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digitalmars.D.learn - Idiomatic way to generate all possible values a static array of ubyte

reply jkpl <jkpl nowhere.org> writes:
Let's say I have a ubyte[256]. I want to test all the possible 
values this array can have on a function.

Currently I fill it for each new test with std.random.uniform but 
I'm sure that I loose some time with randomizing and with the 
tests that are repeated. Is there a simple way to do this ? 
Without thinking much, it seems that the loops to generate this 
would be seriously awefull.

By thinking a bit more maybe with a fixed-size big integer it 
would work, since the value could be casted as the right array 
type (as long as its length is power of 2) ?
Apr 02 2016
next sibling parent reply rikki cattermole <rikki cattermole.co.nz> writes:
On 02/04/2016 9:20 PM, jkpl wrote:

 Let's say I have a ubyte[256]. I want to test all the possible values
 this array can have on a function.

 Currently I fill it for each new test with std.random.uniform but I'm
 sure that I loose some time with randomizing and with the tests that are
 repeated. Is there a simple way to do this ? Without thinking much, it
 seems that the loops to generate this would be seriously awefull.

 By thinking a bit more maybe with a fixed-size big integer it would
 work, since the value could be casted as the right array type (as long
 as its length is power of 2) ?


Actually I'd use a hex string.

So:
static ubyte[256] DATA = cast(ubyte[256])x"00 01 02 03";
I'm sure you get the idea. That can be created easily enough.
Apr 02 2016
parent reply jkpl <jkpl nowhere.org> writes:
On Saturday, 2 April 2016 at 08:27:07 UTC, rikki cattermole wrote:

 On 02/04/2016 9:20 PM, jkpl wrote:

 Let's say I have a ubyte[256]. I want to test all the possible 
 values
 this array can have on a function.


 Actually I'd use a hex string.

 So:
 static ubyte[256] DATA = cast(ubyte[256])x"00 01 02 03";
 I'm sure you get the idea. That can be created easily enough.


No I don't get the idea. I think that I haven't well explained. 
By static array I meant "not dynamic". The 256^256 combinations 
must be generated on the same ubyte[256], which is a variable, 
during the program execution.
Apr 02 2016
parent reply rikki cattermole <rikki cattermole.co.nz> writes:
On 02/04/2016 9:36 PM, jkpl wrote:

 On Saturday, 2 April 2016 at 08:27:07 UTC, rikki cattermole wrote:

 On 02/04/2016 9:20 PM, jkpl wrote:

 Let's say I have a ubyte[256]. I want to test all the possible values
 this array can have on a function.


 Actually I'd use a hex string.

 So:
 static ubyte[256] DATA = cast(ubyte[256])x"00 01 02 03";
 I'm sure you get the idea. That can be created easily enough.


 No I don't get the idea. I think that I haven't well explained. By
 static array I meant "not dynamic". The 256^256 combinations must be
 generated on the same ubyte[256], which is a variable, during the
 program execution.


Okay that is a problem then.
Stick with generating it I think, can't hard code that number of 
combinations.
Apr 02 2016
parent reply jkpl <jkpl nowhere.org> writes:
On Saturday, 2 April 2016 at 08:48:10 UTC, rikki cattermole wrote:

 On 02/04/2016 9:36 PM, jkpl wrote:

 On Saturday, 2 April 2016 at 08:27:07 UTC, rikki cattermole 
 wrote:


 Okay that is a problem then.


Yes clearly!

Maybe this, a bit better:


     foreach (b0; randomCover(iota(0,256)))
     foreach (b1; randomCover(iota(0,256)))
     ...
     foreach (b255; randomCover(iota(0,256)))
     {
         ...
     }
Apr 02 2016
parent reply jkpl <jkpl nowhere.org> writes:
On Saturday, 2 April 2016 at 09:11:34 UTC, jkpl wrote:

 On Saturday, 2 April 2016 at 08:48:10 UTC, rikki cattermole 
 wrote:

 On 02/04/2016 9:36 PM, jkpl wrote:

 On Saturday, 2 April 2016 at 08:27:07 UTC, rikki cattermole 
 wrote:


 Okay that is a problem then.


 Yes clearly!

