@inproceedings { buschjaegerSLOHA2021,
  author = {Buschj\"ager, Sebastian and Chen, Jian-Jia and Chen, Kuan-Hsun and G\"unzel, Mario and Morik, Katharina and Novkin, Rodion and Pfahler, Lukas and Yayla, Mikail},
  title = {Bit Error Tolerance Metrics for Binarized Neural Networks},
  booktitle = {Workshop on System-level Design Methods for Deep Learning on Heterogeneous Architectures (SLOHA)},
  year = {2021},
  url = {https://arxiv.org/abs/2102.00818},
  keywords = {kuan},
  confidential = {n},
  abstract = {To reduce the resource demand of neural network (NN) inference systems, it has been proposed to use approximate
memory, in which the supply voltage and the timing parameters are tuned trading accuracy with energy consumption and performance. Tuning these parameters aggressively leads to bit errors, which can be tolerated by NNs when bit flips are injected during training. However, bit flip training, which is the state of the art for achieving bit error tolerance, does not scale well; it leads to massive overheads and cannot be applied for high bit error rates (BERs). Alternative methods to achieve bit error tolerance in NNs are needed, but the underlying principles behind the bit error tolerance of NNs have not been reported yet. With this lack of understanding, further progress in the research on NN bit error tolerance will be restrained.

In this study, our objective is to investigate the internal changes in the NNs that bit flip training causes, with a focus on  Binarized NNs (BNNs). To this end, we quantify the properties of bit error tolerant BNNs with two metrics. First, we propose a neuron-level bit error tolerance metric, which calculates the margin between the pre-activation values and batch normalization thresholds. Secondly, to capture the effects of bit error tolerance on the interplay of neurons, we propose an inter-neuron bit error tolerance metric, which measures the importance of each neuron and computes the variance over all importance values. Our experimental results support that these two metrics are strongly related to bit error tolerance.},
}

@inproceedings { buschjaeger/etal/2021,
  author = {Buschj\"ager, Sebastian and Chen, Jian-Jia and Chen, Kuan-Hsun and G\"unzel, Mario and Hakert, Christian and Morik, Katharina and Novkin, Rodion and Pfahler, Lukas and Yayla, Mikail},
  title = {Margin-Maximization in Binarized Neural Networks for Optimizing Bit Error Tolerance},
  booktitle = {Design, Automation and Test in Europe Conference (DATE), accepted},
  year = {2021},
  note = {Best Paper Award Candidate},
  keywords = {kuan, nvm-oma},
  file = {http://ls12-www.cs.tu-dortmund.de/daes/media/documents/publications/downloads/2021dateyayla.pdf},
  confidential = {n},
  abstract = {To overcome the memory wall in neural network (NN) inference systems, recent studies have proposed to use approximate memory, in which the supply voltage and access latency parameters are tuned, for lower energy consumption and faster access at the cost of reliability. To tolerate the occuring bit errors, the state-of-the-art approaches apply bit flip injections to the NNs during training, which require high overheads and do not scale well for large NNs and high bit error rates. In this work, we focus on binarized NNs (BNNs), whose simpler structure allows better exploration of bit error tolerance metrics based on margins. We provide formal proofs to quantify the maximum number of bit flips that can be tolerated. With the proposed margin-based metrics and the well-known hinge loss for maximum margin classification in support vector machines (SVMs), we are able to construct a modified hinge loss (MHL) to train BNNs for bit error tolerance without any bit flip injections. Our experimental results indicate that the MHL enables the possibility for BNNs to tolerate higher bit error rates than with bit flip training and, therefore, allows to further lower the requirements on approximate memories used for BNNs. },
}

