Re: alien use causes gratuitous GC

Will wrote:
> Here are the relevant alien definitions.
>
> ;; These are C functions called from the Lisp system of equations
> function.
> (def-alien-routine get_sysvar_n int)
> (def-alien-routine get_sysvar_val double  (i int))
> (def-alien-routine get_sysvar_dotval double  (i int))
> (def-alien-routine set_sysvar_val void  (i int)  (x double))
> (def-alien-routine set_sysvar_dotval void  (i int)  (x double))
>
>   
Alien routines should be declared inline to reduce/eliminate consing, 
according to the manual.
> ;; this builds a part of the equations that calls C from
> ;; Lisp: get_sysvar_val(i), is a simple function that lets
> ;; Lisp access an array stored in C. 
> (defun cvode-assign-sys-vars ()
>   (let ((syslst))
>     (dotimes (i (length *system-variables*) syslst)
>       (push `(setf (aref *system-variables* ,i) 
> 		   (get_sysvar_val ,i))
> 	    syslst))))
>
> ;; here's the declaration of get_sysvar_val from above
> double get_sysvar_val(int i) {return sys_var.vals[i];}
>
>   
You could, if desired, declare the alien structure in Lisp and access 
them directly.  But the alien interface should work fine too.
> ;; i call this function once for each of n variables for each 
> ;; explicit time step passed to the solver.  so, for one full
> ;; simulation, this function could be called hundreds of 
> ;; times.
>   
Which function are you talking about?  get_sysvar_val?  If so, declaring 
inline should help.
> (DEF-CALLBACK MS_MODEL
>                   (VOID
>                    (TIME
>                      DOUBLE))
>                   (DECLARE (OPTIMIZE (SPEED 3) (SAFETY 0)))
>                   (SETF (AREF *SYSTEM-VARIABLES* 1) (GET_SYSVAR_VAL 1))
>                   (SETF (AREF *SYSTEM-VARIABLES* 0) (GET_SYSVAR_VAL 0))
>   
Is *system-variables* declared to be an array of double-floats?  That 
will reduce consing.
>                   (SET_SYSVAR_DOTVAL 1
>                                      (EQUATION-AGGREGATOR
>   
EQUATION-AGGREGATOR will also cons.  That seems unavoidable unless you 
make it a local function , inline it, or use block compilation.

It's not quite clear to me, but is ms_model generated once and solved?  
Then a new ms_model is generated and solved again for a different problem?

To reduce consing, I think the defcallback needs to be compiled too.

That's all I can think of right now, after looking at your code for a 
few minutes,

Ray