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I am trying to serialize a 2D array of strings to send over a network.
I have a couple ideas but I seem to be blocked by api or efficiency. I really don't want to serialize and send a small 2D array across a network 10 times a second when I only need it when I collide with something and ask for the information.
I have a list of items a player has in his cart. I want to make it okay to steal from that cart, so the other player has to be able to see what's in the cart.
If I use onphotonserializeview I thought I could convert the flatten the 2d array of strings into a 1D array of strings with a delimiter and stream.sendnext the delimited line and reconstitute on the other side, or some variation of that functionality.
public void serialize_merchandise_list() {
int width = 0;
int length = 0;
while((width < cart_list_width) && (length < cart_list_width)) {
width++;
if (width >= cart_list_width) {
length++;
width = 0;
}
// convert to bytes and then to string and append
System.Text.ASCIIEncoding.ASCII.GetBytes(merchandise_items[width, length]));
}
}
But doing that unnecessarily is an operation time nightmare, I want it on demand.
I was going to do a punrpc but I can't get a return value or ref parameter. What is the best approach here?
I want:
collide with cart
do you want to steal from cart --> yes --> show list
else --> go on your way
Afaik a one-dimensional array of strings would be no problem for Photon.
So I guess you could just flatten the array and additionally send the second size - lets name it element size (in contrary to the first one - the element count) as parameters.
Like e.g. lets say your array looks like
string[,] array2D = new string[4,2]{{"a", "b"}, {"c","d"}, {"e","f"}, {"g","h"}};
Then you would know the second (elementSize) dimension using either hardcoded or GetLength(int)
var elementSize = array2D.GetLength(1);
and you would simply flatten the array using
string[] arrayFlat = array2D.Cast<string>().ToArray();
So you would send these two informations via photon (I don't know photon in detail) but afaik you can do this one time without having to send it continiously. The two parameters would be
int elementSize, string[] arrayFlat
in this case with the values
2, string[8]{"a","b","c","d","e","f","g","h"}
So together:
public void SendArray2D()
{
int elementSize = array2D.GetLength(1);
string[] arrayFlat = array2D.Cast<string>().ToArray();
photonView.RPC(nameof(ReceiveArray2D), RpcTarget.All, elementSize, (object) arrayFlat);
}
Then on the receiver part you are getting
int elementSize = 2, string[] arrayFlat = string[8]{"a","b","c","d","e","f","g","h"}
and have to convert it back. You already know the second dimension elementSize = 2 so in order to get also the first one you simply do
var elementCount = arrayFlat.Length / elementSize; // = 4
so you know the 2D array you will have to fill would be
string[,] array2D = new string[elementCount, elementSize]; // = 4,2
and then you can simply iterate it and do something like
for (var x = 0; x < elementCount; x++)
{
for (int y = 0; y < elementSize; y++)
{
array2D[x, y] = arrayFlat[x * elementSize + y];
}
}
So together
[PunRpc]
public void ReceiveArray2D(int elementSize, string[] arrayFlat)
{
var elementCount = arrayFlat.Length / elementSize;
array2D = new string[elementCount, elementSize];
for (var x = 0; x < elementCount; x++)
{
for (int y = 0; y < elementSize; y++)
{
array2D[x, y] = arrayFlat[x * elementSize + y];
}
}
// Could also e.g. call some event like
OnReceivedArray2D?.Invoke (array2D);
}
public event Action<string[,]> OnReceivedArray2D;
So you could attach listeners to the event via
reference.OnReceivedArray2D += SomeHandler;
private void SomeHandler(string [,])
{
// ...
