feat: add safe_HomotopyContinuationProblem

Author: AayushSabharwal

ext/MTKHomotopyContinuationExt.jl

@@ -96,16 +96,22 @@ All other keyword arguments are forwarded to `HomotopyContinuation.solver_starts
 """
 function MTK.HomotopyContinuationProblem(
         sys::NonlinearSystem, u0map, parammap = nothing; kwargs...)
+    prob = MTK._safe_HomotopyContinuationProblem(sys, u0map, parammap; kwargs...)
+    prob isa MTK.HomotopyContinuationProblem || throw(prob)
+    return prob
+end
+
+function MTK._safe_HomotopyContinuationProblem(sys, u0map, parammap = nothing; kwargs...)
     if !iscomplete(sys)
         error("A completed `NonlinearSystem` is required. Call `complete` or `structural_simplify` on the system before creating a `HomotopyContinuationProblem`")
     end
     transformation = MTK.PolynomialTransformation(sys)
     if transformation isa MTK.NotPolynomialError
-        throw(transformation)
+        return transformation
     end
     result = MTK.transform_system(sys, transformation)
     if result isa MTK.NotPolynomialError
-        throw(result)
+        return result
     end
     MTK.HomotopyContinuationProblem(sys, transformation, result, u0map, parammap; kwargs...)
 end

src/systems/nonlinear/homotopy_continuation.jl

@@ -48,6 +48,27 @@ function HomotopyContinuationProblem(::AbstractSystem, _u0, _p; kwargs...)
     error("HomotopyContinuation.jl is required to create and solve `HomotopyContinuationProblem`s. Please run `Pkg.add(\"HomotopyContinuation\")` to continue.")
 end
 
+"""
+    $(TYPEDSIGNATURES)
+
+Utility function for `safe_HomotopyContinuationProblem`, implemented in the extension.
+"""
+function _safe_HomotopyContinuationProblem end
+
+"""
+    $(TYPEDSIGNATURES)
+
+Return a `HomotopyContinuationProblem` if the extension is loaded and the system is
+polynomial. If the extension is not loaded, return `nothing`. If the system is not
+polynomial, return the appropriate `NotPolynomialError`.
+"""
+function safe_HomotopyContinuationProblem(sys::NonlinearSystem, args...; kwargs...)
+    if Base.get_extension(ModelingToolkit, :MTKHomotopyContinuationExt) === nothing
+        return nothing
+    end
+    return _safe_HomotopyContinuationProblem(sys, args...; kwargs...)
+end
+
 SymbolicIndexingInterface.symbolic_container(p::HomotopyContinuationProblem) = p.sys
 SymbolicIndexingInterface.state_values(p::HomotopyContinuationProblem) = p.u0
 function SymbolicIndexingInterface.set_state!(p::HomotopyContinuationProblem, args...)

test/extensions/homotopy_continuation.jl

@@ -1,6 +1,19 @@
 using ModelingToolkit, NonlinearSolve, SymbolicIndexingInterface
+import ModelingToolkit as MTK
 using LinearAlgebra
 using Test
+
+@testset "Safe HCProblem" begin
+    @variables x y z
+    eqs = [0 ~ x^2 + y^2 + 2x * y
+           0 ~ x^2 + 4x + 4
+           0 ~ y * z + 4x^2]
+    @mtkbuild sys = NonlinearSystem(eqs)
+    prob = MTK.safe_HomotopyContinuationProblem(sys, [x => 1.0, y => 1.0, z => 1.0], [])
+    @test prob === nothing
+end
+
+
 import HomotopyContinuation
 
 @testset "No parameters" begin
@@ -78,30 +91,37 @@ end
     @test_throws ["Cannot convert", "Unable", "symbolically solve",
         "Exponent", "not an integer", "not a polynomial"] HomotopyContinuationProblem(
         sys, [])
+    @test MTK.safe_HomotopyContinuationProblem(sys, []) isa MTK.NotPolynomialError
     @mtkbuild sys = NonlinearSystem([x^x - x ~ 0])
     @test_throws ["Cannot convert", "Unable", "symbolically solve",
         "Exponent", "unknowns", "not a polynomial"] HomotopyContinuationProblem(
         sys, [])
+    @test MTK.safe_HomotopyContinuationProblem(sys, []) isa MTK.NotPolynomialError
     @mtkbuild sys = NonlinearSystem([((x^2) / sin(x))^2 + x ~ 0])
     @test_throws ["Cannot convert", "both polynomial", "non-polynomial",
         "recognized", "sin", "not a polynomial"] HomotopyContinuationProblem(
         sys, [])
+    @test MTK.safe_HomotopyContinuationProblem(sys, []) isa MTK.NotPolynomialError
 
     @variables y = 2.0
     @mtkbuild sys = NonlinearSystem([x^2 + y^2 + 2 ~ 0, y ~ sin(x)])
     @test_throws ["Cannot convert", "recognized", "sin", "not a polynomial"] HomotopyContinuationProblem(
         sys, [])
+    @test MTK.safe_HomotopyContinuationProblem(sys, []) isa MTK.NotPolynomialError
 
     @mtkbuild sys = NonlinearSystem([x^2 + y^2 - 2 ~ 0, sin(x + y) ~ 0])
     @test_throws ["Cannot convert", "function of multiple unknowns"] HomotopyContinuationProblem(
         sys, [])
+    @test MTK.safe_HomotopyContinuationProblem(sys, []) isa MTK.NotPolynomialError
 
     @mtkbuild sys = NonlinearSystem([sin(x)^2 + 1 ~ 0, cos(y) - cos(x) - 1 ~ 0])
     @test_throws ["Cannot convert", "multiple non-polynomial terms", "same unknown"] HomotopyContinuationProblem(
         sys, [])
+    @test MTK.safe_HomotopyContinuationProblem(sys, []) isa MTK.NotPolynomialError
 
     @mtkbuild sys = NonlinearSystem([sin(x^2)^2 + sin(x^2) - 1 ~ 0])
     @test_throws ["import Nemo"] HomotopyContinuationProblem(sys, [])
+    @test MTK.safe_HomotopyContinuationProblem(sys, []) isa MTK.NotPolynomialError
 end
 
 import Nemo