This repository provides a script and recipe to train the Transformer-XL model to achieve state-of-the-art accuracy, and is tested and maintained by NVIDIA.

• Model overview
  • Model architecture
  • Default configuration
  • Feature support matrix
    • Features
  • Mixed precision training
    • Enabling mixed precision
• Setup
  • Requirements
• Quick Start Guide
• Advanced
  • Scripts and sample code
  • Parameters
  • Command-line options
  • Getting the data
    • Dataset guidelines
    • Multi-dataset
  • Training process
  • Inference process
• Performance
  • Benchmarking
    • Training performance benchmark
    • Inference performance benchmark
  • Results
    • Training accuracy results
      • Training accuracy: NVIDIA DGX-1 (8x V100 16G)
      • Training accuracy: NVIDIA DGX-2 (16x V100 32G)
      • Training stability test
    • Training performance results
      • Training performance: NVIDIA DGX-1 (8x V100 16G)
      • Training performance: NVIDIA DGX-2 (16x V100 32G)
    • Inference performance results
      • Inference performance: NVIDIA DGX-1 (1x V100 16G)
      • Inference performance: NVIDIA T4
• Release notes
  • Changelog
  • Known issues

This repository provides an implementation of the Transformer-XL model in PyTorch from the paper Transformer-XL: Attentive Language Models Beyond a Fixed-Length Context. Transformer-XL is a transformer-based language model with a segment-level recurrence and a novel relative positional encoding. Enhancements introduced in Transformer-XL help capture better long-term dependencies by attending to tokens from multiple previous segments.

Our implementation is based on the codebase published by the authors of the Transformer-XL paper. Our implementation uses modified model architecture hyperparameters. Our modifications were made to achieve better hardware utilization and to take advantage of Tensor Cores. Similar modifications were also proposed in an implementation available from github.com/cybertronai/transformer-xl. Refer to the Model architecture section for more details.

This model is trained with mixed precision using Tensor Cores on NVIDIA Volta GPUs and evaluated on Volta and Turing GPUs. Therefore, researchers can get results up to 2.5x faster than training without Tensor Cores, while experiencing the benefits of mixed precision training. This model is tested against each NGC monthly container release to ensure consistent accuracy and performance over time.

The Transformer-XL "base" model for WikiText-103 dataset available in this repository was modified to use the following values of hyperparameters:

Changes described above were made to align certain hyperparameters with powers of two, with this modification, the model is able to achieve better hardware utilization, and therefore higher training throughput.

The Transformer-XL model addresses the limitations of vanilla transformer-based language models, which are only able to use relatively short context, bounded by the segment length. The Transformer-XL introduces a recurrence mechanism, which is able to use a cached hidden state from previous segments. During training, the context consists of a concatenation of current segment's hidden state and cached states from previous iterations. Gradients are backpropagated only through the current segment, although the model is able to take advantage of the extra information stored in the cache and therefore is able to model long-term dependencies.

An illustration of the recurrence mechanism taken from the Transformer-XL paper is shown below.

The following features were implemented in this model:

• general

  • single-node, data-parallel multi-GPU training,
  • training and inference with mixed precision using Tensor Cores,
  • mixed precision training implemented using Apex AMP, with O2 optimization level and with a dynamic loss scaling,

• model

  • a 16-layer base Transformer-XL model with hidden size 512, 8 attention heads, each head with hidden size 64,
  • the model trained on WikiText-103 dataset, using word-level vocabulary and adaptive softmax,
  • embedding weights are tied with weights in the classifier,

• training

  • training with LAMB optimizer,
  • linear learning rate warmup for 1000 iterations, followed by cosine learning rate schedule, initial learning rate is set to 0.01, final learning rate is set to 0.001,
  • training for 40,000 steps, using batch size of 256,
  • support for a training with a gradient accumulation,

• inference

  • support for multi-gpu inference,
  • support for TorchScript and pure Python inference,
  • target length is set to 64, length of memory is set to 640,
  • positional embeddings are clamped after 400 time steps,
  • each token is using the same size of the context from previous time steps.

The following features are supported by this model:

Apex AMP - a tool that enables Tensor Core-accelerated training. Refer to the Enabling mixed precision section for more details.

