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On Aug 8, 2013, at 10:46 AM, David Tweed <david.tweed at arm.com> wrote: > | I believe that 2-state Ising models can be reduced to max-flow/min-cut (eg, Finding ground states in random-field Ising ferromagnets by F Barahona) > > I hadn't been following D-Wave; upon looking I see that they're using problem reductions to Ising models which aren't ferromagnet models (sign is different), and those problems are known to be NP-hard. Haven't thought about what kind of models LLVM is usin...

...gn a register to a range and want | to decide if we should split one of the already assigned ranges? Just as general comments not related to the specific implementation in LLVM: I believe that 2-state Ising models can be reduced to max-flow/min-cut (eg, Finding ground states in random-field Ising ferromagnets by F Barahona) , so were a guaranteed polynomial time solution wanted that could be used although as Jakob mentioned, with "easy" problems as simple iterative thing is often quicker in practice. (That's assuming it is an exact Ising model: I hadn't realized LLVM was using that an...

With the D-Wave computer in the news recently, you may find it interesting that LLVM’s register allocator is using Ising models to compute regions for live range splitting. The problem of finding a region for splitting a live range is mapped to an Ising model with the help of the edge bundle graph, see EdgeBundles.h. A node in the edge bundle graph represents a set of CFG edges that enter or

On Aug 8, 2013, at 9:01 AM, David Tweed <David.Tweed at arm.com> wrote: > Just as general comments not related to the specific implementation in LLVM: > > I believe that 2-state Ising models can be reduced to max-flow/min-cut (eg, Finding ground states in random-field Ising ferromagnets by F Barahona) , so were a guaranteed polynomial time solution wanted that could be used although as Jakob mentioned, with "easy" problems as simple iterative thing is often quicker in practice. (That's assuming it is an exact Ising model: I hadn't realized LLVM was using that an...

...e exceptions: Hard disc manufacturers use size tags in MByte, with 1 MByte = 1000000 Bytes... > Early on in the days of computer memory, it was realized that > memory is best organized in powers of 2. > I think that this dates back to the days when "core" memory > was little ferromagnetic cores (like a 0.1 mm donut) storing > one bit It's not that difficult and has nothing to do with history: to address a couple of memory bits, you have to select an address, and you will have to use a fixed set of address lines to transmit this address. Now, all these address lines carry d...

On 7 August 2013 17:06, Jakob Stoklund Olesen <stoklund at 2pi.dk> wrote: > With the D-Wave computer in the news recently, you may find it interesting that LLVM’s register allocator is using Ising models to compute regions for live range splitting. > > The problem of finding a region for splitting a live range is mapped to an Ising model with the help of the edge bundle graph, see