tstops doesn't work probably when tspan tupel is given as integers

[cwittens]

Describe the bug 🐞

When using tstops with non-adaptive methods, the elements of tstops need to be integers if tspan is given as a tuple of integers.

Expected behavior

It shouldn't matter if one uses integers or floats for the tspan tuple. In both cases you should be able to pass floats as tstops.

Minimal Reproducible Example 👇

julia> tstops = [0.33, 0.66, 1.0]
3-element Vector{Float64}:
 0.33
 0.66
 1.0

julia> sol_float = solve(ODEProblem((du,u,p,t)->du .= u, [1.0], (0.0, 1.0)), Euler(), tstops = tstops)
retcode: Success
Interpolation: 3rd order Hermite
t: 4-element Vector{Float64}:
 0.0
 0.33
 0.66
 1.0
u: 4-element Vector{Vector{Float64}}:
 [1.0]
 [1.33]
 [1.7689000000000001]
 [2.370326]

julia> sol_int = solve(ODEProblem((du,u,p,t)->du .= u, [1.0], (0,1)), Euler(), tstops = tstops)
ERROR: InexactError: Int64(0.33)
Stacktrace:
  [1] Int64
    @ .\float.jl:912 [inlined]
  [2] convert
    @ .\number.jl:7 [inlined]
  [3] push!
    @ .\array.jl:1118 [inlined]
  [4] heappush!
    @ C:\Users\Uni\.julia\packages\DataStructures\95DJa\src\heaps\arrays_as_heaps.jl:72 [inlined]
  [5] push!
    @ C:\Users\Uni\.julia\packages\DataStructures\95DJa\src\heaps\binary_heap.jl:91 [inlined]
  [6] initialize_tstops
    @ C:\Users\Uni\.julia\packages\OrdinaryDiffEq\0tf1M\src\solve.jl:598 [inlined]
  [7] __init(prob::ODEProblem{…}, alg::Euler, timeseries_init::Tuple{}, ts_init::Tuple{}, ks_init::Tuple{}, recompile::Type{…}; saveat::Tuple{}, tstops::Vector{…}, d_discontinuities::Tuple{}, save_idxs::Nothing, save_everystep::Bool, save_on::Bool, save_start::Bool, save_end::Nothing, callback::Nothing, dense::Bool, calck::Bool, dt::Int64, dtmin::Int64, dtmax::Int64, force_dtmin::Bool, adaptive::Bool, gamma::Int64, abstol::Nothing, reltol::Nothing, qmin::Int64, qmax::Int64, qsteady_min::Int64, qsteady_max::Int64, beta1::Nothing, beta2::Nothing, qoldinit::Int64, controller::Nothing, fullnormalize::Bool, failfactor::Int64, maxiters::Int64, internalnorm::typeof(DiffEqBase.ODE_DEFAULT_NORM), internalopnorm::typeof(LinearAlgebra.opnorm), isoutofdomain::typeof(DiffEqBase.ODE_DEFAULT_ISOUTOFDOMAIN), unstable_check::typeof(DiffEqBase.ODE_DEFAULT_UNSTABLE_CHECK), verbose::Bool, timeseries_errors::Bool, dense_errors::Bool, advance_to_tstop::Bool, stop_at_next_tstop::Bool, initialize_save::Bool, progress::Bool, progress_steps::Int64, progress_name::String, progress_message::typeof(DiffEqBase.ODE_DEFAULT_PROG_MESSAGE), progress_id::Symbol, userdata::Nothing, allow_extrapolation::Bool, initialize_integrator::Bool, alias_u0::Bool, alias_du0::Bool, initializealg::OrdinaryDiffEq.DefaultInit, kwargs::@Kwargs{})
    @ OrdinaryDiffEq C:\Users\Uni\.julia\packages\OrdinaryDiffEq\0tf1M\src\solve.jl:237
  [8] __init (repeats 5 times)
    @ C:\Users\Uni\.julia\packages\OrdinaryDiffEq\0tf1M\src\solve.jl:11 [inlined]
  [9] #__solve#766
    @ C:\Users\Uni\.julia\packages\OrdinaryDiffEq\0tf1M\src\solve.jl:6 [inlined]
 [10] __solve
    @ C:\Users\Uni\.julia\packages\OrdinaryDiffEq\0tf1M\src\solve.jl:1 [inlined]
 [11] #solve_call#44
    @ C:\Users\Uni\.julia\packages\DiffEqBase\WyGjp\src\solve.jl:612 [inlined]
 [12] solve_up(prob::ODEProblem{…}, sensealg::Nothing, u0::Vector{…}, p::SciMLBase.NullParameters, args::Euler; kwargs::@Kwargs{…})
    @ DiffEqBase C:\Users\Uni\.julia\packages\DiffEqBase\WyGjp\src\solve.jl:1080
 [13] solve_up
    @ C:\Users\Uni\.julia\packages\DiffEqBase\WyGjp\src\solve.jl:1066 [inlined]
 [14] solve(prob::ODEProblem{…}, args::Euler; sensealg::Nothing, u0::Nothing, p::Nothing, wrap::Val{…}, kwargs::@Kwargs{…})
    @ DiffEqBase C:\Users\Uni\.julia\packages\DiffEqBase\WyGjp\src\solve.jl:1003
 [15] top-level scope
    @ REPL[9]:1
Some type information was truncated. Use `show(err)` to see complete types.

