A Reference GLL Implementation

The Generalised-LL (GLL) context-free parsing algorithmwas introduced at the 2009 LDTA workshop, and since then aseries of variant algorithms and implementations have beendescribed. There is a wide variety of optimisations that maybe applied to GLL, some of which were already present inthe originally published form.This paper presents a reference GLL implementation shornof all optimisations as a common baseline for the real-worldcomparison of performance across GLL variants. This baselineversion has particular value for non-specialists, sinceits simple form may be straightforwardly encoded in theimplementer’s preferred programming language.We also describe our approach to low level memory managementof GLL internal data structures. Our evaluation onlarge inputs shows a factor 3–4 speedup over a naïve implementationusing the standard Java APIs and a factor 4–5reduction in heap requirements. We conclude with noteson some algorithm-level optimisations that may be appliedindependently of the internal data representation

Purely functional GLL parsing

Generalised parsing has become increasingly important in the context of software language design and several compiler generators and language workbenches have adopted generalised parsing algorithms such as GLR and GLL. The original GLL parsing algorithms are described in low-level pseudo-code as the output of a parser generator. This paper explains GLL parsing differently, defining the FUN-GLL algorithm as a collection of pure, mathematical functions and focussing on the logic of the algorithm by omitting implementation details. In particular, the data structures are modelled by abstract sets and relations rather than specialised implementations. The description is further simplified by omitting lookahead and adopting the binary subtree representation of derivations to avoid the clerical overhead of graph construction. Conventional parser combinators inherit the drawbacks from the recursive descent algorithms they implement. Based on FUN-GLL, this paper defines generalised parser combinators that overcome these problems. Th

Happy-GLL: modular, reusable and complete top-down parsers for parameterized nonterminals

Parser generators and parser combinator libraries are the most popular tools for producing parsers. Parser combinators use the host language to provide reusable components in the form of higher-order functions with parsers as parameters. Very few parser generators support this kind of reuse through abstraction and even fewer generate parsers that are as modular and reusable as the parts of the grammar for which they are produced. This paper presents a strategy for generating modular, reusable and complete top-down parsers from syntax descriptions with parameterized nonterminals, based on the FUN-GLL variant of the GLL algorithm. The strategy is discussed and demonstrated as a novel back-end for the Happy parser generator. Happy grammars can contain `parameterized nonterminals' in which parameters abstract over grammar symbols, granting an abstraction mechanism to define reusable grammar operators. However, the existing Happy back-ends do not deliver on the full potential of parameterized nonterminals as parameterized nonterminals cannot be reused across grammars. Moreover, the parser generation process may fail to terminate or may result in exponentially large parsers generated in an exponential amount of time. The GLL back-end presented in this paper implements parameterized nonterminals successfully by generating higher-order functions that resemble parser combinators, inheriting all the advantages of top-down parsing. The back-end is capable of generating parsers for the full class of context-free grammars, generates parsers in linear time and generates parsers that find all derivations of the input string. To our knowledge, the presented GLL back-end makes Happy the first parser generator that combines all these features. This paper describes the translation procedure of the GLL back-end and compares it to the LALR and GLR back-ends of Happy in several experiments.Comment: 15 page

Targeting Prostaglandin E2 Receptor EP2 for Treatment of High-Risk Neuroblastoma

Prostaglandin E2 (PGE2) is a predominant proinflammatory regulator that plays pivotal roles in regulating tumor cell proliferation, migration, and invasion. It fosters an inflammation-enriched microenvironment that facilitates angiogenesis and immune evasion. Neuroblastoma (NB) is a lethal pediatric malignancy. PGE2 has been reported to promote high-risk NB proliferation and progression. However, the PGE2 receptor subtype (EP1-EP4) which potentially contributed to NB growth remained elusive. In this research, at first, we demonstrated that EP2 receptor was highly correlated with NB aggressiveness, and acted as a predominant Gαs-coupled receptor mediating PGE2-initiated cyclic AMP (cAMP) signaling in NB cells with high-risk factors, including chromosome 11q deletion and MYCN amplification. CRISPR/Cas9 induced EP2 knockout blocked the development of NB xenografts in athymic nude mice. Additionally, EP2 conditional knockdown prevented established tumors from progressing in vivo. Pharmacological inhibition of EP2 by our recently developed antagonist TG6-129 substantially suppressed the NB tumor growth in both nude mice and syngeneic immunocompetent hosts, with the observable anti-inflammatory, anti-angiogenic, and apoptotic effects. Next, based on the scaffold of TG6-129, we developed, and identified a novel robust EP2 antagonizing compound GLL-618. GLL-618 demonstrated enhanced EP2 binding potency. Meanwhile, it also showed advanced pharmacokinetic features such as prolonged plasma half-life and im-proved bioavailability. Applied as a single treatment reagent, GLL-618 could significantly inhibited high-risk NB neuro-spheres development and suppressed high-risk NB xenograft tumors growth by 50%. Subsequently, we combined GLL-618 with vincristine, a prevalently used chemotherapy drug for the treatment of high-risk NB. GLL-618 could synergistically increase the anti-tumor effect of vincristine, which was evidenced by an overall 70% tumor weight reduction at the treatment endpoint in an immunocompetent allograft model, accompanied with quenched proinflammatory signaling within the tumor microenvironment and elevated expression of apoptotic markers. In conclusion, this study suggested that the PGE2/EP2 signaling pathway might contribute to NB development and progression. EP2 inhibition with our drug-like compounds could be potentially applied as an alternative, and adjunctive treatment strategy for this deadly pediatric cancer

Multi-Cell Massive MIMO in LoS

We consider a multi-cell Massive MIMO system in a line-of-sight (LoS) propagation environment, for which each user is served by one base station, with no cooperation among the base stations. Each base station knows the channel between its service antennas and its users, and uses these channels for precoding and decoding. Under these assumptions we derive explicit downlink and uplink effective SINR formulas for maximum-ratio (MR) processing and zero-forcing (ZF) processing. We also derive formulas for power control to meet pre-determined SINR targets. A numerical example demonstrating the usage of the derived formulas is provided.Comment: IEEE Global Communications Conference (GLOBECOM) 201

Fracture control plan for propellant and pressurant tanks

To assure the functional integrity of the GLL-RPM fuel and pressurized gas tank, all activities during entire lifetime of the tank, from manufacture to the end of the mission, must be monitored. Specifications are given for all procedures which influence the tank structure including design, manufacture, cleaning, test operations, and storage. Tests to be conducted to demonstrate that requirements of the fracture control plan are satisfied include static tests, cyclic load tests, proof tests, He-leak test, and acceptance tests

Generically transitive actions on multiple flag varieties

Let $G$ be a semisimple algebraic group whose decomposition into a product of simple components does not contain simple groups of type $A$, and $P\subseteq G$ be a parabolic subgroup. Extending the results of Popov [7], we enumerate all triples $(G, P, n)$ such that (a) there exists an open $G$-orbit on the multiple flag variety $G/P\times G/P\times\ldots\times G/P$ ($n$ factors), (b) the number of $G$-orbits on the multiple flag variety is finite.Comment: 10 page