Question

var examples = new double[1000][][];

 for (int i = 0; i < 1000; i++)
 {
  examples[i]= new double[2][]; //the Set
  examples[i][0] = new double[] { x(i), y(i) }; //the Inputs
  examples[i][1] = new double[] { Math.Sin(x(i) * y(i)), Math.Sin(x(i) / y(i)) }; //the Target
 }

x(i) means x depend on i

And I need to collect the inputs like that examples[][0] = new double[1000][]
because It will consume more memory to create a new array like that

for (int i = 0; i < 1000; i++)
{
   input[i][0]=x(i);
   input[i][1]=y(i);
}

Answer 1

My first thought would be to reconsider the design decision that ended up with a [1000][2][2] array which you want to pull a flattened [1000][2] array out of by taking a specific center-array value…

As far as accessing it without re-allocating memory, you’re not going to get it as an array without using more memory sorry, but what you could do is get an IEnumerable<double[]> which may suffice depending on your purposes by using yield (Which will make it evaluate each result individually as you enumerate over it).

EG:

public IEnumerable<double[]> GetResults()
{
  for (int i = 0; i < 1000; x++)
  {
    yield return examples[i][0];
  }
}

How useful that is will depend on how you plan to use the results, but you won’t get a new array without using more memory.