Environment (please complete the following information):

• Output of using Pkg; Pkg.status()

julia> using Pkg; Pkg.status()
Status `C:\Users\Uni\.julia\environments\v1.10\Project.toml`
  [f6369f11] ForwardDiff v0.10.36
  [7073ff75] IJulia v1.24.2
  [2774e3e8] NLsolve v4.5.1
  [1dea7af3] OrdinaryDiffEq v6.75.0
  [91a5bcdd] Plots v1.40.4
  [c3e4b0f8] Pluto v0.19.42
  [37e2e46d] LinearAlgebra

• Output of using Pkg; Pkg.status(; mode = PKGMODE_MANIFEST)

Status `C:\Users\Uni\.julia\environments\v1.10\Manifest.toml`
⌅ [47edcb42] ADTypes v0.2.7
  [7d9f7c33] Accessors v0.1.36
  [79e6a3ab] Adapt v4.0.4
  [ec485272] ArnoldiMethod v0.4.0
  [4fba245c] ArrayInterface v7.10.0
  [4c555306] ArrayLayouts v1.9.2
  [d1d4a3ce] BitFlags v0.1.8
  [62783981] BitTwiddlingConvenienceFunctions v0.1.5
  [2a0fbf3d] CPUSummary v0.2.4
  [d360d2e6] ChainRulesCore v1.23.0
  [fb6a15b2] CloseOpenIntervals v0.1.12
  [944b1d66] CodecZlib v0.7.4
  [35d6a980] ColorSchemes v3.25.0
  [3da002f7] ColorTypes v0.11.5
  [c3611d14] ColorVectorSpace v0.10.0
  [5ae59095] Colors v0.12.10
  [38540f10] CommonSolve v0.2.4
  [bbf7d656] CommonSubexpressions v0.3.0
  [34da2185] Compat v4.15.0
  [a33af91c] CompositionsBase v0.1.2
  [2569d6c7] ConcreteStructs v0.2.3
  [f0e56b4a] ConcurrentUtilities v2.4.1
  [8f4d0f93] Conda v1.10.0
  [5218b696] Configurations v0.17.6
  [187b0558] ConstructionBase v1.5.5
  [d38c429a] Contour v0.6.3
  [adafc99b] CpuId v0.3.1
  [9a962f9c] DataAPI v1.16.0
  [864edb3b] DataStructures v0.18.20
  [e2d170a0] DataValueInterfaces v1.0.0
  [8bb1440f] DelimitedFiles v1.9.1
  [2b5f629d] DiffEqBase v6.149.2
  [163ba53b] DiffResults v1.1.0
  [b552c78f] DiffRules v1.15.1
  [b4f34e82] Distances v0.10.11
  [ffbed154] DocStringExtensions v0.9.3
  [4e289a0a] EnumX v1.0.4
⌃ [f151be2c] EnzymeCore v0.6.6
  [460bff9d] ExceptionUnwrapping v0.1.10
  [d4d017d3] ExponentialUtilities v1.26.1
  [e2ba6199] ExprTools v0.1.10
  [21656369] ExpressionExplorer v1.0.2
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  [c87230d0] FFMPEG v0.4.1
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  [1a297f60] FillArrays v1.11.0
  [6a86dc24] FiniteDiff v2.23.1
  [53c48c17] FixedPointNumbers v0.8.4
  [1fa38f19] Format v1.3.7
  [f6369f11] ForwardDiff v0.10.36
  [069b7b12] FunctionWrappers v1.1.3
  [77dc65aa] FunctionWrappersWrappers v0.1.3
  [fb4132e2] FuzzyCompletions v0.5.4
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  [28b8d3ca] GR v0.73.5
  [c145ed77] GenericSchur v0.5.4
  [86223c79] Graphs v1.11.0
  [42e2da0e] Grisu v1.0.2
