Make global variables constant (#286)

* Make global variables constant

* Add test for `clearmemory`

Author: ericphanson

src/Convex.jl

@@ -84,9 +84,10 @@ include("utilities/broadcast.jl")
 
 #Temporary workaround for memory leak (https://github.com/JuliaOpt/Convex.jl/issues/83)
 function clearmemory()
-    global id_to_variables = Dict{UInt64, Variable}()
-    global var_to_ranges = Dict{UInt64, Tuple{Int, Int}}()
-    global conic_constr_to_constr = Dict{ConicConstr, Constraint}()
+    global id_to_variables
+    empty!(id_to_variables)
+    global conic_constr_to_constr 
+    empty!(conic_constr_to_constr)
     GC.gc()
 end
 

src/constraints/constraints.jl

@@ -2,7 +2,7 @@ import Base.==, Base.<=, Base.>=, Base.<, Base.>
 export EqConstraint, LtConstraint, GtConstraint
 export ==, <=, >=
 
-conic_constr_to_constr = Dict{ConicConstr, Constraint}()
+const conic_constr_to_constr = Dict{ConicConstr, Constraint}()
 
 ### Linear equality constraint
 mutable struct EqConstraint <: Constraint

src/variable.jl

@@ -57,7 +57,7 @@ end
 # the expression tree will only utilize variable ids during construction
 # full information of the variables will be needed during stuffing
 # and after solving to populate the variables with values
-id_to_variables = Dict{UInt64, Variable}()
+const id_to_variables = Dict{UInt64, Variable}()
 
 function vexity(x::Variable)
     return x.vexity

test/test_utilities.jl

@@ -1,5 +1,22 @@
 @testset "Utilities" begin
 
+    @testset "clearmemory" begin
+        # solve a problem to populate globals
+        x = Variable()
+        p = minimize(-x, [x <= 0])
+        @test vexity(p) == AffineVexity()
+        solve!(p, solvers[1])
+
+        @test !isempty(Convex.id_to_variables)
+        @test !isempty(Convex.conic_constr_to_constr)
+
+        Convex.clearmemory()
+
+        # check they are cleared
+        @test isempty(Convex.id_to_variables)
+        @test isempty(Convex.conic_constr_to_constr)
+    end
+
     @testset "ConicObj" for T = [UInt32, UInt64]
         c = ConicObj()
         z = zero(T)