On palimpsests in neural memory: an information theory viewpoint

The finite capacity of neural memory and the reconsolidation phenomenon suggest it is important to be able to update stored information as in a palimpsest, where new information overwrites old information. Moreover, changing information in memory is metabolically costly. In this paper, we suggest that information-theoretic approaches may inform the fundamental limits in constructing such a memory system. In particular, we define malleable coding, that considers not only representation length but also ease of representation update, thereby encouraging some form of recycling to convert an old codeword into a new one. Malleability cost is the difficulty of synchronizing compressed versions, and malleable codes are of particular interest when representing information and modifying the representation are both expensive. We examine the tradeoff between compression efficiency and malleability cost, under a malleability metric defined with respect to a string edit distance. This introduces a metric topology to the compressed domain. We characterize the exact set of achievable rates and malleability as the solution of a subgraph isomorphism problem. This is all done within the optimization approach to biology framework.Accepted manuscrip

Malleable coding: compressed palimpsests

A malleable coding scheme considers not only compression efficiency but also the ease of alteration, thus encouraging some form of recycling of an old compressed version in the formation of a new one. Malleability cost is the difficulty of synchronizing compressed versions, and malleable codes are of particular interest when representing information and modifying the representation are both expensive. We examine the trade-off between compression efficiency and malleability cost under a malleability metric defined with respect to a string edit distance. This problem introduces a metric topology to the compressed domain. We characterize the achievable rates and malleability as the solution of a subgraph isomorphism problem. This can be used to argue that allowing conditional entropy of the edited message given the original message to grow linearly with block length creates an exponential increase in code length.First author draf

Malleable coding for updatable cloud caching

In software-as-a-service applications provisioned through cloud computing, locally cached data are often modified with updates from new versions. In some cases, with each edit, one may want to preserve both the original and new versions. In this paper, we focus on cases in which only the latest version must be preserved. Furthermore, it is desirable for the data to not only be compressed but to also be easily modified during updates, since representing information and modifying the representation both incur cost. We examine whether it is possible to have both compression efficiency and ease of alteration, in order to promote codeword reuse. In other words, we study the feasibility of a malleable and efficient coding scheme. The tradeoff between compression efficiency and malleability cost-the difficulty of synchronizing compressed versions-is measured as the length of a reused prefix portion. The region of achievable rates and malleability is found. Drawing from prior work on common information problems, we show that efficient data compression may not be the best engineering design principle when storing software-as-a-service data. In the general case, goals of efficiency and malleability are fundamentally in conflict.This work was supported in part by an NSF Graduate Research Fellowship (LRV), Grant CCR-0325774, and Grant CCF-0729069. This work was presented at the 2011 IEEE International Symposium on Information Theory [1] and the 2014 IEEE International Conference on Cloud Engineering [2]. The associate editor coordinating the review of this paper and approving it for publication was R. Thobaben. (CCR-0325774 - NSF Graduate Research Fellowship; CCF-0729069 - NSF Graduate Research Fellowship)Accepted manuscrip

Malleable Coding with Fixed Reuse

In cloud computing, storage area networks, remote backup storage, and similar settings, stored data is modified with updates from new versions. Representing information and modifying the representation are both expensive. Therefore it is desirable for the data to not only be compressed but to also be easily modified during updates. A malleable coding scheme considers both compression efficiency and ease of alteration, promoting codeword reuse. We examine the trade-off between compression efficiency and malleability cost-the difficulty of synchronizing compressed versions-measured as the length of a reused prefix portion. Through a coding theorem, the region of achievable rates and malleability is expressed as a single-letter optimization. Relationships to common information problems are also described

A study of word association aids in information retrieval

Issued as Final project reports [nos. 1-2], Project no. G-36-65

Low latency optical switch for high performance computing with minimized processor energy load [Invited]

