Cool, thanks. On Sunday, July 21, 2013 12:59:16 PM UTC-7, Alex Fowler wrote: > > Glad you've found it! :D > > As an off-topic side-note: please, use no underscores in naming, use > hyphens instead, this is lisp's style... like "sizes_r" become "sizes-r". > Many ppl will thank you later :) > > On Sunday, July 21, 2013 11:39:17 PM UTC+4, Brian Craft wrote: >> >> Using getComponentType, it appears to be handling different primitive >> array types ok: >> >> (defn fconcat [& arrays] >> (let [sizes (map count arrays) >> sizes_r (vec (reductions + sizes)) >> offsets (cons 0 (drop-last sizes_r)) >> total (last sizes_r) >> out (make-array (.getComponentType (class (first arrays))) total)] >> (dorun (map #(System/arraycopy %2 0 out %1 %3) offsets arrays sizes)) >> out)) >> >> >> >> On Sunday, July 21, 2013 12:26:26 PM UTC-7, Brian Craft wrote: >>> >>> (make-array (.getComponentType (class arr)) n) seems to work. >>> >>> On Sunday, July 21, 2013 12:22:41 PM UTC-7, Brian Craft wrote: >>>> >>>> Is there a way to create an array with the type of another array? (type >>>> arr) returns the array type, but make-array wants the element type not the >>>> array type, so >>>> >>>> (make-array (type arr) n) >>>> >>>> doesn't work as one might hope. >>>> >>>> >>>> On Sunday, July 21, 2013 8:36:22 AM UTC-7, Alex Fowler wrote: >>>>> >>>>> Java's System.arraycopy is the fastest you can get, since it delegates >>>>> execution to a function implemented in C inside JVM. Simply, this is the >>>>> fastest that your computer hardware can get. All in all Java arrays meet >>>>> the same difficulties and implications as C arrays and that is why >>>>> concationation of raw arrays is so "complex", in contrast to higher-level >>>>> collections which use objects and pointers (e.g. LinkedList). In other >>>>> words, difficulties you experience are natural outcome of how computer's >>>>> memory management is made and there is no way around them. You get the >>>>> most >>>>> of the speed from arrays because they are solid (not fragmented) chunks >>>>> of >>>>> bytes allocated in memory in the moment of their creation. For that very >>>>> reason you cannot extend an existing array (the size cannot be changed >>>>> after creation) and you can't concatenate it with another array since >>>>> first >>>>> it would have to be concatenated. >>>>> >>>>> The natural outcome also is that only arrays of same types can be >>>>> concatenated with System.arraycopy since only array pointers store type >>>>> data, and the contents are simply untyped bytes. And this is why it is >>>>> byte-level and no type-checks are ever done besiedes the initial >>>>> type-check. Again, higher-level pointer-based data structures like >>>>> LinkedList or Queue can introduce boxed typed values, but that'd be waaay >>>>> slower. Considering that only arrays of same type are concatenateable, >>>>> creating a polymorphic function is easy - simply check the argument type >>>>> like: >>>>> >>>>> ; first save types to use them later >>>>> (def arr-type-int (class (ints 3))) >>>>> ; ... same for other primitives... >>>>> >>>>> ; then in your func: >>>>> (cond >>>>> (= (class arr) arr-type-int) (do-int-concat) >>>>> ...) >>>>> >>>>> For more reference: >>>>> http://docs.oracle.com/javase/tutorial/java/nutsandbolts/arrays.html >>>>> http://docstore.mik.ua/orelly/java-ent/jnut/ch02_09.htm >>>>> >>>>> As an alternative, try looking into Java NIO buffers - they too are >>>>> fast and too have some limits. But maybe you could make good of them, >>>>> depends on your use case. >>>>> >>>>> Although somewhat in another vein, but still relating fast data >>>>> management is >>>>> https://groups.google.com/forum/?hl=en#!topic/clojure/BayfuaqMzvs which >>>>> brings in C-like structs in. >>>>> >>>>> On Sunday, July 21, 2013 2:39:38 AM UTC+4, Brian Craft wrote: >>>>>> >>>>>> Here are some experiments that aren't polymorphic. The >>>>>> System/arraycopy version is fastest, by far. Is there any good way to >>>>>> make >>>>>> the other versions faster, or make them handle any array type? >>>>>> >>>>>> (defn bconcat [& arrays] >>>>>> (let [sizes (map count arrays) >>>>>> sizes_r (vec (reductions + sizes)) >>>>>> offsets (cons 0 (drop-last sizes_r)) >>>>>> total (last sizes_r) >>>>>> out (float-array total)] >>>>>> (dorun (map #(System/arraycopy %2 0 out %1 %3) offsets arrays >>>>>> sizes)) >>>>>> out)) >>>>>> >>>>>> (defn cconcat [& arrays] >>>>>> (let [vs (map vec arrays) >>>>>> cc (apply concat vs)] >>>>>> (float-array cc))) >>>>>> >>>>>> (defn dconcat [& arrays] >>>>>> (let [vs (map vec arrays) >>>>>> cc (reduce into [] vs)] >>>>>> (float-array cc))) >>>>>> >>>>>> (defn econcat [& arrays] >>>>>> (let [cc (reduce into [] arrays)] >>>>>> (float-array cc))) >>>>>> >>>>>> >>>>>> On Saturday, July 20, 2013 2:24:14 PM UTC-7, Brian Craft wrote: >>>>>>> >>>>>>> Is there an easy, fast way to concat primitive arrays? I was hoping >>>>>>> java arrays had some common interface for this, but I haven't found >>>>>>> much of >>>>>>> use. I mostly see code like this: >>>>>>> >>>>>>> byte[] c = new byte[a.length + b.length]; >>>>>>> System.arraycopy(a, 0, c, 0, a.length); >>>>>>> System.arraycopy(b, 0, c, a.length, b.length); >>>>>>> >>>>>>> which only works for bytes (in this case). >>>>>>> >>>>>>
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