Update to latest version of AMPL

knapsack-ampl/README.md

@@ -20,8 +20,8 @@ The most important files created are `main.py`, `input.json`, and
 * `main.py` implements a MIP knapsack solver.
 * `input.json` is a sample input file.
 * `KEY.template` is a file demonstrating how to use the AMPL UUID license key.
-  Copy this file into a `KEY` file and replace the contents with your actual
-  license key.
+  Remove the `.template` extension and replace the contents with your actual
+  license key to be left with a file named `KEY`.
 
 Follow these steps to run locally.
 

knapsack-ampl/main.py

@@ -8,24 +8,14 @@
 import time
 from typing import Any
 
-from amplpy import AMPL, modules
+from amplpy import AMPL, ErrorHandler, OutputHandler, modules
 
 # Duration parameter for the solver.
 SUPPORTED_PROVIDER_DURATIONS = {
-    "baron": "maxtime",
-    "cbc": "timelimit",
-    "conopt": "maxftime",
     "copt": "timelimit",
-    "cplex": "timelimit",
-    "gcg": "timelimit",
     "gurobi": "timelimit",
     "highs": "timelimit",
-    "ilogcp": "timelimit",
-    "knitro": "maxtime_cpu",
     "lgo": "timelim",
-    "lindoglobal": "maxtime",
-    "loqo": "timlim",
-    "mosek": "timelimit",
     "scip": "timelimit",
     "xpress": "timelimit",
 }
@@ -41,6 +31,28 @@
 ]
 
 
+class CollectOutput(OutputHandler):
+    def __init__(self):
+        self.buffer = ""
+
+    def output(self, kind, msg):
+        self.buffer += msg
+
+
+output_handler = CollectOutput()
+
+
+class CollectWarnings(ErrorHandler):
+    def __init__(self):
+        self.buffer = ""
+
+    def warning(self, exception):
+        self.buffer += str(exception)
+
+
+error_handler = CollectWarnings()
+
+
 def main() -> None:
     """Entry point for the template."""
 
@@ -74,10 +86,10 @@ def main() -> None:
 
     # Read input "data", solve the problem and write the solution.
     input_data = read_input(args.input)
-    # log("Solving knapsack problem:")
-    # log(f"  - items: {len(input_data.get('items', []))}")
-    # log(f"  - capacity: {input_data.get('weight_capacity', 0)}")
-    # log(f"  - max duration: {args.duration} seconds")
+    log("Solving knapsack problem:")
+    log(f"  - items: {len(input_data.get('items', []))}")
+    log(f"  - capacity: {input_data.get('weight_capacity', 0)}")
+    log(f"  - max duration: {args.duration} seconds")
     solution = solve(input_data, args.duration, args.provider)
     write_output(args.output, solution)
 
@@ -87,50 +99,47 @@ def solve(input_data: dict[str, Any], duration: int, provider: str) -> dict[str,
 
     start_time = time.time()
 
-    # Make sure the provider is supported.
-    if provider not in SUPPORTED_PROVIDER_DURATIONS:
-        raise ValueError(
-            f"Unsupported provider: {provider}. The supported providers are: "
-            f"{', '.join(SUPPORTED_PROVIDER_DURATIONS.keys())}"
-        )
-
     # Defines the model.
     ampl = AMPL()
+    ampl.set_output_handler(output_handler)
+    ampl.set_error_handler(error_handler)
     ampl.eval(
-        """
-    # Sets
-    set I; # Set of items.
+        r"""
+        # Sets
+        set I; # Set of items.
 
-    # Parameters
-    param W >= 0; # Maximum weight capacity.
-    param v {I} >= 0; # Value of each item.
-    param w {I} >= 0; # Weight of each item.
+        # Parameters
+        param W >= 0; # Maximum weight capacity.
+        param v {I} >= 0; # Value of each item.
+        param w {I} >= 0; # Weight of each item.
 