Apex DistributedDataParallel - a module wrapper that enables easy multiprocess distributed data parallel training, similar to torch.nn.parallel.DistributedDataParallel. DistributedDataParallel is optimized for use with NCCL. It achieves high performance by overlapping communication with computation during backward() and bucketing smaller gradient transfers to reduce the total number of transfers required.

Mixed precision is the combined use of different numerical precisions in a computational method. Mixed precision training offers significant computational speedup by performing operations in half-precision format, while storing minimal information in single-precision to retain as much information as possible in critical parts of the network. Since the introduction of Tensor Cores in the Volta and Turing architectures, significant training speedups are experienced by switching to mixed precision -- up to 3x overall speedup on the most arithmetically intense model architectures. Using mixed precision training previously required two steps:

1. Porting the model to use the FP16 data type where appropriate.
2. Manually adding loss scaling to preserve small gradient values.

The ability to train deep learning networks with lower precision was introduced in the Pascal architecture and first supported in CUDA 8 in the NVIDIA Deep Learning SDK.

For information about:

• How to train using mixed precision, see the Mixed Precision Training paper and Training With Mixed Precision documentation.
• Techniques used for mixed precision training, see the Mixed-Precision Training of Deep Neural Networks blog.
• APEX tools for mixed precision training, see the NVIDIA Apex: Tools for Easy Mixed-Precision Training in PyTorch .

The pytorch/train.py training script launches mixed precision training with Tensor Cores if the flag --fp16 is set.

Mixed precision is enabled in PyTorch by using the Automatic Mixed Precision (AMP), library from APEX that casts variables to half-precision upon retrieval, while storing variables in single-precision format. Furthermore, to preserve small gradient magnitudes in backpropagation, a loss scaling step must be included when applying gradients. In PyTorch, loss scaling can be easily applied by using scale_loss() method provided by AMP. The scaling value to be used can be dynamic or fixed.

For an in-depth walk through on AMP, check out sample usage here. APEX is a PyTorch extension that contains utility libraries, such as AMP, which require minimal network code changes to leverage Tensor Cores performance.

The following steps were needed to enable mixed precision training in Transformer-XL:

1. Import AMP from APEX:

from apex import amp

2. Initialize AMP and wrap the model and the optimizer before starting the training:

model, optimizer = amp.initialize(
    model,
    optimizer,
    opt_level='O2',
    )

3. Apply scale_loss context manager:

with amp.scale_loss(loss, optimizer) as scaled_loss:
    scaled_loss.backward()

4. Apply gradient clipping on single precision master weights:

torch.nn.utils.clip_grad_norm_(amp.master_params(optimizer), args.clip)

The following section lists the requirements that you need to meet in order to start training the Transformer-XL model.

This repository contains Dockerfile which extends the PyTorch NGC container and encapsulates some dependencies. Aside from these dependencies, ensure you have the following components:

• NVIDIA Docker
• PyTorch 19.09-py3 NGC container
• NVIDIA Volta or Turing based GPU

For more information about how to get started with NGC containers, see the following sections from the NVIDIA GPU Cloud Documentation and the Deep Learning DGX Documentation:

• Getting Started Using NVIDIA GPU Cloud,
• Accessing And Pulling From The NGC container registry,
• Running PyTorch.

For those unable to use the Pytorch NGC container, to set up the required environment or create your own container, see the versioned NVIDIA Container Support Matrix.

To train your model using mixed precision with Tensor Cores or using FP32, perform the following steps using the default parameters of the Transformer-XL base model on the WikiText-103 dataset.

For the specifics concerning training and inference, see the Advanced section.

1. Clone the repository.

git clone https://github.com/enod/Nvidia-Transformer-XL.git
cd Nvidia-Transformer-XL

2. Download and preprocess the dataset. Don't forget to replace URL_HERE

bash getdata.sh

3. Build the Transformer-XL PyTorch NGC container.

From now on, all scripts should be executed from the pytorch directory.

cd pytorch
bash scripts/docker/build.sh

4. Start an interactive session in the NGC container to run training/inference.

bash scripts/docker/interactive.sh

5. Start training.

To start 8 GPU mixed precision training on DGX-1, run:

bash run_wt103_base.sh train 8 --vocab word --adaptive --fp16 --batch_chunk 1 

To start 8 GPU FP32 training on DGX-1, run:

bash run_mn_base.sh train 8 --vocab word --adaptive --fp16 --batch_chunk 1

To start 16 GPU mixed precision training on DGX-2, run:

bash run_mn_base.sh train 16 --vocab word --adaptive --fp16 --batch_chunk 1 

To start 16 GPU FP32 training on DGX-2, run:

bash run_mn_base.sh train 16 --vocab word --adaptive --batch_chunk 1

For more information on the available options, refer to the Training process section.

