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

[Son Tran-Nguyen]

Hello,

While the choice of C may not be changed, I would suggest writing your
algorithm in Rust
and use something like https://github.com/hansihe/rustler.

It's still NIF, but Rust will handle bad codes for you, making your NIF
safe.

Just a thought.

On Mon, Jul 10, 2017 at 12:32 PM, Dmitry Kolesnikov <dmkolesnikov@REDACTED>
wrote:

> 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> 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
>
> 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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