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Software Release Notes

On This Page

Software Release Notes

The following are the release notes for the Cerebras software.

Release 1.3.0

New features and enhancements

PyTorch models

  • Supports Variable Tensor Shapes (VTS) for Transformer, T5 and BERT models, which boosts performance significantly

  • Added support for BERT Finetuning tasks: SQUAD (Q&A), Classifier (SST) and Summarization (SUM)

  • Supports fixed positional embeddings.

  • Upgrades to the latest version of PyTorch 1.11.

Weight streaming mode

  • GPT-J 6B-parameter model in Tensorflow is supported for pretraining on single CS-2 system

  • The abstractive summarization fine-tuning task supported for GPT-J (6B parameters).

  • Eval metrics supported for GPT-2, GPT-3 variants, GPT-J. Metrics include perplexity, accuracy and BPB, BPC, BPW.

Note

If you are interested in these models, contact Cerebras support by sending email to support@cerebras.net.

Multi-replica mode

  • Multi-replica mode is now supported across Transformer and BERT Tensorflow models.

  • Multi-replica mode also adds Variable Tensor Shape support to further boost performance for these models.

Known issues

GPT-J (6B parameters) model

  • There is a non-determinism on the GPU side we are currently debugging, so in order to match the GPU reference, CS-2 run should start from the same initial checkpoint.

  • There is an unexplained shuffle happening when the input function runs out of data and needs to repeat the dataset. So, in order to get the exact match, the reference should run for less number of steps than the dataset, or the dataset needs to be extended, so that repeat doesn’t happen.

  • When running the GPT-J 6B model, each weight streaming server should be configured to have 512 GB of total memory. It is recommended to have at least 128 GB of physical memory and any remainder as swap space.

Running eval on Cerebras system

When running in eval mode on CS-1 system, if --nodes and --tasks_per_node value pairs are not set to one of the following, then the session may hang. This issue exists for both TensorFlow and PyTorch.

  1. --nodes==1 --tasks_per_node=2, or

  2. --nodes==2 --tasks_per_node=1

    • Workaound: Make sure that you use one of the above settings for --nodes and --tasks_per_node. For example:

      --nodes=1 --tasks_per_node=2
      

      The eval performance is not affected by these Slurm resource settings. See the example command below:

      csrun_wse python run.py --mode=eval \
          --nodes=1 --tasks_per_node=2 \
          --params configs/your-params-file.yaml \
          --model_dir your-model-dir \
          --cs_ip=10.255.253.0
      

Release 1.2.0

New features and enhancements

PyTorch models

  • Train and Eval mode is now supported for PyTorch BERT Base with sequences upto 4k tokens and BERT Large with sequences upto 2k tokens. Includes support for common eval metrics (eval loss, MLM accuracy, NSP accuracy, perplexity).

  • Train and Eval mode is now supported for RoBERTa configuration in PyTorch BERT.

  • Adds support for BERT-NER finetuning

  • Train and Eval mode is now supported for the PyTorch Transformer-Attention is All You Need model.

  • Train and Eval mode is now supported for PyTorch T5 model with configurations up to ~500M parameters, e.g., T5-Small 60M and T5-Base 220M

  • Train and Eval mode is now supported for PyTorch GPT-2 model with configurations with up to ~770M parameters, e.g., GPT-2 Small 117M, GPT-2 Medium 345M, GPT-2 Large 774M

Weight streaming execution mode

  • A new execution mode, called weight streaming mode, to run extremely large models, is introduced as an early release. See Cerebras Execution Modes for a detailed explanation of the weight streaming concept.

  • In weight streaming mode, support is added for eval on GPU.

  • In weight streaming mode, support is added to store checkpoints and resume training from checkpoints.

  • Support is added in weight streaming mode to track training runs with TensorBoard.

Weight streaming models

The following models support weight streaming mode. These models are in early beta.

  • GPT-3 XL (1.3 billion total parameters) running on a single CS-2 system.

Note

If you are interested in these models, contact Cerebras support by sending email to support@cerebras.net.

Input analyzer for Slurm resources

  • The cs_input_analyzer is a new Bash script that recommends Slurm resource settings you need to run on Cerebras system. These recommendations are generated by this script for a given input_fn and model. To use this tool, run it manually. See The cs_input_analyzer Script.