6. Start evaluation.

To start mixed precision inference on the test set using <#GPUs> GPUs, run:

bash run_wt103_base.sh eval <#GPUs> [--fp16] [--type {pytorch, torchscript}]

The --fp16 flag is optional, however, if it's specified, then the script launches mixed precision inference with Tensor Cores. If the flag is not present, then the script launches FP32 inference. By default, the script is loading the checkpoint from LM-TFM/checkpoint_best.pt, which contains the model corresponding to the lowest value of the validation loss from the previous training run. Path to the checkpoint can be customized by setting the --model flag.

Inference can use pure Python execution or TorchScript from using the --type flag.

Supported values for <#GPUs> are: 1, 2, 4, 8, 16.

Additionally, one can pass the input text directly from the command-line using the --manual flag. This mode of operation supports only 1 GPU and batch size of 1. The script outputs average loss and perplexity for the provided input text.

Examples:

bash run_wt103_base.sh eval 1 \
  --model LM-TFM/checkpoint_best.pt \
  --fp16 \
  --manual "recognize speech"

===============================================================================
| test loss  6.20 | test ppl   494.291
===============================================================================

bash run_wt103_base.sh eval 1 \
  --model LM-TFM/checkpoint_best.pt \
  --fp16 \
  --manual "wreck a nice beach"

===============================================================================
| test loss  8.04 | test ppl  3099.706
===============================================================================

For more information on the available options, refer to the Inference process section.

The following sections provide greater details of the dataset, running training and inference, and the training results.

In the pytorch directory, the most important files are:

• Dockerfile: container with the basic set of dependencies to run Transformer-XL
• data_utils.py: data loading utilities
• eval.py: serves as the entry point to launch the evaluation and inference
• lamb.py: implementation of LAMB optimizer
• mem_transformer.py: implementation of the Transformer-XL model
• requirements.txt: set of extra requirements for running Transformer-XL
• train.py: serves as the entry point to launch the training

The pytorch/utils directory contains the following additional modules:

• adaptive_softmax.py: implementation of adaptive softmax
• data_parallel.py: implementation of BalancedDataParallel class
• distributed.py: utility functions for running distributed training
• exp_utils.py: utility functions for running training and benchmarking
• log_uniform_sampler.py: implementation of log-uniform sampler
• proj_adaptive_softmax.py: implementation of projected adaptive softmax
• vocabulary.py: implementation of word-level vocabulary and BPE-based vocabulary

Training

The complete list of available parameters for the pytorch/train.py training script contains:

general setup:
  --work_dir WORK_DIR   Directory for the results (default: LM-TFM)
  --append_dataset      Automatically append dataset name to work_dir
                        (default: False)
  --append_time         Automatically append current time to work_dir
                        (default: False)
  --cuda                Use CUDA (default: False)
  --fp16                Run training in fp16/mixed precision (default: False)
  --restart RESTART     Restart training from the saved checkpoint (default: )
  --debug               Run in debug mode (do not create exp dir) (default:
                        False)
  --log_all_ranks       Enable logging from all distributed ranks (default:
                        False)
  --save-all            Save all checkpoints (default: False)
  --log_interval LOG_INTERVAL
                        Report interval (default: 10)
  --target_throughput TARGET_THROUGHPUT
                        Target training throughput (for benchmarking)
                        (default: None)
  --target_perplexity TARGET_PERPLEXITY
                        Target validation perplexity (for benchmarking)
                        (default: None)

dataset setup:
  --data DATA           Location of the data corpus (default:
                        ../data/wikitext-103)
  --dataset {wt103,lm1b,enwik8,text8}
                        Dataset name (default: wt103)
  --vocab {word,bpe}    Type of vocabulary (default: word)

