Fixed bug in presolve algorithm when the partial solution to fix cont…

…ains deactivated variables

docs/src/man/presolve.md

@@ -2,7 +2,7 @@
 
 >### Ruslan Sadykov, 20/10/2023, revised 16/01/2024
 
-The document presents the presolve algorithm implemented in _Coluna_. Is it particularly important to run the this algorithm after augmenting the partial solution in rounding and diving heuristics. 
+The document presents the presolve algorithm implemented in _Coluna_. It is particularly important to run this algorithm after augmenting the partial solution in rounding and diving heuristics. 
 
 ## 1. Augmenting the partial solution
 

src/Algorithm/presolve/interface.jl

@@ -517,6 +517,7 @@ function run!(
     local_restr_partial_sol = propagate_partial_sol_into_master!(
         reform, presolve_reform, input.partial_sol_to_fix, algo.verbose
     )
+    isnothing(local_restr_partial_sol) && return PresolveOutput(false)
 
     # Perform several rounds of presolve.
     for i in 1:3

src/Algorithm/presolve/propagation.jl

@@ -55,6 +55,13 @@ function get_partial_sol(
 )
     new_partial_sol = zeros(Float64, length(presolve_form.col_to_var))
     for (var_id, value) in partial_sol_to_fix
+        if !haskey(presolve_form.var_to_col, var_id) 
+            if iszero(value)
+                continue
+            else 
+                return nothing
+            end
+        end
         new_partial_sol[presolve_form.var_to_col[var_id]] += value
     end
     return new_partial_sol
@@ -251,6 +258,7 @@ function propagate_partial_sol_into_master!(
     # Create the local partial solution from the restricted master presolve representation.
     # This local partial solution must then be "fixed" & propagated.
     local_restr_partial_sol = get_partial_sol(presolve_restricted_master, partial_sol_to_fix)
+    isnothing(local_restr_partial_sol) && return nothing
 
     # Compute the rhs of all constraints.
     # Non-robust and convexity constraints rhs can only be computed using this representation.

test/unit/Presolve/presolve.jl

@@ -601,7 +601,17 @@ function test_presolve_full()
           | MC_1 = [x_1 = 1.0 ] = 1.0
           └ value = 1.00 
           """    
+
+
+    input = Coluna.Algorithm.PresolveInput(Dict(master_vars["MC_1"] => 0.0))        
+    output = Coluna.Algorithm.run!(presolve_algorithm, env, reform, input)
+    @test output.feasible == true    
+
+    input = Coluna.Algorithm.PresolveInput(Dict(master_vars["MC_1"] => 1.0))        
+    output = Coluna.Algorithm.run!(presolve_algorithm, env, reform, input)
+    @test output.feasible == false    
+
     return nothing
 end
 
-register!(unit_tests, "presolve_reformulation", test_presolve_full)
+register!(unit_tests, "presolve_reformulation", test_presolve_full, f = true)