train.py

#BSD 3-Clause License
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#Copyright (c) 2022, FourCastNet authors
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#   this list of conditions and the following disclaimer in the documentation
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#THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
#AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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#FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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#OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#The code was authored by the following people:
#
#Jaideep Pathak - NVIDIA Corporation
#Shashank Subramanian - NERSC, Lawrence Berkeley National Laboratory
#Peter Harrington - NERSC, Lawrence Berkeley National Laboratory
#Sanjeev Raja - NERSC, Lawrence Berkeley National Laboratory 
#Ashesh Chattopadhyay - Rice University 
#Morteza Mardani - NVIDIA Corporation 
#Thorsten Kurth - NVIDIA Corporation 
#David Hall - NVIDIA Corporation 
#Zongyi Li - California Institute of Technology, NVIDIA Corporation 
#Kamyar Azizzadenesheli - Purdue University 
#Pedram Hassanzadeh - Rice University 
#Karthik Kashinath - NVIDIA Corporation 
#Animashree Anandkumar - California Institute of Technology, NVIDIA Corporation

import os
import time
import numpy as np
import argparse
import h5py
import torch
import cProfile
import re
import torchvision
from torchvision.utils import save_image
import torch.nn as nn
import torch.cuda.amp as amp
import torch.distributed as dist
from torch.nn.parallel import DistributedDataParallel
import logging
from utils import logging_utils
logging_utils.config_logger()
from utils.YParams import YParams
from utils.data_loader_multifiles import get_data_loader
from networks.afnonet import AFNONet, PrecipNet
from utils.img_utils import vis_precip
import wandb
from utils.weighted_acc_rmse import weighted_acc, weighted_rmse, weighted_rmse_torch, unlog_tp_torch
from apex import optimizers
from utils.darcy_loss import LpLoss
import matplotlib.pyplot as plt
from collections import OrderedDict
import pickle
DECORRELATION_TIME = 36 # 9 days
import json
from ruamel.yaml import YAML
from ruamel.yaml.comments import CommentedMap as ruamelDict

class Trainer():
  def count_parameters(self):
    return sum(p.numel() for p in self.model.parameters() if p.requires_grad)

  def __init__(self, params, world_rank):
    
    self.params = params
    self.world_rank = world_rank
    self.device = torch.cuda.current_device() if torch.cuda.is_available() else 'cpu'

    if params.log_to_wandb:
      wandb.init(config=params, name=params.name, group=params.group, project=params.project, entity=params.entity)

    logging.info('rank %d, begin data loader init'%world_rank)
    self.train_data_loader, self.train_dataset, self.train_sampler = get_data_loader(params, params.train_data_path, dist.is_initialized(), train=True)
    self.valid_data_loader, self.valid_dataset = get_data_loader(params, params.valid_data_path, dist.is_initialized(), train=False)
    self.loss_obj = LpLoss()
    logging.info('rank %d, data loader initialized'%world_rank)

    params.crop_size_x = self.valid_dataset.crop_size_x
    params.crop_size_y = self.valid_dataset.crop_size_y
    params.img_shape_x = self.valid_dataset.img_shape_x
    params.img_shape_y = self.valid_dataset.img_shape_y

    # precip models
    self.precip = True if "precip" in params else False
    
    if self.precip:
      if 'model_wind_path' not in params:
        raise Exception("no backbone model weights specified")
      # load a wind model 
      # the wind model has out channels = in channels
      out_channels = np.array(params['in_channels'])
      params['N_out_channels'] = len(out_channels)

      if params.nettype_wind == 'afno':
        self.model_wind = AFNONet(params).to(self.device)
      else:
        raise Exception("not implemented")

      if dist.is_initialized():
        self.model_wind = DistributedDataParallel(self.model_wind,
                                            device_ids=[params.local_rank],
                                            output_device=[params.local_rank],find_unused_parameters=True)
      self.load_model_wind(params.model_wind_path)
      self.switch_off_grad(self.model_wind) # no backprop through the wind model


    # reset out_channels for precip models
    if self.precip:
      params['N_out_channels'] = len(params['out_channels'])

    if params.nettype == 'afno':
      self.model = AFNONet(params).to(self.device) 
    else:
      raise Exception("not implemented")
     