model setup:
  --n_layer N_LAYER     Number of total layers (default: 16)
  --n_head N_HEAD       Number of heads (default: 8)
  --d_head D_HEAD       Head dimension (default: 64)
  --d_embed D_EMBED     Embedding dimension (default: -1)
  --d_model D_MODEL     Model dimension (default: 512)
  --d_inner D_INNER     Inner dimension in feedforward layer (default: 2048)
  --dropout DROPOUT     Global dropout rate (default: 0.1)
  --dropatt DROPATT     Attention probability dropout rate (default: 0.0)
  --pre_lnorm           Apply LayerNorm to the input instead of the output
                        (default: False)
  --attn_type ATTN_TYPE
                        Attention type. 0 for ours, 1 for Shaw et al,2 for
                        Vaswani et al, 3 for Al Rfou et al. (default: 0)
  --not_tied            Do not tie the word embedding and softmax weights
                        (default: False)
  --clamp_len CLAMP_LEN
                        Use the same pos embeddings after clamp_len (default:
                        -1)
  --adaptive            Use adaptive softmax (default: False)
  --div_val DIV_VAL     Dividend value for adaptive input and softmax
                        (default: 1)
  --sample_softmax SAMPLE_SOFTMAX
                        Number of samples in sampled softmax (default: -1)
  --init INIT           Parameter initializer to use (default: normal)
  --emb_init EMB_INIT   Parameter initializer to use (default: normal)
  --init_range INIT_RANGE
                        Parameters initialized by U(-init_range, init_range)
                        (default: 0.1)
  --emb_init_range EMB_INIT_RANGE
                        Parameters initialized by U(-init_range, init_range)
                        (default: 0.01)
  --init_std INIT_STD   Parameters initialized by N(0, init_std) (default:
                        0.02)
  --proj_init_std PROJ_INIT_STD
                        Parameters initialized by N(0, init_std) (default:
                        0.01)

optimizer setup:
  --optim {adam,sgd,adagrad,lamb}
                        Optimizer to use (default: lamb)
  --lr LR               Initial learning rate (default: 0.01)
  --mom MOM             Momentum for sgd (default: 0.0)
  --scheduler {cosine,inv_sqrt,dev_perf,constant}
                        LR scheduler to use (default: cosine)
  --max_step_scheduler MAX_STEP_SCHEDULER
                        Max number of training steps for LR scheduler
                        (default: None)
  --warmup_step WARMUP_STEP
                        Number of iterations for LR warmup (default: 1000)
  --decay_rate DECAY_RATE
                        Decay factor when ReduceLROnPlateau is used (default:
                        0.5)
  --lr_min LR_MIN       Minimum learning rate during annealing (default: 0.0)
  --clip CLIP           Gradient clipping (default: 0.25)
  --weight_decay WEIGHT_DECAY
                        Weight decay for adam|lamb (default: 0.0)
  --clip_nonemb         Only clip the gradient of non-embedding params
                        (default: False)
  --patience PATIENCE   Patience (default: 0)
  --eta_min ETA_MIN     Min learning rate for cosine scheduler (default:
                        0.001)

training setup:
  --max_step MAX_STEP   Max number of training steps (default: 40000)
  --batch_size BATCH_SIZE
                        Global batch size (default: 256)
  --batch_chunk BATCH_CHUNK
                        Split batch into chunks to save memory (default: 1)
  --roll                Enable random shifts within each data stream (default:
                        False)
  --tgt_len TGT_LEN     Number of tokens to predict (default: 192)
  --ext_len EXT_LEN     Length of the extended context (default: 0)
  --mem_len MEM_LEN     Length of the retained previous heads (default: 192)
  --seed SEED           Random seed (default: 1111)
  --multi_gpu {ddp,dp}  Use multiple GPU (default: None)
  --gpu0_bsz GPU0_BSZ   Batch size on gpu 0 (for "dp" backend) (default: -1)
  --same_length         Use the same attn length for all tokens (default:
                        False)
  --varlen              Use variable length (default: False)

validation setup:
  --eval_tgt_len EVAL_TGT_LEN
                        Number of tokens to predict for evaluation (default:
                        192)
  --eval_batch_size EVAL_BATCH_SIZE
                        Eval batch size (default: 16)
  --eval_max_steps EVAL_MAX_STEPS
                        Max eval steps (default: -1)
  --eval_interval EVAL_INTERVAL
                        Evaluation interval (default: 5000)

