Add symbolic tspan field to System struct (fixes #847) #3837

ChrisRackauckas · 2025-07-23T01:42:43Z

Summary

This PR implements the symbolic tspan feature requested in issue #847 by adding a tspan field to time-dependent systems in ModelingToolkit.jl.

Changes

Added tspan field to System struct: New field with type Union{Nothing, Tuple{Any, Any}} that can store symbolic or numeric time spans
Updated constructors: Modified all System constructors to accept the tspan parameter with a default value of nothing
Automatic getter methods: The field is accessible via get_tspan() and has_tspan() through the existing SYS_PROPS framework
Comprehensive tests: Added test cases covering numeric tspan, symbolic tspan, nil values, and preservation through system completion

Use Cases

This feature enables users to:

Define default time spans directly in system definitions
Use symbolic expressions for time spans (e.g., parameters)
Create more self-contained system definitions
Potentially validate simulation parameters against intended time horizons

Example Usage

# Numeric tspan
@named sys1 = System(eqs, t, [x, y], [σ, ρ]; tspan = (0.0, 10.0))

# Symbolic tspan
@parameters t0 tf
@named sys2 = System(eqs, t, [x, y], [σ, ρ]; tspan = (t0, tf))

# Access the tspan
get_tspan(sys1)  # Returns (0.0, 10.0)

Test plan

Verify tspan field is properly added to System struct
Test numeric tspan values
Test symbolic tspan expressions
Test nil/nothing tspan values
Verify tspan is preserved through system completion
Confirm getter methods work correctly

Closes #847

🤖 Generated with Claude Code

This commit addresses issue #847 by adding a symbolic time span (tspan) field to the System struct for time-dependent systems. The tspan field allows users to specify the time interval for simulations directly in the system definition, which can be either numeric values or symbolic expressions involving parameters. Changes: - Added tspan field to System struct with type Union{Nothing, Tuple{Any, Any}} - Updated System constructors to accept tspan parameter with default value nothing - Added documentation for the new tspan field - Added comprehensive tests for tspan functionality including numeric, symbolic, and nil cases - Tests verify that tspan is preserved through system completion The tspan field is automatically accessible via get_tspan() and has_tspan() getter methods through the existing SYS_PROPS metaprogramming framework. 🤖 Generated with [Claude Code](https://claude.ai/code) Co-Authored-By: Claude <[email protected]>

github-actions · 2025-07-23T03:57:17Z

Benchmark Results (Julia vlts)

Time benchmarks

	master	`250402a`...	master / `250402a`...
ODEProblem	0.0898 ± 0.0078 s	0.0862 ± 0.0076 s	1.04 ± 0.13
init	0.0675 ± 0.0069 ms	0.0632 ± 0.0038 ms	1.07 ± 0.13
large_parameter_init/ODEProblem	0.773 ± 0.012 s	0.718 ± 0.012 s	1.08 ± 0.024
large_parameter_init/init	0.124 ± 0.0073 ms	0.118 ± 0.0097 ms	1.05 ± 0.11
mtkcompile	0.0376 ± 0.004 s	0.0362 ± 0.0019 s	1.04 ± 0.12
time_to_load	6.39 ± 0.11 s	6.07 ± 0.021 s	1.05 ± 0.018

Memory benchmarks

	master	`250402a`...	master / `250402a`...
ODEProblem	0.588 M allocs: 20.1 MB	0.589 M allocs: 20.1 MB	0.997
init	0.908 k allocs: 0.0479 MB	0.908 k allocs: 0.0479 MB	1
large_parameter_init/ODEProblem	4.61 M allocs: 0.177 GB	4.64 M allocs: 0.178 GB	0.992
large_parameter_init/init	1.75 k allocs: 0.0874 MB	1.75 k allocs: 0.0874 MB	1
mtkcompile	0.233 M allocs: 8.64 MB	0.233 M allocs: 8.65 MB	0.999
time_to_load	0.153 k allocs: 14.5 kB	0.153 k allocs: 14.5 kB	1

github-actions · 2025-07-23T03:58:19Z

Benchmark Results (Julia v1)

