[Gcl-devel] generic function performance

[Peter Wood]

Hi

In another post, I showed how we can make some functions (like typep,
subtypep and coerce) be generic, using #'pcl::make-specializable.  It
is really a big advantage to be able to use this technique since we
can automatically reuse the present code, with small modifications,
and build some fancy-ansi stuff on top.  However, I suggested that it
might have negative performance implications.

Well I've been doing some informal testing, and I'm not sure that the
performance impact is very significant.

> (symbol-function 'typep)

#<compiled-closure #:SPECIALIZED-TYPEP>

> (time (typep 'foo 'symbol))

real time : 0.000 secs
run time  : 0.000 secs
T

> (symbol-function 'subtypep)

#<compiled-closure #:SPECIALIZED-SUBTYPEP>

> (time (subtypep 'symbol 't))

real time : 0.000 secs
run time  : 0.000 secs
T
T

> (defclass foo ()())

#<Standard-Class FOO 1041116550>

> (defclass bar (foo)())

#<Standard-Class BAR 1041062404>

> (subtypep (find-class 'bar) (find-class 'foo))

(#<Standard-Class FOO 1041116550>
 #<Standard-Class STANDARD-OBJECT 1030554554>
 #<Slot-Class PCL::SLOT-OBJECT 1030553344>
 #<Built-In-Class T 1030553264>)
T

; the first value is true (a generalized boolean ie, not nil).

> (time (subtypep (find-class 'bar) (find-class 'foo)))

real time : 0.000 secs
run time  : 0.000 secs
(#<Standard-Class FOO 1041116550>
 #<Standard-Class STANDARD-OBJECT 1030554554>
 #<Slot-Class PCL::SLOT-OBJECT 1030553344>
 #<Built-In-Class T 1030553264>)
T

> (setf f1 (make-instance 'foo))

#<FOO 1041011700>

> (time (typep f1 (find-class 'foo)))

real time : 0.000 secs
run time  : 0.000 secs
#<FOO 1041011700>

It looks ok to me.

Whaddya think?

Regards,
Peter