Two posts in as many days - a brand new record for me.
I talked a little while ago about the future of programming being parallel / multi-core: Good Threaded Code.
Trawling through the one of my favourite web sites I came upon this piece: The Register: Deconstructing databases with Jim Gray. The title is a little misleading, as Mr. Gray actually spends more time talking about the use of GPUs for massively parallel processing and the future of programming in such an environment. He mentions that a common language called 'Accelerator' is already being defined for programming GPUs for parallel processing within a Microsoft environment. Now what I want to know is whether there is similar functionality available for Java? If there isn't I suppose that we'll need to start something in this area.
I want to be able to implement this algorithm and see how well we can get it accelerated: Bitonic Sort.
May 31, 2006
May 30, 2006
Process Singleton or Cluster Mutex.
My friend Neil and I have been discussing this pattern for some time. I finally came up with a couple of sober yet pithy names for it as to date we've been calling it the 'Talking Stick Pattern'. This pattern is intended to be used primarily in clustered applications though there is nothing to prevent it being used elsewhere.
The singleton pattern is well known and various attempts have been made to implement it within a cluster. For most instances a node-singleton is sufficient as the singleton pattern is used to prevent excessive memory usage - effectively a pool of one. However on occasions the singleton pattern is used to provide access control to a shared resource that cannot support multiple concurrent accesses or to control the running of a business process that could have issues if run concurrently. Failover is the weakness with implementing a cluster-singleton: You are either dependent on a vendor-specific approach or you have to come up with a solution of your own.
The solution that Neil and I have arrived at is derived from the 'Talking Stick' idea used in group discussions. Rather than have a pell-mell of competing voices, the talking stick is handed to an individual who can then talk, when he is done the talking stick is handed on to the next individual who is allowed to talk. When you do not have the talking stick you are not allowed to talk.
We apply this to a set of objects. Before the object can act, it must get hold of the 'talking stick'. This means that only one object can act at a time. The implementation of the talking stick must be robust in the event of a failure and we have two tried and tested implementations that work.
The first talking stick implementation is a little database dependent. The use of a row-lock in a database that supports either a read-past semantic or like Oracle supports SELECT...FOR UPDATE NOWAIT. When the transaction commits, the lock is released for the next access. If something goes wrong the database transaction rolls back and the row lock becomes available for another transaction.
The second implementation relies on a transactional JMS implementation and a message on a queue is used as the talking stick. An object waits on the queue for a message and when it has it, it is allowed to act. When it has finished it places the message back on the queue for the next object to access. Again, when a failure occurs, the transaction tolls back and the talking stick becomes available again.
Depending on whether it is being used to manage processes or manage access control I would call it a Process Singleton or a Cluster Mutex.
Edit - Gil, a colleague working with me, pointed out that the talking stick is a form of Token.
The singleton pattern is well known and various attempts have been made to implement it within a cluster. For most instances a node-singleton is sufficient as the singleton pattern is used to prevent excessive memory usage - effectively a pool of one. However on occasions the singleton pattern is used to provide access control to a shared resource that cannot support multiple concurrent accesses or to control the running of a business process that could have issues if run concurrently. Failover is the weakness with implementing a cluster-singleton: You are either dependent on a vendor-specific approach or you have to come up with a solution of your own.
The solution that Neil and I have arrived at is derived from the 'Talking Stick' idea used in group discussions. Rather than have a pell-mell of competing voices, the talking stick is handed to an individual who can then talk, when he is done the talking stick is handed on to the next individual who is allowed to talk. When you do not have the talking stick you are not allowed to talk.
We apply this to a set of objects. Before the object can act, it must get hold of the 'talking stick'. This means that only one object can act at a time. The implementation of the talking stick must be robust in the event of a failure and we have two tried and tested implementations that work.
The first talking stick implementation is a little database dependent. The use of a row-lock in a database that supports either a read-past semantic or like Oracle supports SELECT...FOR UPDATE NOWAIT. When the transaction commits, the lock is released for the next access. If something goes wrong the database transaction rolls back and the row lock becomes available for another transaction.
The second implementation relies on a transactional JMS implementation and a message on a queue is used as the talking stick. An object waits on the queue for a message and when it has it, it is allowed to act. When it has finished it places the message back on the queue for the next object to access. Again, when a failure occurs, the transaction tolls back and the talking stick becomes available again.