Known issues

Running eval on Cerebras system

When running in eval mode on CS-1 system, if --nodes and --tasks_per_node value pairs are not set to one of the following, then the session may hang. This issue exists for both TensorFlow and PyTorch.

  1. --nodes==1 --tasks_per_node=2, or

  2. --nodes==2 --tasks_per_node=1

    • Workaound: Make sure that you use one of the above settings for --nodes and --tasks_per_node. For example:

      --nodes=1 --tasks_per_node=2
      

      The eval performance is not affected by these Slurm resource settings. See the example command below:

      csrun_wse python run.py --mode=eval \
          --nodes=1 --tasks_per_node=2 \
          --params configs/your-params-file.yaml \
          --model_dir your-model-dir \
          --cs_ip=10.255.253.0
      

Release 1.1.0

New features and enhancements

PyTorch

  • The PyTorch support is enhanced. Key changes include but not limited to:

    • Support for eval mode is added for BERT and FC-MNIST PyTorch models. These models now support both train and eval modes.

    • Simplified cerebras.framework.torch.Session().

    • Enhanced the flexibility in specifying the cerebras.framework.torch.initialize().

    • Use of cbfloat16 data format (see CB16 half-precision) is now supported.

    • Made mixed precision interface more intuitive, via GradScaler (see PyTorch Dynamic Loss Scaling).

    • Fixed several bugs in the areas of numerics, convergence and performance.

PyTorch models

The following PyTorch models are supported.

  • A PyTorch version of FC-MNIST.

  • The PyTorch versions of BERT Base and BERT Large.

    • RoBERTa (Next Sentence Prediction (NSP) only) configurations are supported. See roberta_base.yaml and roberta_large.yaml.

    • Longer Maximum Sequence Length (MSL) configurations are supported, at least up to MSL 4096.

  • The PyTorch Transformer-Attention is All You Need model is added as a Beta feature.

    This model can be compiled using run.py with the --compile_only flag, as well as run on CPU or GPU using run_cpu_gpu.py.

    To train this model on the Cerebras System at your own risk, comment out the following lines from run.py:

    if not runconfig_params["compile_only"]:
        raise ValueError(
            "Running the Transformer model on the Cerebras System is in beta."
            "Convergence is not guaranteed. Remove this exception to proceed."
        )
    

Note

If you are interested in these models, contact Cerebras support by sending email to support@cerebras.net.

Supported PyTorch ops

Multi-replica data parallel training

A new feature called multi-replica data parallel training is released. Currently this feature is available only for TensorFlow models. When you use this feature, the Cerebras compiler uses several copies (replicas) of the same model to run data parallel training. See Multiple Models for detailed documentation.

  • For a list of TensorFlow models supporting the multi-replica data parallel training, see Supported models. This feature is not yet supported for PyTorch models.

Known issues

T5 and Transformer (Attention is All You Need)

  • The TensorFlow versions of the T5 and Transformer models are not guaranteed to converge. These models can still be compiled to the Cerebras system. However, to train these models on the Cerebras System at your own risk, comment out the following lines from run.py of the model:

    if not runconfig_params["compile_only"]:
        raise ValueError(
            "Running the Transformer model on the Cerebras System is in beta."
            "Convergence is not guaranteed. Remove this exception to proceed."
        )
    
  • When you train the TensorFlow Transformer model on Cerebras system, you will see a modest increase in loss volatility, compared to the runs on GPUs. This is due to numerical differences. The pre-training eval accuracy is expected to be within a few percent of the equivalent model trained on a GPU.

Note

If you are interested in these models, contact Cerebras support by sending email to support@cerebras.net.

Running eval on Cerebras system

When running in eval mode on CS-1 system, if --nodes and --tasks_per_node value pairs are not set to one of the following, then the session may hang. This issue exists for both TensorFlow and PyTorch.

  1. --nodes==1 --tasks_per_node=2, or

  2. --nodes==2 --tasks_per_node=1

    • Workaound: Make sure that you use one of the above settings for --nodes and --tasks_per_node. For example:

      --nodes=1 --tasks_per_node=2
      

      The eval performance is not affected by these Slurm resource settings. See the example command below:

      csrun_wse python run.py --mode=eval \
          --nodes=1 --tasks_per_node=2 \
          --params configs/your-params-file.yaml \
          --model_dir your-model-dir \
          --cs_ip=10.255.253.0
      

Multi-replica data parallel training

  • Dynamic loss scaling is not yet supported with Multi-replica Data Parallel Training.

