Top posting just to say thanks to Peter, typed-records are a huge benefit for me. I much appreciate the detailed response.
On Mon, Jul 25, 2016 at 11:49 PM, Peter Bex <[email protected]> wrote: > On Sun, Jul 24, 2016 at 11:06:32AM -0700, Matt Welland wrote: > > For years now I've been using inlined vectors instead of records or coops > > for data structures due to performance concerns. Recently I was training > > someone on how to maintain my code and I felt quite lame explaining the > > vector records. So I started switching to defstruct records. However I've > > started to hit some performance issues and one factor seems to be the > > records (more work to do to confirm this). > > > > Below is a simplistic benchmark comparing using inlined vectors, inlined > > vectors with a type check, defstruct and coops. Where performance matters > > using vectors or type checked vectors seems to help. The benchmark seems > > enough to hint to me to switch back to vectors - especially in cases > where > > I'm slinging around 10's of thousands of records. > > Hello Matt, > > The reason for this is pretty simple: record types do not have inlineable > accessors. This means that accessors (and constructors) will require > that they are invoked in full CPS context. If you have a procedure which > calls such an accessor, it will always be split up into at least 2 C > functions. > > This is because records have an API defined by the procedures which are > created by the define-record(-type)/defstruct macros; the objects > themselves do not contain enough information to have a generic accessor, > and when you're calling an accessor, the compiler doesn't know that it's > a record accessor. Vectors, on the other hand, have a common interface: > they can be referenced by one and the same accessor: vector-ref. > This is inlineable in C, as C_i_vector_ref(). In the next version of > CHICKEN, we'll even be able to rewrite those directly to C_slot() if > the vector is of a known length and the index is within bounds. > > > My question: can anyone offer insight into a better way to balance > > performance with elegance/flexibility of records? > > Luckily, there's a simple solution. Felix wrote a wonderful little egg > called "typed-records", which provides drop-in replacements for > define-record(-type) *and* defstruct which will emit specialisations > for records. > > That is, if an object is known to be a record of the given type, the > accessor is rewritten to (##sys#slot <record> <slot>). > > For instance, with (defstruct foo bar qux), (foo-qux x) is rewritten > to (##sys#slot x 2) if x is known to be of type (struct foo). > The only disadvantage of this is that if you change your definition > of a record, you'll need to recompile all the units that access these > records, because they've been inlined as numbered slot references. > > Changing the sample code in your e-mail by simply replacing "defstruct" > in your "use" line with "typed-records" results in noticeable > performance improvement: > > Using vectors > 1.148s CPU time, 33162750 mutations, 0/2309 GCs (major/minor) > Using vectors (safe mode) > 2.308s CPU time, 0.02s GC time (major), 49744125 mutations, 15/20266 GCs > (major/minor) > Using defstruct > 1.66s CPU time, 33162750 mutations, 5/11665 GCs (major/minor) > Using coops > 20.608s CPU time, 0.628s GC time (major), 33162760 mutations, 960/231731 > GCs (major/minor) > > Before making that one-word replacement, it was: > > Using vectors > 1.112s CPU time, 33162750 mutations, 0/2309 GCs (major/minor) > Using vectors (safe mode) > 2.34s CPU time, 0.02s GC time (major), 49744125 mutations, 15/20266 GCs > (major/minor) > Using defstruct > 4.224s CPU time, 0.012s GC time (major), 33162750 mutations, 36/40736 GCs > (major/minor) > Using coops > 20.572s CPU time, 0.608s GC time (major), 33162760 mutations, 938/231753 > GCs (major/minor) > > Not too bad, especially considering that typed-records is _safe_: it > will only perform the rewrites when the compiler can prove that the given > object is of the required type. > > If it cannot, you can always add a check to your code like this: > (if (not (my-type? x)) (error "wrong type") (begin ...)) > The use of a predicate will tell the compiler that in the else branch, > x can only be of the required type. > > If you're using separate compilation, you need to remember to ask the > compiler to emit the type declarations to a file, and use that file while > compiling the users of the API. > > Cheers, > Peter > > _______________________________________________ > Chicken-users mailing list > [email protected] > https://lists.nongnu.org/mailman/listinfo/chicken-users > >
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