex(xs) - 1 => typemin(eltype(xs)))
    return mapreduce(singleton_max2, merge_max2, xs, eachindex(xs); init = (init0, init0))
end

using Test

@testset "(4 => 6, 3 => 5)" begin
    xs = CuArray([3, 0, 5, 6, 1])
    @test findmax2_floop(xs) == (4 => 6, 3 => 5)
    @test findmax2_cuda(xs) == (4 => 6, 3 => 5)
end

@testset "(300 => 3, 200 => 2)" begin
    xs = CUDA.rand(1000_0000)
    xs[200] = 2
    xs[300] = 3
    @test findmax2_floop(xs) == (300 => 3, 200 => 2)
    @test findmax2_cuda(xs) == (300 => 3, 200 => 2)
end

@testset "(1 => 1.0f0, 262144 => 0.5f0)" begin
    xs = CUDA.zeros(512, 512)
    xs[1] = 1
    xs[end] = 0.5
    @test findmax2_floop(xs) == (1 => 1.0f0, 262144 => 0.5f0)
    @test findmax2_cuda(xs) == (1 => 1.0f0, 262144 => 0.5f0)
end

Project.toml

[deps]
Baselet = "9718e550-a3fa-408a-8086-8db961cd8217"
CUDA = "052768ef-5323-5732-b1bb-66c8b64840ba"
FLoops = "cc61a311-1640-44b5-9fba-1b764f453329"
FoldsCUDA = "6cd66ae4-5932-4b96-926d-e73e578e42cc"
Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"