Deprecate get_fitted_map_saas_ensemble in favor of EnsembleMapSaasGP (#3036)

Summary:

With `EnsembleMapSaasGP`, we no longer need a helper that constructs a `SaasFullyBayasianSingleTaskGP` from individually fitted models.

Differential Revision: D83782823

Author: saitcakmak

botorch/fit.py

@@ -8,15 +8,14 @@
 
 from __future__ import annotations
 
+import warnings
 from collections.abc import Callable, Sequence
 from copy import deepcopy
 from functools import partial
 from itertools import filterfalse
 from typing import Any
 from warnings import catch_warnings, simplefilter, warn_explicit, WarningMessage
 
-import torch
-
 from botorch.exceptions.errors import ModelFittingError, UnsupportedError
 from botorch.exceptions.warnings import OptimizationWarning
 from botorch.logging import logger
@@ -27,7 +26,7 @@
     SaasFullyBayesianSingleTaskGP,
 )
 from botorch.models.fully_bayesian_multitask import SaasFullyBayesianMultiTaskGP
-from botorch.models.map_saas import get_map_saas_model
+from botorch.models.map_saas import EnsembleMapSaasSingleTaskGP, get_map_saas_model
 from botorch.models.model_list_gp_regression import ModelListGP
 from botorch.models.transforms.input import InputTransform
 from botorch.models.transforms.outcome import OutcomeTransform
@@ -45,6 +44,7 @@
     TensorCheckpoint,
 )
 from botorch.utils.dispatcher import Dispatcher, type_bypassing_encoder
+from botorch.utils.types import _DefaultType, DEFAULT
 from gpytorch.likelihoods import Likelihood
 from gpytorch.mlls._approximate_mll import _ApproximateMarginalLogLikelihood
 from gpytorch.mlls.exact_marginal_log_likelihood import ExactMarginalLogLikelihood
@@ -53,7 +53,6 @@
 from linear_operator.utils.errors import NotPSDError
 from pyro.infer.mcmc import MCMC, NUTS
 from torch import device, Tensor
-from torch.distributions import HalfCauchy
 from torch.nn import Parameter
 from torch.utils.data import DataLoader
 
@@ -443,13 +442,15 @@ def get_fitted_map_saas_ensemble(
     train_Y: Tensor,
     train_Yvar: Tensor | None = None,
     input_transform: InputTransform | None = None,
-    outcome_transform: OutcomeTransform | None = None,
+    outcome_transform: OutcomeTransform | _DefaultType | None = DEFAULT,
     taus: Tensor | list[float] | None = None,
     num_taus: int = 4,
     optimizer_kwargs: dict[str, Any] | None = None,
 ) -> SaasFullyBayesianSingleTaskGP:
     """Get a fitted SAAS ensemble using several different tau values.
 
+    DEPRECATED: Please use `EnsembleMapSaasSingleTaskGP` directly!
+
     Args:
         train_X: Tensor of shape `n x d` with training inputs.
         train_Y: Tensor of shape `n x 1` with training targets.
@@ -464,57 +465,23 @@ def get_fitted_map_saas_ensemble(
             to fit_gpytorch_mll.
 