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  [bdcacae8] LoopVectorization v0.12.170
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  [99f44e22] MsgPack v1.2.1
  [46d2c3a1] MuladdMacro v0.2.4
  [d41bc354] NLSolversBase v7.8.3
  [2774e3e8] NLsolve v4.5.1
  [77ba4419] NaNMath v1.0.2
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  [6fe1bfb0] OffsetArrays v1.14.0
  [4d8831e6] OpenSSL v1.4.3
  [bac558e1] OrderedCollections v1.6.3
  [1dea7af3] OrdinaryDiffEq v6.75.0
  [65ce6f38] PackageExtensionCompat v1.0.2
  [d96e819e] Parameters v0.12.3
  [69de0a69] Parsers v2.8.1
  [b98c9c47] Pipe v1.3.0
  [ccf2f8ad] PlotThemes v3.1.0
  [995b91a9] PlotUtils v1.4.1
  [91a5bcdd] Plots v1.40.4
  [c3e4b0f8] Pluto v0.19.42
  [72656b73] PlutoDependencyExplorer v1.0.4
  [f517fe37] Polyester v0.7.13
  [1d0040c9] PolyesterWeave v0.2.1
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  [91cefc8d] PrecompileSignatures v3.0.3
  [aea7be01] PrecompileTools v1.2.1
  [21216c6a] Preferences v1.4.3
  [3cdcf5f2] RecipesBase v1.3.4
  [01d81517] RecipesPipeline v0.6.12
  [731186ca] RecursiveArrayTools v3.16.0
  [f2c3362d] RecursiveFactorization v0.2.23
  [189a3867] Reexport v1.2.2
  [2792f1a3] RegistryInstances v0.1.0
  [05181044] RelocatableFolders v1.0.1
  [ae029012] Requires v1.3.0
  [7e49a35a] RuntimeGeneratedFunctions v0.5.13
  [94e857df] SIMDTypes v0.1.0
  [476501e8] SLEEFPirates v0.6.42
  [0bca4576] SciMLBase v2.36.1
  [c0aeaf25] SciMLOperators v0.3.8
  [53ae85a6] SciMLStructures v1.1.0
  [6c6a2e73] Scratch v1.2.1
  [efcf1570] Setfield v1.1.1
  [992d4aef] Showoff v1.0.3
  [777ac1f9] SimpleBufferStream v1.1.0
  [727e6d20] SimpleNonlinearSolve v1.8.0
  [699a6c99] SimpleTraits v0.9.4
  [ce78b400] SimpleUnPack v1.1.0
  [b85f4697] SoftGlobalScope v1.1.0
  [a2af1166] SortingAlgorithms v1.2.1
⌃ [47a9eef4] SparseDiffTools v2.18.0
  [e56a9233] Sparspak v0.3.9
  [276daf66] SpecialFunctions v2.4.0
  [aedffcd0] Static v0.8.10
  [0d7ed370] StaticArrayInterface v1.5.0
  [90137ffa] StaticArrays v1.9.3
  [1e83bf80] StaticArraysCore v1.4.2
  [82ae8749] StatsAPI v1.7.0
  [2913bbd2] StatsBase v0.34.3
  [7792a7ef] StrideArraysCore v0.5.6
  [2efcf032] SymbolicIndexingInterface v0.3.21
  [3783bdb8] TableTraits v1.0.1
  [bd369af6] Tables v1.11.1
  [62fd8b95] TensorCore v0.1.1
  [8290d209] ThreadingUtilities v0.5.2
  [a759f4b9] TimerOutputs v0.5.23
  [3bb67fe8] TranscodingStreams v0.10.8
  [d5829a12] TriangularSolve v0.2.0
  [410a4b4d] Tricks v0.1.8
  [781d530d] TruncatedStacktraces v1.4.0
  [5c2747f8] URIs v1.5.1
  [3a884ed6] UnPack v1.0.2
  [1cfade01] UnicodeFun v0.4.1
  [1986cc42] Unitful v1.19.0
