From 8f23a8af661af10b31f71b0110537857feb6e09f Mon Sep 17 00:00:00 2001 From: FilippoOlivo Date: Thu, 16 Oct 2025 15:20:58 +0200 Subject: [PATCH] Add pointnet --- .../{data_module.py => graph_datamodule.py} | 1 - ThermalSolver/model/point_net.py | 574 ++++++++++++++++++ ThermalSolver/point_datamodule.py | 171 ++++++ ThermalSolver/point_module.py | 92 +++ 4 files changed, 837 insertions(+), 1 deletion(-) rename ThermalSolver/{data_module.py => graph_datamodule.py} (99%) create mode 100644 ThermalSolver/model/point_net.py create mode 100644 ThermalSolver/point_datamodule.py create mode 100644 ThermalSolver/point_module.py diff --git a/ThermalSolver/data_module.py b/ThermalSolver/graph_datamodule.py similarity index 99% rename from ThermalSolver/data_module.py rename to ThermalSolver/graph_datamodule.py index a8289af..c5d4ce5 100644 --- a/ThermalSolver/data_module.py +++ b/ThermalSolver/graph_datamodule.py @@ -24,7 +24,6 @@ class GraphDataModule(LightningDataModule): self.hf_repo = hf_repo self.split_name = split_name self.dataset_dict = {} - # self.geometry = None self.geometry_dict = {} self.train_size = train_size self.val_size = val_size diff --git a/ThermalSolver/model/point_net.py b/ThermalSolver/model/point_net.py new file mode 100644 index 0000000..700e286 --- /dev/null +++ b/ThermalSolver/model/point_net.py @@ -0,0 +1,574 @@ +import torch +import torch.nn as nn + + +class ResidualBlock(nn.Module): + """Residual block base class. Implementation of a residual block. + + Reference: https://arxiv.org/pdf/1512.03385.pdf : Equation #2 + """ + + def __init__(self, input_dim, output_dim, hidden_dim, spectral_norm=False): + """Residual block constructor + + :param input_dim: dimension of the input + :type input_dim: int + :param output_dim: dimension of the output + :type output_dim: int + :param hidden_dim: hidden dimension for mapping the input (first block) + :type hidden_dim: int + :param spectral_norm: apply spectral normalization, defaults to False + :type spectral_norm: bool, optional + """ + super().__init__() + + self._spectral_norm = spectral_norm + self._input_dim = input_dim + self._output_dim = output_dim + self._hidden_dim = hidden_dim + + self.l1 = self._spect_norm(nn.Linear(input_dim, hidden_dim)) + self.l2 = self._spect_norm(nn.Linear(hidden_dim, output_dim)) + self.l3 = self._spect_norm(nn.Linear(input_dim, output_dim)) + + def forward(self, x): + y = self.activation(self.l1(x)) + y = self.l2(y) + x = self.l3(x) + return y + x + + def _spect_norm(self, x): + return nn.utils.spectral_norm(x) if self._spectral_norm else x + + @property + def spectral_norm(self): + return self._spectral_norm + + @property + def input_dim(self): + return self._input_dim + + @property + def output_dim(self): + return self._output_dim + + @property + def hidden_dim(self): + return self._hidden_dim + + +class MLP(torch.nn.Module): + """Multi-layer Perceptron base class""" + + def __init__( + self, + input_dim, + output_dim, + inner_size=20, + n_layers=2, + func=nn.Tanh, + layers=None, + batch_norm=False, + spectral_norm=False, + ): + """Deep neural network model + + :param input_dim: input channel for the network + :type input_dim: int + :param output_dim: output channel for the network + :type output_dim: int + :param inner_size: inner size of each hidden layer, defaults to 20 + :type inner_size: int, optional + :param n_layers: number of layers in the network, defaults to 2 + :type n_layers: int, optional + :param func: function(s) to pass to the network, defaults to nn.Tanh + :type func: (list of) torch.nn function(s), optional + :param layers: list of layers for the network, defaults to None + :type layers: list[int], optional + :param batch_norm: apply batch normalization layer + :type bool, default False + :param spectral_norm: apply spectral normalization layer + :type bool, default False + """ + super().