Adds balancing code and tests

src/compound.jl

@@ -87,3 +87,176 @@ component_coefficients(s::Num) = component_coefficients(MT.value(s))
 function component_coefficients(s)
     return [c => co for (c, co) in zip(components(s), coefficients(s))]
 end
+
+
+### Balancing Code
+
+function create_matrix(reaction::Catalyst.Reaction)
+    compounds = [reaction.substrates; reaction.products]
+    atoms = []
+    n_atoms = 0
+    A = zeros(Int, 0, length(compounds))
+
+    for (j, compound) in enumerate(compounds)
+        if iscompound(compound)
+            pairs = component_coefficients(compound)
+            if pairs == Nothing 
+                continue
+            end
+        else 
+            pairs = [(compound, 1)]
+        end
+
+        for pair in pairs
+            atom, coeff = pair
+            i = findfirst(x -> isequal(x, atom), atoms)
+            if i === nothing  
+                push!(atoms, atom)
+                n_atoms += 1
+                A = [A; zeros(Int, 1, length(compounds))]
+                i = n_atoms
+            end
+            coeff = any(map(p -> isequal(p, compounds[j]), reaction.products)) ? -coeff : coeff
+            A[i, j] = coeff
+        end
+    end
+        # Append a row with last element as 1 
+        new_row = zeros(Int, 1, size(A, 2))
+        new_row[end] = 1
+        A = vcat(A, new_row)
+    return A
+end
+
+function get_stoich(reaction::Reaction)
+    # Create the matrix A using create_matrix function.
+    A = create_matrix(reaction)
+
+    # Create the vector b. The last element is 1 and others are 0.
+    B = zeros(Int64, size(A,1))
+    B[end] = 1
+
+    # Concatenate B to A to form an augmented matrix   
+    AB = [A B]
+
+    # Apply the Bareiss algorithm
+    ModelingToolkit.bareiss!(AB)
+
+    # Extract the transformed A and B
+    A_transformed = AB[:, 1:end-1]
+    B_transformed = AB[:, end]
+
+    # Convert A_transformed to rational numbers
+    A_transformed_rational = Rational.(A_transformed)
+
+    # Convert B_transformed to rational numbers
+    B_transformed_rational = Rational.(B_transformed)
+
+    # Perform the division
+    X = A_transformed_rational \ B_transformed_rational
+
+    # Get the denominators of the rational numbers in X
+    denominators = denominator.(X)
+
+    # Compute the LCM of the denominators
+    lcm_value = reduce(lcm, denominators)
+
+    # Multiply each element in X by the LCM of the denominators
+    X_multiplied = X .* lcm_value
+
+    # Convert the rational numbers to integers
+    X_integers = numerator.(X_multiplied)
+
+    return X_integers
+end
+
+function balance(reaction::Reaction)
+    # Calculate the stoichiometric coefficients for the balanced reaction.
+    stoichiometries = get_stoich(reaction)
+
+    # Divide the stoichiometry vector into substrate and product stoichiometries.
+    substoich = stoichiometries[1:length(reaction.substrates)]
+    prodstoich = stoichiometries[(length(reaction.substrates)) + 1:end]
+
+    # Create a new reaction with the balanced stoichiometries
+    balanced_reaction = Reaction(reaction.rate, reaction.substrates, reaction.products, substoich, prodstoich)
+
+    # Return the balanced reaction
+    return balanced_reaction
+end
+
+# function get_stoich(reaction::Reaction) ## Gaussian Elimination
+#     # Create the matrix A using create_matrix function.
+#     A = create_matrix(reaction)
+
+#     # Create the vector b. The last element is 1 and others are 0.
+#     B = zeros(Int64, size(A,1))
+#     B[end] = 1
+
+#     # Convert A and B to sparse matrices
+#     A = sparse(A)
+
+#     # Apply the LU factorization (Gaussian elimination)
+#     lu_f = lu(A)
+
+#     # Convert B to a dense vector
+#     B_dense = Vector(B)
+
+#     # Solve for X using the LU factorization
+#     X = lu_f \ B_dense
+
+#     # Get the smallest positive value in X
+#     smallest_value = minimum(X[X .> 0])  
+
+#     # Normalize X to be integers
+#     X_normalized = round.(Int64, X / smallest_value)
+
+#     return X_normalized
+# end
+
+# function get_stoich(reaction::Reaction) ##Bareiss Algorithm (Does not avoid floating points)
+#     # Create the matrix A using create_matrix function.
+#     A = create_matrix(reaction)
+
+#     # Create the vector b. The last element is 1 and others are 0.
+#     B = zeros(Int64, size(A,1))
+#     B[end] = 1
+
+#     # Concatenate B to A to form an augmented matrix   
+#     AB = [A B]
+
+#     # Apply the Bareiss algorithm
+#     ModelingToolkit.bareiss!(AB)
+
+#     # Extract the transformed A and B
+#     A_transformed = AB[:, 1:end-1]
+#     B_transformed = AB[:, end]
+
+#     # Solve for X using back substitution
+#     X = A_transformed \ B_transformed
+
+#     # Get the smallest positive value in X
+#     smallest_value = minimum(X[X .> 0])  
+
+#     # Normalize X to be integers
+#     X_normalized = round.(Int64, X / smallest_value)
+
+#     return X_normalized
+# end
+
+# @variables t
+# @parameters k
+# @species C(t) H(t) O(t) 
+# @compound O2(t) 2O
+# @compound CO2(t) 1C 2O
+# @compound H2O(t) 2H 1O
+# @compound C6H12O6(t) 6C 12H 6O
+# rx = Reaction(k,[CO2,H2O],[C6H12O6,O2])
+
+# using LinearAlgebra
+# using SparseArrays
+# using SuiteSparse.UMFPACK
+
+# gcd_value = gcd(X...)
+# X_scaled = X ./ gcd_value
+
+# X = [1,1,0.2,1]

test/miscellaneous_tests/compound_macro.jl

@@ -96,3 +96,39 @@ end
 #     @test isequal(coefficients(C10H12)[1], 2)
 # end
 
+#Check that balancing works.
+let 
+    @variables t
+    @parameters k
+    @species H(t) O(t)
+    @compound H2(t) 2H
+    @compound O2(t) 2O
+    @compound H2O(t) 2H 1O
+
+    rx = Reaction(k,[H2,O2],[H2O])
+
+    @test isequal(create_matrix(rx),[2 0 -2; 0 2 -1; 0 0 1;])
+    @test isequal(get_stoich(rx),[2, 1, 2])
+
+    balanced_rx = Reaction(k,[H2,O2],[H2O],[2,1],[2])
+    @test isequal(balanced_rx, balance(rx))
+
+end
+
+let 
+    @variables t
+    @parameters k
+    @species C(t) H(t) O(t) 
+    @compound O2(t) 2O
+    @compound CO2(t) 1C 2O
+    @compound H2O(t) 2H 1O
+    @compound C6H12O6(t) 6C 12H 6O
+
+    rx = Reaction(k,[CO2,H2O],[C6H12O6,O2])
+
+    @test isequal(create_matrix(rx),[ 1 0 -6 0; 2 1 -6 -2; 0 2 -12 0; 0 0 0 1;])
+    @test isequal(get_stoich(rx),[6, 6, 1, 6])
+
+    balanced_rx = Reaction(k,[CO2,H2O],[C6H12O6,O2],[6, 6], [1,6])
+    @test isequal(balanced_rx, balance(rx))
+end