  • Eval on Cerebras system is not yet supported for multi-replica data parallel trained models. You can run eval on CPU or GPU for these models.

PyTorch

  • For PyTorch, when you are targeting GPU, the following warning will be displayed. This can be safely ignored. This issue does not exist when you target Cerebras system for your acceleration.

    UserWarning: Detected call of ``lr_scheduler.step()`` before
    ``optimizer.step()``. In PyTorch 1.1.0 and later, you should
    call them in the opposite order: ``optimizer.step()`` before
    ``lr_scheduler.step()``.  Failure to do this will result in
    PyTorch skipping the first value of the learning rate schedule.
    
  • For PyTorch models only, to run the training on the Cerebras system, the cs_ip flag must include both the IP address and the port number of the CS system. Only the IP address, for example: --cs_ip 192.168.1.1, will not be sufficient. You must also include the port number, for example: --cs_ip 192.168.1.1:9000. See Train on CS system in the PyTorch quickstart document.


Release 1.0.0

New features and enhancements

PyTorch (BETA)

Support is added, in beta phase only, for the PyTorch framework. The models and quickstart provided are strictly intended as advanced information only.

  • A PyTorch version of FC-MNIST is added as a part of PyTorch (BETA) support.

    This version only supports compiling on a CPU node with the train mode. To train this model on the Cerebras System at your own risk, edit the run.py file and comment out the entire raise ValueError() function, as shown below:

    elif runconfig_params["mode"] == TRAIN:
            # raise ValueError(
            #    "Training PyTorch models on the Cerebras System is in beta "
            #    "and is only validated with the default config provided in the "
            #    "Model Zoo. Remove this exception and use the provided config to"
            #    "proceed."
            #)
            runner.train(train_loader)
    
  • The PyTorch versions of BERT Base and BERT Large are added as a part of PyTorch (BETA) support.

    These versions only support compiling on a CPU node with the train mode. To train these models on the Cerebras System at your own risk, edit the run.py file and comment out the entire raise ValueError() function, as shown below:

    elif runconfig_params["mode"] == TRAIN:
            #raise ValueError(
            #"Training PyTorch models on the Cerebras System is in beta "
            #"and is only validated with the default configs provided in the "
            #"Model Zoo. Remove this exception and use one of the provided "
            #"configs to proceed."
            #)
            runner.train(train_loader)
    

RevBERT

A new TensorFlow model, the RevBERT is introduced. The RevBERT is a Cerebras-specific BERT model that improves the BERT performance on Cerebras accelerator. Using the RevBERT model you can run up to 20x larger batch sizes and 2.7x larger models on the Cerebras System. This version of RevBERT is only supported with TensorFlow and only supports the train mode.

Note

If you are interested in these models, contact Cerebras support by sending email to support@cerebras.net.

Transformer (Attention Is All You Need)

Support is added in the train mode for Variable Sequence Length (VSL) on the CS system.

T5 model

  • Support is enhanced from loss-only eval to full eval metrics.

  • Support is added in the train mode for Variable Sequence Length (VSL) on the CS system.

GPT-2

Support is added in the train mode for Variable Sequence Length (VSL) on the CS system.


Release 0.9.0

New features and enhancements

Improved Slurm wrapper scripts

Two new Slurm wrapper scripts are introduced to make it easy to run on CS system and on the CPU. These scripts will replace srun_train and salloc_node. See below:

  • The csrun_wse script can be used to execute training, evaluation and prediction on the CS system. See Train, Eval and Predict.

  • The csrun_cpu script can be used to launch a given user command on a CPU, within the Cerebras Singularity container. See Compile on CPU for more on this.

Transformer (Attention Is All You Need)

Support is added for the Transformer (Attention Is All You Need), with the following capabilities:

  • Example dataset and preprocessing scripts for English-to-German translation included.

  • On CS system: Training, and Eval (loss only).

  • On GPU: Train, Eval (eval and eval_all).

T5 model

Support is added for the following T5 family of models:

  • Small model:
    • dmodel = 512

    • dff = 2,048.

    • 8-headed attention.

    • 6 layers each in the encoder and decoder.

    • About 60 million parameters.

