While static program analyzers based on abstract interpretation implement precision-improving techniques to reduce false alarms, such as loop unrolling, their computational cost requires carefully devised heuristics for selective application. Manually designing such heuristics is non-trivial and error-prone, possibly leading to state explosion.This paper presents LOUPE, a novel end-to-end approach for automatically learning loop unrolling heuristics for static program analysis. Unlike previous data-driven methods, LOUPE leverages Graph Neural Networks (GNNs) to learn directly from graph-based program representations. To enable supervised learning, we use the static analyzer itself to automatically label training data. We implement LOUPE on top of FRAMA-C/EVA, an open source C static analyzer, and demonstrate that the best performing heuristic (GINE) outperforms the FRAMA-C/EVA built-in heuristic on real-world programs, reducing false alarms by 1.5x while improving analysis performance by 56%. Remarkably, GINE accurately predicts loop unrolling decisions made by expert FRAMA-C/EVA engineers, while maintaining acceptable false-positive rates. Finally, we show that LOUPE can effectively learn heuristics for other static analyzers such as MOPSA.

In this work, we introduce a new architectural component to Neural Network (NN), i.e., trainable and spectrally initializable matrix transformations on feature maps. While previous literature has already demonstrated the possibility of adding static spectral transformations as feature processors, our focus is on more general trainable transforms. We study the transforms in various architectural configurations on four datasets of different nature: from medical (ColorectalHist, HAM10000) and natural (Flowers) images to historical documents (CB55). With rigorous experiments that control for the number of parameters and randomness, we show that networks utilizing the introduced matrix transformations outperform vanilla neural networks. The observed accuracy increases appreciably across all datasets. In addition, we show that the benefit of spectral initialization leads to significantly faster convergence, as opposed to randomly initialized matrix transformations. The transformations are implemented as auto-differentiable PyTorch modules that can be incorporated into any neural network architecture. The entire code base is open-source.

This paper introduces a new way for text-line extraction by integrating deep-learning based pre-classification and state-of-the-art segmentation methods. Text-line extraction in complex handwritten documents poses a significant challenge, even to the most modern computer vision algorithms. Historical manuscripts are a particularly hard class of documents as they present several forms of noise, such as degradation, bleed-through, interlinear glosses, and elaborated scripts. In this work, we propose a novel method which uses semantic segmentation at pixel level as intermediate task, followed by a text-line extraction step. We measured the performance of our method on a recent dataset of challenging medieval manuscripts and surpassed state-of-the-art results by reducing the error by 80.7%. Furthermore, we demonstrate the effectiveness of our approach on various other datasets written in different scripts. Hence, our contribution is two-fold. First, we demonstrate that semantic pixel segmentation can be used as strong denoising pre-processing step before performing text line extraction. Second, we introduce a novel, simple and robust algorithm that leverages the high-quality semantic segmentation to achieve a text-line extraction performance of 99.42% line IU on a challenging dataset.

Automatic analysis of scanned historical documents comprises a wide range of image analysis tasks, which are often challenging for machine learning due to a lack of human-annotated learning samples. With the advent of deep neural networks, a promising way to cope with the lack of training data is to pre-train models on images from a different domain and then fine-tune them on historical documents. In the current research, a typical example of such cross-domain transfer learning is the use of neural networks that have been pre-trained on the ImageNet database for object recognition. It remains a mostly open question whether or not this pre-training helps to analyse historical documents, which have fundamentally different image properties when compared with ImageNet. In this paper, we present a comprehensive empirical survey on the effect of ImageNet pre-training for diverse historical document analysis tasks, including character recognition, style classification, manuscript dating, semantic segmentation, and content-based retrieval. While we obtain mixed results for semantic segmentation at pixel-level, we observe a clear trend across different network architectures that ImageNet pre-training has a positive effect on classification as well as content-based retrieval.