Power density and cooling issues are limiting the performance of high performance chip multiprocessors (CMPs), and off-chip communications currently consume more than 20% of power for memory, coherence, PCI, and Ethernet links. Photonic transceivers integrated with CMPs are being developed to overcome these issues, potentially allowing low hop count switched connections between chips or data center servers. However, latency in setting up optical connections is critically important in all computing applications, and having transceivers integrated on the processor chip also pushes other network functions and their associated power consumption onto the chip. In this paper, we propose a low latency optical switch architecture that minimizes the power consumed on the processor chip for two scenarios: multiple-socket shared memory coherence networks and optical top-of-rack switches for data centers. The switch architecture reduces power consumed on the CMP using a control plane with a simplified send and forget server interface and the use of a hybrid Mach–Zehnder interferometer and semiconductor optical amplifier integrated optical switch with electronic buffering. Results show that the proposed architecture offers a 42% reduction in head latency at low loads compared with a conventional scheduled optical switch as well as offering increased performance for streaming and incast traffic patterns. Power dissipated on the server chip is shown to be reduced by more than 60% compared with a scheduled optical switch architecture with ring resonator switching.This work was supported by the UK Engineering and Physical Sciences Research Council (EPSRC) INTERNET program grant and an EPSRC Fellowship grant to Philip Watts. Both University College London and the University of Cambridge are members of GreenTouch.This paper was published in the Journal of Optical Communications and Networking and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsinfobase.org/jocn/abstract.cfm?uri=jocn-7-3-A498. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law. This is the accepted manuscript of a paper published in the Journal of Optical Communications and Networking, Vol. 7, Issue 3, pp. A498-A510 (2015) http://dx.doi.org/10.1364/JOCN.7.00A49

An effective AutoCAD curriculum for the high school student

The instruction of computer assisted drafting (CAD) in the high school classroom presents unique problems and challenges that typical colleges, technical schools, and industry do not address. Including issues such as cross curriculum instruction, beginning and advanced students in the same class, several courses in the same room, CAD and manual drafting taught concurrently

