set_used(0); vs clear(); - Which is better to use? (array)

[MasterGod]

I understand both methods clears the array so which should I use?

Thanks.

[rogerborg]

I understand both methods clears the array so which should I use?

You may want to revisit your understanding.

Code: Select all

	void set_used(u32 usedNow)
	{
		if (allocated < usedNow)
			reallocate(usedNow);

		used = usedNow;
	}

set_used(0) does not destroy any objects or free any memory.

[MasterGod]

I understand both methods clears the array so which should I use?

You may want to revisit your understanding.

Code: Select all

	void set_used(u32 usedNow)
	{
		if (allocated < usedNow)
			reallocate(usedNow);

		used = usedNow;
	}

set_used(0) does not destroy any objects or free any memory.

So what can it be used for? (I've seen it in the smgr->drawAll() method..) - What's the purpose of it..

[Halifax]

I understand both methods clears the array so which should I use?

You may want to revisit your understanding.

Code: Select all

	void set_used(u32 usedNow)
	{
		if (allocated < usedNow)
			reallocate(usedNow);

		used = usedNow;
	}

set_used(0) does not destroy any objects or free any memory.

So what can it be used for? (I've seen it in the smgr->drawAll() method..) - What's the purpose of it..

If I recall, that was answered in your last topic where you specifically asked about what set_used(0) was used for.

And if you feel too lazy to search for it, I did it myself:

OnRegisterSceneNode() is called for every scene node in the scene graph. That function will be called regardless of what the contents of the other render queues look like.

That is just the way it is written. Scene nodes register themselves every render in OnRegisterSceneNode(). If they didn't do it that way, then they would need to register themselves for rendering when they are added to the scene graph, and they would have to be removed from the render queues when they were removed from the scene graph.

If you don't clear the array before/after each render, but you continue to call OnRegisterSceneNode(), the render queue will have many pointers to the same nodes.

Travis

[bitplane]

reallocating memory is an expensive job, so it is better to mark the render queues as unused instead of clearing them each frame. iirc it used to do this in Irrlicht 1.0 but we changed it

[MasterGod]

reallocating memory is an expensive job, so it is better to mark the render queues as unused instead of clearing them each frame. iirc it used to do this in Irrlicht 1.0 but we changed it

So when do they actually get cleared then?

[bitplane]

It's cleared in CSceneManager's destructor.

Try this code yourself, try different values for size, put some real timers around them if it runs too fast for you to be able to see anything.

Code: Select all

core::array<s32> Numbers1;
core::array<s32> Numbers2;
s32 i, j, size = 5000;

cout << "Test 1 start\n";

// test 1- 
for (j=0; j < size; ++j)
{
    Numbers1.clear();
    for (i=0; i < size; ++i)
        Numbers1.push_back(i);
}

cout << "Test 2 start\n";

// test 2- 
for (j=0; j < size; ++j)
{
    Numbers2.set_used(0);
    for (i=0; i < size; ++i)
        Numbers2.push_back(i);
}

cout << "Test 2 end";

[MasterGod]

reallocating memory is an expensive job...

With that example your words has much greater effect
It's much more faster with the set_used, wow.. - Thanks for showing me that.