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Menu. Weather forecasting. Explanation. Overview picture. Data collection. Sensors. Data logging. The Grid System. Weather station. Radiosonde. Satellites. Radar. Weather ships. Supercomputers. Parallel Processing. Software. Pressing Weather forecasting on any slide will bring you back to this menu.
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1. We currently have two Cray T3E supercomputers, which are used to run the daily weather forecasts and to run large scale climate studies. These are both Massively Parallel Processor (MPP) systems, which is to say that they contain a large number of processors (CPUs), each with it's own separate portion of volatile RAM which serves as main memory. The individual portions of memory are relatively low, 128 MB per processor on one T3E and 256 MB on the other, but because of the numbers of processors involved this gives total memory sizes of 118 GB on the T3E-900 and 168 GB on the T3E-1200E respectively. In order to run programs with very high memory requirements, it is necessary for the programmer to break down the forecast or climate data into smaller sections and distribute it across a number of processors. Each processor can access it's own local memory with normal load/store operations, but data on held remote processors must be accessed using special software routines, such as the Message Passing Interface (MPI) or Cray's SHMEM system. The T3Es run an operating system called Unicos/mk. This is based on the Unix operating system, but it has been extensively modified to allow it to run across a large number of processors simultaneously. Unicos/mk is best thought of as an interactive system which has the capacity to run batch work, rather than the other way round. The batch facilities are provided by an additional piece of Cray software called the Network Queueing System (NQS). For reasons of efficiency, the majority of the workload on the Crays, including the weather forecasts, are run in batch mode. This allows us to ensure that the supercomputers are run at full capacity over weekends and holiday periods, as well as allowing us to allocate extra computing power to our scientists when it is not required for to produce the daily forecasts.
2. We currently have two Cray T3E supercomputers, which are used to run the daily weather forecasts and to run large scale climate studies. These are both Massively Parallel Processor (MPP) systems, which is to say that they contain a large number of processors (CPUs), each with it's own separate portion of volatile RAM which serves as main memory. The individual portions of memory are relatively low, 128 MB per processor on one T3E and 256 MB on the other, but because of the numbers of processors involved this gives total memory sizes of 118 GB on the T3E-900 and 168 GB on the T3E-1200E respectively. In order to run programs with very high memory requirements, it is necessary for the programmer to break down the forecast or climate data into smaller sections and distribute it across a number of processors. Each processor can access it's own local memory with normal load/store operations, but data on held remote processors must be accessed using special software routines, such as the Message Passing Interface (MPI) or Cray's SHMEM system. The T3Es run an operating system called Unicos/mk. This is based on the Unix operating system, but it has been extensively modified to allow it to run across a large number of processors simultaneously. Unicos/mk is best thought of as an interactive system which has the capacity to run batch work, rather than the other way round. The batch facilities are provided by an additional piece of Cray software called the Network Queueing System (NQS). For reasons of efficiency, the majority of the workload on the Crays, including the weather forecasts, are run in batch mode. This allows us to ensure that the supercomputers are run at full capacity over weekends and holiday periods, as well as allowing us to allocate extra computing power to our scientists when it is not required for to produce the daily forecasts.
3. > decision to make. We can rewrite our codes for each computer system we > buy in order to make it run really fast and efficiently on that system. > This costs us a lot of money in employing people to rewite our code. > Alternatively we can write code that may not be as fast and efficient, > but that runs well on many different systems. This is closer to the > approach we actually take - in reality it's a bit of both - but as far > as possible we aim for code that is highly portable to different > computers. > > Slide 32: > Again a very complex idea to explain! Can't think off the top of my head > of a good analogy to use here. I'll let you know if I can think of > something... > > Slide 34: > Similar comments to 32> decision to make. We can rewrite our codes for each computer system we> buy in order to make it run really fast and efficiently on that system.> This costs us a lot of money in employing people to rewite our code.> Alternatively we can write code that may not be as fast and efficient,> but that runs well on many different systems. This is closer to the> approach we actually take - in reality it's a bit of both - but as far> as possible we aim for code that is highly portable to different> computers.> > Slide 32:> Again a very complex idea to explain! Can't think off the top of my head> of a good analogy to use here. I'll let you know if I can think of> something...> > Slide 34:> Similar comments to 32
4. Weather forecasting
42. Teachers note.
You could do this as a class exercise to show how parallel processing works.
Ask 12 pupils ..( if your class is smaller than 26 you can make this group smaller, as long as you have one person in this group you can demonstrate the concept) Call them Group A to write out the seven times table.
Ask another 12 pupils .. Call them Group B to write out one line of the seven times table. So Ann does 1*7
Branwen does 2*7, Sabeen does 3*7, Lucy does 4*7 and so on.
Then have one pupil time the first person in Group A to finish writing out the tables.
Have another pupil time how long it takes for everybody in Group B to have written down their answers.
Group B should be much faster.
This is the idea behind Parallel ProcessingTeachers note.
You could do this as a class exercise to show how parallel processing works.
Ask 12 pupils ..( if your class is smaller than 26 you can make this group smaller, as long as you have one person in this group you can demonstrate the concept) Call them Group A to write out the seven times table.
Ask another 12 pupils .. Call them Group B to write out one line of the seven times table. So Ann does 1*7
Branwen does 2*7, Sabeen does 3*7, Lucy does 4*7 and so on.
Then have one pupil time the first person in Group A to finish writing out the tables.
Have another pupil time how long it takes for everybody in Group B to have written down their answers.
Group B should be much faster.
This is the idea behind Parallel Processing
49. There are two photos in this presentation, the polar satellite and the buoy whose owners I could not trace. I did try. I hope they will be pleased to see their work helping people learn how weather forecasting works.There are two photos in this presentation, the polar satellite and the buoy whose owners I could not trace. I did try. I hope they will be pleased to see their work helping people learn how weather forecasting works.
