Portail HAL des publications du LIRMM
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Punxa: A Python‐Based RISC‐V System Simulator for Education
No full textInternational audienceThe analysis and verification of the integration of hardware and software components is challenging. Traditional HDL simulators, which are often slow and provide low‐level analysis tools, are not always effective for simulating the software of processor‐based systems. This work presents an interactive co‐simulation framework that enhances students' understanding of computer architecture concepts typically obscured by hardware intricacies. This framework facilitates a unified environment for iterative design, enabling detailed analysis and generation of reports and traces to identify system performance, bottlenecks, and find implementation errors. By prioritizing analysis features over performance, this framework serves as a valuable tool for educational purposes and comprehensive examination of the interactions between hardware and software
Breast Ultrasound Image Detection Based on Dual-Branch Faster R-CNN
No full textInternational audienceThis paper proposes a novel dual-branch Faster R-CNN model, termed D-faster R-CNN, for breast ultrasound image detection. It adds a new parallel backbone, Pyramid Vision Transformer (PVT), to the original ResNet50 backbone, forming a dual-branch feature extraction structure of ResNet50 and PVT. To enhance the extracted features on the PVT and ResNet50 branches, a simple feature pyramid network and an asymptotic feature pyramid network are used, respectively, and the enhanced features are merged for the subsequent region proposal and RoI Align. The proposed model is validated on a publicly available breast ultrasound image dataset (BUSI). The experimental results show that compared with the baseline models, the proposed D-faster R-CNN with dual-feature extraction backbone can effectively improve tumor detection performance, and the average precision is significantly improved
Opcode Analysis of Real Encryption-Based Microarchitectural Attacks Using gem5
No full textInternational audienceModern processors use performance-boosting techniques like speculative execution and multi-level caching. Unfortunately, these same optimizations can unintentionally create security vulnerabilities known as microarchitectural sidechannels. The core novelty of this work is a precise, simulationdriven method to pinpoint exactly how individual cryptographic instructions leak information. We present a systematic analysis of common AES instructions (such as AESENC, AESDEC, and AESKEYGENASSIST), measuring their vulnerability to Flush+Reload side-channel attacks. By using cycle-accurate gem5 simulations, we were able to isolate and analyze each instruction's unique leakage pattern. The AESENC instruction causes significant timing variations and L1 data cache misses (76%) due to its S-box table lookups. The AESKEYGENASSIST instruction shows the highest latency, stemming from its iterative key expansion process. Nearby branch instructions (like JNE) worsen the leakage by introducing frequent mispredictions. A key finding is that our gem5 simulation environment reliably mirrors real hardware behaviour, achieving 89% key recovery accuracy compared to 96% on a physical Intel CPU. This validation confirms that simulations can effectively capture these subtle vulnerabilities without real-world noise. We also show that smaller caches amplify leakage by concentrating memory accesses, while larger caches only reduce, not eliminate, the risk. Ultimately, our findings provide actionable insights for developers to harden cryptographic code and for designers creating future detection tools. This work demonstrates the critical role of architectural simulation in identifying and understanding security vulnerabilities before chips are even built
Adapting BERT and AgriBERT for Agroecology: A Small-Corpus Pretraining Approach
No full textInternational audienceSource variables, or observable properties, used to describe agroecological experiments are often heterogeneous, non-standardized, and multilingual, making them challenging to understand, explain, and utilize in cropping system modeling and multicriteria evaluations of agroecological system performance. A potential solution is data annotation via a controlled vocabulary, known as candidate variables, from the Agroecological Global Information System (AEGIS). However, matching source and candidate variables via their textual descriptions remains a challenging task in agroecology. Domain-general language models, such as BERT, often struggle with domain-specific tasks due to their general-purpose training data. In the literature, these models are adapted to specialized domains through further pretraining, pretraining from scratch, and/or fine-tuning on downstream tasks. However, pretraining a domain-general model on a domain-specific corpus is resource-intensive, requiring substantial time, energy, and computational resources. To the best of our knowledge, no study has further pretrained a domain-general model on a small corpus (less than 100 MB) to adapt it to a domain-specific task and evaluated it on downstream tasks without fine-tuning. To address these shortcomings, this paper proposes further pretraining BERT and AgriBERT on a small agroecology-related corpus. This approach is designed to be both time- and resource-efficient while enhancing domain adaptation. We evaluate the pretrained models on the task of matching source and candidate variable descriptions without fine-tuning. Our results show that our further pretrained AgriBERT (+ Experts + Core) model outperforms all others by more than 8% from P@1 to P@10. These findings showed that small-scale pretraining can significantly improve performance on domain-specific tasks without requiring fine-tuning
Revisiting Directed Disjoint Paths on Tournaments (And Relatives)
