[swift-users] Proper syntax for 2D table with initial values

[Daniel Dunbar]

The type inference used in Swift can perform poorly when used in this fashion.

You may be able to get acceptable performance by inserting explicit casts, like:
  [...] as [UInt8]
around each of your individual arrays.

If not, my suggestion would be to embed your data in a C function, and expose it to Swift using a simple C function which you import.

In any case it is probably worth filing a bug with your example test case.

 - Daniel

> On May 23, 2016, at 11:04 AM, Ken Burgett via swift-users <swift-users at swift.org> wrote:
> 
> I have a large 2D table defined within a C .h file, as follows:
> 
> static const uint8_t blake2b_kat[256][64] =
> {
>  {
>    0x78, 0x6A, 0x02, 0xF7, 0x42, 0x01, 0x59, 0x03,
>    0xC6, 0xC6, 0xFD, 0x85, 0x25, 0x52, 0xD2, 0x72,
>    0x91, 0x2F, 0x47, 0x40, 0xE1, 0x58, 0x47, 0x61,
>    0x8A, 0x86, 0xE2, 0x17, 0xF7, 0x1F, 0x54, 0x19,
>    0xD2, 0x5E, 0x10, 0x31, 0xAF, 0xEE, 0x58, 0x53,
>    0x13, 0x89, 0x64, 0x44, 0x93, 0x4E, 0xB0, 0x4B,
>    0x90, 0x3A, 0x68, 0x5B, 0x14, 0x48, 0xB7, 0x55,
>    0xD5, 0x6F, 0x70, 0x1A, 0xFE, 0x9B, 0xE2, 0xCE
>  }
>   ... shortened for clarity ...
> }
> There are 16384	elements in this array.  The C compiler accepts it with no difficulty
> 
> I converted it to a .swift file like so:
> 
> let blake2b_kat: [[UInt8]] =
> [
> [
>  0x78, 0x6A, 0x02, 0xF7, 0x42, 0x01, 0x59, 0x03,
>  0xC6, 0xC6, 0xFD, 0x85, 0x25, 0x52, 0xD2, 0x72,
>  0x91, 0x2F, 0x47, 0x40, 0xE1, 0x58, 0x47, 0x61,
>  0x8A, 0x86, 0xE2, 0x17, 0xF7, 0x1F, 0x54, 0x19,
>  0xD2, 0x5E, 0x10, 0x31, 0xAF, 0xEE, 0x58, 0x53,
>  0x13, 0x89, 0x64, 0x44, 0x93, 0x4E, 0xB0, 0x4B,
>  0x90, 0x3A, 0x68, 0x5B, 0x14, 0x48, 0xB7, 0x55,
>  0xD5, 0x6F, 0x70, 0x1A, 0xFE, 0x9B, 0xE2, 0xCE
> ]
> ...
> ]
> 
> When I attempt a swift compile, the compiler seems to go away and never return.  I tried the same test with the REPL and saw all the text list (2600 lines), but then the same thing happened.  I left the REPL running for 10 minutes or so, with no output. I have tried the same swift table definition with fewer rows and columns, and it produces the correct 2D array.
> 
> My question is whether this is just an issue with the current Swift compiler (I am using the May 9th version for Ubuntu 14.04) or is this a recognized limitation in scale?  In order to get my 2D table filled and work around this issue, I will have to read the file with file I/O and do my own parsing.
> -- 
> Ken Burgett
> Principal Software Engineer
> Email: kenb at iotone.io
> Office: 530.693.4449
> Mobile: 831.332.6846
> URL: www.iotone.co
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