    # precip model
    if self.precip:
      self.model = PrecipNet(params, backbone=self.model).to(self.device)

    if self.params.enable_nhwc:
      # NHWC: Convert model to channels_last memory format
      self.model = self.model.to(memory_format=torch.channels_last)

    if params.log_to_wandb:
      wandb.watch(self.model)

    if params.optimizer_type == 'FusedAdam':
      self.optimizer = optimizers.FusedAdam(self.model.parameters(), lr = params.lr)
    else:
      self.optimizer = torch.optim.Adam(self.model.parameters(), lr = params.lr)

    if params.enable_amp == True:
      self.gscaler = amp.GradScaler()

    if dist.is_initialized():
      self.model = DistributedDataParallel(self.model,
                                           device_ids=[params.local_rank],
                                           output_device=[params.local_rank],find_unused_parameters=True)

    self.iters = 0
    self.startEpoch = 0
    if params.resuming:
      logging.info("Loading checkpoint %s"%params.checkpoint_path)
      self.restore_checkpoint(params.checkpoint_path)
    if params.two_step_training:
      if params.resuming == False and params.pretrained == True:
        logging.info("Starting from pretrained one-step afno model at %s"%params.pretrained_ckpt_path)
        self.restore_checkpoint(params.pretrained_ckpt_path)
        self.iters = 0
        self.startEpoch = 0
        #logging.info("Pretrained checkpoint was trained for %d epochs"%self.startEpoch)
        #logging.info("Adding %d epochs specified in config file for refining pretrained model"%self.params.max_epochs)
        #self.params.max_epochs += self.startEpoch

            
    self.epoch = self.startEpoch

    if params.scheduler == 'ReduceLROnPlateau':
      self.scheduler = torch.optim.lr_scheduler.ReduceLROnPlateau(self.optimizer, factor=0.2, patience=5, mode='min')
    elif params.scheduler == 'CosineAnnealingLR':
      self.scheduler = torch.optim.lr_scheduler.CosineAnnealingLR(self.optimizer, T_max=params.max_epochs, last_epoch=self.startEpoch-1)
    else:
      self.scheduler = None

    '''if params.log_to_screen:
      logging.info(self.model)'''
    if params.log_to_screen:
      logging.info("Number of trainable model parameters: {}".format(self.count_parameters()))

  def switch_off_grad(self, model):
    for param in model.parameters():
      param.requires_grad = False

  def train(self):
    if self.params.log_to_screen:
      logging.info("Starting Training Loop...")

    best_valid_loss = 1.e6
    for epoch in range(self.startEpoch, self.params.max_epochs):
      if dist.is_initialized():
        self.train_sampler.set_epoch(epoch)
#        self.valid_sampler.set_epoch(epoch)

      start = time.time()
      tr_time, data_time, train_logs = self.train_one_epoch()
      valid_time, valid_logs = self.validate_one_epoch()
      if epoch==self.params.max_epochs-1 and self.params.prediction_type == 'direct':
        valid_weighted_rmse = self.validate_final()



      if self.params.scheduler == 'ReduceLROnPlateau':
        self.scheduler.step(valid_logs['valid_loss'])
      elif self.params.scheduler == 'CosineAnnealingLR':
        self.scheduler.step()
        if self.epoch >= self.params.max_epochs:
          logging.info("Terminating training after reaching params.max_epochs while LR scheduler is set to CosineAnnealingLR")
          exit()

      if self.params.log_to_wandb:
        for pg in self.optimizer.param_groups:
          lr = pg['lr']
        wandb.log({'lr': lr})

      if self.world_rank == 0:
        if self.params.save_checkpoint:
          #checkpoint at the end of every epoch
          self.save_checkpoint(self.params.checkpoint_path)
          if valid_logs['valid_loss'] <= best_valid_loss:
            #logging.info('Val loss improved from {} to {}'.format(best_valid_loss, valid_logs['valid_loss']))
            self.save_checkpoint(self.params.best_checkpoint_path)
            best_valid_loss = valid_logs['valid_loss']

      if self.params.log_to_screen:
        logging.info('Time taken for epoch {} is {} sec'.format(epoch + 1, time.time()-start))
        #logging.info('train data time={}, train step time={}, valid step time={}'.format(data_time, tr_time, valid_time))
        logging.info('Train loss: {}. Valid loss: {}'.format(train_logs['loss'], valid_logs['valid_loss']))
#        if epoch==self.params.max_epochs-1 and self.params.prediction_type == 'direct':
#          logging.info('Final Valid RMSE: Z500- {}. T850- {}, 2m_T- {}'.format(valid_weighted_rmse[0], valid_weighted_rmse[1], valid_weighted_rmse[2]))



