FIXP allocations for simple looping?

[RyanBurnside]

In testing my math library, quite often I'm doing thousands of operations with TIME.
One thing I noticed is that just looping seems to allocate many FIXP values. You can see I've compiled the function there to give Medley a chance to optimise.

Is this correct or am I misunderstanding it?

[MattHeffron]

Notice that the 34466 FIXP allocated is just about exactly the difference between the 100000 value of N and MAX.SMALLP (65535). Since there's no automatic determination that A could/should be an unboxed integer, it must be a generic value cell, so FIXP for any value greater than MAX.SMALLP.

[RyanBurnside]

That makes sense.
I tested it below that threshold and there was no consing!

Is there a way to decorate this kind of thing to avoid consing with bignums?

[MattHeffron]

consing with bignums

FIXP are not BIGNUM.
MAX.FIXP is 0x7FFFFFFF.
So, no consing until there for integers.

I don't know if either compiler deals with type declarations, or if one would need to use special functions that the compiler(s) handle specially.

[masinter]

In the Medley Interlisp Common Lisp architecture, there isn't much it can do with type declarations. The original opcodes PLUS MINUS TIMES QUOTIENT and IPLUS ITIMES IQUOTIENT IMINUS etc. assume the stack contains legitimate pointers. There are some "unboxed arithmetic" subrs and opcodes that were added later and quite possibly some ways to use optimizers??

[MattHeffron]

lispusers/UNBOXEDOPS contains the code for unboxed FLOAT arithmetic.
As noted in lispusers/UNBOXEDOPS.TEDIT these are for the Interlisp Byte compiler, not the XCL compiler. (At least as of Lyric.)

[masinter]

if you really want to avoid boxing, I can think of two ways

• you could change the iteration so intermediate results were SMALLPs

(LET ((A 0))
(if (> N MAX.SMALLP)
then (for I from 1 to MAX.SMALLP do (SETQ A I))
(SETQ N (- N MAX.SMALLP)))
(for I from 1 to N do (SETQ A I)))

• there are Maiko opcodes boxiplus and boxidifference that take as their first argument a pointer to a fixp-sized box (32 bits), and perform the integer operation on that. {MAIKO}arithops.c