-    # Variables
-    var x {I} binary; # 1 if item is selected, 0 otherwise.
+        # Variables
+        var x {I} binary; # 1 if item is selected, 0 otherwise.
 
-    # Objective
-    maximize z: sum {i in I} v[i] * x[i];
+        # Objective
+        maximize z: sum {i in I} v[i] * x[i];
 
-    # Constraints
-    s.t. weight_limit: sum {i in I} w[i] * x[i] <= W;
-    """
+        # Constraints
+        s.t. weight_limit: sum {i in I} w[i] * x[i] <= W;
+        """
     )
 
     # Sets the solver and options.
     ampl.option["solver"] = provider
-    ampl.option[f"{provider}_options"] = f"{SUPPORTED_PROVIDER_DURATIONS[provider]}={duration}"
-    ampl.option["solver_msg"] = 0
-    ampl.option["outlev"] = 0
+    if provider in SUPPORTED_PROVIDER_DURATIONS:
+        ampl.option[f"{provider}_options"] = f"{SUPPORTED_PROVIDER_DURATIONS[provider]}={duration}"
 
     # Set the data on the model.
     ampl.set["I"] = [item["id"] for item in input_data["items"]]
     ampl.param["W"] = input_data["weight_capacity"]
     ampl.param["v"] = {item["id"]: item["value"] for item in input_data["items"]}
     ampl.param["w"] = {item["id"]: item["weight"] for item in input_data["items"]}
 
-    # Solves the problem.
-    ampl.solve()
+    # Solves the problem. Verbose mode is turned off to avoid printing to
+    # stdout. Only the output should be printed to stdout.
+    ampl.solve(verbose=False)
+    log(f"AMPL output after solving: {output_handler.buffer}")
+    log(f"AMPL errors after solving: {error_handler.buffer}")
 
     # Convert to solution format.
     value = ampl.get_objective("z")
@@ -151,10 +160,10 @@ def solve(input_data: dict[str, Any], duration: int, provider: str) -> dict[str,
     statistics = {
         "result": {
             "custom": {
-                "constraints": ampl.get_constraints().size(),
+                "constraints": ampl.get_value("_ncons"),
                 "provider": provider,
                 "status": status,
-                "variables": ampl.get_variables().size(),
+                "variables": ampl.get_value("_nvars"),
             },
             "duration": ampl.get_value("_total_solve_time"),
             "value": value.value(),

knapsack-ampl/requirements.txt

@@ -1,32 +1,22 @@
-ampl-module-amplgsl==20231107
-ampl-module-baron==20230405
+# Look for AMPL’s packages in the AMPL package index.
+--index-url https://pypi.ampl.com
+--extra-index-url https://pypi.org/simple
+
+# AMPL packages.
+amplpy==0.13.3
+ampltools==0.7.4
 ampl-module-base==20240126
-ampl-module-cbc==20240115
-ampl-module-coin==20240115
-ampl-module-conopt==20211109
 ampl-module-copt==20240115
-ampl-module-cplex==20240115
-ampl-module-gcg==20230919
 ampl-module-gecode==20220504
-ampl-module-gjh==20231111
+ampl-module-gokestrel==20211022
 ampl-module-gurobi==20240115
 ampl-module-highs==20240115
-ampl-module-ilogcp==20230228
-ampl-module-knitro==20240209
 ampl-module-lgo==20190908
-ampl-module-lindoglobal==20210406
-ampl-module-loqo==20210410
-ampl-module-minos==20211109
-ampl-module-mosek==20240118
 ampl-module-open==20240121
-ampl-module-plugins==20240102
 ampl-module-scip==20240121
-ampl-module-snopt==20211109
 ampl-module-xpress==20240115
-amplpy==0.13.2
-ampltools==0.7.4
-certifi==2024.2.2
-charset-normalizer==3.3.2
-idna==3.6
-requests==2.31.0
-urllib3==2.2.1
+
+# Other packages.
+numpy==1.26.4
+pandas==2.2.0
+scipy==1.12.0