@article { guenzel2020emsoft,
  author = {G\"unzel, Mario and Br\"uggen, Georg and Chen, Jian-Jia},
  title = {Suspension-Aware Earliest-Deadline-First Scheduling Analysis},
  journal = {IEEE Trans. Comput. Aided Des. Integr. Circuits Syst. (presented in ACM Conference on Embedded Software, EMSOFT)},
  year = {2020},
  volume = {39},
  number = {11},
  pages = {4205--4216},
  url = {https://ieeexplore.ieee.org/document/9211430},
  keywords = {sus, mario, Georg},
  confidential = {n},
  abstract = {While the earliest-deadline-first (EDF) scheduling algorithm has extensively been utilized in  real-time systems, there is almost no literature considering EDF for task sets with dynamic self-suspension behavior. To be precise, there is no specialized result for uniprocessor systems, besides the trivial suspension-oblivious approach. The work by Liu and Anderson (in ECRTS 2013) and Dong and Liu (in RTSS 2016) for suspension-aware multiprocessor global EDF can also be applied to uniprocessor systems and therefore be considered the state-of-the-art.

In this work, two novel schedulability analyses (one for sporadic and one for periodic task sets) for suspension-aware EDF on uniprocessor systems are proposed, which outperform the state-of-the-art on such systems in empirical and theoretical comparison. We further show that the analysis by Dong and Liu is in fact not suspension-aware for uniprocessor systems.},
}

@article { buschjger2020explainable,
  author = {Buschj\"ager, Sebastian and Chen, Jian-Jia and Chen, Kuan-Hsun and G\"unzel, Mario and Hakert, Christian and Morik, Katharina and Novkin, Rodion and Pfahler, Lukas and Yayla, Mikail},
  title = {Towards Explainable Bit Error Tolerance of Resistive RAM-Based Binarized Neural Networks},
  journal = {CoRR},
  year = {2020},
  volume = {abs/2002.00909},
  url = {https://arxiv.org/pdf/2002.00909.pdf},
  keywords = {kuan, nvm-oma, mario},
  confidential = {n},
  abstract = {Non-volatile memory, such as resistive RAM (RRAM), is an emerging energy-efficient storage, especially for low-power machine learning models on the edge. It is reported, however, that the bit error rate of RRAMs can be up to 3.3% in the ultra low-power setting, which might be crucial for many use cases. Binary neural networks (BNNs), a resource efficient variant of neural networks (NNs), can tolerate a certain percentage of errors without a loss in accuracy and demand lower resources in computation and storage. The bit error tolerance (BET) in BNNs can be achieved by flipping the weight signs during training, as proposed by Hirtzlin et al., but their method has a significant drawback, especially for fully connected neural networks (FCNN): The FCNNs overfit to the error rate used in training, which leads to low accuracy under lower error rates. In addition, the underlying principles of BET are not investigated. In this work, we improve the training for BET of BNNs and aim to explain this property. We propose straight-through gradient approximation to improve the weight-sign-flip training, by which BNNs adapt less to the bit error rates. To explain the achieved robustness, we define a metric that aims to measure BET without fault injection. We evaluate the metric and find that it correlates with accuracy over error rate for all FCNNs tested. Finally, we explore the influence of a novel regularizer that optimizes with respect to this metric, with the aim of providing a configurable trade-off in accuracy and BET.},
}

@article { DBLP:journals/rts/GunzelC20,
  author = {G\"unzel, Mario and Chen, Jian-Jia},
  title = {Correspondence Article: Counterexample for suspension-aware schedulability analysis of EDF scheduling},
  journal = {Real Time Systems Journal},
  year = {2020},
  volume = {56},
  number = {4},
  pages = {490--493},
  url = {https://link.springer.com/article/10.1007%2Fs11241-020-09353-0},
  keywords = {sus, mario},
  confidential = {n},
}

@article { DBLP:journals/corr/abs-2001-05747,
  author = {G\"unzel, Mario and Chen, Jian-Jia},
  title = {On Schedulability Analysis of EDF Scheduling by Considering Suspension as Blocking},
  journal = {CoRR},
  year = {2020},
  volume = {abs/2001.05747},
  url = {https://arxiv.org/abs/2001.05747},
  keywords = {sus, mario},
  confidential = {n},
}