__init__() + + self._input_dim = input_dim + self._output_dim = output_dim + self._inner_size = inner_size + self._n_layers = n_layers + self._layers = layers + self._bnorm = batch_norm + self._spectnorm = spectral_norm + + if layers is None: + layers = [inner_size] * n_layers + + tmp_layers = layers.copy() + tmp_layers.insert(0, self._input_dim) + tmp_layers.append(self._output_dim) + + self._layers = [] + self._batchnorm = [] + for i in range(len(tmp_layers) - 1): + + self._layers.append( + self.spect_norm(nn.Linear(tmp_layers[i], tmp_layers[i + 1])) + ) + + self._batchnorm.append(nn.LazyBatchNorm1d()) + + if isinstance(func, list): + self._functions = func + else: + self._functions = [func for _ in range(len(self._layers) - 1)] + + unique_list = [] + for layer, func, bnorm in zip( + self._layers[:-1], self._functions, self._batchnorm + ): + + unique_list.append(layer) + if func is not None: + if batch_norm: + unique_list.append(bnorm) + unique_list.append(func()) + + unique_list.append(self._layers[-1]) + + self.model = nn.Sequential(*unique_list) + + def spect_norm(self, x): + return nn.utils.spectral_norm(x) if self._spectnorm else x + + def forward(self, x): + """Forward method for NeuralNet class + + :param x: network input data + :type x: torch.tensor + :return: network output + :rtype: torch.tensor + """ + return self.model(x) + + @property + def input_dim(self): + return self._input_dim + + @property + def output_dim(self): + return self._output_dim + + @property + def inner_size(self): + return self._inner_size + + @property + def n_layers(self): + return self._n_layers + + @property + def functions(self): + return self._functions + + @property + def layers(self): + return self._layers + + +class TNet(nn.Module): + """T-Net base class. Implementation of T-Network. + + Reference: Charles R. Qi et al. https://arxiv.org/pdf/1612.00593.pdf + """ + + def __init__(self, input_dim): + """T-Net block constructor + + :param input_dim: input dimension of point cloud + :type input_dim: int + """ + super().__init__() + + function = nn.Tanh + + self._mlp1 = MLP( + input_dim=input_dim, + output_dim=1024, + layers=[64, 128], + func=function, + batch_norm=True, + ) + + self._mlp2 = MLP( + input_dim=1024, + output_dim=input_dim * input_dim, + layers=[512, 256], + func=function, + batch_norm=True, + ) + + self._function = function() + self._bn1 = nn.LazyBatchNorm1d() + + def forward(self, X): + """Forward pass for T-Net + + :param X: input tensor, shape [batch, N, $input_{dim}$] + with batch the batch size, N number of points and $input_{dim}$ + the input dimension of the point cloud. + :type X: torch.tensor + :return: output affine matrix transformation, shape + [batch, $input_{dim} \times input_{dim}$] with batch + the batch size and $input_{dim}$ the input dimension + of the point cloud. + :rtype: torch.tensor + """ + + batch, input_dim = X.shape[0], X.shape[2] + + # encoding using first MLP + X = self._mlp1(X) + X = self._function(self._bn1(X)) + + # applying symmetric function to aggregate information (using max as default) + X, _ = torch.max(X, dim=1) + + # decoding using third MLP + X = self._mlp2(X) + + return X.reshape(batch, input_dim, input_dim) + + +class PointNet(nn.Module): + """Point-Net base class. Implementation of Point Network for segmentation. + + Reference: Charles R. Qi et al. https://arxiv.org/pdf/1612.00593.pdf + """ + + def __init__(self, input_dim, output_dim, tnet=False): + """Point-Net block constructor + + :param input_dim: input dimension of point cloud + :type input_dim: int + :param output_dim: output dimension of point cloud + :type output_dim: int + :param tnet: apply T-Net transformation, defaults to False + :type tnet: bool, optional + """ + super().