Dear all,
Waldek Hebisch <[EMAIL PROTECTED]> writes:
> Some source of inefficiency is clear: profile shows that access to matrix
> elements is done via function calls and that those calls take substantial
> time (more than arithmetic). Also aritmetic in Z_p is done via function
> calls which is much slower than inline code.
and a little later:
> Let us at maxColIndex. In IIARRAY2.lsp we have:
>
> (DEFUN |IIARRAY2;maxColIndex;$I;7| (|m| $)
> (- (+ (SPADCALL |m| (QREFELT $ 28)) (QREFELT $ 8)) 1))
>
> which means:
> 1) maxColIndex get m as normal argument, and has the second argument
> called '$' which is a "domain vector" (a vector which is a runtime
> representation of a type).
> 2) first we take element 28 from domain vector of current domain and call
> it giving it m as argument. The call also must pass correct domain
> vector, I am too lazy to check what this will be, but the SPADCALL
> macro is responsible for passing it.
> 3) next, we fetch element number 8 from domain vestor and add it
> to the result of previous call.
> 4) finally we substract 1 to get final result.
>
> Note that Lisp compiler have no idea what m can be. Also, since we have:
>
> maxColIndex m == ncols m + mnCol - 1
>
> I can deduce that (SPADCALL |m| (QREFELT $ 28)) corresponds to ncols m, but
> Lisp compiler have no idea which function will be called.
I was looking a little closer at the lisp code generated by the SPAD compiler.
There are still a few things I do not understand:
a) how is some function like |IIARRAY2;maxColIndex;$I;7| actually called? More
precisely, where does it get it's second argument (the domain vector) from?
b) isn't the domain vector constant for domains and packages? I guess it won't
be constant for default domains, right? I believe it should be that way,
because there is no way that a function definition in a domain or package
can be overridden, contrary to default definitions in categories.
c) how does SPADCALL work? I tried:
(1) -> )lisp (macroexpand '(SPADCALL |m| (QREFELT $ 28)))
Value = (LET ((#:G1406 (QREFELT $ 28)))
(THE (VALUES T) (FUNCALL (CAR #:G1406) |m| (CDR #:G1406))))
and I know that (QREFELT $ 28) produces element number 28 from the domain
vector, but I was (so far) unable to find out what it looks like precisely.
At the end of IIARRAY2.NRLIB/code.lsp I find a MAKEPROP statement which
seems to take three arguments, the third one being a list with a couple of
elements, whose car is a vector that has as element 28
|IIARRAY2;ncols;$Nni;9|. So, that has clearly something to do with the
domain vector, but it's only half the story...
In fact, b) may be the most important question: if I'm right and the domain
vector is indeed constant for domains, then there may be some room for
optimization -- given that a lisp compiler will not optimize away the FUNCALL
in
(LET ((#:G1406 (QREFELT $ 28)))
(THE (VALUES T) (FUNCALL (CAR #:G1406) |m| (CDR #:G1406))))
???
I believe -- since IIARRAY2 is a domain --
maxColIndex m == ncols m + mnCol - 1
which currently translates to
(DEFUN |IIARRAY2;maxColIndex;$I;7| (|m| $)
(- (+ (SPADCALL |m| (QREFELT $ 28)) (QREFELT $ 8)) 1))
could become something like
(DEFUN |IIARRAY2;maxColIndex;$I;7| (|m| $)
(- (+ (|IIARRAY2;ncols;$Nni;9| |m| $) (QREFELT $ 8)) 1))
Martin
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