Inference

The complete list of available parameters for the eval.py inference script contains:

  --work_dir WORK_DIR   experiment directory (default: LM-TFM)
  --debug               run in debug mode (do not create exp dir) (default:
                        False)
  --data DATA           location of the data corpus (default:
                        ../data/wikitext-103)
  --manual MANUAL [MANUAL ...]
                        run model on raw input data (default: None)
  --dataset {wt103,lm1b,enwik8,text8}
                        dataset name (default: wt103)
  --split {all,valid,test}
                        which split to evaluate (default: all)
  --type {pytorch,torchscript,onnx}
                        type of runtime to use (default: pytorch)
  --batch_size BATCH_SIZE
                        batch size (default: 16)
  --tgt_len TGT_LEN     number of tokens to predict (default: 64)
  --ext_len EXT_LEN     length of the extended context (default: 0)
  --mem_len MEM_LEN     length of the retained previous heads (default: 640)
  --clamp_len CLAMP_LEN
                        max positional embedding index (default: -1)
  --cuda                use CUDA (default: False)
  --model MODEL         path to the checkpoint (default: )
  --fp16                Run training in fp16/mixed precision (default: False)
  --log_all_ranks       Enable logging for all distributed ranks (default:
                        False)
  --same_length         set same length attention with masking (default:
                        False)
  --target_perplexity TARGET_PERPLEXITY
                        target perplexity (default: None)
  --target_throughput TARGET_THROUGHPUT
                        target throughput (default: None)
  --save_data           save latency and throughput data to a file (default:
                        False)
  --repeat REPEAT       loop over the dataset REPEAT times (default: 1)
  --max_size MAX_SIZE   run inference on up to MAX_SIZE batches (default:
                        None)
  --percentiles PERCENTILES [PERCENTILES ...]
                        percentiles for latency confidence intervals (default:
                        [90, 95, 99])
  --save_torchscript SAVE_TORCHSCRIPT
                        save torchscript model to a file (default: None)
  --load_torchscript LOAD_TORCHSCRIPT
                        load torchscript model from a file (default: None)

To see the full list of available options and their descriptions, use the -h or --help command-line option. For example, for training:

python3 train.py --help

usage: train.py [-h] [--work_dir WORK_DIR] [--append_dataset] [--append_time]
                [--cuda] [--fp16] [--restart RESTART] [--debug]
                [--log_all_ranks] [--save-all] [--log_interval LOG_INTERVAL]
                [--target_throughput TARGET_THROUGHPUT]
                [--target_perplexity TARGET_PERPLEXITY] [--data DATA]
                [--dataset {wt103,lm1b,enwik8,text8}] [--vocab {word,bpe}]
                [--n_layer N_LAYER] [--n_head N_HEAD] [--d_head D_HEAD]
                [--d_embed D_EMBED] [--d_model D_MODEL] [--d_inner D_INNER]
                [--dropout DROPOUT] [--dropatt DROPATT] [--pre_lnorm]
                [--attn_type ATTN_TYPE] [--not_tied] [--clamp_len CLAMP_LEN]
                [--adaptive] [--div_val DIV_VAL]
                [--sample_softmax SAMPLE_SOFTMAX] [--init INIT]
                [--emb_init EMB_INIT] [--init_range INIT_RANGE]
                [--emb_init_range EMB_INIT_RANGE] [--init_std INIT_STD]
                [--proj_init_std PROJ_INIT_STD]
                [--optim {adam,sgd,adagrad,lamb}] [--lr LR] [--mom MOM]
                [--scheduler {cosine,inv_sqrt,dev_perf,constant}]
                [--max_step_scheduler MAX_STEP_SCHEDULER]
                [--warmup_step WARMUP_STEP] [--decay_rate DECAY_RATE]
                [--lr_min LR_MIN] [--clip CLIP] [--weight_decay WEIGHT_DECAY]
                [--clip_nonemb] [--patience PATIENCE] [--eta_min ETA_MIN]
                [--max_step MAX_STEP] [--batch_size BATCH_SIZE]
                [--batch_chunk BATCH_CHUNK] [--roll] [--tgt_len TGT_LEN]
                [--ext_len EXT_LEN] [--mem_len MEM_LEN] [--seed SEED]
                [--multi_gpu {ddp,dp}] [--gpu0_bsz GPU0_BSZ] [--same_length]
                [--varlen] [--eval_tgt_len EVAL_TGT_LEN]
                [--eval_batch_size EVAL_BATCH_SIZE]
                [--eval_max_steps EVAL_MAX_STEPS]
                [--eval_interval EVAL_INTERVAL] [--local_rank LOCAL_RANK]

