Merge pull request #1345 from n0rbed/tests

Tests for solve_interms_ofvar and bug fixes

Author: ChrisRackauckas

src/solver/ia_rules.jl

@@ -50,7 +50,7 @@ function solve_interms_ofvar(eq, s; dropmultiplicity=true, warns=true)
     coeffs, constant = polynomial_coeffs(eq, [s])
     eqs = wrap.(collect(values(coeffs)))
 
-    solve_multivar(eqs, vars, dropmultiplicity=dropmultiplicity, warns=warns)
+    symbolic_solve(eqs, vars, dropmultiplicity=dropmultiplicity, warns=warns)
 end
 
 # an attempt at using ia_solve recursively.

src/solver/main.jl

@@ -286,7 +286,7 @@ function solve_univar(expression, x; dropmultiplicity=true)
     factors_subbed = map(factor -> ssubs(factor, subs), factors)
     arr_roots = []
 
-    if degree < 5 && length(factors) == 1
+    if degree < 5 && isequal(factors_subbed[1], wrap(expression))
         arr_roots = get_roots(expression, x)
 
         # multiplicities (repeated roots)
@@ -296,10 +296,8 @@ function solve_univar(expression, x; dropmultiplicity=true)
                 append!(arr_roots, og_arr_roots)
             end
         end
-    end
-
-    if length(factors) != 1
-        for i in eachindex(factors_subbed)
+    elseif length(factors) > 1 || (length(factors) == 1 && !isequal(factors_subbed[1], wrap(expression)))
+        for i in eachindex(factors_subbed) 
             if !any(isequal(x, var) for var in get_variables(factors[i]))
                 continue
             end

test/solver.jl

@@ -54,7 +54,24 @@ function check_approx(arr1, arr2)
     return true
 end
 
-@variables x y z a b c d e
+@variables x y z a b c d e s
+
+@testset "Solving in terms of a constant var" begin
+    eq = ((s^2 + 1)/(s^2 + 2*s + 1)) - ((s^2 + a)/(b*c*s^2 + (b+c)*s + d))
+    calcd_roots = sort_arr(Symbolics.solve_interms_ofvar(eq, s), [a,b,c,d])
+    known_roots = sort_arr([Dict(a=>1, b=>1, c=>1, d=>1)], [a,b,c,d])
+    @test check_approx(calcd_roots, known_roots)   
+
+    eq = (a+b)*s^2 - 2s^2 + 2*b*s - 3*s
+    calcd_roots = sort_arr(Symbolics.solve_interms_ofvar(eq, s), [a,b])
+    known_roots = sort_arr([Dict(a=>1/2, b=>3/2)], [a,b])
+    @test check_approx(calcd_roots, known_roots)   
+
+    eq = (a*x^2+b)*s^2 - 2s^2 + 2*b*s - 3*s + 2(x^2)*(s^3) + 10*s^3
+    calcd_roots = sort_arr(Symbolics.solve_interms_ofvar(eq, s), [a,b])
+    known_roots = sort_arr([Dict(a=>-1/10, b=>3/2, x=>-im*sqrt(5)), Dict(a=>-1/10, b=>3/2, x=>im*sqrt(5))], [a,b,x])
+    @test check_approx(calcd_roots, known_roots)   
+end
 
 @testset "Invalid input" begin
     @test_throws AssertionError symbolic_solve(x, x^2)