From c5585a196e267a9828393d915d913ad147e055c3 Mon Sep 17 00:00:00 2001
From: Zengjian Hu <zengjian.hu@relational.ai>
Date: Thu, 21 Sep 2023 17:26:55 -0700
Subject: [PATCH 01/13] implement solve_all

---
 src/optimize.jl                   |  75 ++++++++++++++------
 test/examples/nqueens_solveall.jl | 114 ++++++++++++++++++++++++++++++
 2 files changed, 167 insertions(+), 22 deletions(-)
 create mode 100644 test/examples/nqueens_solveall.jl

diff --git a/src/optimize.jl b/src/optimize.jl
index 16f827e..b0f564f 100644
--- a/src/optimize.jl
+++ b/src/optimize.jl
@@ -25,23 +25,25 @@ mutable struct Optimizer{T} <: MOI.AbstractOptimizer
     inner::Model{T}
     solver_status::String
     primal_objective::T
-    primal_solution::Dict{MOI.VariableIndex,T}
+    primal_solutions::Vector{Dict{MOI.VariableIndex, T}} # all solutions
     options::Dict{String,Any}
+    n_sols::Int # Max number of solutions
     time_limit_sec::Union{Nothing,Float64}
     solve_time_sec::Float64
     function Optimizer{T}(solver::String) where {T}
         if solver == "chuffed"
             solver = Chuffed()
         end
-        primal_solution = Dict{MOI.VariableIndex,T}()
-        options = Dict{String,Any}("model_filename" => "")
+        primal_solutions = Vector{Dict{MOI.VariableIndex,T}}()
+        options = Dict{String,Any}("model_filename" => "", "all_solutions" => false)
         return new(
             solver,
             Model{T}(),
             "",
             zero(T),
-            primal_solution,
+            primal_solutions,
             options,
+            1,
             nothing,
             NaN,
         )
@@ -77,13 +79,23 @@ function _run_minizinc(dest::Optimizer)
     end
     output = joinpath(dir, "model.ozn")
     _stdout = joinpath(dir, "_stdout.txt")
+
+    dest.n_sols = if dest.options["all_solutions"]
+        get(dest.options, "num_solutions", (Int)(typemax(Int32)))
+    else
+        1 # only one solution if all_solutions is false
+    end
+
     _minizinc_exe() do exe
-        cmd = if dest.time_limit_sec !== nothing
+        cmd = `$(exe) --solver $(dest.solver) --output-objective -o $(output) $(filename)`
+
+        if dest.time_limit_sec !== nothing 
             limit = round(Int, 1_000 * dest.time_limit_sec::Float64)
-            `$(exe) --solver $(dest.solver) --output-objective --time-limit $limit -o $(output) $(filename)`
-        else
-            `$(exe) --solver $(dest.solver) --output-objective -o $(output) $(filename)`
+            cmd = `$cmd --time-limit $limit` 
         end
+        if dest.n_sols > 1 # only add --num-solutions if n_sols > 1
+            cmd = `$cmd --num-solutions $(dest.n_sols)`
+        end 
         return run(pipeline(cmd, stdout = _stdout))
     end
     if isfile(output)
@@ -115,7 +127,7 @@ function MOI.empty!(model::Optimizer{T}) where {T}
     empty!(model.inner.ext)
     model.solver_status = ""
     model.primal_objective = zero(T)
-    empty!(model.primal_solution)
+    empty!(model.primal_solutions)
     model.solve_time_sec = NaN
     return
 end
@@ -172,8 +184,10 @@ end
 function MOI.optimize!(dest::Optimizer{T}, src::MOI.ModelLike) where {T}
     time_start = time()
     MOI.empty!(dest.inner)
-    empty!(dest.primal_solution)
+    empty!(dest.primal_solutions)
     index_map = MOI.copy_to(dest.inner, src)
+
+
     ret = _run_minizinc(dest)
     if !isempty(ret)
         m_stat = match(r"=====(.+)=====", ret)
@@ -186,15 +200,19 @@ function MOI.optimize!(dest::Optimizer{T}, src::MOI.ModelLike) where {T}
                 MOI.get(dest.inner, MOI.VariableName(), x) => x for
                 x in MOI.get(src, MOI.ListOfVariableIndices())
             )
+
+            primal_solution = Dict{MOI.VariableIndex, T}()
             for line in split(ret, "\n")
                 m_var = match(r"(.+) \= (.+)\;", line)
                 if m_var === nothing
+                    isempty(primal_solution) || push!(dest.primal_solutions, primal_solution) # add solution
+                    primal_solution = Dict{MOI.VariableIndex, T}()
                     continue
                 elseif m_var[1] == "_objective"
                     dest.primal_objective = _parse_result(T, m_var[2])
                 else
                     x = variable_map[m_var[1]]
-                    dest.primal_solution[x] = _parse_result(T, m_var[2])
+                    primal_solution[x] = _parse_result(T, m_var[2])
                 end
             end
         end
@@ -209,7 +227,7 @@ end
 
 function _has_solution(model::Optimizer)
     return model.solver_status == "SATISFIABLE" &&
-           !isempty(model.primal_solution)
+           !isempty(model.primal_solutions)
 end
 
 MOI.get(model::Optimizer, ::MOI.RawStatusString) = model.solver_status
@@ -218,7 +236,11 @@ function MOI.get(model::Optimizer, ::MOI.TerminationStatus)
     if model.solver_status == "UNSATISFIABLE"
         return MOI.INFEASIBLE
     elseif _has_solution(model)
-        return MOI.OPTIMAL
+        if model.n_sols > 1 && length(model.primal_solutions) >= model.n_sols
+            return MOI.SOLUTION_LIMIT
+        else 
+            return MOI.OPTIMAL
+        end
     else
         return MOI.OTHER_ERROR
     end
@@ -234,23 +256,32 @@ end
 
 MOI.get(::Optimizer, ::MOI.DualStatus) = MOI.NO_SOLUTION
 
-function MOI.get(model::Optimizer, ::MOI.ResultCount)
-    return _has_solution(model) ? 1 : 0
-end
+MOI.get(model::Optimizer, ::MOI.ResultCount) = length(model.primal_solutions)
 
 function MOI.get(model::Optimizer, attr::MOI.ObjectiveValue)
     MOI.check_result_index_bounds(model, attr)
     return model.primal_objective
 end
 