For example, for inference:

python3 eval.py --help

usage: eval.py [-h] [--work_dir WORK_DIR] [--debug] [--data DATA]
               [--manual MANUAL [MANUAL ...]]
               [--dataset {wt103,lm1b,enwik8,text8}]
               [--split {all,valid,test}] [--type {pytorch,torchscript,onnx}]
               [--batch_size BATCH_SIZE] [--tgt_len TGT_LEN]
               [--ext_len EXT_LEN] [--mem_len MEM_LEN] [--clamp_len CLAMP_LEN]
               [--cuda] [--model MODEL] [--fp16] [--log_all_ranks]
               [--same_length] [--target_perplexity TARGET_PERPLEXITY]
               [--target_throughput TARGET_THROUGHPUT] [--save_data]
               [--repeat REPEAT] [--max_size MAX_SIZE]
               [--percentiles PERCENTILES [PERCENTILES ...]]
               [--save_torchscript SAVE_TORCHSCRIPT]
               [--load_torchscript LOAD_TORCHSCRIPT] [--local_rank LOCAL_RANK]

The Transformer-XL base model was trained on the WikiText-103 dataset. The WikiText-103 dataset is a collection of over 100 million tokens extracted from the set of verified Good and Featured articles on Wikipedia.

This repository contains the getdata.sh download script which automatically downloads and extracts the training, validation and test datasets. By default, data is downloaded to the data directory.

In order to test with other datasets, the script needs to be customized accordingly.

The WikiText-103 dataset was already pre-tokenized with word-level tokens. The dataset features a large vocabulary of 267,735 tokens and retains the original case, punctuation and numbers.

The getdata.sh script downloads the data, extracts the archive and renames the training, validation and test set to train.txt, valid.txt, test.txt respectively.

Using other datasets requires changes in the following files:

• pytorch/train.py:
  • name of the new dataset should be added to the dataset argument in the parse_args() function
  • desired values of cutoffs for adaptive softmax should be added in the main() function, after the section which builds train/valid/test data iterators
• pytorch/data_utils.py:
  • support for the new dataset needs to be added to the Corpus class: names of files containing training, validation and test data, options for the tokenizer, and dataset iterator

The current codebase supports training with word-level vocabulary (automatically generated based on the provided dataset) and with BPE vocabulary (using pre-built vocabulary from pretrained GPT2 model imported from github.com/huggingface/transformers.

Additionally, using other datasets may require changes in some hyperparameters (for example, batch size, learning rate, number of training steps, configuration of learning rate scheduler).

The default training configuration can be launched by running the run_wt103_base.sh script with the first argument set to train. By default, the training results are saved to the LM-TFM directory; this can be customized by setting the --work_dir parameter.

The training script launches a single node data-parallel training with a fixed global batch size of 256, optionally with gradient accumulation to allow training on configurations with less than 8 GPUs. Logs from the training are automatically saved to the LM-TFT/log.log file.

Command-line

bash run_wt103_base.sh train <#GPUs> --vocab word --adaptive [--fp16] [--batch_chunk CHUNK]

Launches training of Transformer-XL base model on WikiText-103 dataset with word-based vocabulary and adaptive softmax using <#GPUs> GPUs.

The --fp16 flag is optional, if it's specified, then the script launches mixed precision training with Tensor Cores, if the flag is not present, then the script launches FP32 training.

