on 06-Mar-2018 (Tue)

A thread is a basic unit of CPU utilization; it comprises a thread ID,aprogram counter, a register set, and a stack

It shares with other threads belonging to the same process its code section, data section, and other operating-system resources, such as open files and signals

Responsiveness. Multithreading an interactive application may allow a program to continue running even if part of it is blocked or is performing a lengthy operation, thereby increasing responsiveness to the user. This quality is especially useful in designing user interfaces

Resource sharing. Processes can only share resources through techniques such as shared memory and message passing. Such techniques must be explicitly arranged by the programmer. However, threads share the memory and the resources of the process to which they belong by default

Economy. Allocating memory and resources for process creation is costly. Because threads share the resources of the process to which they belong, it is more economical to create and context-switch threads

Scalability. The benefits of multithreading can be even greater in a multiprocessor architecture, where threads may be running in parallel on different processing cores

Modern Intel CPUs frequently support two threads per core, while the Oracle T4 CPU supports eight threads per core. This support means that multiple threads can be loaded into the core for fast switching

1 Introduction The nineteenth century saw in primitive religions two peculiarities which separated them as a block from the great religions of the world. One was that they were inspired by fear, the other that they were inextricably confused with defilement and hygiene

1 Introduction The nineteenth century saw in primitive religions two peculiarities which separated them as a block from the great religions of the world. One was that they were inspired by fear, the other that they were inextricably confused with defilement and hygiene. Almost any missionary’s or traveller’s account of a primitive religion talks about the fear, terror or dread in which its adherents live. The source is traced to beliefs in horrible disasters which overtake those who inadvertently cross some forbidden line or develop some impure condition. And as fear inhibits reason it can be held accountable for other peculiarities in primitive thought, notably the idea of defilement. As Ricoeur sums it up: ‘La souillure elle-même est à peine une representation et celle-ci est noyée dans une peur spécifique qui bouche la réflexion; avec la souillure nous entrons au règne de la Terreur.’ (p. 31) But anthropologists who have ventured further into these primitive cultures find little trace of fear. Evans-Pritchard’s study of witchcraft was made among the people who struck him as the most happy and carefree of the Sudan, the Azande. The feelings of an Azande man, on finding that he has been bewitched, are not terror, but hearty indignation as one of us might feel on finding himself the victim of embezzlement

So primitive religious fear, together with the idea that it blocks the functioning of the mind, seems to be a false trail for understanding these religions.

Data parallelism focuses on distributing subsets of the same data across multiple computing cores and performing the same operation on each core

Hygiene, by contrast, turns out to be an excellent route, so long as we can follow it with some self-knowledge. As we know it, dirt is essentially disorder. There is no such thing as absolute dirt: it exists in the eye of the beholder. If we shun dirt, it is not because of craven fear, still less dread of holy terror. Nor do our ideas about disease account for the range of our behaviour in cleaning or avoiding dirt. Dirt offends against order. Eliminating it is not a negative movement, but a positive effort to organise the environment.

In this book I have tried to show that rituals of purity and impurity create unity in experience

Pollution ideas work in the life of society at two levels, one largely instrumental, one expressive

At the first level, the more obvious one, we find people trying to influence one another’s behaviour. Beliefs reinforce social pressures: all the powers of the universe are called in to guarantee an old man’s dying wish, a mother’s dignity, the rights of the weak and innocent.

the ideal order of society is guarded by dangers which threaten transgressors. These danger- beliefs are as much threats which one man uses to coerce another as dangers which he himself fears to incur by his own lapses from righteousness.

At this level the laws of nature are dragged in to sanction the moral code: this kind of disease is caused by adultery, that by incest; this meteorological disaster is the effect of political disloyalty, that the effect of impiety. The whole universe is harnessed to men’s attempts to force one another into good citizenship.

as we examine pollution beliefs we find that the kind of contacts which are thought dangerous also carry a symbolic load.

The two sexes can serve as a model for the collaboration and distinctiveness of social units. So also can the processes of ingestion portray political absorption. Sometimes bodily orifices seem to represent points of entry or exit to social units, or bodily perfection can symbolise an ideal theocracy

Everything that can happen to a man in the way of disaster should be catalogued according to the active principles involved in the universe of his particular culture. Sometimes words trigger off cataclysms, sometimes acts, sometimes physical conditions. Some dangers are great and others small. We cannot start to compare primitive religions until we know the range of powers and dangers they recognise.