 Maybe this, a bit better:


     foreach (b0; randomCover(iota(0,256)))
     foreach (b1; randomCover(iota(0,256)))
     ...
     foreach (b255; randomCover(iota(0,256)))
     {
         ...
     }


Still not the right approach,


import std.stdio;
import std.random;
import std.range;

void testRunner(bool function(ubyte[128]) test)
{
     uint[32] arr;

     foreach (v0;  randomCover(iota(0U,uint.max)))
     foreach (v1;  randomCover(iota(0U,uint.max)))
     foreach (v2;  randomCover(iota(0U,uint.max)))
     foreach (v3;  randomCover(iota(0U,uint.max)))
     foreach (v4;  randomCover(iota(0U,uint.max)))
     foreach (v5;  randomCover(iota(0U,uint.max)))
     foreach (v6;  randomCover(iota(0U,uint.max)))
     foreach (v7;  randomCover(iota(0U,uint.max)))
     foreach (v8;  randomCover(iota(0U,uint.max)))
     foreach (v9;  randomCover(iota(0U,uint.max)))
     foreach (v10; randomCover(iota(0U,uint.max)))
     foreach (v11; randomCover(iota(0U,uint.max)))
     foreach (v12; randomCover(iota(0U,uint.max)))
     foreach (v13; randomCover(iota(0U,uint.max)))
     foreach (v14; randomCover(iota(0U,uint.max)))
     foreach (v15; randomCover(iota(0U,uint.max)))
     foreach (v16; randomCover(iota(0U,uint.max)))
     foreach (v17; randomCover(iota(0U,uint.max)))
     foreach (v18; randomCover(iota(0U,uint.max)))
     foreach (v19; randomCover(iota(0U,uint.max)))
     foreach (v20; randomCover(iota(0U,uint.max)))
     foreach (v21; randomCover(iota(0U,uint.max)))
     foreach (v22; randomCover(iota(0U,uint.max)))
     foreach (v23; randomCover(iota(0U,uint.max)))
     foreach (v24; randomCover(iota(0U,uint.max)))
     foreach (v25; randomCover(iota(0U,uint.max)))
     foreach (v26; randomCover(iota(0U,uint.max)))
     foreach (v27; randomCover(iota(0U,uint.max)))
     foreach (v28; randomCover(iota(0U,uint.max)))
     foreach (v29; randomCover(iota(0U,uint.max)))
     foreach (v30; randomCover(iota(0U,uint.max)))
     foreach (v31; randomCover(iota(0U,uint.max)))
     {
         arr = [v0,v1,v2,v3,v4,v5,v6,v7,v8,v9,
                v10,v11,v12,v13,v14,v15,v16,v17,v18,v19,
                v20,v21,v22,v23,v24,v25,v26,v27,v28,v29,
                v30, v31
         ];

         writeln(arr);

         //if (test(cast(ubyte[128]) arr))
             return;
     }
}

bool test(ubyte[128] arr)
{
     if (arr[0] == 0U)
         return true;
     else
         return false;
}

void main()
{
     testRunner(&test);
}
Apr 02 2016
parent reply jkpl <jkpl nowhere.org> writes:
gives: core.exception.OutOfMemoryError src/core/exception.d(693): 
Memory allocation failed
Apr 02 2016
parent reply Steven Schveighoffer <schveiguy yahoo.com> writes:
On 4/2/16 5:47 AM, jkpl wrote:

 gives: core.exception.OutOfMemoryError src/core/exception.d(693): Memory
 allocation failed


Probably because randomCover needs to allocate a bool for all the 
elements it has already covered, so you are allocating 32 * 4G bools. 
How much RAM do you have? Note that D's GC is conservative, so false 
pointers, especially for large arrays also can cause problems.

I'll note that even if it worked, this code will never complete in your 
lifetime, or even your great great grandchild's lifetime. I don't 
understand the point of doing this.

I'll also note that if you just want to test a *subset* of all the 
possible inputs (given the length of time taken to test all these), you 
probably want to change different elements each time through the loop. 
Your code spends a long time testing the same elements in the first 
slots. Given your test code is just looking at the first element, this 
isn't very good test coverage.

I honestly think you are better off just generating random arrays, even 
if it results in some overlap (unlikely to be relevant).

-Steve
Apr 02 2016
parent jkpl <jkpl nowhere.org> writes:
On Saturday, 2 April 2016 at 18:32:03 UTC, Steven Schveighoffer 
wrote:

 I honestly think you are better off just generating random 
 arrays, even if it results in some overlap (unlikely to be 
 relevant).

 -Steve


Yes I know, I've realized how it's silly. just foreach(xn; 0 .. 
range) foreach(xn; 0 .. range) foreach(xn; 0 .. range) 
foreach(xn; 0 .. range) is enough. But still silly in term of 
complexity. I have to go for a heuristic approach. UNtil that I 
still use a prng.
Apr 02 2016
prev sibling parent =?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:
[Probably a repost.]

On 04/02/2016 01:20 AM, jkpl wrote:

 Let's say I have a ubyte[256]. I want to test all the possible values
 this array can have on a function.


nextPermutation():

   https://dlang.org/phobos/std_algorithm_sorting.html#nextPermutation

Ali
Apr 02 2016