The --batch_chunk CHUNK parameter controls gradient accumulation. With gradient accumulation the batch size is split into CHUNK chunks of equal size, the training script executes the forward and backward pass using each chunk and then executes the optimizer using accumulated gradients.

Examples

bash run_wt103_base.sh train 16 --fp16 --vocab word --adaptive --batch_chunk 1

Launches mixed precision training of Transformer-XL base model on WikiText-103 using 16 GPUs. Batch size per GPU is equal to the default global batch size of 256 divided by the product of the number of GPUs times the number of chunks, in this case batch size per GPU is equal to 256 / (16 * 1) = 16.

bash run_wt103_base.sh train 8 --vocab word --adaptive --batch_chunk 2

Launches a FP32 training using 8 GPUs, the batch size per GPU is equal to 16 (--batch_chunk was set to 2 because a local batch size of 32 runs out of memory on a DGX-1 with Tesla V100 16G in FP32 training).

A summary of the training progress is printed after every 10 training iterations; this can be customized by setting the --log_interval parameter.

The summary is printed in the following format:

| epoch  18 step    36000 | batches    283 / 2101 | lr 1.220e-03 | ms/batch 185.1 | tok/s  265585 | loss  3.12 | ppl     22.71

which contains information about a current training epoch, current training step, number of batches processed within the current epoch, current learning rate, execution time in milliseconds per batch, throughput in tokens per second, current training loss and training perplexity.

The script saves two checkpoints: checkpoint_best.pt which contains the model corresponding to the lowest value of the validation loss and checkpoint_last.pt which contains the model corresponding to the last execution of the validation step. By default, the validation is executed every 5000 training steps, this can be customized by setting the --eval_interval parameter. The summary of results on the validation dataset is printed in the following format:

| Eval   7 at step    35000 | time:  1.37s | valid loss  3.14 | valid ppl    23.132

which contains information about the current epoch, current training step, time needed to execute the validation, current validation loss and validation perplexity.

Inference can be run by launching the run_wt103_base.sh script with the first argument set to eval. Running inference requires a pre-trained model checkpoint.

The script supports single node multi-GPU inference, each batch is split equally among all GPUs running the inference and the loss is averaged over the global batch.

Command-line

bash run_wt103_base.sh eval <#GPUs> --model <PATH TO THE CHECKPOINT> [--fp16] [--type {pytorch, torchscript}]

The --fp16 flag is optional, if it's specified, then the script launches inference with Tensor Cores, if the flag is not present, then the script launches FP32 inference.

The --type flag selects between pure Python pytorch execution and TorchScript execution.

Supported values for <#GPUs> are: 1, 2, 4, 8, 16.

Examples

bash run_wt103_base.sh eval 8 --model LM-TFM/checkpoint_best.pt --fp16 --type torchscript

Launches TorchScript mixed precision inference on 8 GPUs using a checkpoint loaded from LM-TFM/checkpoint_best.pt.

bash run_wt103_base.sh eval 1 --model LM-TFM/checkpoint_best.pt --type pytorch

Launches pure Python FP32 inference on a single GPU using a checkpoint loaded from LM-TFM/checkpoint_best.pt.

After the execution, the script prints a summary in the following format:

Evaluating with math fp16 type torchscript bsz 16 tgt_len 64 ext_len 0 mem_len 640 clamp_len 400
Time : 5.29s, 22.05ms/segment
====================================================================================================
| test loss  3.15 | test ppl    23.304
====================================================================================================

which contains information about runtime parameters, execution time, loss and perplexity on the test dataset.

The following section shows how to run benchmarks measuring the model performance in training and inference modes.

To benchmark the training performance on a specific global batch size <BS>, with a specific number of GPUs <#GPUs> for a specific number of training iterations <ITER> run:

bash run_wt103_base.sh train <#GPUs> --batch_size <BS> --max_step <ITER> --vocab word --adaptive --log_interval 1 --debug [--fp16] [--batch_chunk CHUNK]

It's recommended to launch at least 500 training steps to get a reliable estimate of training performance. For more information about the available options, refer to the Training process section.