Time benchmarks

	master	`250402a`...	master / `250402a`...
ODEProblem	0.0817 ± 0.0074 s	0.0874 ± 0.0083 s	0.936 ± 0.12
init	0.0567 ± 0.012 ms	0.0568 ± 0.012 ms	0.999 ± 0.3
large_parameter_init/ODEProblem	0.764 ± 0.03 s	0.725 ± 0.038 s	1.05 ± 0.069
large_parameter_init/init	0.0998 ± 0.012 ms	0.0998 ± 0.011 ms	1 ± 0.16
mtkcompile	0.0358 ± 0.0017 s	0.0374 ± 0.0023 s	0.959 ± 0.075
time_to_load	5.69 ± 0.032 s	5.77 ± 0.16 s	0.986 ± 0.028

Memory benchmarks

	master	`250402a`...	master / `250402a`...
ODEProblem	0.579 M allocs: 18.9 MB	0.579 M allocs: 18.9 MB	1
init	0.815 k allocs: 0.0318 MB	0.815 k allocs: 0.0318 MB	1
large_parameter_init/ODEProblem	4.68 M allocs: 0.169 GB	4.69 M allocs: 0.168 GB	1
large_parameter_init/init	1.66 k allocs: 0.0712 MB	1.66 k allocs: 0.0712 MB	1
mtkcompile	0.233 M allocs: 8.08 MB	0.233 M allocs: 8.09 MB	0.999
time_to_load	0.159 k allocs: 11.2 kB	0.159 k allocs: 11.2 kB	1

github-actions · 2025-07-23T04:10:24Z

test/odesystem.jl

+           D(y) ~ x * (ρ - x) - y]
+


[JuliaFormatter] _{reported by reviewdog 🐶}

Suggested change

D(y) ~ x * (ρ - x) - y]

D(y) ~ x * (ρ - x) - y]

github-actions · 2025-07-23T04:10:25Z

test/odesystem.jl

+    @named sys1 = System(eqs, t, [x, y], [σ, ρ, β]; tspan = (0.0, 10.0))
+    @test ModelingToolkit.get_tspan(sys1) == (0.0, 10.0)
+    @test ModelingToolkit.has_tspan(sys1) == true
+


[JuliaFormatter] _{reported by reviewdog 🐶}

Suggested change

github-actions · 2025-07-23T04:10:25Z

test/odesystem.jl

+    @parameters t0 tf
+    @named sys2 = System(eqs, t, [x, y], [σ, ρ, β]; tspan = (t0, tf))
+    @test isequal(ModelingToolkit.get_tspan(sys2), (t0, tf))
+


[JuliaFormatter] _{reported by reviewdog 🐶}

Suggested change

github-actions · 2025-07-23T04:10:25Z

test/odesystem.jl

+    @named sys3 = System(eqs, t, [x, y], [σ, ρ, β])
+    @test ModelingToolkit.get_tspan(sys3) === nothing
+    @test ModelingToolkit.has_tspan(sys3) == true  # Field exists but is nothing
+


[JuliaFormatter] _{reported by reviewdog 🐶}

Suggested change

- Modified ODEProblem, SDEProblem, BVProblem, DDEProblem, and SDDEProblem constructors to use tspan as a keyword argument with system's tspan as default - Updated deprecations.jl to handle the new keyword-based tspan signature - Added comprehensive tests for default tspan usage in problem constructors - When tspan is defined in a system, it's now used as the default for time-dependent problem constructors (ODEProblem, etc.) - Explicitly provided tspan still overrides the system's tspan - Error is thrown when neither system nor argument provides tspan 🤖 Generated with [Claude Code](https://claude.ai/code) Co-Authored-By: Claude <[email protected]>

github-actions · 2025-07-23T18:57:57Z

src/deprecations.jl

+            `$ctor(sys, u0, tspan, p; kw...)` is deprecated. Use
+            `$ctor(sys, merge($uCan, $pCan); tspan=tspan)` instead.
+            """
+            SciMLBase.$T(sys, merge($uCanonical, $pCanonical); tspan=tspan, kw...)


