Shared memory concept for multi-core is 'flawed' By David Manners. Electronicsweekly.com
Leading microprocessor developers Intel and AMD may never totally solve the problems of programming general purpose multi-core processors if they carry on with a shared memory approach, according to two UK multiprocessing experts. "I believe there’s not a solution to the problem the way Intel and AMD are approaching it" said Flemming Christensen, managing director of multiprocessor system developer Sundance, "in my view the whole concept of multi-processing using shared memory is flawed."
Agreeing with Christensen, Peter Robertson, managing director of Edinburgh multiprocessing design tool company 3L told EW: "The shared memory approach to general purpose multi-core processing is like building Hadrian’s Wall with 100 builders spread between Newcastle and Carlisle with one guy with a wheelbarrow delivering the bricks." The problems become worst as the number of processor cores on one chip increases.
According to Robertson: "Designers try to take a sequential language like C to capture parallelism. People want to take code written for uni-processors and magically turn it into something that will run on multiple processors and can be made to run as fast as you like just by throwing more processors at it. This is nonsense." Robertson continued: "Our approach is that you have to recognise you need a vast number of processors - only some of which talk to each other - and none of which talk to the whole system. Then you have to write the programme in such a way that the bits that need to talk to each other - do talk to each other.” “You have to break the problems down, then you have a hope of distributing them across the processors," said Robertson.
Last week, Chris Rowen, CEO of multi-processor specialist Tensilica, said: "The challenge of writing software for programming general purpose computing applications is generally recognised in the scientific computing community as the biggest single unsolved, and perhaps unsolvable, computing problem."
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