-function MOI.get(
-    model::Optimizer,
-    attr::MOI.VariablePrimal,
-    x::MOI.VariableIndex,
-)
+function MOI.get(model::Optimizer, attr::MOI.VariablePrimal, x::MOI.VariableIndex)
     MOI.check_result_index_bounds(model, attr)
     MOI.throw_if_not_valid(model, x)
-    return model.primal_solution[x]
+    if attr.result_index > length(model.primal_solutions)
+        throw(ErrorException("Result index out of bounds."))
+    end
+    return model.primal_solutions[attr.result_index][x]
 end
 
 MOI.get(model::Optimizer, ::MOI.SolveTimeSec) = model.solve_time_sec
+
+function MOI.set(model::Optimizer, attr::MOI.RawOptimizerAttribute, value)
+    if attr.name == "all_solutions"
+        value === true ||
+            value === false ||
+            throw(ErrorException("Invalid value $value for $(attr.name)."))
+    elseif attr.name == "num_solutions"
+        (value isa Int && value >= 1) ||
+            throw(ErrorException("Invalid value $value for $(attr.name)."))
+    end
+    model.options[attr.name] = value
+end
\ No newline at end of file
diff --git a/test/examples/nqueens_solveall.jl b/test/examples/nqueens_solveall.jl
new file mode 100644
index 0000000..e1a83c6
--- /dev/null
+++ b/test/examples/nqueens_solveall.jl
@@ -0,0 +1,114 @@
+# Copyright (c) 2022 MiniZinc.jl contributors
+#
+# Use of this source code is governed by an MIT-style license that can be found
+# in the LICENSE.md file or at https://opensource.org/licenses/MIT.
+
+# N-queens example
+# based on MiniZinc example nqueens.mzn
+# queen in column i is in row q[i]
+
+n = 8
+
+function init_model()
+    model = MOI.instantiate(
+        () -> MiniZinc.Optimizer{Int}("chuffed");
+        with_cache_type = Int,
+        with_bridge_type = Int,
+    )
+    MOI.set(model, MOI.RawOptimizerAttribute("model_filename"), "test.mzn")
+    q = MOI.add_variables(model, n)
+    MOI.add_constraint.(model, q, MOI.Interval(1, n))
+    MOI.add_constraint(model, MOI.VectorOfVariables(q), MOI.AllDifferent(n))
+    for op in (+, -)
+        f = MOI.Utilities.vectorize([op(q[i], i) for i in eachindex(q)])
+        MOI.add_constraint(model, f, MOI.AllDifferent(n))
+    end
+
+    return model, q
+end
+
+function check_result(
+    model,
+    q,
+    actual_count = 92,
+    termination_status = MOI.OPTIMAL,
+)
+    @test MOI.get(model, MOI.TerminationStatus()) === termination_status
+    res_count = MOI.get(model, MOI.ResultCount())
+    @test res_count == actual_count
+
+    for i in 1:res_count
+        q_sol = MOI.get(model, MOI.VariablePrimal(i), q)
+        @test allunique(q_sol)
+        @test allunique(q_sol .+ (1:n))
+        @test allunique(q_sol .- (1:n))
+    end
+    @test MOI.get(model, MOI.SolveTimeSec()) < 4.0
+    return rm("test.mzn")
+end
+
+function run_nqueens(option)
+    if option == "solve_all1" # solve all
+        @info "test solve_all with num_solution not set"
+        model, q = init_model()
+        MOI.set(model, MOI.RawOptimizerAttribute("all_solutions"), true)
+        MOI.optimize!(model)
+        check_result(model, q)
+    elseif option == "solve_all2" # solve all with limit > 92
+        @info "test solve_all with limit > 92"
+        model, q = init_model()
+        MOI.set(model, MOI.RawOptimizerAttribute("all_solutions"), true)
+        MOI.set(model, MOI.RawOptimizerAttribute("num_solutions"), 100)
+        MOI.optimize!(model)
+        check_result(model, q)
+    elseif option == "solve_all3" # solve all with limit = 25 
+        @info "test solve_all with limit = 25"
+        model, q = init_model()
+        MOI.set(model, MOI.RawOptimizerAttribute("all_solutions"), true)
+        MOI.set(model, MOI.RawOptimizerAttribute("num_solutions"), 25)
+        MOI.optimize!(model)
+        check_result(model, q, 25, MOI.SOLUTION_LIMIT)
+    elseif option == "solve_one" # solve one
+        @info "test solve_one"
+        model, q = init_model()
+        MOI.set(model, MOI.RawOptimizerAttribute("all_solutions"), false)
+        MOI.set(model, MOI.RawOptimizerAttribute("num_solutions"), 100)
+        MOI.optimize!(model)
+        check_result(model, q, 1)
+    elseif option == "throw"
+        @info "test throw"
+        model, q = init_model()
+        @test_throws ErrorException MOI.set(
+            model,
+            MOI.RawOptimizerAttribute("all_solutions"),
+            1,
+        )
+        @test_throws ErrorException MOI.set(
+            model,
+            MOI.RawOptimizerAttribute("num_solutions"),
+            -1,
+        )
+        @test_throws ErrorException MOI.set(
+            model,
+            MOI.RawOptimizerAttribute("num_solutions"),
+            0,
+        )
+        @test_throws ErrorException MOI.set(
+            model,
+            MOI.RawOptimizerAttribute("num_solutions"),
+            1.1,
+        )
+        @test_throws ErrorException MOI.set(
+            model,
+            MOI.RawOptimizerAttribute("num_solutions"),
+            "two",
+        )
+    end
+    return
+end
+
+test_nqueens1() = run_nqueens("solve_all1")
+test_nqueens2() = run_nqueens("solve_all2")
+test_nqueens3() = run_nqueens("solve_all3")
+test_nqueens4() = run_nqueens("solve_one")
+test_nqueens5() = run_nqueens("throw")