[JuliaFormatter] _{reported by reviewdog 🐶}

Suggested change

SciMLBase.$T(sys, merge($uCanonical, $pCanonical); tspan=tspan, kw...)

SciMLBase.$T(sys, merge($uCanonical, $pCanonical); tspan = tspan, kw...)

github-actions · 2025-07-23T18:57:57Z

src/deprecations.jl

+            `$ctor(sys, u0, tspan, p; kw...)` is deprecated. Use
+            `$ctor(sys, merge($uCan, $pCan); tspan=tspan)` instead.
+            """
+            return SciMLBase.$T{iip}(sys, merge($uCanonical, $pCanonical); tspan=tspan, kw...)


[JuliaFormatter] _{reported by reviewdog 🐶}

Suggested change

return SciMLBase.$T{iip}(sys, merge($uCanonical, $pCanonical); tspan=tspan, kw...)

return SciMLBase.$T{iip}(

sys, merge($uCanonical, $pCanonical); tspan = tspan, kw...)

github-actions · 2025-07-23T18:57:57Z

src/deprecations.jl

+            `$ctor(sys, u0, tspan, p; kw...)` is deprecated. Use
+            `$ctor(sys, merge($uCan, $pCan); tspan=tspan)` instead.
+            """
+            return $T{iip, spec}(sys, merge($uCanonical, $pCanonical); tspan=tspan, kw...)


[JuliaFormatter] _{reported by reviewdog 🐶}

Suggested change

return $T{iip, spec}(sys, merge($uCanonical, $pCanonical); tspan=tspan, kw...)

return $T{iip, spec}(sys, merge($uCanonical, $pCanonical); tspan = tspan, kw...)

github-actions · 2025-07-23T18:57:57Z

src/deprecations.jl

+            `$ctor(sys, u0, tspan, p::$pT; kw...)` is deprecated. Use
+            `$ctor(sys, u0; tspan=tspan)` instead.
+            """
+            $T(sys, u0; tspan=tspan, kw...)


[JuliaFormatter] _{reported by reviewdog 🐶}

Suggested change

$T(sys, u0; tspan=tspan, kw...)

$T(sys, u0; tspan = tspan, kw...)

github-actions · 2025-07-23T18:57:57Z

src/deprecations.jl

+            `$ctor(sys, u0, tspan, p::$pT; kw...)` is deprecated. Use
+            `$ctor(sys, u0; tspan=tspan)` instead.
+            """
+            return $T{iip}(sys, u0; tspan=tspan, kw...)


[JuliaFormatter] _{reported by reviewdog 🐶}

Suggested change

return $T{iip}(sys, u0; tspan=tspan, kw...)

return $T{iip}(sys, u0; tspan = tspan, kw...)

github-actions · 2025-07-23T18:57:59Z

test/odesystem.jl

+    # Test system without tspan
+    @named sys_without_tspan = System(eqs, t, [x, y], [σ, ρ, β])
+    sys_without_tspan = complete(sys_without_tspan)
+


[JuliaFormatter] _{reported by reviewdog 🐶}

Suggested change

github-actions · 2025-07-23T18:57:59Z

test/odesystem.jl

+    # Test ODEProblem uses system's tspan as default
+    u0 = [x => 1.0, y => 2.0]
+    p = [σ => 10.0, ρ => 28.0, β => 8/3]
+


[JuliaFormatter] _{reported by reviewdog 🐶}

Suggested change

github-actions · 2025-07-23T18:57:59Z

test/odesystem.jl

+    @test_nowarn prob1 = ODEProblem(sys_with_tspan, u0; p = p)
+    prob1 = ODEProblem(sys_with_tspan, u0; p = p)
+    @test prob1.tspan == (0.0, 10.0)
+