  • Model:
    • Base, BERT Base-sized encoder and decoder.

    • About ~ 220 million parameters.

  • Model: Large, BERT Large-sized encoder and decoder.
    • dmodel = 1,024.

    • dff = 4,096.

    • dkv = 64.

    • 16-headed attention.

    • 24 layers each in the encoder and decoder.

    • Around 770 million parameters.

  • Sample dataset: Colossal Clean Crawled Corpus (C4) dataset.

  • On CS system: Pre-training, Eval (loss only).

  • On GPU: Train, Eval (eval and eval_all).

Variable Sequence Length

The variable sequence length (VSL) performance of BERT-style encoder-decoder models is enhanced. Previously, a sequence of less than pre-defined maximum sequence length is padded up to the maximum sequence length. The compute and memory are also spent on processing these tokens used for padding, resulting in a significant loss of performance.

With this enhancement, by taking advantage of the sparsity the tokens used for padding are not processed, thereby enhancing the performance of the variable length sequences.

VSL-enhanced models

The performance-optimized variable sequence length is now available for the following models on the CS system:

  • BERT Pre-training (training only).

  • RNN Language Model (LM) (training only).

  • RNN Sentiment (training only).

Enhanced BERT- and GPT-style models

Performance is enhanced for long sequences (MSL up to 8K for smaller models) for BERT- and GPT-style models. This is accomplished by making use of sparse attention to reduce memory requirements.

Known issues

  • When you use AdamW Optimizer and if both the following conditions are true:

    • The parameter weight_decay is set to a non-zero value, and

    • The parameter loss_scaling_factor is not set to “dynamic”.

    then the execution will stop with the following error message:

    Error

    “When using the AdamW optimizer with weight decay, set the loss_scaling_factor to dynamic.”

  • For the models T5 and Transformer (Attention Is All You Need), the performance in samples-per-sec is optimal when the source max_seq_len and the target max_seq_len are equal.

  • When running evaluation with a BERT model, if the max_predictions_per_seq parameter is set to an odd value and if the following conditions are true:

    • The tensor is multi-dimensional (>1D).

    • The inner dimension is an odd value.

    • The datatype is < 4 bytes, i.e., FP16 or INT16 or UINT16.

    then this leads to a compile failure in 0.9.0 and execution failure in 0.8.0.

    Workaround: Set the max_predictions_per_seq parameter to an even value.

Note

If you are interested in these models, contact Cerebras support by sending email to support@cerebras.net.


Release 0.8.0

New features and enhancements

Inference support

  • Inference is now supported for the following models:

    • Graph Convolutional Network

    • Graph Attention Network

Note

If you are interested in these models, contact Cerebras support by sending email to support@cerebras.net.

Multi-model inference

  • A new feature, multi-model inference, is introduced. Using this you can run multiple neural network models on the CS system, send inference requests to these models and receive prediction responses. See Multi-model Inference.

Early stopping

  • Early stopping is now supported using a custom hook called CerebrasEarlyStoppingHook. Using this hook, you can terminate early a neural network training based on some logic. See Early Stopping.


Release 0.7.1

New features and enhancements

Support for BERT evaluation and prediction

  • Evaluation and prediction are now supported on the CS system for BERT networks. While executing the run.py, you can run evaluation or prediction with your network as follows:

    • Evaluation: Use --mode eval to use the evaluation feature.

    • Prediction: Use --mode predict to use the prediction feature.

    See the following for additional documentation:


Release 0.7.0

New features and enhancements

Enhanced BERT Large performance

  • Performance is improved for BERT Large models with MSL 512. This is accomplished by making a tradeoff that mitigates the need for large buffer memory.

Support for combined loss

  • Support is added for combined Dice loss and Softmax Cross-entropy (CE) loss.

Summary ops

New data type

  • A new datatype called CB16 is introduced. The CB16 is Cerebras’ 16-bit format, also referred to as cbfloat16. The CB16 is a floating-point format with 6-bit exponent and 9-bit explicit mantissa. This allows for double the dynamic range of FP16. See Data Formats.

Compile report

  • A new feature that projects the performance of your network is added to the Cerebras Graph Compiler (CGC). Now when your compile is successful, the generated report includes projections on how your network might perform on the CS system. See Compile Report.

