How do I use JSON with Minizinc?

[mrakgr]

I have no idea how to use enum fields in non-.dzn files. When I try to run minizinc prototype.mzn prototype.json I get the Error: type error: initialisation value for predictions' has invalid type-inst: expected array[_] of record(MODELS: model, float: price, float: workload)', actual array[_] of record(string: model, int: price, int: workload)'`. Here is the file:

{
    "MODELS": ["LLAMA4_SMALL_ON_OPENROUTER", "LLAMA4_MEDIUM_ON_S19", "SOME_NEW_LARGE_MODEL_ON_UNKNOWN_MARKETPLACE"],
    "MACHINES": ["M1", "M2", "M3"],
    "TYPES": ["HGX"],
    "gpus_per_model": [1, 1, 1],
    "machines": [
        {"gpus": 8, "machine_type": "HGX", "cost_per_gpu": 0.0001},
        {"gpus": 8, "machine_type": "HGX", "cost_per_gpu": 0.0001},
        {"gpus": 8, "machine_type": "HGX", "cost_per_gpu": 0.0001}
    ],
    "workload_per_type_per_model": [[3.0, 2.0, 1.0]],
    "predictions": [
        {"model": "LLAMA4_SMALL_ON_OPENROUTER", "price": 10, "workload": 10},
        {"model": "LLAMA4_MEDIUM_ON_S19", "price": 10, "workload": 10},
        {"model": "SOME_NEW_LARGE_MODEL_ON_UNKNOWN_MARKETPLACE", "price": 10, "workload": 10}
    ]
}

[mrakgr]

The original .dzn file is this:

MODELS = {LLAMA4_SMALL_ON_OPENROUTER, LLAMA4_MEDIUM_ON_S19, SOME_NEW_LARGE_MODEL_ON_UNKNOWN_MARKETPLACE};
MACHINES = {M1, M2, M3};
TYPES = {HGX};

gpus_per_model = [1, 1, 1];
machines = [
    (gpus: 8, machine_type: HGX, cost_per_gpu: 0.0001), 
    (gpus: 8, machine_type: HGX, cost_per_gpu: 0.0001), 
    (gpus: 8, machine_type: HGX, cost_per_gpu: 0.0001)
    ];
workload_per_type_per_model = [|3.0, 2.0, 1.0|];

predictions = [
    (model: LLAMA4_SMALL_ON_OPENROUTER, price: 10, workload: 10), 
    (model: LLAMA4_MEDIUM_ON_S19, price: 10, workload: 10), 
    (model: SOME_NEW_LARGE_MODEL_ON_UNKNOWN_MARKETPLACE, price: 10, workload: 10),
    ];

[mrakgr]

Could I do the same thing via the Python interface somehow? I tried the following amongst others and it failed with the same error.

from enum import Enum
from minizinc import Instance, Model, Solver

# Load the model
model = Model('/home/mrakgr/inference-servers/icf/prototype.mzn')

# Create a solver instance
gecode = Solver.lookup('gecode')
instance = Instance(gecode, model)

models = Enum("MODELS", ["LLAMA4_SMALL_ON_OPENROUTER", "LLAMA4_MEDIUM_ON_S19", "SOME_NEW_LARGE_MODEL_ON_UNKNOWN_MARKETPLACE"])
machines = Enum("MACHINES", ["M1", "M2", "M3"])
types = Enum("TYPES", ["HGX"])

data = {
    "MODELS": models,
    "MACHINES": machines,
    "TYPES": types,
    "gpus_per_model": [1, 1, 1],
    "machines": [
        {"gpus": 8, "machine_type": "HGX", "cost_per_gpu": 0.0001},
        {"gpus": 8, "machine_type": "HGX", "cost_per_gpu": 0.0001},
        {"gpus": 8, "machine_type": "HGX", "cost_per_gpu": 0.0001}
    ],
    "workload_per_type_per_model": [[3.0, 2.0, 1.0]],
    "predictions": [
        {"model": "LLAMA4_SMALL_ON_OPENROUTER", "price": 10, "workload": 10},
        {"model": "LLAMA4_MEDIUM_ON_S19", "price": 10, "workload": 10},
        {"model": "SOME_NEW_LARGE_MODEL_ON_UNKNOWN_MARKETPLACE", "price": 10, "workload": 10}
    ]
}