From d3c69e95699c6af051c93f85d062354646b515ee Mon Sep 17 00:00:00 2001
From: Zengjian Hu <zengjian.hu@relational.ai>
Date: Thu, 21 Sep 2023 17:32:13 -0700
Subject: [PATCH 02/13] format

---
 src/optimize.jl | 41 +++++++++++++++++++++++------------------
 1 file changed, 23 insertions(+), 18 deletions(-)

diff --git a/src/optimize.jl b/src/optimize.jl
index b0f564f..25bac9f 100644
--- a/src/optimize.jl
+++ b/src/optimize.jl
@@ -25,9 +25,9 @@ mutable struct Optimizer{T} <: MOI.AbstractOptimizer
     inner::Model{T}
     solver_status::String
     primal_objective::T
-    primal_solutions::Vector{Dict{MOI.VariableIndex, T}} # all solutions
+    primal_solutions::Vector{Dict{MOI.VariableIndex,T}} # all solutions
     options::Dict{String,Any}
-    n_sols::Int # Max number of solutions
+    ub_sols::Int # Max number of solutions
     time_limit_sec::Union{Nothing,Float64}
     solve_time_sec::Float64
     function Optimizer{T}(solver::String) where {T}
@@ -35,7 +35,8 @@ mutable struct Optimizer{T} <: MOI.AbstractOptimizer
             solver = Chuffed()
         end
         primal_solutions = Vector{Dict{MOI.VariableIndex,T}}()
-        options = Dict{String,Any}("model_filename" => "", "all_solutions" => false)
+        options =
+            Dict{String,Any}("model_filename" => "", "all_solutions" => false)
         return new(
             solver,
             Model{T}(),
@@ -80,7 +81,7 @@ function _run_minizinc(dest::Optimizer)
     output = joinpath(dir, "model.ozn")
     _stdout = joinpath(dir, "_stdout.txt")
 
-    dest.n_sols = if dest.options["all_solutions"]
+    dest.ub_sols = if dest.options["all_solutions"]
         get(dest.options, "num_solutions", (Int)(typemax(Int32)))
     else
         1 # only one solution if all_solutions is false
@@ -89,13 +90,13 @@ function _run_minizinc(dest::Optimizer)
     _minizinc_exe() do exe
         cmd = `$(exe) --solver $(dest.solver) --output-objective -o $(output) $(filename)`
 
-        if dest.time_limit_sec !== nothing 
+        if dest.time_limit_sec !== nothing
             limit = round(Int, 1_000 * dest.time_limit_sec::Float64)
-            cmd = `$cmd --time-limit $limit` 
+            cmd = `$cmd --time-limit $limit`
+        end
+        if dest.ub_sols > 1 # only add --num-solutions if ub_sols > 1
+            cmd = `$cmd --num-solutions $(dest.ub_sols)`
         end
-        if dest.n_sols > 1 # only add --num-solutions if n_sols > 1
-            cmd = `$cmd --num-solutions $(dest.n_sols)`
-        end 
         return run(pipeline(cmd, stdout = _stdout))
     end
     if isfile(output)
@@ -187,7 +188,6 @@ function MOI.optimize!(dest::Optimizer{T}, src::MOI.ModelLike) where {T}
     empty!(dest.primal_solutions)
     index_map = MOI.copy_to(dest.inner, src)
 
-
     ret = _run_minizinc(dest)
     if !isempty(ret)
         m_stat = match(r"=====(.+)=====", ret)
@@ -201,12 +201,13 @@ function MOI.optimize!(dest::Optimizer{T}, src::MOI.ModelLike) where {T}
                 x in MOI.get(src, MOI.ListOfVariableIndices())
             )
 
-            primal_solution = Dict{MOI.VariableIndex, T}()
+            primal_solution = Dict{MOI.VariableIndex,T}()
             for line in split(ret, "\n")
                 m_var = match(r"(.+) \= (.+)\;", line)
                 if m_var === nothing
-                    isempty(primal_solution) || push!(dest.primal_solutions, primal_solution) # add solution
-                    primal_solution = Dict{MOI.VariableIndex, T}()
+                    isempty(primal_solution) ||
+                        push!(dest.primal_solutions, primal_solution) # add solution
+                    primal_solution = Dict{MOI.VariableIndex,T}()
                     continue
                 elseif m_var[1] == "_objective"
                     dest.primal_objective = _parse_result(T, m_var[2])
@@ -236,9 +237,9 @@ function MOI.get(model::Optimizer, ::MOI.TerminationStatus)
     if model.solver_status == "UNSATISFIABLE"
         return MOI.INFEASIBLE
     elseif _has_solution(model)
-        if model.n_sols > 1 && length(model.primal_solutions) >= model.n_sols
+        if model.ub_sols > 1 && length(model.primal_solutions) >= model.ub_sols
             return MOI.SOLUTION_LIMIT
-        else 
+        else
             return MOI.OPTIMAL
         end
     else
@@ -263,7 +264,11 @@ function MOI.get(model::Optimizer, attr::MOI.ObjectiveValue)
     return model.primal_objective
 end
 
-function MOI.get(model::Optimizer, attr::MOI.VariablePrimal, x::MOI.VariableIndex)
+function MOI.get(
+    model::Optimizer,
+    attr::MOI.VariablePrimal,
+    x::MOI.VariableIndex,
+)
     MOI.check_result_index_bounds(model, attr)
     MOI.throw_if_not_valid(model, x)
     if attr.result_index > length(model.primal_solutions)
@@ -283,5 +288,5 @@ function MOI.set(model::Optimizer, attr::MOI.RawOptimizerAttribute, value)
         (value isa Int && value >= 1) ||
             throw(ErrorException("Invalid value $value for $(attr.name)."))
     end
-    model.options[attr.name] = value
-end
\ No newline at end of file
+    return model.options[attr.name] = value
+end

From 32902580799b8461fd1cf93321f62495da2eeff7 Mon Sep 17 00:00:00 2001
From: Zengjian Hu <zengjian.hu@relational.ai>
Date: Thu, 21 Sep 2023 19:44:09 -0700
Subject: [PATCH 03/13] address Oscar's comments