}
Or alternatively you could implement a class that stores your data in a flat array but lets you access it like if it would be a 2D array (in general a 2D array is anyway stored in memory as a flat one)
[Serializable]
public class SerializableArray2D
{
public readonly string[] ArrayFlat;
public readonly ElementSize;
public SerializableArray2D(int elementSize, string[] arrayFlat)
{
ElementSize = elementSize;
ArrayFlat = arrayFlat;
}
public SerializableArray2D(string[,] array2D) : this(array2D.GetLength(1), array2D.Cast<string>().ToArray()) { }
public SerializableArray2D(int elementSize, int elementCount) : this(elementSize, new string[elementCount]){}
public string this[int x, int y]
{
get { return ArrayFlat[x * ElementSize + y]; }
set { ArrayFlat[x * ElementSize + y] = value; }
}
}
usage would be e.g. Initialize it
var array2D = new string[4,2]{{"a", "b"}, {"c","d"}, {"e","f"}, {"g","h"}};
var serializableArray2D = new SerializableArray2D(array2D);
For accessing specific indices like in a 2D array
string example = serializableArray2D[1,1];
serializableArray2D[3,0] = "example";
For sending it
photonView.RPC(nameof(Receive), RpcTarget.All, serializableArray2D.ElementSize, (object)serializableArray2D.ArrayFlat);
And when receiving it
[PunRPC]
public void Receive(int elementSize, string[] arrayFlat)
{
serializableArray2D = new SerializableArray2D(elementSize, arrayFlat);
// Again e.g. call an event
OnReceivedSerializableArray2D?.Invoke(serializableArray2D);
}
public event Action<SerializableArray2D> OnReceivedSerializableArray2D;
I'm getting the error:
"Ambiguity between 'game.Form1.WallCheckerArray' and
'game.Form1.WallCheckerArray'"
Because I use it twice. Why can't I use the same array name twice with different values? My code is below. The array exists out of cordinates.
my array:
private int[,] WallCheckerArray = new int[28, 4];// <<----- was the problem
int[,] WallCheckerArray = {
{220,250,13,64},//1
{24,58,24,55},//2
{104,206,22,55},//3
{264,370,22,55},//4
{382,450,22,55},//5
{24,92,74,109},//6
{104,136,74,185},//7
{136,206,114,138},//8
{150,326,74,98},//9
{225,255,98,140},//10
{345,365,74,185},//11
{275,355,114,138},//12
{384,445,74,109},//13
{104,136,200,270},//14
{150,330,240,270},//15
{225,255,270,315},//16
{340,370,200,270},//17
{20,85,285,305},//18
{50,85,305,345},//19
{104,214,285,315},//20
{274,368,285,315},//21
{378,445,285,305},//22
{378,415,305,345},//23
{24,195,365,375},//24
{104,154,335,375},//25
{165,339,335,345},//26
{215,245,335,375},//27
{265,445,365,375},//28
{355,365,335,375}//29
};
int i = 0;
for( i = 0; i < 29; i++)
{
if (((x >= WallCheckerArray[i, 0] && x <= WallCheckerArray[i, 1]) && (y >= WallCheckerArray[i, 2] && y <= WallCheckerArray[i, 3])))//-----------------------------------}-
{
InsideWC();
System.Console.WriteLine(WallCheckerArray[i, 1]);
}
}
A line of code like int[,] WallCheckerArray = something is read by the compiler as "Make a new int[,] named WallCheckerArray. And the problem is, you do that twice in a row; you can't have two different variables with the same name. If you don't give a variable an access modifier, the C# compiler will assume you wanted it to be Private.
To make your code work:
private int[,] WallCheckerArray = new int[28, 4];
WallCheckerArray = {
/* Your Data */
};
FYI: you can actually make your array and fill it with data in the same statement, like so:
private int[,] WallCheckerArray = {
{220,250,13,64},
{24,58,24,55},
{104,206,22,55},
// and so on
};
This way, you don't have to worry about declaring the size of the array, it'll be handled for you.
Had to delete "private int[,] WallCheckerArray = new int[28, 4];"
So it turns out all arrays are not created equal. Multi-dimensional arrays can have non-zero lower bounds. See for example Excel PIA's Range.Value property object[,] rectData = myRange.Value;
I need to convert these data into a jagged array. My first try below smells of complexity. Any suggestions to optimize it? It needs to handle the general case where lower bounds may not be zero.
