Hi Ezra,
This is admittedly a little confusing, but you're hinting 's' with the type
of the *element*. Here you've created a sequence containing a single
'ints-and-floats' struct, so you'd want to do this:
user> (v/get-in s [0 :floats 4])
4.0
user> (v/get-in s [0])
{:ints (0 1 2 3 4 5 6 7 8 9), :floats (0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0
9.0)}
I'll try to make this clearer in the documentation. Let me know if you
have any other questions.
Zach
On Wed, Jul 31, 2013 at 10:10 AM, Ezra Lee <lee.e...@gmail.com> wrote:
> Hi,
> I'm trying out vertigo and hoping you can help me figure out what I am
> missing, I get an error when I use get-in:
>
> ; nREPL 0.1.8-preview
> user> (use 'vertigo.structs)
> nil
> user> (def-typed-struct ints-and-floats :ints (array uint32 10) :floats
> (array float32 10))
> #'user/ints-and-floats
> user> (def x {:ints (range 10) :floats (map float (range 10))})
> #'user/x
> user> (require '[vertigo.core :as v])
> nil
> user> (def ^:ints-and-floats s (v/marshal-seq ints-and-floats [x]))
> #'user/s
> user> (v/get-in s [:floats 4])
> IllegalArgumentException Invalid field '4' for type ints-and-floats
> vertigo.core/validate-lookup (core.clj:177)
> user> (v/get-in s [4 :floats])
> IllegalArgumentException java.nio.Buffer.position (Buffer.java:216)
>
> Thanks,
> Ezra
>
> On Tuesday, July 9, 2013 11:56:03 PM UTC-4, Zach Tellman wrote:
>>
>> Last year, I gave a talk at the Conj on my attempt to write an AI for the
>> board game Go. Two things I discovered is that it was hard to get
>> predictable performance, but even once I made sure I had all the right type
>> hints, there was still a lot of room at the bottom for performance
>> improvements. Towards the end [1], I mentioned a few ideas for
>> improvements, one of which was simply using ByteBuffers rather than objects
>> to host the data. This would remove all the levels of indirection, giving
>> much better cache coherency, and also allow for fast unsynchronized
>> mutability when the situation called for it.
>>
>> So, ten months and several supporting libraries [2] [3] later, here it
>> is:
>> https://github.com/**ztellman/vertigo<https://github.com/ztellman/vertigo>
>>
>> At a high level, this library is useful whenever your datatype has a
>> fixed layout and is used more than once. Depending on your type, it will
>> give you moderate to large memory savings, and if you're willing to forgo
>> some of core library in favor of Vertigo's operators, you can get
>> significant performance gains on batch operations. And, in the cases where
>> performance doesn't matter, it will behave exactly like any other Clojure
>> data structure.
>>
>> I want to point out that something like this would be more or less
>> impossible in Java; reading from an offset in a ByteBuffer without the
>> compile-time inference and validation provided by this library would be
>> pointlessly risky. There's not a lot of low-level Clojure libraries, but
>> there's an increasing amount of production usage where people are using
>> Clojure for performance-sensitive work. I'm looking forward to seeing what
>> people do with Vertigo and libraries like it.
>>
>> Zach
>>
>> [1] http://www.youtube.com/**watch?feature=player_**
>> detailpage&v=v5dYE0CMmHQ#t=**1828s<http://www.youtube.com/watch?feature=player_detailpage&v=v5dYE0CMmHQ#t=1828s>
>> [2]
>> https://github.com/ztellman/**primitive-math<https://github.com/ztellman/primitive-math>
>> [3]
>> https://github.com/**ztellman/byte-streams<https://github.com/ztellman/byte-streams>
>>
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