---
 src/optimize.jl                   |  36 +++------
 test/examples/nqueens_solveall.jl | 126 ++++++++++++++----------------
 2 files changed, 70 insertions(+), 92 deletions(-)

diff --git a/src/optimize.jl b/src/optimize.jl
index 25bac9f..e8b554c 100644
--- a/src/optimize.jl
+++ b/src/optimize.jl
@@ -27,16 +27,14 @@ mutable struct Optimizer{T} <: MOI.AbstractOptimizer
     primal_objective::T
     primal_solutions::Vector{Dict{MOI.VariableIndex,T}} # all solutions
     options::Dict{String,Any}
-    ub_sols::Int # Max number of solutions
     time_limit_sec::Union{Nothing,Float64}
     solve_time_sec::Float64
     function Optimizer{T}(solver::String) where {T}
         if solver == "chuffed"
             solver = Chuffed()
         end
-        primal_solutions = Vector{Dict{MOI.VariableIndex,T}}()
-        options =
-            Dict{String,Any}("model_filename" => "", "all_solutions" => false)
+        primal_solutions = Dict{MOI.VariableIndex,T}[]
+        options = Dict{String,Any}("model_filename" => "", "num_solutions" => 1)
         return new(
             solver,
             Model{T}(),
@@ -44,7 +42,6 @@ mutable struct Optimizer{T} <: MOI.AbstractOptimizer
             zero(T),
             primal_solutions,
             options,
-            1,
             nothing,
             NaN,
         )
@@ -81,12 +78,6 @@ function _run_minizinc(dest::Optimizer)
     output = joinpath(dir, "model.ozn")
     _stdout = joinpath(dir, "_stdout.txt")
 
-    dest.ub_sols = if dest.options["all_solutions"]
-        get(dest.options, "num_solutions", (Int)(typemax(Int32)))
-    else
-        1 # only one solution if all_solutions is false
-    end
-
     _minizinc_exe() do exe
         cmd = `$(exe) --solver $(dest.solver) --output-objective -o $(output) $(filename)`
 
@@ -94,8 +85,9 @@ function _run_minizinc(dest::Optimizer)
             limit = round(Int, 1_000 * dest.time_limit_sec::Float64)
             cmd = `$cmd --time-limit $limit`
         end
-        if dest.ub_sols > 1 # only add --num-solutions if ub_sols > 1
-            cmd = `$cmd --num-solutions $(dest.ub_sols)`
+
+        if dest.options["num_solutions"] > 1
+            cmd = `$cmd --num-solutions $(dest.options["num_solutions"])`
         end
         return run(pipeline(cmd, stdout = _stdout))
     end
@@ -141,11 +133,6 @@ function MOI.get(model::Optimizer, attr::MOI.RawOptimizerAttribute)
     return get(model.options, attr.name, nothing)
 end
 
-function MOI.set(model::Optimizer, attr::MOI.RawOptimizerAttribute, value)
-    model.options[attr.name] = value
-    return
-end
-
 MOI.supports(::Optimizer, ::MOI.TimeLimitSec) = true
 
 MOI.get(model::Optimizer, ::MOI.TimeLimitSec) = model.time_limit_sec
@@ -237,7 +224,8 @@ function MOI.get(model::Optimizer, ::MOI.TerminationStatus)
     if model.solver_status == "UNSATISFIABLE"
         return MOI.INFEASIBLE
     elseif _has_solution(model)
-        if model.ub_sols > 1 && length(model.primal_solutions) >= model.ub_sols
+        if model.options["num_solutions"] > 1 &&
+           length(model.primal_solutions) >= model.options["num_solutions"]
             return MOI.SOLUTION_LIMIT
         else
             return MOI.OPTIMAL
@@ -280,13 +268,11 @@ end
 MOI.get(model::Optimizer, ::MOI.SolveTimeSec) = model.solve_time_sec
 
 function MOI.set(model::Optimizer, attr::MOI.RawOptimizerAttribute, value)
-    if attr.name == "all_solutions"
-        value === true ||
-            value === false ||
-            throw(ErrorException("Invalid value $value for $(attr.name)."))
-    elseif attr.name == "num_solutions"
+    if attr.name == "num_solutions"
         (value isa Int && value >= 1) ||
             throw(ErrorException("Invalid value $value for $(attr.name)."))
     end
-    return model.options[attr.name] = value
+
+    model.options[attr.name] = value
+    return
 end
diff --git a/test/examples/nqueens_solveall.jl b/test/examples/nqueens_solveall.jl
index e1a83c6..013b301 100644
--- a/test/examples/nqueens_solveall.jl
+++ b/test/examples/nqueens_solveall.jl
@@ -3,13 +3,13 @@
 # Use of this source code is governed by an MIT-style license that can be found
 # in the LICENSE.md file or at https://opensource.org/licenses/MIT.
 
-# N-queens example
+# N-queens example - solve_all
 # based on MiniZinc example nqueens.mzn
 # queen in column i is in row q[i]
 
 n = 8
 
-function init_model()
+function _init_model()
     model = MOI.instantiate(
         () -> MiniZinc.Optimizer{Int}("chuffed");
         with_cache_type = Int,
@@ -27,7 +27,7 @@ function init_model()
     return model, q
 end
 
-function check_result(
+function _check_result(
     model,
     q,
     actual_count = 92,
@@ -43,72 +43,64 @@ function check_result(
         @test allunique(q_sol .+ (1:n))
         @test allunique(q_sol .- (1:n))
     end
+
     @test MOI.get(model, MOI.SolveTimeSec()) < 4.0
-    return rm("test.mzn")
+    rm("test.mzn")
+    return
 end
 