__init__() + + function = nn.Tanh + self._use_tnet = tnet + + self._mlp1 = MLP( + input_dim=input_dim, + output_dim=64, + inner_size=64, + n_layers=1, + func=function, + batch_norm=True, + ) + + self._mlp2 = MLP( + input_dim=64, + output_dim=1024, + inner_size=128, + n_layers=1, + func=function, + batch_norm=True, + ) + + self._mlp3 = MLP( + input_dim=1088, + output_dim=128, + layers=[512, 256], + func=function, + batch_norm=True, + ) + + self._mlp4 = MLP( + input_dim=128, + output_dim=output_dim, + n_layers=0, + func=function, + batch_norm=True, + ) + + if self._use_tnet: + self._tnet_transform = TNet(input_dim=input_dim) + self._tnet_feature = TNet(input_dim=64) + + self._function = function() + self._bn1 = nn.LazyBatchNorm1d() + self._bn2 = nn.LazyBatchNorm1d() + self._bn3 = nn.LazyBatchNorm1d() + + def concat(self, embedding, input_): + """Returns concatenation of global and local features for Point-Net + + :param embedding: global features of Point-Net, shape [batch, $input_{dim}$] + with batch the batch size and $input_{dim}$ the input dimension + of the point cloud. + :type embedding: torch.tensor + :param input_: local features of Point-Net, shape [batch, N, $input_{dim}$] + with batch the batch size, N number of points and $input_{dim}$ + the input dimension of the point cloud. + :type input_: torch.tensor + :return: concatenation vector, shape [batch, N, $input_{dim}$] + with batch the batch size, N number of points and $input_{dim}$ + :rtype: torch.tensor + """ + n_points = input_.shape[1] + embedding = embedding.repeat(n_points, 1, 1).permute(1, 0, 2) + return torch.cat([embedding, input_], dim=2) + + def forward(self, X): + """Forward pass for Point-Net + + :param X: input tensor, shape [batch, N, $input_{dim}$] + with batch the batch size, N number of points and $input_{dim}$ + the input dimension of the point cloud. + :type X: torch.tensor + :return: segmentation vector, shape [batch, N, $output_{dim}$] + with batch the batch size, N number of points and $output_{dim}$ + the output dimension of the point cloud. + :rtype: torch.tensor + """ + + # using transform tnet if needed + if self._use_tnet: + transform = self._tnet_transform(X) + X = torch.matmul(X, transform) + + # encoding using first MLP + X = self._mlp1(X) + X = self._function(self._bn1(X)) + + # using transform tnet if needed + if self._use_tnet: + transform = self._tnet_feature(X) + X = torch.matmul(X, transform) + + # saving latent representation for later concatanation + latent = X + + # encoding using second MLP + X = self._mlp2(X) + X = self._function(self._bn2(X)) + + # applying symmetric function to aggregate information (using max as default) + X, _ = torch.max(X, dim=1) + + # concatenating with latent vector + X = self.concat(X, latent) + + # decoding using third MLP + X = self._mlp3(X) + X = self._function(self._bn3(X)) + + # decoding using fourth MLP + X = self._mlp4(X) + + return X + + +class ConvTNet(nn.Module): + """T-Net base class. Implementation of T-Network with convolutional layers. + + Reference: Ali Kashefi et al. https://arxiv.org/abs/2208.13434 + """ + + def __init__(self, input_dim): + """T-Net block constructor + + :param input_dim: input dimension of point cloud + :type input_dim: int + """ + super().__init__() + + function = nn.Tanh + self._function = function() + + self._block1 = nn.Sequential( + nn.Conv1d(input_dim, 64, 1), + nn.BatchNorm1d(64), + self._function, + nn.Conv1d(64, 128, 1), + nn.BatchNorm1d(128), + self._function, + nn.Conv1d(128, 1024, 1), + nn.BatchNorm1d(1024), + self._function, + ) + + self._block2 = MLP( + input_dim=1024, + output_dim=input_dim * input_dim, + layers=[512, 256], + func=function, + batch_norm=True, + ) + + def forward(self, X): + """Forward pass for T-Net + + :param X: input tensor, shape [batch, $input_{dim}$, N] + with batch the batch size, N number of points and $input_{dim}$ + the input dimension of the point cloud. + :type X: torch.tensor + :return: output affine matrix transformation, shape + [batch, $input_{dim} \times input_{dim}$] with batch + the batch size and $input_{dim}$ the input dimension + of the point cloud. + :rtype: