[fpc-pascal] Where is the best place to declare an array?

[spir ☣]

[OT -- not fpc-related -- just a side note]

On Fri, 7 May 2010 00:34:11 +0200
Jonas Maebe <jonas.maebe at elis.ugent.be> wrote:

> in general my bias would be much more against than in favour of global variables from a speed perspective

In _some_ dynamic languages using a virtual machine at least (eg Lua), local variables are actually stored in an array, after a one->one replacement from name to index at "compile"-time. While global ones are still looked up in a symbol table (associative array implemented as hash table) by name.
This indeed makes some speed difference ;-) (~ 50% in Lua) For instance:

<code lang=lua>
require "os" ; time = os.time
format = string.format
N = 333333333

f = function()
   a = 1			-- implicitely global
   local b = 0
   for i = 1,N do b=a end
end
g = function()
   local a = 1
   local b = 0
   for i = 1,N do b=a end
end

-- global case
t = time()
f()
t = time() - t
print(format("global : %2.0fs", t))	-- 25s
-- local case
t = time()
g()
t = time() - t
print(format("local  : %2.0fs", t))	-- 13s
</code>


Denis
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