Optimize my code =)

[Chris Williams]

On Friday, 14 February 2014 at 16:00:09 UTC, Robin wrote:
> this(size_t rows, size_t cols) {
> 	this.dim = Dimension(rows, cols);
> 	this.data = new T[this.dim.size];
> 	enum nil = to!T(0);
> 	foreach(ref T element; this.data) element = nil;
> }

Your foreach here is unnecessary. You can zero out an array using 
the syntax:

this.data[] = 0; // probably compiles out as memset()

And while I would expect to!T(0) to compile down to something 
with no particular logic, it still is a function call not a 
macro, so you're better to let the compiler figure out the best 
conversion from 0 for type T than to use a library function for 
it.

> I think and hope that this is getting optimized via inlining. =)
> This works similar for opIndexAssign.

 From complaints that I have seen, very little gets inlined at the 
moment.


> Matrix opMul(ref const(Matrix) other) {
> 	if (this.dim.rows != other.dim.cols || this.dim.cols != 
> ther.dim.rows) {
> 		// TODO - still have to learn exception handling first ...
> 	}
> 	auto m = new Matrix(this.dim.rows, other.dim.cols);
> 	auto s = new Matrix(other).transposeAssign();

Since you don't return s, it's probably better to not allocate an 
instance. I would also be curious to see your constructor which 
copies one matrix into a new one.

> Besides that I can't find a way how to make a use of move 
> semantics like in C++. For example a rvalue-move-constructor or 
> a move-assign would be a very nice thing for many tasks.

Do you mean something like this?

this.data[] = other.data[]; // probably compiles out as memcpy()
this.data = other.data.dup; // different syntax, but should be 
the same

> Another nice thing to know would be if it is possible to 
> initialize an array before it is default initialized with 
> T.init where T is the type of the array's fields.

I believe so, but I would have to scour about to find the syntax. 
Hopefully, someone else knows.