torch.tensor + """ + + batch, input_dim = X.shape[0], X.shape[1] + + # encoding using first MLP + X = self._block1(X) + + # applying symmetric function to aggregate information (using max as default) + X, _ = torch.max(X, dim=-1) + + # decoding using third MLP + X = self._block2(X) + + return X.reshape(batch, input_dim, input_dim) + + +class ConvPointNet(nn.Module): + """Point-Net base class. Implementation of Point Network for segmentation. + + Reference: Ali Kashefi et al. https://arxiv.org/abs/2208.13434 + """ + + def __init__(self, input_dim, output_dim, tnet=False): + """Point-Net block constructor + + :param input_dim: input dimension of point cloud + :type input_dim: int + :param output_dim: output dimension of point cloud + :type output_dim: int + :param tnet: apply T-Net transformation, defaults to False + :type tnet: bool, optional + """ + super().__init__() + + self._function = nn.Tanh() + self._use_tnet = tnet + + self._block1 = nn.Sequential( + nn.Conv1d(input_dim, 64, 1), + nn.BatchNorm1d(64), + self._function, + nn.Conv1d(64, 64, 1), + nn.BatchNorm1d(64), + self._function, + ) + + self._block2 = nn.Sequential( + nn.Conv1d(64, 64, 1), + nn.BatchNorm1d(64), + self._function, + nn.Conv1d(64, 128, 1), + nn.BatchNorm1d(128), + self._function, + nn.Conv1d(128, 1024, 1), + nn.BatchNorm1d(1024), + self._function, + ) + + self._block3 = nn.Sequential( + nn.Conv1d(1088, 512, 1), + nn.BatchNorm1d(512), + self._function, + nn.Conv1d(512, 256, 1), + nn.BatchNorm1d(256), + self._function, + nn.Conv1d(256, 128, 1), + nn.BatchNorm1d(128), + self._function, + ) + + self._block4 = nn.Conv1d(128, output_dim, 1) + + if self._use_tnet: + self._tnet_transform = ConvTNet(input_dim=input_dim) + self._tnet_feature = ConvTNet(input_dim=64) + + def concat(self, embedding, input_): + """ + Returns concatenation of global and local features for Point-Net + + :param embedding: global features of Point-Net, shape [batch, $input_{dim}$] + with batch the batch size and $input_{dim}$ the input dimension + of the point cloud. + :type embedding: torch.tensor + :param input_: local features of Point-Net, shape [batch, N, $input_{dim}$] + with batch the batch size, N number of points and $input_{dim}$ + the input dimension of the point cloud. + :type input_: torch.tensor + :return: concatenation vector, shape [batch, N, $input_{dim}$] + with batch the batch size, N number of points and $input_{dim}$ + :rtype: torch.tensor + """ + n_points = input_.shape[-1] + embedding = embedding.unsqueeze(2).repeat(1, 1, n_points) + return torch.cat([embedding, input_], dim=1) + + def forward(self, X): + """Forward pass for Point-Net + + :param X: input tensor, shape [batch, N, $input_{dim}$] + with batch the batch size, N number of points and $input_{dim}$ + the input dimension of the point cloud. + :type X: torch.tensor + :return: segmentation vector, shape [batch, N, $output_{dim}$] + with batch the batch size, N number of points and $output_{dim}$ + the output dimension of the point cloud. + :rtype: torch.tensor + """ + + # permuting indeces + X = X.permute(0, 2, 1) + + # using transform tnet if needed + if self._use_tnet: + transform = self._tnet_transform(X) + X = X.transpose(2, 1) + X = torch.matmul(X, transform) + X = X.transpose(2, 1) + + # encoding using first MLP + X = self._block1(X) + + # using transform tnet if needed + if self._use_tnet: + transform = self._tnet_feature(X) + X = X.transpose(2, 1) + X = torch.matmul(X, transform) + X = X.transpose(2, 1) + + # saving latent representation for later concatanation + latent = X + + # encoding using second MLP + X = self._block2(X) + + # applying symmetric function to aggregate information (using max as default) + X, _ = torch.max(X, dim=-1) + + # concatenating with latent vector + X = self.concat(X, latent) + + # decoding using third MLP + X = self._block3(X) + + # decoding using fourth MLP + X = self._block4(X) + + # permuting