Hi Leo, sorry for the delayed answer. I was looking to something smart to say over this topic, but nothing came :) Indeed, I don't have tested yet patterns like expression template to make any pertinent remark there.
> you should probably also set `TAILCALLS` to -1 Thx for pointing this out. >This also means that unconditionally inlining recursive functions can send the compiler into an infinite loop. For C++ (the only interpreter I know a little), this is left under the user responsibility. When such infinite loop occurs, then the user payback its freedom spending a lot of time to blindly understand why its interpreter rose an exception. I don't know whether it is a good idea or not. > This is conceptually simpler, but would bloat the syntax tree and mostly (?) not help much. See remark above. In a first phase, having inlined version of fn:fold-left (maybe naming it as hof:fold-left would be safer ?) should be enough, and safer, since you should know in advance the call depth. Shall (INLINE = ?) control the depth call ? I did not have a look to the code yet, but I was wondering how can you detect recursive calls ? The self recursive case seems easy to detect, but if I glue two functions together, it seems trickier. Cheers Jean-Marc 2013/11/24 Leo Wörteler <l...@basex.org> > Jean-Marc, > > Am 23.11.2013 17:52, schrieb jean-marc Mercier: > > A drawback is that the stack trace is inefficient, hardening the >> debugging. Thus it is better to set INLINE = 0 in dev phase. >> > > yes; you should probably also set `TAILCALLS` to -1 if you want the stack > trace to always be accurate. As BaseX performs tail-call optimization [1], > the stack will otherwise never contain more than a fixed number (currently > 256) of tail-call frames. > > > Could you be kind enough to point me out the link to your code at Basex >> repository ? >> > > Sure, function inlining is triggered in StaticFuncCall [2] and DynFuncCall > [3]. > > > Motivation : I would like to try evaluating whether inlining recursive >> functions is possible or not. You are welcome to suggestions ! >> > > The hard part about inlining recursive functions is figuring out when to > stop. As they have a call to themselves in the function body, each time you > inline them at least one new call is inserted. This also means that > unconditionally inlining recursive functions can send the compiler into an > infinite loop. > > Inlining is indeed possible for all functions for which we can guarantee > that the number of replacements will be finite. I'm currently implementing > this for `fn:fold-left`, `fn:fold-right` and `fn:for-each` (basically loop > unrolling) when the sequence is short and known at compile time. It would > definitely be possible to implement this for user-defined functions, too, > but we'd need to identify (a subset of) the correct ones. > > Another option would be to always inline recursive functions up to a fixed > depth. This is conceptually simpler, but would bloat the syntax tree and > mostly (?) not help much. > > What are your ideas? > Leo > > [1] http://en.wikipedia.org/wiki/Tail_call > [2] https://github.com/BaseXdb/basex/blob/next/basex-core/ > src/main/java/org/basex/query/func/StaticFuncCall.java#L71 > [3] https://github.com/BaseXdb/basex/blob/next/basex-core/ > src/main/java/org/basex/query/func/DynFuncCall.java#L57 >
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