  [45397f5d] UnitfulLatexify v1.6.3
  [41fe7b60] Unzip v0.2.0
  [3d5dd08c] VectorizationBase v0.21.67
  [81def892] VersionParsing v1.3.0
  [19fa3120] VertexSafeGraphs v0.2.0
  [c2297ded] ZMQ v1.2.2
  [6e34b625] Bzip2_jll v1.0.8+1
  [83423d85] Cairo_jll v1.18.0+1
  [2702e6a9] EpollShim_jll v0.0.20230411+0
  [2e619515] Expat_jll v2.6.2+0
⌅ [b22a6f82] FFMPEG_jll v4.4.4+1
  [a3f928ae] Fontconfig_jll v2.13.96+0
  [d7e528f0] FreeType2_jll v2.13.1+0
  [559328eb] FriBidi_jll v1.0.14+0
  [0656b61e] GLFW_jll v3.3.9+0
  [d2c73de3] GR_jll v0.73.5+0
  [78b55507] Gettext_jll v0.21.0+0
  [7746bdde] Glib_jll v2.80.0+0
  [3b182d85] Graphite2_jll v1.3.14+0
  [2e76f6c2] HarfBuzz_jll v2.8.1+1
  [1d5cc7b8] IntelOpenMP_jll v2024.1.0+0
  [aacddb02] JpegTurbo_jll v3.0.3+0
  [c1c5ebd0] LAME_jll v3.100.2+0
⌅ [88015f11] LERC_jll v3.0.0+1
  [1d63c593] LLVMOpenMP_jll v15.0.7+0
  [dd4b983a] LZO_jll v2.10.2+0
⌅ [e9f186c6] Libffi_jll v3.2.2+1
  [d4300ac3] Libgcrypt_jll v1.8.11+0
  [7e76a0d4] Libglvnd_jll v1.6.0+0
  [7add5ba3] Libgpg_error_jll v1.49.0+0
  [94ce4f54] Libiconv_jll v1.17.0+0
  [4b2f31a3] Libmount_jll v2.40.1+0
⌅ [89763e89] Libtiff_jll v4.5.1+1
  [38a345b3] Libuuid_jll v2.40.1+0
  [856f044c] MKL_jll v2024.1.0+0
  [e7412a2a] Ogg_jll v1.3.5+1
  [458c3c95] OpenSSL_jll v3.0.13+1
  [efe28fd5] OpenSpecFun_jll v0.5.5+0
  [91d4177d] Opus_jll v1.3.2+0
  [30392449] Pixman_jll v0.42.2+0
  [c0090381] Qt6Base_jll v6.5.3+1
  [a44049a8] Vulkan_Loader_jll v1.3.243+0
  [a2964d1f] Wayland_jll v1.21.0+1
  [2381bf8a] Wayland_protocols_jll v1.31.0+0
  [02c8fc9c] XML2_jll v2.12.6+0
  [aed1982a] XSLT_jll v1.1.34+0
  [ffd25f8a] XZ_jll v5.4.6+0
  [f67eecfb] Xorg_libICE_jll v1.1.1+0
  [c834827a] Xorg_libSM_jll v1.2.4+0
  [4f6342f7] Xorg_libX11_jll v1.8.6+0
  [0c0b7dd1] Xorg_libXau_jll v1.0.11+0
  [935fb764] Xorg_libXcursor_jll v1.2.0+4
  [a3789734] Xorg_libXdmcp_jll v1.1.4+0
  [1082639a] Xorg_libXext_jll v1.3.6+0
  [d091e8ba] Xorg_libXfixes_jll v5.0.3+4
  [a51aa0fd] Xorg_libXi_jll v1.7.10+4
  [d1454406] Xorg_libXinerama_jll v1.1.4+4
  [ec84b674] Xorg_libXrandr_jll v1.5.2+4
  [ea2f1a96] Xorg_libXrender_jll v0.9.11+0
  [14d82f49] Xorg_libpthread_stubs_jll v0.1.1+0
  [c7cfdc94] Xorg_libxcb_jll v1.15.0+0
  [cc61e674] Xorg_libxkbfile_jll v1.1.2+0
  [e920d4aa] Xorg_xcb_util_cursor_jll v0.1.4+0
  [12413925] Xorg_xcb_util_image_jll v0.4.0+1
  [2def613f] Xorg_xcb_util_jll v0.4.0+1
  [975044d2] Xorg_xcb_util_keysyms_jll v0.4.0+1
  [0d47668e] Xorg_xcb_util_renderutil_jll v0.3.9+1
  [c22f9ab0] Xorg_xcb_util_wm_jll v0.4.1+1
  [35661453] Xorg_xkbcomp_jll v1.4.6+0
