[Swift-devel] Re: [Swift-user] what is wrong with restart5.swift?

[Ben Clifford]

(moved to swift-devel)

On Mon, 26 May 2008, Mihael Hategan wrote:

> > I also think that is(was?) the only correctness problem with restarts at 
> > the moment.
> 
> There was also the ability to persuade a mapper (in particular temp
> mappers) to use specific files instead of something of their choice.

If by temporary mappers you mean the concurrent mapper, then there is not 
a correctness problem there at the moment, I think.

There is a problem (I think) with input mappers, where if the input file 
set is changed between restarts then mappings will be different.

An example of this (which I have seen a real user do) is when a workflow 
outputs files that match an input file specification - subsequent runs 
then had more input files, and in some cases those would be mapped 
differently.

That is a fairly broad problem, though. Forcing mapping of some subset of 
a mappers files would not address this; forcing all mapping to be 
enumerated and stored ready for restarts would. But that changes how 
mappers fit in (for example, not letting them invent mappings 
dynamically).

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