-function run_nqueens(option)
-    if option == "solve_all1" # solve all
-        @info "test solve_all with num_solution not set"
-        model, q = init_model()
-        MOI.set(model, MOI.RawOptimizerAttribute("all_solutions"), true)
-        MOI.optimize!(model)
-        check_result(model, q)
-    elseif option == "solve_all2" # solve all with limit > 92
-        @info "test solve_all with limit > 92"
-        model, q = init_model()
-        MOI.set(model, MOI.RawOptimizerAttribute("all_solutions"), true)
-        MOI.set(model, MOI.RawOptimizerAttribute("num_solutions"), 100)
-        MOI.optimize!(model)
-        check_result(model, q)
-    elseif option == "solve_all3" # solve all with limit = 25 
-        @info "test solve_all with limit = 25"
-        model, q = init_model()
-        MOI.set(model, MOI.RawOptimizerAttribute("all_solutions"), true)
-        MOI.set(model, MOI.RawOptimizerAttribute("num_solutions"), 25)
-        MOI.optimize!(model)
-        check_result(model, q, 25, MOI.SOLUTION_LIMIT)
-    elseif option == "solve_one" # solve one
-        @info "test solve_one"
-        model, q = init_model()
-        MOI.set(model, MOI.RawOptimizerAttribute("all_solutions"), false)
-        MOI.set(model, MOI.RawOptimizerAttribute("num_solutions"), 100)
-        MOI.optimize!(model)
-        check_result(model, q, 1)
-    elseif option == "throw"
-        @info "test throw"
-        model, q = init_model()
-        @test_throws ErrorException MOI.set(
-            model,
-            MOI.RawOptimizerAttribute("all_solutions"),
-            1,
-        )
-        @test_throws ErrorException MOI.set(
-            model,
-            MOI.RawOptimizerAttribute("num_solutions"),
-            -1,
-        )
-        @test_throws ErrorException MOI.set(
-            model,
-            MOI.RawOptimizerAttribute("num_solutions"),
-            0,
-        )
-        @test_throws ErrorException MOI.set(
-            model,
-            MOI.RawOptimizerAttribute("num_solutions"),
-            1.1,
-        )
-        @test_throws ErrorException MOI.set(
-            model,
-            MOI.RawOptimizerAttribute("num_solutions"),
-            "two",
-        )
-    end
-    return
+function test_solve_all1() # solve all with limit > 92
+    @info "test solve_all with limit > 92"
+    model, q = _init_model()
+    MOI.set(model, MOI.RawOptimizerAttribute("num_solutions"), 100)
+    MOI.optimize!(model)
+    return _check_result(model, q)
+end
+
+function test_solve_all2() # solve all with limit = 25 
+    @info "test solve_all with limit = 25"
+    model, q = _init_model()
+    MOI.set(model, MOI.RawOptimizerAttribute("num_solutions"), 25)
+    MOI.optimize!(model)
+    return _check_result(model, q, 25, MOI.SOLUTION_LIMIT)
+end
+
+function test_solve_one1() # solve one with limit not set
+    @info "test solve_one with limit not set"
+    model, q = _init_model()
+    MOI.optimize!(model)
+    return _check_result(model, q, 1)
 end
 
-test_nqueens1() = run_nqueens("solve_all1")
-test_nqueens2() = run_nqueens("solve_all2")
-test_nqueens3() = run_nqueens("solve_all3")
-test_nqueens4() = run_nqueens("solve_one")
-test_nqueens5() = run_nqueens("throw")
+function test_solve_one2() # solve one with limit = 1
+    @info "test solve_one with limit = 1"
+    model, q = _init_model()
+    MOI.set(model, MOI.RawOptimizerAttribute("num_solutions"), 1)
+    MOI.optimize!(model)
+    return _check_result(model, q, 1)
+end
+
+function test_throw() # test throw
+    @info "test throw"
+    model, _ = _init_model()
+    @test_throws ErrorException MOI.set(
+        model,
+        MOI.RawOptimizerAttribute("num_solutions"),
+        -1,
+    )
+    @test_throws ErrorException MOI.set(
+        model,
+        MOI.RawOptimizerAttribute("num_solutions"),
+        0,
+    )
+    @test_throws ErrorException MOI.set(
+        model,
+        MOI.RawOptimizerAttribute("num_solutions"),
+        1.1,
+    )
+    @test_throws ErrorException MOI.set(
+        model,
+        MOI.RawOptimizerAttribute("num_solutions"),
+        "two",
+    )
+end

From 608540bbc2458f578981c37094e7fb194b885e99 Mon Sep 17 00:00:00 2001
From: zengjian-hu-rai <106710107+zengjian-hu-rai@users.noreply.github.com>
Date: Thu, 21 Sep 2023 19:50:43 -0700
Subject: [PATCH 04/13] Apply suggestions from code review

Co-authored-by: Oscar Dowson <odow@users.noreply.github.com>
---
 src/optimize.jl                   | 12 ++++++++----
 test/examples/nqueens_solveall.jl |  2 --
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/optimize.jl b/src/optimize.jl
index e8b554c..00798bd 100644
--- a/src/optimize.jl
+++ b/src/optimize.jl
@@ -25,7 +25,7 @@ mutable struct Optimizer{T} <: MOI.AbstractOptimizer
     inner::Model{T}
     solver_status::String
     primal_objective::T
-    primal_solutions::Vector{Dict{MOI.VariableIndex,T}} # all solutions
+    primal_solutions::Vector{Dict{MOI.VariableIndex,T}}
     options::Dict{String,Any}
     time_limit_sec::Union{Nothing,Float64}
     solve_time_sec::Float64
@@ -174,7 +174,6 @@ function MOI.optimize!(dest::Optimizer{T}, src::MOI.ModelLike) where {T}
     MOI.empty!(dest.inner)
     empty!(dest.primal_solutions)
     index_map = MOI.copy_to(dest.inner, src)
-
     ret = _run_minizinc(dest)
     if !isempty(ret)
         m_stat = match(r"=====(.+)=====", ret)
@@ -187,14 +186,19 @@ function MOI.optimize!(dest::Optimizer{T}, src::MOI.ModelLike) where {T}
                 MOI.get(dest.inner, MOI.VariableName(), x) => x for
                 x in MOI.get(src, MOI.ListOfVariableIndices())
             )
-
             primal_solution = Dict{MOI.VariableIndex,T}()
             for line in split(ret, "\n")
                 m_var = match(r"(.+) \= (.+)\;", line)
                 if m_var === nothing
                     isempty(primal_solution) ||
                         push!(dest.primal_solutions, primal_solution) # add solution
-                    primal_solution = Dict{MOI.VariableIndex,T}()
+                    if !isempty(primal_solution)
+                        # We found a line in the output that is not a variable
+                        # statement. It must divide the solutions, so append
+                        # the current.
+                        push!(dest.primal_solutions, copy(primal_solution))
+                        empty!(primal_solution)
+                    end
                     continue
                 elseif m_var[1] == "_objective"
                     dest.primal_objective = _parse_result(T, m_var[2])
diff --git a/test/examples/nqueens_solveall.jl b/test/examples/nqueens_solveall.jl
index 013b301..87717b4 100644
--- a/test/examples/nqueens_solveall.jl
+++ b/test/examples/nqueens_solveall.jl
@@ -23,7 +23,6 @@ function _init_model()
         f = MOI.Utilities.vectorize([op(q[i], i) for i in eachindex(q)])
         MOI.add_constraint(model, f, MOI.AllDifferent(n))
     end
-
     return model, q
 end
 