  def train_one_epoch(self):
    self.epoch += 1
    tr_time = 0
    data_time = 0
    self.model.train()
    
    for i, data in enumerate(self.train_data_loader, 0):
      self.iters += 1
      # adjust_LR(optimizer, params, iters)
      data_start = time.time()
      inp, tar = map(lambda x: x.to(self.device, dtype = torch.float), data)      
      if self.params.orography and self.params.two_step_training:
          orog = inp[:,-2:-1] 


      if self.params.enable_nhwc:
        inp = inp.to(memory_format=torch.channels_last)
        tar = tar.to(memory_format=torch.channels_last)


      if 'residual_field' in self.params.target:
        tar -= inp[:, 0:tar.size()[1]]
      data_time += time.time() - data_start

      tr_start = time.time()

      self.model.zero_grad()
      if self.params.two_step_training:
          with amp.autocast(self.params.enable_amp):
            gen_step_one = self.model(inp).to(self.device, dtype = torch.float)
            loss_step_one = self.loss_obj(gen_step_one, tar[:,0:self.params.N_out_channels])
            if self.params.orography:
                gen_step_two = self.model(torch.cat( (gen_step_one, orog), axis = 1)  ).to(self.device, dtype = torch.float)
            else:
                gen_step_two = self.model(gen_step_one).to(self.device, dtype = torch.float)
            loss_step_two = self.loss_obj(gen_step_two, tar[:,self.params.N_out_channels:2*self.params.N_out_channels])
            loss = loss_step_one + loss_step_two
      else:
          with amp.autocast(self.params.enable_amp):
            if self.precip: # use a wind model to predict 17(+n) channels at t+dt
              with torch.no_grad():
                inp = self.model_wind(inp).to(self.device, dtype = torch.float)
              gen = self.model(inp.detach()).to(self.device, dtype = torch.float)
            else:
              gen = self.model(inp).to(self.device, dtype = torch.float)
            loss = self.loss_obj(gen, tar)

      if self.params.enable_amp:
        self.gscaler.scale(loss).backward()
        self.gscaler.step(self.optimizer)
      else:
        loss.backward()
        self.optimizer.step()

      if self.params.enable_amp:
        self.gscaler.update()

      tr_time += time.time() - tr_start
    
    try:
        logs = {'loss': loss, 'loss_step_one': loss_step_one, 'loss_step_two': loss_step_two}
    except:
        logs = {'loss': loss}

    if dist.is_initialized():
      for key in sorted(logs.keys()):
        dist.all_reduce(logs[key].detach())
        logs[key] = float(logs[key]/dist.get_world_size())

    if self.params.log_to_wandb:
      wandb.log(logs, step=self.epoch)

    return tr_time, data_time, logs

  def validate_one_epoch(self):
    self.model.eval()
    n_valid_batches = 20 #do validation on first 20 images, just for LR scheduler
    if self.params.normalization == 'minmax':
        raise Exception("minmax normalization not supported")
    elif self.params.normalization == 'zscore':
        mult = torch.as_tensor(np.load(self.params.global_stds_path)[0, self.params.out_channels, 0, 0]).to(self.device)

    valid_buff = torch.zeros((3), dtype=torch.float32, device=self.device)
    valid_loss = valid_buff[0].view(-1)
    valid_l1 = valid_buff[1].view(-1)
    valid_steps = valid_buff[2].view(-1)
    valid_weighted_rmse = torch.zeros((self.params.N_out_channels), dtype=torch.float32, device=self.device)
    valid_weighted_acc = torch.zeros((self.params.N_out_channels), dtype=torch.float32, device=self.device)

    valid_start = time.time()

    sample_idx = np.random.randint(len(self.valid_data_loader))
    with torch.no_grad():
      for i, data in enumerate(self.valid_data_loader, 0):
        if (not self.precip) and i>=n_valid_batches:
          break    
        inp, tar  = map(lambda x: x.to(self.device, dtype = torch.float), data)
        if self.params.orography and self.params.two_step_training:
            orog = inp[:,-2:-1]