Valukappaleiden parametrinen mallinnus ja laadunvarmistus

Even though 3D modelling and 3D scanning have been industry standards in casting design and measurement for a long time, casting tolerance standards still usually rely on complete definition of castings in 2D drawings and linear dimensional tolerances. ISO 8062-4, published in 2017, is based on a general surface profile tolerance instead of separate dimensional tolerances, thus forming a logical connection between 3D modelling, tolerancing and 3D scanning. As the contemporary 3D methods are prominently used, the outdated ISO 8062-3 should be replaced with the new standard in casting tolerance definition. In this thesis, possibilities to include casting tolerances in casting CAD models are examined. The aim is to create dependent but separate 3D models that depict the allowed minimum and maximum state of the casting as allowed by the casting tolerance. The benefits of these tolerance models are evaluated considering quality verification, strength calculations and collision detection. ISO 8062-4 casting tolerance and a traction sheave from an NMX hoisting machine are used for modelling case study. In addition, different measurement methods are reviewed to determine guidelines for casting measurement based on contemporary methods and standards. The case study revealed that tolerance model construction is difficult and time-consuming compared to the achieved benefits. Therefore, no implementation to every casting by default is recommended. Attention was also paid to modelling techniques and conventions that should be followed regardless of the tolerance models. 3D scanning should be utilised in casting quality verification because of its coverage, speed and ability to compare scanned 3D model directly to the nominal model. Measurement instructions were determined considering the requirements of ISO 8062-4 and the possibilities and restrictions of 3D scanning. An exemplary casting drawing of the traction sheave was created according to ISO 8062-4. Digital 3D product definition and 3D scanning were taken into account when determining the drawing indication.Vaikka 3D-mallinnus sekä 3D-skannaus ovat jo pitkään olleet vallitsevat suunnittelu- ja mittausmenetelmät valuteollisuudessa, valutoleranssistandardit nojaavat pitkälti vielä valujen täydelliseen esittämiseen 2D-kuvissa sekä lineaaristen mittojen tolerointiin. Vuonna 2017 julkaistu ISO 8062-4 perustuu yleiseen pinnanmuototoleranssiin yksittäisten mittojen toleroinnin sijaan, jolloin uusi standardi muodostaa ehyen ja loogisen jatkumon 3D-mallinnuksen ja 3D-skannauksen kanssa. Nykyaikaisia menetelmiä käytettäessä onkin syytä korvata vanhentuneisiin työkaluihin perustuva ISO 8062-3 uudella standardilla valutoleranssien määrityksessä. Tässä työssä selvitetään, miten valutoleranssin saa parametrisesti sisällytettyä valukappaleen CAD-malliin, jolloin erilliset mallit kuvaisivat toleranssin sallimia valun minimi- ja maksimitiloja. Minimi- ja maksimitilojen mallien hyötyjä arvioidaan laadunvarmistuksen, lujuuslaskennan ja törmäystarkasteluiden kannalta. Toleranssimallien luonnissa käytetään standardin ISO 8062-4 mukaisia toleransseja sekä malliesimerkkinä NMX-hissimoottorin vetopyörää. Lisäksi tarkastellaan eri mittausmenetelmiä, ja pyritään määrittämään suuntaviivat nykyaikaisiin menetelmiin ja standardeihin perustuvaa mittausohjetta varten. Tarkasteluissa havaittiin toleranssimallien mallinnuksen olevan työlästä saatavaan hyötyyn nähden, jolloin niiden sisällyttäminen oletuksena jokaiseen valuun ei ole järkevää. Tarkastelun yhteydessä kiinnitettiin huomiota myös mallinnustekniikkaan ja tapoihin, joita tulisi valusuunnittelussa noudattaa riippumatta toleranssimallien käytöstä. Valujen mittaamisessa tulisi ensisijaisesti hyödyntää 3D-skannausta, jossa nimellistä CAD-mallia verrataan skannattuun 3D-malliin, ja joka kattavuutensa ja nopeutensa ansiosta onkin yleisesti käytössä valuteollisuudessa. Mittausprosessin kulku määritettiin samalla huomioiden standardin ISO 8062-4 vaatimukset sekä 3D-skannauksen mahdollisuudet ja rajoitteet. Malliesimerkkinä käytetystä vetopyörästä laadittiin ISO 8062-4:n mukainen valupiirustus, jossa huomioidaan myös nimellisen muodon määritys CAD-mallilla sekä 3Dskannauksen käyttö laadunvarmistuksessa

Multiparametric interfaces for fine-grained control of digital music

Digital technology provides a very powerful medium for musical creativity, and the way in which we interface and interact with computers has a huge bearing on our ability to realise our artistic aims. The standard input devices available for the control of digital music tools tend to afford a low quality of embodied control; they fail to realise our innate expressiveness and dexterity of motion. This thesis looks at ways of capturing more detailed and subtle motion for the control of computer music tools; it examines how this motion can be used to control music software, and evaluates musicians’ experience of using these systems. Two new musical controllers were created, based on a multiparametric paradigm where multiple, continuous, concurrent motion data streams are mapped to the control of musical parameters. The first controller, Phalanger, is a markerless video tracking system that enables the use of hand and finger motion for musical control. EchoFoam, the second system, is a malleable controller, operated through the manipulation of conductive foam. Both systems use machine learning techniques at the core of their functionality. These controllers are front ends to RECZ, a high-level mapping tool for multiparametric data streams. The development of these systems and the evaluation of musicians’ experience of their use constructs a detailed picture of multiparametric musical control. This work contributes to the developing intersection between the fields of computer music and human-computer interaction. The principal contributions are the two new musical controllers, and a set of guidelines for the design and use of multiparametric interfaces for the control of digital music. This work also acts as a case study of the application of HCI user experience evaluation methodology to musical interfaces. The results highlight important themes concerning multiparametric musical control. These include the use of metaphor and imagery, choreography and language creation, individual differences and uncontrol. They highlight how this style of interface can fit into the creative process, and advocate a pluralistic approach to the control of digital music tools where different input devices fit different creative scenarios