Incremental compile

  • A new feature called incremental compile is added to the Cerebras Graph Compiler (CGC). After you compile your model the first time, the incremental compile feature of CGC will automatically speed up the subsequent compile runs of your model by reusing, wherever possible, the optimizations already performed. See Incremental Compile.

Enhanced input function analyzer

  • The input function analyzer is enhanced. Now called analyze_input_fn_compile, this tool provides a detailed log identifying any missing functions and provides recommendations on parameter values to enhance the training performance on the CS system. See Input Function Report.

CS_AUTOTUNE

  • Introduced a new method called Cerebras AUTOTUNE (CS_AUTOTUNE), which is similar to the TensorFlow tf.data.AUTOTUNE. When you are targeting the CS system, using CS_AUTOTUNE instead of tf.data.AUTOTUNE will result in a better specification of parameters such as:

    • num_parallel_calls

    • cycle_length

    • num_parallel_reads

    See The CS_AUTOTUNE.

Keras model to CerebrasEstimator

  • A new function, KerasModelToCerebrasEstimator, is provided to convert a Keras model so the model can be run using the CerebrasEstimator. See Keras Model to CerebrasEstimator.

Simplified Slurm cluster resolver

  • While setting the runtime configuration options, in v0.6.3 and earlier versions you were required to add the following code for the Slurm cluster resolver.

    from cerebras.tf.cs_slurm_cluster_resolver import CSSlurmClusterResolver
    slurm_cluster_resolver = CSSlurmClusterResolver()
    cluster_spec = slurm_cluster_resolver.cluster_spec()
    task_type, task_id = slurm_cluster_resolver.get_task_info()
    os.environ['TF_CONFIG'] = json.dumps({
        'cluster': cluster_spec.as_dict(),
        'task': {'type': task_type, 'index': task_id}
    })
    

    Now this is done automatically. This means that your Slurm-orchestrated TensorFlow code that contains the above statements should be edited as follows:

    # Do not remove the following import statement.
    
    from cerebras.tf.cs_slurm_cluster_resolver import CSSlurmClusterResolver
    
    # Remove the following lines starting CGC v0.7.0.
    
     slurm_cluster_resolver = CSSlurmClusterResolver()
     cluster_spec = slurm_cluster_resolver.cluster_spec()
     task_type, task_id = slurm_cluster_resolver.get_task_info()
     os.environ['TF_CONFIG'] = json.dumps({
         'cluster': cluster_spec.as_dict(),
         'task': {'type': task_type, 'index': task_id}
     })
    

    See the examples in Step 4: Edit RunConfig and The run.py Template.

Breaking changes

  • The use_cs parameter in the The CerebrasEstimator Interface is removed and will result in compiler error if used in this API. The target hardware will now be automatically determined from a combination of the runtime configuration parameter cs_ip and the use_cs parameter setting in the method definitions for train.

  • The format of the YAML config files for all the models is changed as follows:

    • All the training-related parameters have been moved to the runconfig section.

    • The max_steps parameter is added as a default parameter to control the duration of training.

Known issues

Incremental compile

  • For BERT, a change in the max_gradient_norm hyperparameter value will not result in reduced incremental compile times.

Loss scaling factor

  • In v0.6.3, in some cases, when you enable dynamic loss scaling and an arbitrary operation is performed on the computed loss, then the Cerebras compiler may give error and fail to compile.

    Workaround: In v0.7.0 you can workaround this error by disabling the dynamic loss scaling by setting loss_scaling_factor to a constant value either equal to or greater than 1.0.


Release 0.6.3

New features and enhancements

  • The overall performance is improved for BERT for max sequence length 128 (MSL128) variants. This improvement varies based on the fabric and model configuration. Enable the following custom Cerebras configuration flag only for BERT MSL128 variants to see this performance improvement:

    config.matching.kernel.no_dcache_spill_splits = True
    

    Tip

    The Cerebras implementation sets this flag by default for BERT runs with MSL128.

  • The kernel matching phase of the Cerebras Graph Compiler (CGC) is enhanced to significantly reduce the kernel matching time and improve flexibility. With this enhancement, the kernel matching phase is completed within 60 seconds in a majority of cases. As a result, the overall compile time will be reduced in these cases.

Resolved issues

  • Resolved a kernel matching issue with 1DConv models with embeddings, when a Conv1D layer is stacked on top of an embedding layer.