But the society does not exist in a neutral, uncharged vacuum. It is subject to external pressures; that which is not with it, part of it and subject to its laws, is potentially against it. In describing these pressures on boundaries and margins I admit to having made society sound more systematic than it really is.

It is only by exaggerating the difference between within and without, about and below, male and female, with and against, that a semblance of order is created. In this sense I am not afraid of the charge of having made the social structure seem over- rigid.

The same impulse to impose order which brings them into existence can be supposed to be continually modifying or enriching them. This is a very important point.

deas about contagion can certainly be traced to reaction to anomaly. But they are more than the disquiet of a laboratory rat who suddenly finds one of his familiar exits from the maze is blocked.

The initial recognition of anomaly leads to anxiety and from there to suppression or avoidance; so far, so good. But we must look for a more energetic organising principle to do justice to the elaborate cosmologies which pollution symbols reveal.

The native of any culture naturally thinks of himself as receiving passively his ideas of power and danger in the universe, discounting any minor modifications he himself may have contributed. In the same way we think of ourselves as passively receiving our native language and discount our responsibility for shifts it undergoes in our life time.

I emphatically deny that a proliferation of ideas about purity and contagion implies a rigid mental outlook or rigid social institutions. The contrary may be true.

The more we know about primitive religions the more clearly it appears that in their symbolic structures there is scope for meditation on the great mysteries of religion and philosophy. Reflection on dirt involves reflection on the relation of order to disorder, being to non-being, form to formlessness, life to death.

This is why an understanding of rules of purity is a sound entry to comparative religion. The Pauline antithesis of blood and water, nature and grace, freedom and necessity, or the Old Testament idea of Godhead can be illuminated by Polynesian or Central African treatment of closely related themes.

Our idea of dirt is compounded of two things, care for hygiene and respect for conventions.

The rules of hygiene change, of course, with changes in our state of knowledge. As for the conventional side of dirt-avoidance, these rules can be set aside for the sake of friendship.

Whether they are rigorously observed or violated, there is nothing in our rules of cleanness to suggest any connection between dirt and sacredness. Therefore it is only mystifying to learn that primitives make little difference between sacredness and uncleanness.

It could mean that our idea of sanctity has become very specialised, and that in some primitive cultures the sacred is a very general idea meaning little more than prohibition. In that sense the universe is divided between things and actions which are subject to restriction and others which are not; among the restrictions some are intended to protect divinity from profanation, and others to protect the profane from the dangerous intrusion of divinity. Sacred rules are thus merely rules hedging divinity off, and uncleanness is the two-way danger of contact with divinity.

Thus the grand lines ‘Be ye Holy, Because I am Holy’ are rather thinly rendered: ‘I am the Lord your God, who rescued you from the land of Egypt; I am set apart and you must be set apart like me.’

What is clean in relation to one thing may be unclean in relation to another, and vice versa. The idiom of pollution lends itself to a complex algebra which takes into account the variables in each context

Behaviour that usually results in pollution is sometimes intentional in order to show deference and respect; by doing that which under other circumstances would be defiling, an individual expresses his inferior position.

Frazer seems to have thought that confusion between uncleanness and holiness is the distinctive mark of primitive thinking.

Primitive rules Of uncleanness pay attention to the material circumstances of an act and judge it good or bad accordingly. Thus contact with corpses, blood or spittle may be held to transmit danger. Christian rules of holiness, by contrast, disregard the material circumstances and judge according to the motives and disposition of the agent.

In this way a criterion was produced for classing religions as advanced or as primitive. If primitive, then rules of holiness and rules of uncleanness were undistinguishable; if advanced then rules of uncleanness disappeared from religion. They were relegated to the kitchen and bathroom and to municipal sanitation, nothing to do with religion.

Henry Burnett Tylor (1832–1917). He developed a theory and systematically amassed evidence to prove that civilisation is the result of gradual progress from an original state similar to that of contemporary savagery.

Robertson Smith used the idea of survivals to account for the persistence of irrational rules of uncleanness.

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