Depending on whether it is being used to manage processes or manage access control I would call it a Process Singleton or a Cluster Mutex.
Edit - Gil, a colleague working with me, pointed out that the talking stick is a form of Token.
May 21, 2006
Are They Running the Country or Running for Re-Election?
This is an huge question, but one which has a simple answer.
I believe that all political parties in Britain are about running for re-election and running the country is a side issue.
This has not always been the case, but the temptation to run for election is one of the great weaknesses of democracy. It is much harder to get re-elected by doing a good job of running the country than by standing around for photo opportunities and telling us what we want to hear. Especially when you consider that your opponents only have to do the photo opportunities. Of course the machiavelllian solution is to get your opponents deeply enmeshed in running the country 'in the interest of non-partisan politics'. The opposition would get credit for not being out of practice in running the country and for any good work they do. You'd increase the availability of competent people for key positions, tie your opponents up and level the field when it came time for elections. With more competent people, the country would benefit overall and you'd get the credit for that (and of course for the good work that your opposition do...).
The trouble is exacerbated by the press. We are told that a strong fifth estate is one of the great pillars of a strong democracy. Unfortunately at the moment our press is lazy and lets the politicians set the agenda. Many stories are handed to them by the current political leadership and by their opposition in their struggle to be elected. It is also in the press' interest to keep politics partisan as the latest bickering is an easy story that sells papers and airtime.
I wonder whether the press could ever be convinced that the real story is in the fact that politicians are running for re-election and not running the country. What would happen if the press were banned from naming individual politicians except when they were doing something wrong? Can democracy ever produce a leadership that truly focusses on running the country and is able to work together with their opponents for the common good? Any other ideas?
I believe that all political parties in Britain are about running for re-election and running the country is a side issue.
This has not always been the case, but the temptation to run for election is one of the great weaknesses of democracy. It is much harder to get re-elected by doing a good job of running the country than by standing around for photo opportunities and telling us what we want to hear. Especially when you consider that your opponents only have to do the photo opportunities. Of course the machiavelllian solution is to get your opponents deeply enmeshed in running the country 'in the interest of non-partisan politics'. The opposition would get credit for not being out of practice in running the country and for any good work they do. You'd increase the availability of competent people for key positions, tie your opponents up and level the field when it came time for elections. With more competent people, the country would benefit overall and you'd get the credit for that (and of course for the good work that your opposition do...).
The trouble is exacerbated by the press. We are told that a strong fifth estate is one of the great pillars of a strong democracy. Unfortunately at the moment our press is lazy and lets the politicians set the agenda. Many stories are handed to them by the current political leadership and by their opposition in their struggle to be elected. It is also in the press' interest to keep politics partisan as the latest bickering is an easy story that sells papers and airtime.
I wonder whether the press could ever be convinced that the real story is in the fact that politicians are running for re-election and not running the country. What would happen if the press were banned from naming individual politicians except when they were doing something wrong? Can democracy ever produce a leadership that truly focusses on running the country and is able to work together with their opponents for the common good? Any other ideas?
May 19, 2006
Learning: By Rote Vs, Asking Why.
I had a very pleasant lunch yesterday with two Voca colleagues, Roger and Peter. As my lunches tend to always go, we ended up discussing a number of interesting topics, this lunch steered entirely clear of technology.
We discussed counselling, consciousness, upbringing and education. I told Roger and Peter in my typical bombastic manner about a very interesting piece of research I read recently in New Scientist. The article touched on the manners in which humans and our cousins great apes learn from our parents. If you were asked which species is more likely to learn by simple, exact copying of parental activities, which species would you pick?
It turns out that humans are far more likely than any other great ape to shortcut learning by simple imitation. The example that is often quoted is the Mother making a 'pot roast', she cuts off one end of the joint and puts it in the pot beside the main part. Her daughter asks her why she does that and she is forced to reply that she doesn't know, her mother did it that way. So the Mother asks here mother who replies that her own mother always did it that way. The Mother then calls her grandmother who replies that she started doing that because she didn't have a big enough pot.