        if self.params.two_step_training:
            gen_step_one = self.model(inp).to(self.device, dtype = torch.float)
            loss_step_one = self.loss_obj(gen_step_one, tar[:,0:self.params.N_out_channels])

            if self.params.orography:
                gen_step_two = self.model(torch.cat( (gen_step_one, orog), axis = 1)  ).to(self.device, dtype = torch.float)
            else:
                gen_step_two = self.model(gen_step_one).to(self.device, dtype = torch.float)

            loss_step_two = self.loss_obj(gen_step_two, tar[:,self.params.N_out_channels:2*self.params.N_out_channels])
            valid_loss += loss_step_one + loss_step_two
            valid_l1 += nn.functional.l1_loss(gen_step_one, tar[:,0:self.params.N_out_channels])
        else:
            if self.precip:
                with torch.no_grad():
                    inp = self.model_wind(inp).to(self.device, dtype = torch.float)
                gen = self.model(inp.detach())
            else:
                gen = self.model(inp).to(self.device, dtype = torch.float)
            valid_loss += self.loss_obj(gen, tar) 
            valid_l1 += nn.functional.l1_loss(gen, tar)

        valid_steps += 1.
        # save fields for vis before log norm 
        if (i == sample_idx) and (self.precip and self.params.log_to_wandb):
          fields = [gen[0,0].detach().cpu().numpy(), tar[0,0].detach().cpu().numpy()]

        if self.precip:
          gen = unlog_tp_torch(gen, self.params.precip_eps)
          tar = unlog_tp_torch(tar, self.params.precip_eps)

        #direct prediction weighted rmse
        if self.params.two_step_training:
            if 'residual_field' in self.params.target:
                valid_weighted_rmse += weighted_rmse_torch((gen_step_one + inp), (tar[:,0:self.params.N_out_channels] + inp))
            else:
                valid_weighted_rmse += weighted_rmse_torch(gen_step_one, tar[:,0:self.params.N_out_channels])
        else:
            if 'residual_field' in self.params.target:
                valid_weighted_rmse += weighted_rmse_torch((gen + inp), (tar + inp))
            else:
                valid_weighted_rmse += weighted_rmse_torch(gen, tar)


        if not self.precip:
            try:
                os.mkdir(params['experiment_dir'] + "/" + str(i))
            except:
                pass
            #save first channel of image
            if self.params.two_step_training:
                save_image(torch.cat((gen_step_one[0,0], torch.zeros((self.valid_dataset.img_shape_x, 4)).to(self.device, dtype = torch.float), tar[0,0]), axis = 1), params['experiment_dir'] + "/" + str(i) + "/" + str(self.epoch) + ".png")
            else:
                save_image(torch.cat((gen[0,0], torch.zeros((self.valid_dataset.img_shape_x, 4)).to(self.device, dtype = torch.float), tar[0,0]), axis = 1), params['experiment_dir'] + "/" + str(i) + "/" + str(self.epoch) + ".png")

           
    if dist.is_initialized():
      dist.all_reduce(valid_buff)
      dist.all_reduce(valid_weighted_rmse)

    # divide by number of steps
    valid_buff[0:2] = valid_buff[0:2] / valid_buff[2]
    valid_weighted_rmse = valid_weighted_rmse / valid_buff[2]
    if not self.precip:
      valid_weighted_rmse *= mult

    # download buffers
    valid_buff_cpu = valid_buff.detach().cpu().numpy()
    valid_weighted_rmse_cpu = valid_weighted_rmse.detach().cpu().numpy()

    valid_time = time.time() - valid_start
    valid_weighted_rmse = mult*torch.mean(valid_weighted_rmse, axis = 0)
    if self.precip:
      logs = {'valid_l1': valid_buff_cpu[1], 'valid_loss': valid_buff_cpu[0], 'valid_rmse_tp': valid_weighted_rmse_cpu[0]}
    else:
      try:
        logs = {'valid_l1': valid_buff_cpu[1], 'valid_loss': valid_buff_cpu[0], 'valid_rmse_u10': valid_weighted_rmse_cpu[0], 'valid_rmse_v10': valid_weighted_rmse_cpu[1]}
      except:
        logs = {'valid_l1': valid_buff_cpu[1], 'valid_loss': valid_buff_cpu[0], 'valid_rmse_u10': valid_weighted_rmse_cpu[0]}#, 'valid_rmse_v10': valid_weighted_rmse[1]}
    
