Jason,
On 31.03.2015 21:06, Kenny, Jason L wrote:
[...]
So let me think this out load here. The main issues is that I have properties
that I am adding to the node objects and this fails with __slots__ being
defined without a __dict__, because I was adding a cache value to the object,
vs having to look up the value on a different object ( ie the attributes
object) as this could conflict with who-knows-what that was added with the
Tag()/MetaTag() API by the user.
The plus side for having __dict__ added to the base is that it makes it easy to
see what is being added to a node and it makes it easy to prototype new stuff
in a system. Keep in mind that point of __slots__ is not about removing
__dict__, but allowing python to be efficient in pre-allocating memory as an
array vs that of independent items as they would be in the __dict__ object.
Ideally Cpython should be doing something else here, so __slots__ add no value.
( hmm somebody should fix this...) But until then __slots__ add value for this
reason. Add __dict__ by default only mean that the code as any normal python
object. One can argue that the restriction we add by using slots in add new
member dynamically is a good thing or a bad thing. I just want to point out
that the use of __slots__ means that the memory usage is reduced because of
block array allocation ( vs lots of small alloc), and the memory layout of the
object is more machine friendly ( as any CPU like array for quick acce
s
s, and hate everything else). This is why we have a space and speed improvement
in SCons with the nodes as the node are the prime data structure when we build.
I'm mainly interested in reducing memory consumption, and dictionaries require a lot of bytes. So, if you can add your "__dict__"
without directly assigning a fully-blown dict to any Node instance by default...you win me over in the same second.
But this would require some sort of lazy initialization like I did for the abspath/tpath attributes, and I have the feeling that
that's not directly what you're after. ;)
Let me look at what I can do on my end, with a fresh set of eyes.. if you still
feel that adding __dict__ is a bad thing. ( will miss the clean property syntax
)
There are a few other fixes I have here in parts/overrides/nodes.py that would
be nice to have added to the main base. Could you look at these and see if any
seem OK for you to add to the Node classes?
Definitely, I'll have a look.
Regards,
Dirk
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