[PD] symbol anxiety

[Mathieu Bouchard]

On Sun, 22 Feb 2009, Phil Stone wrote:

> A) Is it true that [maketime] would continually grow the symbol table?

yes.

> B) Is it possible to tell how full the symbol table is?  How much memory 
> is allocated to it in the first place?

It never gets full. It just becomes bigger and bigger, as long as you have 
enough RAM. As it gets bigger, symbol-lookup becomes slower, and 
symbol-generation too as it always involves one symbol-lookup. The lookup 
time is always O(n). However, in normal circumstances, it's close to 
n/16384, an extremely small multiple of n, whereas if you're extremely 
unlucky, it could be just n steps. The symbols are spread out in a large 
table in a random-looking manner that is not really random. Each slot in 
the table has a list of symbols which starts being empty and then grows as 
needed.

If the symbols were organised as a tree, it wouldn't be a theoretical 
speed problem, but it would still end up eating up RAM.

The table starts at 64k, or 128k in 64-bit mode, and each symbol takes an 
additional amount of RAM, but it depends on which malloc you use and such.

> C) Wouldn't it be nice to have some truly transient symbols, that could 
> be abstraction-local, or at least, re-usable?

yes, but it's nowhere near happening.

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| Mathieu Bouchard - tél:+1.514.383.3801, Montréal, Québec