It appears that humans are extremely likely to learn by rote. It seems to be a shortcut that we have evolved. I believe that this shortcut emerged because of the volume of information that we are forced to learn in order to survive in our culture. If we questioned every single tiny fact, we would never learn enough to sustain the complexity of our culture before we were 50 years old.
That's not to say that questioning is not important. Without 'Why?' we would never have progressed our culture.
I would suggest that the best education a child can get is one that is primarily by rote that does not suppress the desire to question. In effect there is a balance: sufficient rote learning to provide a basic body of knowledge to survive in the world coupled with time spent teaching how to question this body of knowledge.
I believe that you actually have to have a basic level of knowledge before you can decide which questions are worth asking.
When I say 'Culture' I mean it in the more scientific sense of the set of learnt behaviours and knowledge that we as a species learn rather than are born knowing.
We discussed counselling, consciousness, upbringing and education. I told Roger and Peter in my typical bombastic manner about a very interesting piece of research I read recently in New Scientist. The article touched on the manners in which humans and our cousins great apes learn from our parents. If you were asked which species is more likely to learn by simple, exact copying of parental activities, which species would you pick?
It turns out that humans are far more likely than any other great ape to shortcut learning by simple imitation. The example that is often quoted is the Mother making a 'pot roast', she cuts off one end of the joint and puts it in the pot beside the main part. Her daughter asks her why she does that and she is forced to reply that she doesn't know, her mother did it that way. So the Mother asks here mother who replies that her own mother always did it that way. The Mother then calls her grandmother who replies that she started doing that because she didn't have a big enough pot.
It appears that humans are extremely likely to learn by rote. It seems to be a shortcut that we have evolved. I believe that this shortcut emerged because of the volume of information that we are forced to learn in order to survive in our culture. If we questioned every single tiny fact, we would never learn enough to sustain the complexity of our culture before we were 50 years old.
That's not to say that questioning is not important. Without 'Why?' we would never have progressed our culture.
I would suggest that the best education a child can get is one that is primarily by rote that does not suppress the desire to question. In effect there is a balance: sufficient rote learning to provide a basic body of knowledge to survive in the world coupled with time spent teaching how to question this body of knowledge.
I believe that you actually have to have a basic level of knowledge before you can decide which questions are worth asking.
When I say 'Culture' I mean it in the more scientific sense of the set of learnt behaviours and knowledge that we as a species learn rather than are born knowing.
May 11, 2006
Driving Concentration
When I first started driving I had an old MGB Roadster (known as Summer). It was a spartan driving experience the height of luxury being a heater that had only two settings off and BURN YOU TO DEATH!
My driving was probably at its best when I drove Summer, I kept my temper better, drove more defensively and was generally more considerate.
When I started racking up the motorway miles I got a new car. It was a lovely little Ford Puma (known as Sue). It was immensely more reliable and more luxurious.
However it was with Sue that my driving started to disimprove.
My concentration became worse, I failed to anticipate and, when something happened unexpectedly, I was more inclined to lose my temper. I came to realise that something needed to be done, so I thought about it and finally came to a conclusion.
It was the CD/Radio.
In dear old rackety Summer, there was no point to putting a radio in as I wouldn't have been able to hear it above the engine and the noises of the world outside. I was forced to keep all my concentration on my driving and the environment around me. With Sue the radio almost automatically went on and my concentration drifted. I've now taken to turning the radio off and my driving is beginning to return to the quality that it enjoyed before my fall from grace.
My driving was probably at its best when I drove Summer, I kept my temper better, drove more defensively and was generally more considerate.
When I started racking up the motorway miles I got a new car. It was a lovely little Ford Puma (known as Sue). It was immensely more reliable and more luxurious.
However it was with Sue that my driving started to disimprove.
My concentration became worse, I failed to anticipate and, when something happened unexpectedly, I was more inclined to lose my temper. I came to realise that something needed to be done, so I thought about it and finally came to a conclusion.
It was the CD/Radio.
In dear old rackety Summer, there was no point to putting a radio in as I wouldn't have been able to hear it above the engine and the noises of the world outside. I was forced to keep all my concentration on my driving and the environment around me. With Sue the radio almost automatically went on and my concentration drifted. I've now taken to turning the radio off and my driving is beginning to return to the quality that it enjoyed before my fall from grace.
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