I have this ex method:
public static T[][] AsJagged<T>( this T[,] rect )
{
int row1 = rect.GetLowerBound(0);
int rowN = rect.GetUpperBound(0);
int col1 = rect.GetLowerBound(1);
int colN = rect.GetUpperBound(1);
int height = rowN - row1 + 1;
int width = colN - col1 + 1;
T[][] jagged = new T[height][];
int k = 0;
int l;
for ( int i = row1; i < row1 + height; i++ )
{
l = 0;
T[] temp = new T[width];
for ( int j = col1; j < col1 + width; j++ )
temp[l++] = rect[i, j];
jagged[k++] = temp;
}
return jagged;
}
Used like this:
public void Foo()
{
int[,] iRect1 = { { 1, 1, 1, 1 }, { 1, 1, 1, 1 }, { 1, 1, 1, 1 }, { 1, 1, 1, 1 }, { 1, 1, 1, 1 }, { 1, 1, 1, 1 }, { 1, 1, 1, 1 }, { 1, 1, 1, 1 } };
int[][] iJagged1 = iRect1.AsJagged();
int[] lengths = { 3, 5 };
int[] lowerBounds = { 7, 8 };
int[,] iRect2 = (int[,])Array.CreateInstance(typeof(int), lengths, lowerBounds);
int[][] iJagged2 = iRect2.AsJagged();
}
Curious if Buffer.BlockCopy() would work or be faster?
Edit: AsJagged needs to handle reference types.
Edit: Found bug in AsJagged(). Added int l; and added col1 + width to inner loop.
A view caveats/assumptions up front:
You seem to use only int as your data type (or at least seem to be OK with using Buffer.BlockCopy which would imply you can life with primitive types in general).
For the test data you show, I don't think there will be much different using any somewhat sane approach.
Having that said, the following implementation (which needs to be specialized for a specific primitive type (here int) because it uses fixed) is around 10 times faster than the approach using the inner loop:
unsafe public static int[][] AsJagged2(int[,] rect)
{
int row1 = rect.GetLowerBound(0);
int rowN = rect.GetUpperBound(0);
int col1 = rect.GetLowerBound(1);
int colN = rect.GetUpperBound(1);
int height = rowN - row1 + 1;
int width = colN - col1 + 1;
int[][] jagged = new int[height][];
int k = 0;
for (int i = row1; i < row1 + height; i++)
{
int[] temp = new int[width];
fixed (int *dest = temp, src = &rect[i, col1])
{
MoveMemory(dest, src, rowN * sizeof(int));
}
jagged[k++] = temp;
}
return jagged;
}
[DllImport("kernel32.dll", EntryPoint = "RtlMoveMemory")]
unsafe internal static extern void MoveMemory(void* dest, void* src, int length);
Using the following "test code":
static void Main(string[] args)
{
Random rand = new Random();
int[,] data = new int[100,1000];
for (int i = 0; i < data.GetLength(0); i++)
{
for (int j = 0; j < data.GetLength(1); j++)
{
data[i, j] = rand.Next(0, 1000);
}
}
Stopwatch sw = Stopwatch.StartNew();
for (int i = 0; i < 100; i++)
{
int[][] dataJagged = AsJagged(data);
}
Console.WriteLine("AsJagged: " + sw.Elapsed);
sw = Stopwatch.StartNew();
for (int i = 0; i < 100; i++)
{
int[][] dataJagged2 = AsJagged2(data);
}
Console.WriteLine("AsJagged2: " + sw.Elapsed);
}
Where AsJagged (the first case) is your original function, I get the following output:
AsJagged: 00:00:00.9504376
AsJagged2: 00:00:00.0860492
So there is indeed a faster way of doing it, however depending on the size of the test data, the number of times you actually perform this operation, and your willingness to allow unsafe and P/Invoke code, you're probably not going to need it.
Having that said, we were using large matrixes of double (say 7000x10000 elements) where it indeed did make a huge difference.
Update: about using Buffer.BlockCopy
I might overlook some Marshal or other trick, but I don't think using Buffer.BlockCopy is possible here. This is due to the fact that it requires both the source and destination array to, well, be an Array.
In our example, the destination is an array (e.g. int[] temp = ...) however the source is not. While we "know" that for two dimensional arrays of primitive types the layout is such, that each "row" (i.e. first dimension) is an array of the type in memory, there is no safe (as in unsafe) way to get that array without the overhead of copying it first. So we basically need to use a function that simply deals with memory and doesn't care about the actual content of it - like MoveMemory. BTW, the internal implementation of Buffer.BlockCopy does something similar.