We introduce DeepDIVA: an infrastructure designed to enable quick and intuitive setup of reproducible experiments with a large range of useful analysis functionality. Reproducing scientific results can be a frustrating experience, not only in document image analysis but in machine learning in general. Using DeepDIVA a researcher can either reproduce a given experiment or share their own experiments with others. Moreover, the framework offers a large range of functions, such as boilerplate code, keeping track of experiments, hyper-parameter optimization, and visualization of data and results. To demonstrate the effectiveness of this framework, this paper presents case studies in the area of handwritten document analysis where researchers benefit from the integrated functionality. DeepDIVA is implemented in Python and uses the deep learning framework PyTorch. It is completely open source, and accessible as Web Service through DIVAServices.

Cross-depiction is the problem of identifying the same object even when it is depicted in a variety of manners.This is a common problem in handwritten historical document image analysis, for instance when the same letter or motif is depicted in several different ways. It is a simple task for humans yet conventional computer vision methods struggle to cope with it. In this paper we address this problem using state-of-the-art deep learning techniques on a dataset of historical watermarks containing images created with different methods of reproduction, such as hand tracing, rubbing, and radiography.To study the robustness of deep learning based approaches to the cross-depiction problem, we measure their performance on two different tasks: classification and similarity rankings. For the former we achieve a classification accuracy of 96 % using deep convolutional neural networks. For the latter we have a false positive rate at 95% recall of 0.11. These results outperform state-of-the-art methods by a significant margin.

In this paper, we present a novel approach for initializing deep neural networks, i.e., by using Principal Component Analysis (PCA) to initialize neural layers. Usually, the initialization of the weights of a deep neural network is done in one of the three following ways: 1) with random values, 2) layer-wise, usually as Deep Belief Network or as auto-encoder, and 3) re-use of layers from another network (transfer learning). Therefore, typically, many training epochs are needed before meaningful weights are learned, or a rather similar dataset is required for seeding a fine-tuning of transfer learning. In this paper, we describe how to turn a PCA into an auto-encoder, by generating an encoder layer of the PCA parameters and furthermore adding a decoding layer. We analyze the initialization technique on real documents. First, we show that a PCA-based initialization is quick and leads to a very stable initialization. Furthermore, for the task of layout analysis we investigate the effectiveness of PCA-based initialization and show that it outperforms state-of-the-art random weight initialization methods.

This paper reports on the ICDAR2017 Competition on Layout Analysis for Challenging Medieval Manuscripts (HisDoc-Layout-Comp) and provides further details and discussions. In this competition we introduce a new challenging dataset and state-of-the-art benchmark results for pixel-labelling and text line segmentation. The DIVA-HisDB comprises medieval manuscripts with complex layout in contrast to previous datasets, where rectangular text blocks and only a few decorative elements exist. In particular, the images of this competition contain many interlinear and marginal glosses as well as texts in various sizes and decorated letters. This makes the distinction of the four target labels (text, comment, decoration, and background) more difficult. In addition, to reflect the needs of scholars in the humanities, we request multi-labeling of certain regions (decorated text as text and decoration). Furthermore, we measure not just the accuracy, but the Intersection over Union (IU) of pixel sets, which better reflects the real performance. Indeed, in our results we observe that the accuracy appears to be rather high, but the IU reveals, that there is still room for improvement. For the task of line segmentation, the recognition results are rather low (overall error higher than 5%). Noteworthy, a combination of the best layout analysis method with an adapted seam-carving based method achieves better results than the best contestant.

We study bisimulation and context equivalence in a probabilistic lambda-calculus. The contributions of this paper are threefold. Firstly we show a technique for proving congruence of probabilistic applicative bisimilarity. While the technique follows Howe's method, some of the technicalities are quite different, relying on non-trivial "disentangling" properties for sets of real numbers. Secondly we show that, while bisimilarity is in general strictly finer than context equivalence, coincidence between the two relations is attained on pure lambda-terms. The resulting equality is that induced by Levy-Longo trees, generally accepted as the finest extensional equivalence on pure lambda-terms under a lazy regime. Finally, we derive a coinductive characterisation of context equivalence on the whole probabilistic language, via an extension in which terms akin to distributions may appear in redex position. Another motivation for the extension is that its operational semantics allows us to experiment with a different congruence technique, namely that of logical bisimilarity.