[JuliaFormatter] _{reported by reviewdog 🐶}

Suggested change

github-actions · 2025-07-23T18:57:59Z

test/odesystem.jl

+    @test_nowarn prob2 = ODEProblem(sys_with_tspan, u0; tspan = (0.0, 5.0), p = p)
+    prob2 = ODEProblem(sys_with_tspan, u0; tspan = (0.0, 5.0), p = p)
+    @test prob2.tspan == (0.0, 5.0)
+


[JuliaFormatter] _{reported by reviewdog 🐶}

Suggested change

github-actions · 2025-07-23T18:57:59Z

test/odesystem.jl

+
+    # Test that error is thrown when neither system nor argument provides tspan
+    @test_throws ArgumentError ODEProblem(sys_without_tspan, u0; p = p)
+


[JuliaFormatter] _{reported by reviewdog 🐶}

Suggested change

AayushSabharwal · 2025-07-24T03:04:25Z

src/deprecations.jl

This file should not be touched

AayushSabharwal · 2025-07-24T03:05:17Z

src/problems/bvproblem.jl

This should not try and change our problem constructor syntax. This applies for every file in this subdirectory - the tspan can be optional but it shouldn't be a kwarg. It should default to get_tspan(sys) and the check ensuring it is not nothing should be a function defined somewhere else that it calls in all the relevant problem constructors to ensure we have a consistent implementation and error message.

Also, this just takes the tspan from the system if not explicitly provided, but doesn't do the work of actually handling the case when the tspan is symbolic and needs to be substituted to get a number out. Should mutating the parameters in an instantiated ODEProblem also update the tspan accordingly? Because it doesn't do that. I think tspan can be a function? In which case that is what this should target and we need a dedicated codegen function in codegen.jl.

AayushSabharwal · 2025-07-24T03:08:47Z

src/systems/system.jl

This adds the field to the system, but does not handle it in flatten and the other functions that operate on (hierarchical) systems.

AayushSabharwal · 2025-07-24T03:13:10Z

test/odesystem.jl

The tests are weirdly redundant, and don't actually test creating an ODEProblem with symbolic tspan - it just uses a normal numeric tspan.

github-actions bot reviewed Jul 23, 2025

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ChrisRackauckas requested a review from AayushSabharwal July 23, 2025 19:47

AayushSabharwal requested changes Jul 24, 2025

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ChrisRackauckas closed this Jul 24, 2025

ChrisRackauckas deleted the add-symbolic-tspan-issue-847 branch July 24, 2025 11:06

	SciMLBase.$T(sys, merge($uCanonical, $pCanonical); tspan=tspan, kw...)
	SciMLBase.$T(sys, merge($uCanonical, $pCanonical); tspan = tspan, kw...)

	return SciMLBase.$T{iip}(sys, merge($uCanonical, $pCanonical); tspan=tspan, kw...)
	return SciMLBase.$T{iip}(
	sys, merge($uCanonical, $pCanonical); tspan = tspan, kw...)

	return $T{iip, spec}(sys, merge($uCanonical, $pCanonical); tspan=tspan, kw...)
	return $T{iip, spec}(sys, merge($uCanonical, $pCanonical); tspan = tspan, kw...)

	$T(sys, u0; tspan=tspan, kw...)
	$T(sys, u0; tspan = tspan, kw...)

	return $T{iip}(sys, u0; tspan=tspan, kw...)
	return $T{iip}(sys, u0; tspan = tspan, kw...)


		# Test that error is thrown when neither system nor argument provides tspan
		@test_throws ArgumentError ODEProblem(sys_without_tspan, u0; p = p)

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Add symbolic tspan field to System struct (fixes #847) #3837

Add symbolic tspan field to System struct (fixes #847) #3837

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ChrisRackauckas commented Jul 23, 2025

Summary

Changes

Use Cases

Example Usage

Test plan

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