[erlang-questions] How to implement the A Star find path algorithm using NIF?

[Dmitry Kolesnikov]

Hello,

It looks you are trying to implement a hybrid solution a mix up of Erlang and C code for routing. Unless, I’ve not understood your question. I would either implement A* purely native or purely in Erlang. In both cases, I would target a data structure that best suites your problem and implementation techniques.   

Let’s say, you’ve made decision to implement A* in C then I would design a NIF API to address problem of A* search rather then memory management. In this case the updateBlock routine becomes internal for your C code.   

BTW, Have you consider to use Cpp and NIFpp wrapper for Erlang to integrate existed A* algorithms ?

Best Regards, 
Dmitry


> On 10 Jul 2017, at 20.03, skyman <cloudzen@REDACTED> wrote:
> 
> Hi Dmitry,
> 
> Thanks for your reply.
> The map of our game is large(1000 * 1000 grids). If I use NIF to implement the A Star find path in C, can I allocate the map grid array(1000 * 1000) in C, and when map blocks changed, Erlang calls 'updateBlock' NIF to update the grid state in grid array in C?
> 
> Thanks!
> 
> 
> 
> 
> At 2017-07-11 00:33:34, "Dmitry Kolesnikov" <dmkolesnikov@REDACTED> wrote:
> Hello,
> 
>> On 10 Jul 2017, at 19.11, skyman <cloudzen@REDACTED <mailto:cloudzen@REDACTED>> wrote:
>> 
>> Hi everybody,
>> 
>> Our game is using A Star algorithm to find path. For performance I want to write it in C language, and Erlang calls it by NIF. I don't know whether the map data is maintained in C or in Erlang. Can anyone tell me?
> 
> Map is native data structure. However, you need to use enif interface to interact with it. 
> http://erlang.org/doc/man/erl_nif.html#enif_get_map_value <http://erlang.org/doc/man/erl_nif.html#enif_get_map_value>
>> In addition, is there any better solution than NIF?
> 
> I’ve used to solve a “routing” issues on pure Erlang using ETS, lists, etc. However, this mainly depends on your traffic, latency and size of routing tables. It is hard to give a straight forward answer not knowing this figures.      
> 
> 
>> 
>> Thanks very much!
> 
> Best Regards, 
> Dmitry
> 
> 
>  

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