  [33bec58e] Xorg_xkeyboard_config_jll v2.39.0+0
  [c5fb5394] Xorg_xtrans_jll v1.5.0+0
  [8f1865be] ZeroMQ_jll v4.3.5+0
  [3161d3a3] Zstd_jll v1.5.6+0
  [35ca27e7] eudev_jll v3.2.9+0
⌅ [214eeab7] fzf_jll v0.43.0+0
  [1a1c6b14] gperf_jll v3.1.1+0
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  [009596ad] mtdev_jll v1.1.6+0
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  [1270edf5] x264_jll v2021.5.5+0
  [dfaa095f] x265_jll v3.5.0+0
  [d8fb68d0] xkbcommon_jll v1.4.1+1
  [0dad84c5] ArgTools v1.1.1
  [56f22d72] Artifacts
  [2a0f44e3] Base64
  [ade2ca70] Dates
  [8ba89e20] Distributed
  [f43a241f] Downloads v1.6.0
  [7b1f6079] FileWatching
  [9fa8497b] Future
  [b77e0a4c] InteractiveUtils
  [4af54fe1] LazyArtifacts
  [b27032c2] LibCURL v0.6.4
  [76f85450] LibGit2
  [8f399da3] Libdl
  [37e2e46d] LinearAlgebra
  [56ddb016] Logging
  [d6f4376e] Markdown
  [a63ad114] Mmap
  [ca575930] NetworkOptions v1.2.0
  [44cfe95a] Pkg v1.10.0
  [de0858da] Printf
  [3fa0cd96] REPL
  [9a3f8284] Random
  [ea8e919c] SHA v0.7.0
  [9e88b42a] Serialization
  [1a1011a3] SharedArrays
  [6462fe0b] Sockets
  [2f01184e] SparseArrays v1.10.0
  [10745b16] Statistics v1.10.0
  [4607b0f0] SuiteSparse
  [fa267f1f] TOML v1.0.3
  [a4e569a6] Tar v1.10.0
  [8dfed614] Test
  [cf7118a7] UUIDs
  [4ec0a83e] Unicode
  [e66e0078] CompilerSupportLibraries_jll v1.1.0+0
  [deac9b47] LibCURL_jll v8.4.0+0
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  [05823500] OpenLibm_jll v0.8.1+2
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  [bea87d4a] SuiteSparse_jll v7.2.1+1
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Info Packages marked with ⌃ and ⌅ have new versions available. Those with ⌃ may be upgradable, but those with ⌅ are restricted by compatibility constraints from upgrading. To see why use `status --outdated -m`

• Output of versioninfo()

Julia Version 1.10.2
Commit bd47eca2c8 (2024-03-01 10:14 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Windows (x86_64-w64-mingw32)
  CPU: 8 × 11th Gen Intel(R) Core(TM) i7-1185G7 @ 3.00GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, tigerlake)
Threads: 1 default, 0 interactive, 1 GC (on 8 virtual cores)

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[ChrisRackauckas]

This is just for fixed time step? This is quite an edge case. If someone uses fixed time step then non-floating point step values are allowed, such as integers and rational values, since the user can choose to handle those exactly. For this reason, tspan does not auto-convert to floating point values for fixed time step methods like this.