@@ -36,7 +35,6 @@ function _check_result(
     @test MOI.get(model, MOI.TerminationStatus()) === termination_status
     res_count = MOI.get(model, MOI.ResultCount())
     @test res_count == actual_count
-
     for i in 1:res_count
         q_sol = MOI.get(model, MOI.VariablePrimal(i), q)
         @test allunique(q_sol)

From 7452f07c5504f7a8bfcdf0fa384620a9b8f717fa Mon Sep 17 00:00:00 2001
From: Zengjian Hu <zengjian.hu@relational.ai>
Date: Thu, 21 Sep 2023 19:58:37 -0700
Subject: [PATCH 05/13] address Oscar's comments - 2

---
 src/optimize.jl                   | 5 -----
 test/examples/nqueens_solveall.jl | 4 ++--
 2 files changed, 2 insertions(+), 7 deletions(-)

diff --git a/src/optimize.jl b/src/optimize.jl
index 00798bd..0e8ccfe 100644
--- a/src/optimize.jl
+++ b/src/optimize.jl
@@ -190,8 +190,6 @@ function MOI.optimize!(dest::Optimizer{T}, src::MOI.ModelLike) where {T}
             for line in split(ret, "\n")
                 m_var = match(r"(.+) \= (.+)\;", line)
                 if m_var === nothing
-                    isempty(primal_solution) ||
-                        push!(dest.primal_solutions, primal_solution) # add solution
                     if !isempty(primal_solution)
                         # We found a line in the output that is not a variable
                         # statement. It must divide the solutions, so append
@@ -263,9 +261,6 @@ function MOI.get(
 )
     MOI.check_result_index_bounds(model, attr)
     MOI.throw_if_not_valid(model, x)
-    if attr.result_index > length(model.primal_solutions)
-        throw(ErrorException("Result index out of bounds."))
-    end
     return model.primal_solutions[attr.result_index][x]
 end
 
diff --git a/test/examples/nqueens_solveall.jl b/test/examples/nqueens_solveall.jl
index 87717b4..5981243 100644
--- a/test/examples/nqueens_solveall.jl
+++ b/test/examples/nqueens_solveall.jl
@@ -7,9 +7,8 @@
 # based on MiniZinc example nqueens.mzn
 # queen in column i is in row q[i]
 
-n = 8
-
 function _init_model()
+    n = 8
     model = MOI.instantiate(
         () -> MiniZinc.Optimizer{Int}("chuffed");
         with_cache_type = Int,
@@ -32,6 +31,7 @@ function _check_result(
     actual_count = 92,
     termination_status = MOI.OPTIMAL,
 )
+    n = 8
     @test MOI.get(model, MOI.TerminationStatus()) === termination_status
     res_count = MOI.get(model, MOI.ResultCount())
     @test res_count == actual_count

From 9708d3d9202be1729e0772210712511fdf22617c Mon Sep 17 00:00:00 2001
From: Zengjian Hu <zengjian.hu@relational.ai>
Date: Thu, 21 Sep 2023 20:05:37 -0700
Subject: [PATCH 06/13] minor function name change

---
 test/examples/nqueens_solveall.jl | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/test/examples/nqueens_solveall.jl b/test/examples/nqueens_solveall.jl
index 5981243..b354185 100644
--- a/test/examples/nqueens_solveall.jl
+++ b/test/examples/nqueens_solveall.jl
@@ -47,7 +47,7 @@ function _check_result(
     return
 end
 
-function test_solve_all1() # solve all with limit > 92
+function test_nqueens_solve_all1() # solve all with limit > 92
     @info "test solve_all with limit > 92"
     model, q = _init_model()
     MOI.set(model, MOI.RawOptimizerAttribute("num_solutions"), 100)
@@ -55,7 +55,7 @@ function test_solve_all1() # solve all with limit > 92
     return _check_result(model, q)
 end
 
-function test_solve_all2() # solve all with limit = 25 
+function test_nqueens_solve_all2() # solve all with limit = 25 
     @info "test solve_all with limit = 25"
     model, q = _init_model()
     MOI.set(model, MOI.RawOptimizerAttribute("num_solutions"), 25)
@@ -63,14 +63,14 @@ function test_solve_all2() # solve all with limit = 25
     return _check_result(model, q, 25, MOI.SOLUTION_LIMIT)
 end
 
-function test_solve_one1() # solve one with limit not set
+function test_nqueens_solve_one1() # solve one with limit not set
     @info "test solve_one with limit not set"
     model, q = _init_model()
     MOI.optimize!(model)
     return _check_result(model, q, 1)
 end
 
-function test_solve_one2() # solve one with limit = 1
+function test_nqueens_solve_one2() # solve one with limit = 1
     @info "test solve_one with limit = 1"
     model, q = _init_model()
     MOI.set(model, MOI.RawOptimizerAttribute("num_solutions"), 1)
@@ -78,7 +78,7 @@ function test_solve_one2() # solve one with limit = 1
     return _check_result(model, q, 1)
 end
 
-function test_throw() # test throw
+function test_nqueens_throw() # test throw
     @info "test throw"
     model, _ = _init_model()
     @test_throws ErrorException MOI.set(