    if self.params.log_to_wandb:
      if self.precip:
        fig = vis_precip(fields)
        logs['vis'] = wandb.Image(fig)
        plt.close(fig)
      wandb.log(logs, step=self.epoch)

    return valid_time, logs

  def validate_final(self):
    self.model.eval()
    n_valid_batches = int(self.valid_dataset.n_patches_total/self.valid_dataset.n_patches) #validate on whole dataset
    valid_weighted_rmse = torch.zeros(n_valid_batches, self.params.N_out_channels)
    if self.params.normalization == 'minmax':
        raise Exception("minmax normalization not supported")
    elif self.params.normalization == 'zscore':
        mult = torch.as_tensor(np.load(self.params.global_stds_path)[0, self.params.out_channels, 0, 0]).to(self.device)

    with torch.no_grad():
        for i, data in enumerate(self.valid_data_loader):
          if i>100:
            break
          inp, tar = map(lambda x: x.to(self.device, dtype = torch.float), data)
          if self.params.orography and self.params.two_step_training:
              orog = inp[:,-2:-1]
          if 'residual_field' in self.params.target:
            tar -= inp[:, 0:tar.size()[1]]

        if self.params.two_step_training:
            gen_step_one = self.model(inp).to(self.device, dtype = torch.float)
            loss_step_one = self.loss_obj(gen_step_one, tar[:,0:self.params.N_out_channels])

            if self.params.orography:
                gen_step_two = self.model(torch.cat( (gen_step_one, orog), axis = 1)  ).to(self.device, dtype = torch.float)
            else:
                gen_step_two = self.model(gen_step_one).to(self.device, dtype = torch.float)

            loss_step_two = self.loss_obj(gen_step_two, tar[:,self.params.N_out_channels:2*self.params.N_out_channels])
            valid_loss[i] = loss_step_one + loss_step_two
            valid_l1[i] = nn.functional.l1_loss(gen_step_one, tar[:,0:self.params.N_out_channels])
        else:
            gen = self.model(inp)
            valid_loss[i] += self.loss_obj(gen, tar) 
            valid_l1[i] += nn.functional.l1_loss(gen, tar)

        if self.params.two_step_training:
            for c in range(self.params.N_out_channels):
              if 'residual_field' in self.params.target:
                valid_weighted_rmse[i, c] = weighted_rmse_torch((gen_step_one[0,c] + inp[0,c]), (tar[0,c]+inp[0,c]), self.device)
              else:
                valid_weighted_rmse[i, c] = weighted_rmse_torch(gen_step_one[0,c], tar[0,c], self.device)
        else:
            for c in range(self.params.N_out_channels):
              if 'residual_field' in self.params.target:
                valid_weighted_rmse[i, c] = weighted_rmse_torch((gen[0,c] + inp[0,c]), (tar[0,c]+inp[0,c]), self.device)
              else:
                valid_weighted_rmse[i, c] = weighted_rmse_torch(gen[0,c], tar[0,c], self.device)
            
        #un-normalize
        valid_weighted_rmse = mult*torch.mean(valid_weighted_rmse[0:100], axis = 0).to(self.device)

    return valid_weighted_rmse


  def load_model_wind(self, model_path):
    if self.params.log_to_screen:
      logging.info('Loading the wind model weights from {}'.format(model_path))
    checkpoint = torch.load(model_path, map_location='cuda:{}'.format(self.params.local_rank))
    if dist.is_initialized():
      self.model_wind.load_state_dict(checkpoint['model_state'])
    else:
      new_model_state = OrderedDict()
      model_key = 'model_state' if 'model_state' in checkpoint else 'state_dict'
      for key in checkpoint[model_key].keys():
          if 'module.' in key: # model was stored using ddp which prepends module
              name = str(key[7:])
              new_model_state[name] = checkpoint[model_key][key]
          else:
              new_model_state[key] = checkpoint[model_key][key]
      self.model_wind.load_state_dict(new_model_state)
      self.model_wind.eval()

  def save_checkpoint(self, checkpoint_path, model=None):
    """ We intentionally require a checkpoint_dir to be passed
        in order to allow Ray Tune to use this function """

    if not model:
      model = self.model

    torch.save({'iters': self.iters, 'epoch': self.epoch, 'model_state': model.state_dict(),
                  'optimizer_state_dict': self.optimizer.state_dict()}, checkpoint_path)