No full textInternational audienceIn the Directed Disjoint Paths problem (k-DDP), we are given a digraph and k pairs of terminals, and the goal is to find k pairwise vertex-disjoint paths connecting each pair of terminals. Bang-Jensen and Thomassen [SIAM J. Discrete Math. 1992] claimed that k-DDP is NP-complete on tournaments, and this result triggered a very active line of research about the complexity of the problem on tournaments and natural superclasses. We identify a flaw in their proof, which has been acknowledged by the authors, and provide a new NP-completeness proof. From an algorithmic point of view, Fomin and Pilipczuk [J. Comb. Theory B 2019] provided an FPT algorithm for the edge-disjoint version of the problem on semicomplete digraphs, and showed that their technique cannot work for the vertex-disjoint version. We overcome this obstacle by showing that the version of k-DDP where we allow congestion c on the vertices is FPT on semicomplete digraphs provided that c is greater than k/2. This is based on a quite elaborate irrelevant vertex argument inspired by the edge-disjoint version, and we show that our choice of c is best possible for this technique, with a counterexample with no irrelevant vertices when c ≤ k/2. We also prove that k-DDP on digraphs that can be partitioned into h semicomplete digraphs is W[1]-hard parameterized by k+h, which shows that the XP algorithm presented by Chudnovsky, Scott, and Seymour [J. Comb. Theory B 2019] is essentially optimal
Targeting transcription-replication conflicts using G-quadruplexes stabilizers in multiple myeloma
No full textInternational audienceReplication stress exerts an important role in fueling genomic instability characterizing multiple myeloma (MM) evolution and is a leading cause of drug resistance. Normal and malignant plasma cells (PCs) are associated with a high transcriptional stress due to the huge production of immunoglobulins. Transcription-replication conflicts (TRCs), arising from collisions between replication and transcription machineries, can promote tumor progression and represent an Achilles' heel to cancer cells. We reported a gene signature related to TRCs management (TRC score), overexpressed in malignant vs normal PCs. High TRC score identified patients with MM with a poor prognosis who could benefit from a TRC-enhancing therapy, in independent cohorts of patients with MM treated with high-dose melphalan chemotherapy or anti-CD38 immunotherapy. Here, we investigated the therapeutic interest of increasing TRCs to target specifically malignant PCs using the G-quadruplex (G4) stabilizer pyridostatin (PDS). PDS exerted significant toxicity in MM cell lines and primary MM cells, inducing DNA damage, cell cycle arrest, and apoptosis. Importantly, primary myeloma cells are significantly more sensitive to PDS treatment than normal bone marrow cells. Moreover, PDS improved the efficacy of MM treatments such as melphalan and histone deacetylase (HDAC) or bromodomain (BRD) inhibitors. Thus, our study shows that G4 stabilizers could be used to specifically target MM cells that exhibit concomitant replication stress and a high level of transcription, through the increase of TRCs. These molecules could be used to increase the efficacy of other treatments including melphalan, HDAC inhibitors, and BRD inhibitors
TNURML: Triple-Node-Upset-Recovery Magnetic Latch Design with Non-Volatility for Aerospace Applications
No full textInternational audienceAs semiconductor technology advances, radiative-particle-induced soft errors and power consumption are becoming major concerns for digital circuits in aerospace applications. Radiation hardening by design and magnetic tunnel junctions (MTJs) are widely employed to address these concerns. In this paper, a novel latch, called TNURML, that can completely recover from triple-node upsets (TNUs), is proposed. The embedded MTJs provide non-volatility and are compatible with traditional CMOS processes. The TNURML employs a TNU-recovery module as well as a pair of MTJs for backup and recovery operations. Extensive simulations demonstrate the excellent TNU-recovery capability and nonvolatility of the TNURML latch at the cost of slightly increased area overhead. The proposed TNURML latch reduces 43.63% of delay and 48.23% of power on average when compared to the state-of-the-art latches
Bishop's (up)crossing inequality and lower semicomputable random reals revisited
No full textIn this paper we provide an easy proof of Barmpalias--Lewis-Pye result saying that all computable increasing sequences converging to random reals converge with the same speed (up to a factor) by noting that it immediately follows from Bishop's upcrossing inequality. We also provide a simple derivation of this inequality
PneuNet actuators design: Trade-offs between deformation, force, and resistance to buckling
No full textInternational audienceSoft pneumatic network (PneuNet) actuators and their derived grippers have gained prominence in industrial and medical applications. The performance of PneuNets is typically assessed based on their angular deformation and the tip force they exert. To enhance their effectiveness, several studies have investigated the relationship between design parameters and these critical performance metrics. This paper expands upon existing literature by examining the impact of design parameters on three performance metrics: angular deformation, tip force, and resistance to buckling—the latter proposed for the first time as a performance metric for PneuNets. Resistance to buckling is significant in applications requiring high forces with minimal restrictions on maximum allowable pressure. The angular deformation and tip force are analyzed by introducing additional design parameters previously unexplored in the literature. Moreover, the former is studied in three differentconfigurations. In this context, the configuration of the PneuNet actuator refers to its orientation, such as horizontal or vertical fixation, and whether it bends against or towards gravity. These configurations simulate environmental factors and the diverse positions that PneuNets may encounter in practical applications. It is demonstrated that the influence of some design parameters on angular deformation is configuration-dependent. Furthermore, a comprehensive table is provided to aid users in optimizing PneuNet performance — whether in terms of angular deformation, tip force, or resistance to buckling — according to specific application requirements. Finally, to evaluate the practical applications of these performance metrics, five PneuNet grippers with different shapes are fabricated and tested in two distinct gripping modes
Complement Avoidance in Binary Words
No full textInternational audienceThe complement of a binary word is obtained by changing each in to and vice versa. We study infinite binary words that avoid sufficiently large complementary factors; that is, if is a factor of , then is not a factor of . In particular, we classify such words according to their critical exponents