indeces + X = X.permute(0, 2, 1) + + return X diff --git a/ThermalSolver/point_datamodule.py b/ThermalSolver/point_datamodule.py new file mode 100644 index 0000000..04cb886 --- /dev/null +++ b/ThermalSolver/point_datamodule.py @@ -0,0 +1,171 @@ +import torch +from tqdm import tqdm +from lightning import LightningDataModule +from datasets import load_dataset +import os +from torch.utils.data import DataLoader, TensorDataset +from torch.nn.utils.rnn import pad_sequence + + +class PointDataModule(LightningDataModule): + def __init__( + self, + hf_repo: str, + split_name: str, + train_size: float = 0.2, + val_size: float = 0.1, + test_size: float = 0.1, + batch_size: int = 32, + remove_boundary_edges: bool = True, + ): + super().__init__() + self.hf_repo = hf_repo + self.split_name = split_name + self.dataset_dict = {} + self.geometry_dict = {} + self.train_size = train_size + self.val_size = val_size + self.test_size = test_size + self.batch_size = batch_size + self.remove_boundary_edges = remove_boundary_edges + + def prepare_data(self): + dataset = load_dataset(self.hf_repo, name="snapshots")[self.split_name] + geometry = load_dataset(self.hf_repo, name="geometry")[self.split_name] + + total_len = len(dataset) + train_len = int(self.train_size * total_len) + valid_len = int(self.val_size * total_len) + self.dataset_dict = { + "train": dataset.select(range(0, train_len)), + "val": dataset.select(range(train_len, train_len + valid_len)), + "test": dataset.select(range(train_len + valid_len, total_len)), + } + self.geometry_dict = { + "train": geometry.select(range(0, train_len)), + "val": geometry.select(range(train_len, train_len + valid_len)), + "test": geometry.select(range(train_len + valid_len, total_len)), + } + + def _compute_boundary_mask( + self, bottom_ids, right_ids, top_ids, left_ids, temperature + ): + left_ids = left_ids[~torch.isin(left_ids, bottom_ids)] + right_ids = right_ids[~torch.isin(right_ids, bottom_ids)] + left_ids = left_ids[~torch.isin(left_ids, top_ids)] + right_ids = right_ids[~torch.isin(right_ids, top_ids)] + + bottom_bc = temperature[bottom_ids].median() + bottom_bc_mask = torch.ones(len(bottom_ids)) * bottom_bc + left_bc = temperature[left_ids].median() + left_bc_mask = torch.ones(len(left_ids)) * left_bc + right_bc = temperature[right_ids].median() + right_bc_mask = torch.ones(len(right_ids)) * right_bc + + boundary_values = torch.cat( + [bottom_bc_mask, right_bc_mask, left_bc_mask], dim=0 + ) + boundary_mask = torch.cat([bottom_ids, right_ids, left_ids], dim=0) + + return boundary_mask, boundary_values + + def _build_dataset( + self, + snapshot: dict, + geometry: dict, + ) -> tuple[torch.Tensor, torch.Tensor]: + conductivity = torch.tensor( + snapshot["conductivity"], dtype=torch.float32 + ) + temperature = torch.tensor(snapshot["temperature"], dtype=torch.float32) + pos = torch.tensor(geometry["points"], dtype=torch.float32)[:, :2] + bottom_ids = torch.tensor( + geometry["bottom_boundary_ids"], dtype=torch.long + ) + top_ids = torch.tensor(geometry["top_boundary_ids"], dtype=torch.long) + left_ids = torch.tensor(geometry["left_boundary_ids"], dtype=torch.long) + right_ids = torch.tensor( + geometry["right_boundary_ids"], dtype=torch.long + ) + + boundary_mask, boundary_values = self._compute_boundary_mask( + bottom_ids, right_ids, top_ids, left_ids, temperature + ) + + x = torch.zeros_like(temperature, dtype=torch.float32).unsqueeze(-1) + x[boundary_mask] = boundary_values.unsqueeze(-1) + x = torch.cat([x, conductivity.unsqueeze(-1), pos], dim=-1) + return x, temperature.unsqueeze(-1) + + def setup(self, stage: str = None): + if stage == "fit" or stage is None: + x = [] + y = [] + for snap, geom in tqdm( + zip(self.dataset_dict["train"], self.geometry_dict["train"]), + desc="Building train graphs", + total=len(self.dataset_dict["train"]), + ): + x_i, y_i = self._build_dataset(snap, geom) + x.append(x_i) + y.append(y_i) + self.train_dataset = TensorDataset( + pad_sequence(x, batch_first=True, padding_value=-1), + pad_sequence(y, batch_first=True, padding_value=-1), + ) + + for snap, geom in tqdm( + zip(self.dataset_dict["val"], self.geometry_dict["val"]), + desc="Building val graphs", + total=len(self.dataset_dict["val"]), + ): + x_i, y_i = self._build_dataset(snap, geom) + x.append(x_i) + y.append(y_i) + self.val_dataset = TensorDataset( + pad_sequence(x, batch_first=True, padding_value=-1), + pad_sequence(y, batch_first=True, padding_value=-1), + ) + + if stage == "test" or stage is None: + x = [] + y = [] + for snap, geom in tqdm( + zip(self.dataset_dict["test"], self.geometry_dict["test"]), + desc="Building test graphs", + total=len(self.dataset_dict["test"]), + ): + x_i, y_i = self._build_dataset(snap, geom) + x.append(x_i) + y.append(y_i) + self.test_data = TensorDataset( + pad_sequence(x, batch_first=True, padding_value=-1), + pad_sequence(y, batch_first=True, padding_value=-1), + ) + + def train_dataloader(self): + return DataLoader( + self.train_dataset, + batch_size=self.batch_size, + shuffle=True, + num_workers=8, + pin_memory=True, + ) + + def val_dataloader(self): + return DataLoader( + self.val_dataset, + batch_size=self.batch_size, + shuffle=False, + num_workers=8, + pin_memory=True, + ) + + def test_dataloader(self): + return DataLoader( + self.test_data, + batch_size=self.batch_size, + shuffle=False, + num_workers=8, + pin_memory=True, + ) diff --git a/ThermalSolver/point_module.py b/ThermalSolver/point_module.py new file mode 100644 index 0000000..a3bf592 --- /dev/null +++ b/ThermalSolver/point_module.py @@ -0,0 +1,92 @@ +import torch +from lightning import LightningModule +import importlib +from matplotlib import pyplot as plt +from matplotlib.tri import Triangulation + + +def _plot_mesh(x, y, y_pred): + x = x[0, ...].detach().cpu() + pos = x[0, ...].detach().cpu() + pos = x[x[:, 0] != -1] + y = y[0, ...].detach().cpu() + y = y[x[:, 0] != -1] + y_pred = y_pred[0, ...].detach().cpu() + y_pred = y_pred[x[:, 0] != -1] + + tria = Triangulation(pos[:, 2], pos[:, 3]) + plt.figure(figsize=(12, 5)) + plt.subplot(1, 2, 1) + plt.tricontourf(tria, y.squeeze().numpy(), levels=14) + plt.colorbar() + plt.title("True temperature") + plt.subplot(1, 2, 2) + plt.tricontourf(tria, y_pred.squeeze().numpy(), levels=14) + plt.colorbar() + plt.title("Predicted temperature") + plt.savefig("point_net.png", dpi=300) + + +def import_class(class_path: str): + module_path, class_name = class_path.rsplit(".", 1) # split last dot + module = importlib.import_module(module_path) # import the module + cls = getattr(module, class_name) # get the class + return cls + + +class PointSolver(LightningModule): + def __init__( + self, + model_class_path: str, + model_init_args: dict, + loss: torch.nn.Module = None, + ): + super().__init__() + self.model = import_class(model_class_path)(**model_init_args) + self.loss = loss if loss is not None else torch.nn.MSELoss() + + def forward( + self, + x: torch.Tensor, + ): + return self.model(x) + + def _compute_loss(self, x, y): + return self.loss(x, y) + + def _log_loss(self, loss, batch, stage: str): + self.log( + f"{stage}/loss", + loss, + on_step=False, + on_epoch=True, + prog_bar=True, + batch_size=len(batch), + ) + return loss + + def training_step(self, batch, _): + x, y = batch + y_pred = self(x) + loss = self.loss(y_pred, y) + self._log_loss(loss, batch, "train") + return loss + + def validation_step(self, batch, _): + x, y = batch + y_pred = self(x) + loss = self.loss(y_pred, y) + self._log_loss(loss, batch, "val") + return loss + + def test_step(self, batch, _): + x, y = batch + y_pred = self.model(x) + loss = self._compute_loss(y_pred, y) + self._log_loss(loss, batch, "test") + _plot_mesh(x, y, y_pred) + return loss + + def configure_optimizers(self): + optimizer = torch.optim.Adam(self.parameters(), lr=1e-3) + return optimizer