  def restore_checkpoint(self, checkpoint_path):
    """ We intentionally require a checkpoint_dir to be passed
        in order to allow Ray Tune to use this function """
    checkpoint = torch.load(checkpoint_path, map_location='cuda:{}'.format(self.params.local_rank))
    try:
        self.model.load_state_dict(checkpoint['model_state'])
    except:
        new_state_dict = OrderedDict()
        for key, val in checkpoint['model_state'].items():
            name = key[7:]
            new_state_dict[name] = val 
        self.model.load_state_dict(new_state_dict)
    self.iters = checkpoint['iters']
    self.startEpoch = checkpoint['epoch']
    if self.params.resuming:  #restore checkpoint is used for finetuning as well as resuming. If finetuning (i.e., not resuming), restore checkpoint does not load optimizer state, instead uses config specified lr.
        self.optimizer.load_state_dict(checkpoint['optimizer_state_dict'])

if __name__ == '__main__':
  parser = argparse.ArgumentParser()
  parser.add_argument("--run_num", default='00', type=str)
  parser.add_argument("--yaml_config", default='./config/AFNO.yaml', type=str)
  parser.add_argument("--config", default='default', type=str)
  parser.add_argument("--enable_amp", action='store_true')
  parser.add_argument("--epsilon_factor", default = 0, type = float)

  args = parser.parse_args()

  params = YParams(os.path.abspath(args.yaml_config), args.config)
  params['epsilon_factor'] = args.epsilon_factor

  params['world_size'] = 1
  if 'WORLD_SIZE' in os.environ:
    params['world_size'] = int(os.environ['WORLD_SIZE'])

  world_rank = 0
  local_rank = 0
  if params['world_size'] > 1:
    dist.init_process_group(backend='nccl',
                            init_method='env://')
    local_rank = int(os.environ["LOCAL_RANK"])
    args.gpu = local_rank
    world_rank = dist.get_rank()
    params['global_batch_size'] = params.batch_size
    params['batch_size'] = int(params.batch_size//params['world_size'])

  torch.cuda.set_device(local_rank)
  torch.backends.cudnn.benchmark = True

  # Set up directory
  expDir = os.path.join(params.exp_dir, args.config, str(args.run_num))
  if  world_rank==0:
    if not os.path.isdir(expDir):
      os.makedirs(expDir)
      os.makedirs(os.path.join(expDir, 'training_checkpoints/'))

  params['experiment_dir'] = os.path.abspath(expDir)
  params['checkpoint_path'] = os.path.join(expDir, 'training_checkpoints/ckpt.tar')
  params['best_checkpoint_path'] = os.path.join(expDir, 'training_checkpoints/best_ckpt.tar')

  # Do not comment this line out please:
  args.resuming = True if os.path.isfile(params.checkpoint_path) else False

  params['resuming'] = args.resuming
  params['local_rank'] = local_rank
  params['enable_amp'] = args.enable_amp

  # this will be the wandb name
#  params['name'] = args.config + '_' + str(args.run_num)
#  params['group'] = "era5_wind" + args.config
  params['name'] = args.config + '_' + str(args.run_num)
  params['group'] = "era5_precip" + args.config
  params['project'] = "ERA5_precip"
  params['entity'] = "flowgan"
  if world_rank==0:
    logging_utils.log_to_file(logger_name=None, log_filename=os.path.join(expDir, 'out.log'))
    logging_utils.log_versions()
    params.log()

  params['log_to_wandb'] = (world_rank==0) and params['log_to_wandb']
  params['log_to_screen'] = (world_rank==0) and params['log_to_screen']

  params['in_channels'] = np.array(params['in_channels'])
  params['out_channels'] = np.array(params['out_channels'])
  if params.orography:
    params['N_in_channels'] = len(params['in_channels']) +1
  else:
    params['N_in_channels'] = len(params['in_channels'])

  params['N_out_channels'] = len(params['out_channels'])

  if world_rank == 0:
    hparams = ruamelDict()
    yaml = YAML()
    for key, value in params.params.items():
      hparams[str(key)] = str(value)
    with open(os.path.join(expDir, 'hyperparams.yaml'), 'w') as hpfile:
      yaml.dump(hparams,  hpfile )

  trainer = Trainer(params, world_rank)
  trainer.train()
  logging.info('DONE ---- rank %d'%world_rank)