     Returns:
-        A fitted SaasFullyBayesianSingleTaskGP with a Matern kernel.
+        A fitted EnsembleMapSaasSingleTaskGP with a Matern kernel.
     """
-    tkwargs = {"device": train_X.device, "dtype": train_X.dtype}
-    if taus is None:
-        taus = HalfCauchy(0.1).sample([num_taus]).to(**tkwargs)
-    num_samples = len(taus)
-    if num_samples == 1:
-        raise ValueError(
-            "Use `get_fitted_map_saas_model` if you only specify one value of tau"
-        )
-
-    mean = torch.zeros(num_samples, **tkwargs)
-    outputscale = torch.zeros(num_samples, **tkwargs)
-    lengthscale = torch.zeros(num_samples, train_X.shape[-1], **tkwargs)
-    noise = torch.zeros(num_samples, **tkwargs)
-
-    # Fit a model for each tau and save the hyperparameters
-    for i, tau in enumerate(taus):
-        model = get_fitted_map_saas_model(
-            train_X,
-            train_Y,
-            train_Yvar=train_Yvar,
-            input_transform=input_transform,
-            outcome_transform=outcome_transform,
-            tau=tau,
-            optimizer_kwargs=optimizer_kwargs,
-        )
-        mean[i] = model.mean_module.constant.detach().clone()
-        outputscale[i] = model.covar_module.outputscale.detach().clone()
-        lengthscale[i, :] = model.covar_module.base_kernel.lengthscale.detach().clone()
-        if train_Yvar is None:
-            noise[i] = model.likelihood.noise.detach().clone()
-
-    # Load the samples into a fully Bayesian SAAS model
-    ensemble_model = SaasFullyBayesianSingleTaskGP(
+    warnings.warn(
+        "get_fitted_map_saas_ensemble is deprecated and will be removed in v0.17. "
+        "Please use EnsembleMapSaasSingleTaskGP instead!",
+        DeprecationWarning,
+        stacklevel=2,
+    )
+    model = EnsembleMapSaasSingleTaskGP(
         train_X=train_X,
         train_Y=train_Y,
         train_Yvar=train_Yvar,
-        input_transform=(
-            input_transform.train() if input_transform is not None else None
-        ),
+        num_taus=num_taus,
+        taus=taus,
+        input_transform=input_transform,
         outcome_transform=outcome_transform,
     )
-    mcmc_samples = {
-        "mean": mean,
-        "outputscale": outputscale,
-        "lengthscale": lengthscale,
-    }
-    if train_Yvar is None:
-        mcmc_samples["noise"] = noise
-    ensemble_model.train()
-    ensemble_model.load_mcmc_samples(mcmc_samples=mcmc_samples)
-    ensemble_model.eval()
-    return ensemble_model
+    mll = ExactMarginalLogLikelihood(model=model, likelihood=model.likelihood)
+    fit_gpytorch_mll(mll, optimizer_kwargs=optimizer_kwargs)
+    return model

test/models/test_map_saas.py

@@ -19,7 +19,7 @@
     get_fitted_map_saas_ensemble,
     get_fitted_map_saas_model,
 )
-from botorch.models import SaasFullyBayesianSingleTaskGP, SingleTaskGP
+from botorch.models import SingleTaskGP
 from botorch.models.map_saas import (
     add_saas_prior,
     AdditiveMapSaasSingleTaskGP,
@@ -299,93 +299,21 @@ def test_get_saas_model(self) -> None:
             self.assertTrue(loss < loss_short)
 
