Charles Mills
5/16/2005 11:14:00 PM
Ara.T.Howard wrote:
> i reading some code attm that goes:
>
> static VALUE convertgslmatrixToRubyMatrix(gsl_matrix *dm)
> {
> int i, j;
> volatile VALUE result;
> assert(dm);
> // printf("Trying to convert dm %p\n", dm);
> // printf("With size %d, %d\n", dm->size1, dm->size2);
> volatile VALUE rows = rb_ary_new();
> rb_gc_mark(rows);
> for (i = 0; i < dm->size1; i += 1) {
> volatile VALUE currow = rb_ary_new();
> rb_gc_mark(currow);
> rb_ary_push(rows, currow);
> for (j = 0; j < dm->size2; j += 1) {
> double val = gsl_matrix_get(dm, i, j);
> VALUE rval = rb_float_new(val);
> rb_gc_mark(rval);
> rb_ary_push(currow, rval);
> }
> }
> result = rb_funcall(cMatrix, rb_intern("rows"), 2, rows, Qnil);
> rb_gc_mark(result);
> return result;
> }
>
>
> now, everything i know says this should be something along the lines
of:
>
> static VALUE
> convertgslmatrixToRubyMatrix (gsl_matrix * dm)
> {
> int i, j;
> VALUE result;
> VALUE rows = rb_ary_new ();
> for (i = 0; i < dm->size1; i += 1)
> {
> VALUE currow = rb_ary_new ();
> rb_gc_mark (currow);
> rb_ary_push (rows, currow);
> for (j = 0; j < dm->size2; j += 1)
> {
> double val = gsl_matrix_get (dm, i, j);
> VALUE rval = rb_float_new (val);
> rb_ary_push (currow, rval);
> }
> }
> result = rb_funcall (cMatrix, rb_intern ("rows"), 2, rows,
Qnil);
> return result;
> }
>
> (please correct me if i'm wrong)
>
> or nasty things will happen in memory right? what would it do to
call
> rb_gc_mark on ruby objects like this?
>
You shoud just not call rb_gc_mark at all. Not sure if it even
matters, but it is possible that objects you mark using rb_gc_mark
outside of a mark and sweep cycle will hang around AFTER some of there
fields have been GCed - like an array whose elements have been GCed,
but is still -alive-. This will only happen if the stack does not
overflow when marking and the only way this could be a problem is by
using the object space API.
Anyway, hopefully whoever wrote this code hopefully wasn't modivated by
my overly paranoid/incorrect past posts about the Ruby GC.
Also you could use rb_ary_new2 to save ruby from having to resize the
array since you know the size ahead of time.
-Charlie