for k,v in data.items():
    instance[k] = v

# Solve the instance
result = instance.solve()

# Print the result
print(result)

# python run.py

(main) mrakgr@Marko:~/inference-servers$  cd /home/mrakgr/inference-servers ; /usr/bin/env /home/mrakgr/.venv/main/bin/python /home/mrakgr/.vscode-server/extensions/ms-python.debugpy-2025.8.0-linux-x64/bundled/libs/debugpy/adapter/../../debugpy/launcher 49553 -- /home/mrakgr/inference-servers/icf/run.py 
Traceback (most recent call last):
  File "/usr/lib/python3.12/runpy.py", line 198, in _run_module_as_main
    return _run_code(code, main_globals, None,
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/runpy.py", line 88, in _run_code
    exec(code, run_globals)
  File "/home/mrakgr/.vscode-server/extensions/ms-python.debugpy-2025.8.0-linux-x64/bundled/libs/debugpy/adapter/../../debugpy/launcher/../../debugpy/__main__.py", line 71, in <module>
    cli.main()
  File "/home/mrakgr/.vscode-server/extensions/ms-python.debugpy-2025.8.0-linux-x64/bundled/libs/debugpy/adapter/../../debugpy/launcher/../../debugpy/../debugpy/server/cli.py", line 501, in main
    run()
  File "/home/mrakgr/.vscode-server/extensions/ms-python.debugpy-2025.8.0-linux-x64/bundled/libs/debugpy/adapter/../../debugpy/launcher/../../debugpy/../debugpy/server/cli.py", line 351, in run_file
    runpy.run_path(target, run_name="__main__")
  File "/home/mrakgr/.vscode-server/extensions/ms-python.debugpy-2025.8.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/_pydevd_bundle/pydevd_runpy.py", line 310, in run_path
    return _run_module_code(code, init_globals, run_name, pkg_name=pkg_name, script_name=fname)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/mrakgr/.vscode-server/extensions/ms-python.debugpy-2025.8.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/_pydevd_bundle/pydevd_runpy.py", line 127, in _run_module_code
    _run_code(code, mod_globals, init_globals, mod_name, mod_spec, pkg_name, script_name)
  File "/home/mrakgr/.vscode-server/extensions/ms-python.debugpy-2025.8.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/_pydevd_bundle/pydevd_runpy.py", line 118, in _run_code
    exec(code, run_globals)
  File "/home/mrakgr/inference-servers/icf/run.py", line 37, in <module>
    result = instance.solve()
             ^^^^^^^^^^^^^^^^
  File "/home/mrakgr/.venv/main/lib/python3.12/site-packages/minizinc/instance.py", line 193, in solve
    return asyncio.run(coroutine)
           ^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/asyncio/runners.py", line 194, in run
    return runner.run(main)
           ^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/asyncio/runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/asyncio/base_events.py", line 687, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "/home/mrakgr/.venv/main/lib/python3.12/site-packages/minizinc/instance.py", line 248, in solve_async
    async for result in self.solutions(
  File "/home/mrakgr/.venv/main/lib/python3.12/site-packages/minizinc/instance.py", line 618, in solutions
    async for obj in decode_async_json_stream(
  File "/home/mrakgr/.venv/main/lib/python3.12/site-packages/minizinc/json.py", line 122, in decode_async_json_stream
    raise error_from_stream_obj(obj)
minizinc.error.TypeError: initialisation value for `predictions' has invalid type-inst: expected `array[_] of record(MODELS: model, float: price, float: workload)', actual `array[_] of record(string: model, int: price, int: workload)'