     def test_get_saas_ensemble(self) -> None:
-        for infer_noise, taus in itertools.product([True, False], [None, [0.1, 0.2]]):
-            tkwargs = {"device": self.device, "dtype": torch.double}
-            train_X, train_Y, _ = self._get_data_hardcoded(**tkwargs)
-            d = train_X.shape[-1]
-            train_Yvar = (
-                None
-                if infer_noise
-                else 0.1 * torch.arange(len(train_X), **tkwargs).unsqueeze(-1)
-            )
-            # Fit without specifying tau
-            with torch.random.fork_rng():
-                torch.manual_seed(0)
-                model = get_fitted_map_saas_ensemble(
-                    train_X=train_X,
-                    train_Y=train_Y,
-                    train_Yvar=train_Yvar,
-                    input_transform=Normalize(d=d),
-                    outcome_transform=Standardize(m=1),
-                    taus=taus,
-                )
-            self.assertIsInstance(model, SaasFullyBayesianSingleTaskGP)
-            num_taus = 4 if taus is None else len(taus)
-            self.assertEqual(
-                model.covar_module.base_kernel.lengthscale.shape,
-                torch.Size([num_taus, 1, d]),
-            )
-            self.assertEqual(model.batch_shape, torch.Size([num_taus]))
-            # Make sure the lengthscales are reasonable
-            self.assertGreater(
-                model.covar_module.base_kernel.lengthscale[..., 1:].min(), 50
-            )
-            self.assertLess(
-                model.covar_module.base_kernel.lengthscale[..., 0].max(), 10
-            )
-
-            # testing optimizer_options: short optimization run with maxiter = 3
-            with torch.random.fork_rng():
-                torch.manual_seed(0)
-                fit_gpytorch_mll_mock = mock.Mock(wraps=fit_gpytorch_mll)
-                with mock.patch(
-                    "botorch.fit.fit_gpytorch_mll",
-                    new=fit_gpytorch_mll_mock,
-                ):
-                    maxiter = 3
-                    model_short = get_fitted_map_saas_ensemble(
-                        train_X=train_X,
-                        train_Y=train_Y,
-                        train_Yvar=train_Yvar,
-                        input_transform=Normalize(d=d),
-                        outcome_transform=Standardize(m=1),
-                        taus=taus,
-                        optimizer_kwargs={"options": {"maxiter": maxiter}},
-                    )
-                    kwargs = fit_gpytorch_mll_mock.call_args.kwargs
-                    # fit_gpytorch_mll has "option" kwarg, not "optimizer_options"
-                    self.assertEqual(
-                        kwargs["optimizer_kwargs"]["options"]["maxiter"], maxiter
-                    )
-
-            # compute sum of marginal likelihoods of ensemble after short run
-            # NOTE: We can't put MLL in train mode here since
-            # SaasFullyBayesianSingleTaskGP requires NUTS for training.
-            mll_short = ExactMarginalLogLikelihood(
-                model=model_short, likelihood=model_short.likelihood
+        train_X, train_Y, _ = self._get_data_hardcoded(device=self.device)
+        with self.assertWarnsRegex(
+            DeprecationWarning, "EnsembleMapSaasSingleTaskGP"
+        ), mock.patch("botorch.fit.fit_gpytorch_mll") as mock_fit:
+            model = get_fitted_map_saas_ensemble(
+                train_X=train_X,
+                train_Y=train_Y,
+                input_transform=Normalize(d=train_X.shape[-1]),
+                outcome_transform=Standardize(m=1, batch_shape=torch.Size([4])),
+                optimizer_kwargs={"options": {"maxiter": 3}},
             )
-            train_inputs = mll_short.model.train_inputs
-            train_targets = mll_short.model.train_targets
-            loss_short = -mll_short(model_short(*train_inputs), train_targets)
-            # compute sum of marginal likelihoods of ensemble after standard run
-            mll = ExactMarginalLogLikelihood(model=model, likelihood=model.likelihood)
-            # reusing train_inputs and train_targets, since the transforms are the same
-            loss = -mll(model(*train_inputs), train_targets)
-            # the longer running optimization should have smaller loss than the shorter
-            self.assertLess((loss - loss_short).max(), 0.0)
-
-            # test error message
-            with self.assertRaisesRegex(
-                ValueError, "if you only specify one value of tau"
-            ):
-                model_short = get_fitted_map_saas_ensemble(
-                    train_X=train_X,
-                    train_Y=train_Y,
-                    train_Yvar=train_Yvar,
-                    input_transform=Normalize(d=d),
-                    outcome_transform=Standardize(m=1),
-                    taus=[0.1],
-                )
+        self.assertEqual(
+            mock_fit.call_args.kwargs["optimizer_kwargs"], {"options": {"maxiter": 3}}
+        )
+        self.assertIsInstance(model, EnsembleMapSaasSingleTaskGP)
 
     def test_input_transform_in_train(self) -> None:
         train_X, train_Y, test_X = self._get_data()
@@ -522,7 +450,7 @@ def test_batch_model_fitting(self) -> None:
 
     @mock_optimize
     def test_emsemble_map_saas(self) -> None:
-        train_X, train_Y, test_X = self._get_data()
+        train_X, train_Y, test_X = self._get_data(device=self.device)
         d = train_X.shape[-1]
         num_taus = 8
         for with_options in (False, True):