From d4a3986e2f35c3996310e3fdf201ee14956a5489 Mon Sep 17 00:00:00 2001
From: zengjian-hu-rai <106710107+zengjian-hu-rai@users.noreply.github.com>
Date: Thu, 21 Sep 2023 20:25:12 -0700
Subject: [PATCH 07/13] Update src/optimize.jl

Co-authored-by: Oscar Dowson <odow@users.noreply.github.com>
---
 src/optimize.jl | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/optimize.jl b/src/optimize.jl
index 0e8ccfe..a86fa62 100644
--- a/src/optimize.jl
+++ b/src/optimize.jl
@@ -77,7 +77,6 @@ function _run_minizinc(dest::Optimizer)
     end
     output = joinpath(dir, "model.ozn")
     _stdout = joinpath(dir, "_stdout.txt")
-
     _minizinc_exe() do exe
         cmd = `$(exe) --solver $(dest.solver) --output-objective -o $(output) $(filename)`
 

From bc717dd624d3a327b01e2cbe78f20340d22beca2 Mon Sep 17 00:00:00 2001
From: zengjian-hu-rai <106710107+zengjian-hu-rai@users.noreply.github.com>
Date: Thu, 21 Sep 2023 20:25:20 -0700
Subject: [PATCH 08/13] Update src/optimize.jl

Co-authored-by: Oscar Dowson <odow@users.noreply.github.com>
---
 src/optimize.jl | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/optimize.jl b/src/optimize.jl
index a86fa62..9b4d593 100644
--- a/src/optimize.jl
+++ b/src/optimize.jl
@@ -84,7 +84,6 @@ function _run_minizinc(dest::Optimizer)
             limit = round(Int, 1_000 * dest.time_limit_sec::Float64)
             cmd = `$cmd --time-limit $limit`
         end
-
         if dest.options["num_solutions"] > 1
             cmd = `$cmd --num-solutions $(dest.options["num_solutions"])`
         end

From 2990f3f727880f71c37bcd24436c3b85492eb4b1 Mon Sep 17 00:00:00 2001
From: zengjian-hu-rai <106710107+zengjian-hu-rai@users.noreply.github.com>
Date: Thu, 21 Sep 2023 20:25:29 -0700
Subject: [PATCH 09/13] Update src/optimize.jl

Co-authored-by: Oscar Dowson <odow@users.noreply.github.com>
---
 src/optimize.jl | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/optimize.jl b/src/optimize.jl
index 9b4d593..1c2f1b0 100644
--- a/src/optimize.jl
+++ b/src/optimize.jl
@@ -79,7 +79,6 @@ function _run_minizinc(dest::Optimizer)
     _stdout = joinpath(dir, "_stdout.txt")
     _minizinc_exe() do exe
         cmd = `$(exe) --solver $(dest.solver) --output-objective -o $(output) $(filename)`
-
         if dest.time_limit_sec !== nothing
             limit = round(Int, 1_000 * dest.time_limit_sec::Float64)
             cmd = `$cmd --time-limit $limit`

From 98a30ee1e0ca4239791833bc1670fc0c8eb319a3 Mon Sep 17 00:00:00 2001
From: Oscar Dowson <odow@users.noreply.github.com>
Date: Fri, 22 Sep 2023 15:30:18 +1200
Subject: [PATCH 10/13] Update optimize.jl

---
 src/optimize.jl | 21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/src/optimize.jl b/src/optimize.jl
index 1c2f1b0..853adee 100644
--- a/src/optimize.jl
+++ b/src/optimize.jl
@@ -130,6 +130,14 @@ function MOI.get(model::Optimizer, attr::MOI.RawOptimizerAttribute)
     return get(model.options, attr.name, nothing)
 end
 
+function MOI.set(model::Optimizer, attr::MOI.RawOptimizerAttribute, value)
+    if attr.name == "num_solutions" && !(value isa Int && value >= 1)
+        throw(MOI.SetAttributeNotAllowed("value must be an `Int` that is >= 1"))
+    end
+    model.options[attr.name] = value
+    return
+end
+
 MOI.supports(::Optimizer, ::MOI.TimeLimitSec) = true
 
 MOI.get(model::Optimizer, ::MOI.TimeLimitSec) = model.time_limit_sec
@@ -223,8 +231,7 @@ function MOI.get(model::Optimizer, ::MOI.TerminationStatus)
     if model.solver_status == "UNSATISFIABLE"
         return MOI.INFEASIBLE
     elseif _has_solution(model)
-        if model.options["num_solutions"] > 1 &&
-           length(model.primal_solutions) >= model.options["num_solutions"]
+        if 1 < model.options["num_solutions"] <= length(model.primal_solutions)
             return MOI.SOLUTION_LIMIT
         else
             return MOI.OPTIMAL
@@ -262,13 +269,3 @@ function MOI.get(
 end
 
 MOI.get(model::Optimizer, ::MOI.SolveTimeSec) = model.solve_time_sec
-
-function MOI.set(model::Optimizer, attr::MOI.RawOptimizerAttribute, value)
-    if attr.name == "num_solutions"
-        (value isa Int && value >= 1) ||
-            throw(ErrorException("Invalid value $value for $(attr.name)."))
-    end
-
-    model.options[attr.name] = value
-    return
-end

From 95793b42cb491a6c97682994aba711516ac679fb Mon Sep 17 00:00:00 2001
From: Oscar Dowson <odow@users.noreply.github.com>
Date: Fri, 22 Sep 2023 15:41:00 +1200
Subject: [PATCH 11/13] Update nqueens_solveall.jl

---
 test/examples/nqueens_solveall.jl | 78 +++++++++++--------------------
 1 file changed, 28 insertions(+), 50 deletions(-)

diff --git a/test/examples/nqueens_solveall.jl b/test/examples/nqueens_solveall.jl
index b354185..8105656 100644
--- a/test/examples/nqueens_solveall.jl
+++ b/test/examples/nqueens_solveall.jl
@@ -3,11 +3,7 @@
 # Use of this source code is governed by an MIT-style license that can be found
 # in the LICENSE.md file or at https://opensource.org/licenses/MIT.
 