The training script prints information in the following format:

(...)
| epoch   1 step      499 | batches    499 / 16802 | lr 4.990e-03 | ms/batch 219.9 | tok/s   27947 | loss  6.43 | ppl    620.80
| epoch   1 step      500 | batches    500 / 16802 | lr 5.000e-03 | ms/batch 221.4 | tok/s   27747 | loss  6.42 | ppl    611.70
-------------------------------------------------------------------------------
(...)
Training time: 1.81 minutes
Training throughput: 28508.91 tok/s

The last two lines contain information on the total training time and on the average training throughput measured in tokens per second.

The inference performance and accuracy benchmarks require a checkpoint from a trained model.

To benchmark the inference performance on a specific global batch size <BS> with a specific number of GPUs <#GPUs>, run:

bash run_wt103_base.sh eval <#GPUs> --model <CHECKPOINT> --batch_size <BS> --save_data [--fp16] [--type {pytorch, torchscript}]

The inference script prints information in the following format:

Evaluating with math fp16 type torchscript bsz 16 tgt_len 64 ext_len 0 mem_len 640 clamp_len 400
Time : 5.25s, 21.88ms/segment
====================================================================================================
| test loss  3.15 | test ppl    23.304
====================================================================================================
Throughput Avg: 46316.64 tok/s
Latency Avg: 22.09 ms
Latency 90%: 22.22 ms
Latency 95%: 22.25 ms
Latency 99%: 22.37 ms
====================================================================================================

The output contains information on the achieved test loss and test perplexity, average inference throughput (measured in tokens per second), average inference latency and latency at 90%, 95% and 99% confidence intervals (measured in milliseconds).

The scripts/inference_benchmark.sh benchmarking script is provided for convenience, it automatically launches FP32 and FP16 inference for various batch sizes.

The following sections provide details on how we achieved our performance and accuracy in training and inference.

Our results were obtained by running the pytorch/run_wt103_base.sh training script in the in the pytorch-19.09-py3 NGC container on NVIDIA DGX-1 with 8x V100 16G GPUs.

Our results were obtained by running the pytorch/run_wt103_base.sh training script in the in the pytorch-19.09-py3 NGC container on NVIDIA DGX-2 with 16x V100 32G GPUs.

The Transformer-XL model was trained for 40000 training steps, starting from 20 different initial random seeds. After every 5000 training steps, the model was evaluated on the validation dataset and validation perplexity was recorded. The training was performed in the pytorch-19.09-py3 NGC container on NVIDIA DGX-1 with 8x V100 16G GPUs. The following table summarizes the perplexity on our validation dataset.

After training, the models were evaluated on the test dataset. The following table summarizes the final perplexity on the test set.

Our results were obtained by running the pytorch/run_wt103_base.sh training script in the pytorch-19.09-py3 NGC container on NVIDIA DGX-1 with 8x V100 16G GPUs. Performance numbers (in tokens per second) were averaged 500 training iterations.

To achieve these same results, follow the steps in the Quick Start Guide.

Our results were obtained by running the pytorch/run_wt103_base.sh training script in the pytorch-19.09-py3 NGC container on NVIDIA DGX-2 with 16x V100 32G GPUs. Performance numbers (in tokens per second) were averaged 500 training iterations.

To achieve these same results, follow the steps in the Quick Start Guide.

Our results were obtained by running the pytorch/scripts/inference_benchmark.sh inferencing benchmarking script in the pytorch-19.09-py3 NGC container on NVIDIA DGX-1 with 1x V100 16G GPU.

The command to launch the inference performance benchmark is provided in the Inference performance benchmark section.

FP16, pure Python

FP16, TorchScript

FP32, pure Python

FP32, TorchScript

To achieve these same results, follow the steps in the Quick Start Guide.

Our results were obtained by running the pytorch/scripts/inference_benchmark.sh inferencing benchmarking script in the pytorch-19.09-py3 NGC container on NVIDIA T4.

The command to launch the inference performance benchmark is provided in the Inference performance benchmark section.

FP16, pure Python

FP16, TorchScript

FP32, pure Python

FP32, TorchScript

To achieve these same results, follow the steps in the Quick Start Guide.

• October 2019
  • Initial release
    • Support for FP32 and mixed precision training on NVIDIA DGX-1, NVIDIA DGX-2 and inference on NVIDIA Tesla V100 16G and NVIDIA T4

There are no known issues with this model.