Your complexity is O(N*M) N - number of rows, M - number of columns. That's the best you can get when copying N*M values...
Buffer.BlockCopy might be faster than your inner for loop, but I wouldn't be surprised if the compiler knows how to handle this code properly and you won't gain any further speed. You should test it to make sure.
You may be able to achieve better performance by not copying the data at all (at the potential expense of slightly slower lookups). If you create an 'array row' class, that holds your rect and a row number, and provides an indexer that accesses the correct column, you can create an array of such rows, and save yourself the copying altogether.
The complexity of creating such an array of 'array rows' is O(N).
EDIT: An ArrayRow class, just because it bugs me...
The ArrayRow could look something like this:
class ArrayRow<T>
{
private T[,] _source;
private int _row;
public ArrayRow(T[,] rect, int row)
{
_source = rect;
_row = row;
}
public T this[int col] { get { return _source[_row, col]; } }
}
Now you create an array of ArrayRows, you don't copy anything at all, and the optimizer has a good chance of optimizing accessing an entire row in sequence.
Suppose you have an array like:
double[,] rectArray = new double[10,3];
Now you want the fouth row as a double[] array of 3 elements without doing:
double[] fourthRow = new double[]{rectArray[3,0],
rectArray[3,1],
rectArray[3,2]};
Is it possible someway? Even using a Marshal.Something approach?
Thanks!
You can use Buffer.BlockCopy method:
const int d1 = 10;
const int d2 = 3;
const int doubleSize = 8;
double[,] rectArray = new double[d1, d2];
double[] target = new double[d2];
int rowToGet = 3;
Buffer.BlockCopy(rectArray, doubleSize * d2 * rowToGet, target, 0, doubleSize * d2);
LINQ to the rescue:
var s = rectArray.Cast<double>().Skip(9).Take(3).ToArray();
Explanation: Casting a multi-dimensional array flattens it to a single-dimensional array. After that all we need to do is skip to the element we want (the 4th element in the 2-D array resolves to Skip(9)...) and take 3 elements from it).
Why not make a generic extension method?
public static T[] GetRow<T>(this T[,] input2DArray, int row) where T : IComparable
{
var width = input2DArray.GetLength(0);
var height = input2DArray.GetLength(1);
if (row >= height)
throw new IndexOutOfRangeException("Row Index Out of Range");
// Ensures the row requested is within the range of the 2-d array
var returnRow = new T[width];
for(var i = 0; i < width; i++)
returnRow[i] = input2DArray[i, row];
return returnRow;
}
Like this all you have to code is:
array2D = new double[,];
// ... fill array here
var row = array2D.GetRow(4) // Implies getting 5th row of the 2-D Array
This is useful if you're trying to chain methods after obtaining a row and could be helpful with LINQ commands as well.
You probably want to use a jagged array. That is not an array of 10 by 3 but instead an array of arrays.
Something like :
double[][] rectArray;
....
double [] rowArray = rectArray[3];
There are lots of places to learn more about jagged arrays. For example Dynamically created jagged rectangular array
If you must use a rectangular array and just want to simplify the syntax, you can use a method to get the row like so:
double[] fourthRow = GetRow(rectArray, 3);
public static T[] GetRow<T>(T[,] matrix, int row)
{
var columns = matrix.GetLength(1);
var array = new T[columns];
for (int i = 0; i < columns; ++i)
array[i] = matrix[row, i];
return array;
}
Although this is an old thread, an addition to Joseph Sturtevants answer may be useful. His function crashes in case the matrix's first column is not zero, but another integer.
This is e.g. always the case in case of retrieving data from Excel, like
object[,] objects = null;
Excel.Range range = worksheet.get_Range("A1", "C5");
objects = range.Cells.Value; //columns start at 1, not at 0
The GetRow function could be modified like this:
public static T[] GetRow<T>(T[,] matrix, int row, int firstColumn)
{
var columns = matrix.GetLength(1);
var array = new T[columns];
for (int i = firstColumn; i < firstColumn + columns; ++i)
array[i-firstColumn] = matrix[row, i];
return array;
}
I was shocked to find out today that C# does not support dynamic sized arrays. How then does a VB.NET developer used to using ReDim Preserve deal with this in C#?