-# N-queens example - solve_all
-# based on MiniZinc example nqueens.mzn
-# queen in column i is in row q[i]
-
-function _init_model()
+function _init_nqueens_solve_num_solutions()
     n = 8
     model = MOI.instantiate(
         () -> MiniZinc.Optimizer{Int}("chuffed");
@@ -25,13 +21,14 @@ function _init_model()
     return model, q
 end
 
-function _check_result(
+function _test_nqueens_solve_num_solutions(
     model,
     q,
     actual_count = 92,
     termination_status = MOI.OPTIMAL,
 )
     n = 8
+    MOI.optimize!(model)
     @test MOI.get(model, MOI.TerminationStatus()) === termination_status
     res_count = MOI.get(model, MOI.ResultCount())
     @test res_count == actual_count
@@ -41,64 +38,45 @@ function _check_result(
         @test allunique(q_sol .+ (1:n))
         @test allunique(q_sol .- (1:n))
     end
-
     @test MOI.get(model, MOI.SolveTimeSec()) < 4.0
     rm("test.mzn")
     return
 end
 
-function test_nqueens_solve_all1() # solve all with limit > 92
-    @info "test solve_all with limit > 92"
-    model, q = _init_model()
+function test_nqueens_solve_num_solutions_100()
+    model, q = _init_nqueens_solve_num_solutions()
     MOI.set(model, MOI.RawOptimizerAttribute("num_solutions"), 100)
-    MOI.optimize!(model)
-    return _check_result(model, q)
+    _test_nqueens_solve_num_solutions(model, q)
+    return
 end
 
-function test_nqueens_solve_all2() # solve all with limit = 25 
-    @info "test solve_all with limit = 25"
-    model, q = _init_model()
+function test_nqueens_solve_num_solutions_25()
+    model, q = _init_nqueens_solve_num_solutions()
     MOI.set(model, MOI.RawOptimizerAttribute("num_solutions"), 25)
-    MOI.optimize!(model)
-    return _check_result(model, q, 25, MOI.SOLUTION_LIMIT)
+    _test_nqueens_solve_num_solutions(model, q, 25, MOI.SOLUTION_LIMIT)
+    return
 end
 
-function test_nqueens_solve_one1() # solve one with limit not set
-    @info "test solve_one with limit not set"
-    model, q = _init_model()
-    MOI.optimize!(model)
-    return _check_result(model, q, 1)
+function test_nqueens_solve_num_solutions_not_set()
+    model, q = _init_nqueens_solve_num_solutions()
+    _test_nqueens_solve_num_solutions(model, q, 1)
+    return
 end
 
-function test_nqueens_solve_one2() # solve one with limit = 1
-    @info "test solve_one with limit = 1"
-    model, q = _init_model()
+function test_nqueens_solve_num_solutions_1()
+    model, q = _init_nqueens_solve_num_solutions()
     MOI.set(model, MOI.RawOptimizerAttribute("num_solutions"), 1)
-    MOI.optimize!(model)
-    return _check_result(model, q, 1)
+    _test_nqueens_solve_num_solutions(model, q, 1)
+    return
 end
 
-function test_nqueens_throw() # test throw
-    @info "test throw"
-    model, _ = _init_model()
-    @test_throws ErrorException MOI.set(
-        model,
-        MOI.RawOptimizerAttribute("num_solutions"),
-        -1,
-    )
-    @test_throws ErrorException MOI.set(
-        model,
-        MOI.RawOptimizerAttribute("num_solutions"),
-        0,
-    )
-    @test_throws ErrorException MOI.set(
-        model,
-        MOI.RawOptimizerAttribute("num_solutions"),
-        1.1,
-    )
-    @test_throws ErrorException MOI.set(
-        model,
-        MOI.RawOptimizerAttribute("num_solutions"),
-        "two",
-    )
+function test_nqueens_num_solutions_throw()
+    model, _ = _init_nqueens_solve_num_solutions()
+    for value in (-1, 0, 1.1, "two")
+        @test_throws(
+            MOI.SetAttributeNotAllowed,
+            MOI.set(model, MOI.RawOptimizerAttribute("num_solutions"), -1),
+        )
+    end
+    return
 end

From 4214ee8b1feb6477536fc116f3b4aa3a19dfabe5 Mon Sep 17 00:00:00 2001
From: Oscar Dowson <odow@users.noreply.github.com>
Date: Fri, 22 Sep 2023 15:43:21 +1200
Subject: [PATCH 12/13] Update src/optimize.jl

---
 src/optimize.jl | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/optimize.jl b/src/optimize.jl
index 853adee..0e2b3e7 100644
--- a/src/optimize.jl
+++ b/src/optimize.jl
@@ -202,7 +202,6 @@ function MOI.optimize!(dest::Optimizer{T}, src::MOI.ModelLike) where {T}
                         push!(dest.primal_solutions, copy(primal_solution))
                         empty!(primal_solution)
                     end
-                    continue
                 elseif m_var[1] == "_objective"
                     dest.primal_objective = _parse_result(T, m_var[2])
                 else

From 4acf817b7a61fc90338e3722ce5d9fc1dafac802 Mon Sep 17 00:00:00 2001
From: Oscar Dowson <odow@users.noreply.github.com>
Date: Fri, 22 Sep 2023 15:47:40 +1200
Subject: [PATCH 13/13] Update src/optimize.jl

---
 src/optimize.jl | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/optimize.jl b/src/optimize.jl
index 0e2b3e7..7c90a7a 100644
--- a/src/optimize.jl
+++ b/src/optimize.jl
@@ -132,7 +132,8 @@ end
 
 function MOI.set(model::Optimizer, attr::MOI.RawOptimizerAttribute, value)
     if attr.name == "num_solutions" && !(value isa Int && value >= 1)
-        throw(MOI.SetAttributeNotAllowed("value must be an `Int` that is >= 1"))
+        msg = "value must be an `Int` that is >= 1"
+        throw(MOI.SetAttributeNotAllowed(attr, msg))
     end
     model.options[attr.name] = value
     return