At the beginning of the function I am not sure of the upper bound of the array. This depends on the rows returned from the database.
VB.NET doesn't have the idea of dynamically sized arrays, either - the CLR doesn't support it.
The equivalent of "Redim Preserve" is Array.Resize<T> - but you must be aware that if there are other references to the original array, they won't be changed at all. For example:
using System;
class Foo
{
static void Main()
{
string[] x = new string[10];
string[] y = x;
Array.Resize(ref x, 20);
Console.WriteLine(x.Length); // Prints out 20
Console.WriteLine(y.Length); // Still prints out 10
}
}
Proof that this is the equivalent of Redim Preserve:
Imports System
Class Foo
Shared Sub Main()
Dim x(9) as String
Dim y as String() = x
Redim Preserve x(19)
Console.WriteLine(x.Length)
Console.WriteLine(y.Length)
End Sub
End Class
The two programs are equivalent.
If you truly want a dynamically sized collection, you should use List<T> (or something similar). There are various issues with using arrays directly - see Eric Lippert's blog post for details. That's not to say you should always avoid them, by any means - but you need to know what you're dealing with.
Use ArrayLists or Generics instead
Use a List<T>. It will dynamically size as needed.
You really shouldn't be using ReDim, it can be very expensive. I prefer List(Of T), but there are many options in this area.
That said, you had a question and here is your answer.
x = (int[]) Utils.CopyArray((Array) x, new int[10]);
I couldn't help but notice that none of the above answers approach the concept of multidimensional arrays. That being said, here's an example. The array in question is predefined as x.
int[,] temp = new int[newRows, newCols];
int minRows = Math.Min(newRows, x.GetUpperBound(0) + 1);
int minCols = Math.Min(newCols, x.GetUpperBound(1) + 1);
for (int i = 0; i < minRows ; ++i)
for (int j = 0; j < minCols; ++j)
temp[i, j] = x[i, j];
x = temp;
Just for fun, here's one way to use generics in order to redim/extend a unidimensional array (add one more "row") :
static T[] Redim<T>(T[] arr, bool preserved)
{
int arrLength = arr.Length;
T[] arrRedimed = new T[arrLength + 1];
if (preserved)
{
for (int i = 0; i < arrLength; i++)
{
arrRedimed[i] = arr[i];
}
}
return arrRedimed;
}
And one to add n rows (though this doesn't prevent user from undersizing the array, which will throw an error in the for loop) :
static T[] Redim<T>(T[] arr, bool preserved, int nbRows)
{
T[] arrRedimed = new T[nbRows];
if (preserved)
{
for (int i = 0; i < arr.Length; i++)
{
arrRedimed[i] = arr[i];
}
}
return arrRedimed;
}
I'm sure you get the idea.
For a multidimensional array (two dimensions), here's one possibility:
static T[,] Redim<T>(T[,] arr, bool preserved)
{
int Ubound0 = arr.GetUpperBound(0);
int Ubound1 = arr.GetUpperBound(1);
T[,] arrRedimed = new T[Ubound0 + 1, Ubound1];
if (preserved)
{
for (int j = 0; j < Ubound1; j++)
{
for (int i = 0; i < Ubound0; i++)
{
arrRedimed[i, j] = arr[i, j];
}
}
}
return arrRedimed;
}
In your program, use this with or even without the type specified, the compiler will recognize it :
int[] myArr = new int[10];
myArr = Redim<int>(myArr, true);
or
int[] myArr = new int[10];
myArr = Redim(myArr, true);
Not sure if all this is really relevant though. =D
Please feel free to correct me or improve my code. ;)
Even though it's a long time ago it might help someone looking for a simple solution - I found something great in another forum:
//from Applied Microsoft.NET framework Programming - Jeffrey Richter
public static Array RedimPreserve(Array origArray, Int32 desiredSize)
{
System.Type t = origArray.GetType().GetElementType();
Array newArray = Array.CreateInstance(t, desiredSize);
Array.Copy(origArray, 0, newArray, 0, Math.Min(origArray.Length, desiredSize));
return newArray;
}
Source: https://social.msdn.microsoft.com/Forums/en-US/6759816b-d525-4752-a3c8-9eb5f4a5b194/redim-in-c?forum=csharplanguage