Most storage used explicitly by Muddle programs is obtained from a
pool of free storage managed by a "garbage collector". Storage is
-obtained from this pool by the `SUBR`s which construct objects. When a
-`SUBR` finds that the pool of available storage is exhausted, it
-automatically calls the garbage collector.
+obtained from this pool by the `SUBR`s which construct objects. When
+such a `SUBR` finds that the pool of available storage is exhausted,
+it automatically calls the garbage collector.
The garbage collector has two algorithms available to it: the
"copying" algorithm, which is used by default, and the "mark-sweep"
lose.
Thus, if you just "forget about" an object, that is, lose all possible
-means of referencing it, its storage is automatically reclaimed.
+means of referencing it, its storage area is automatically reclaimed.
"Object" in this context includes that stack-structured storage space
used in `PROCESS`es for functional application.
5. Finally, the "mark-sweep" algorithm sweeps through the storage
space, adding unmarked objects to the internal free lists for
later re-use. The "copying" algorithm maps the inferior process's
- address space into Muddle's own, replacing old garbagey with the
- new compact storage, and the inferior process is destroyed.
+ address space into Muddle's own, replacing old garbagey storage
+ with the new compact storage, and the inferior process is
+ destroyed.
22.5 GC
-------
causes the garbage collector to run and returns the total number of
words of storage reclaimed. All of its arguments are optional: if they
-are not supplied, a call to GC simply causes a "copying" garbage
+are not supplied, a call to `GC` simply causes a "copying" garbage
collection.
If *min* is explicitly supplied as an argument, a garbage-collection
parameter is changed permanently before the garbage collector runs.
*min* is the smallest number of words of "free" (unclaimed, available
for use) movable garbage-collected storage the garbage collector will
-be satisfied with having after it is done. Initially it is 8192 words.
-If the total amount of reclaimed storage is less than *min*, the
-garbage collector will ask the operating system for enough storage (in
-1024 word blocks) to make it up. N.B.: the system may be incivil
-enough not to grant the request; in that case, the garbage collector
-will be content with what it has, **unless** that is not enough to
-satisfy a **pending** request for storage. Then it will inform you
-that it is losing. A large *min* will result in fewer total garbage
-collections, but they will take longer since the total quantity of
-storage to be dealt with will generally be larger. Smaller *min*s
-result in shorter, more frequent garbage collections.
+be satisfied with having after it is done each time. Initially it is
+8192 words. If the total amount of reclaimed storage is less than
+*min*, the garbage collector will ask the operating system for enough
+storage (in 1024-word blocks) to make it up. N.B.: the system may be
+incivil enough not to grant the request; in that case, the garbage
+collector will be content with what it has, **unless** that is not
+enough to satisfy a **pending** request for storage. Then it will
+inform you that it is losing. A large *min* will result in fewer total
+garbage collections, but they will take longer since the total
+quantity of storage to be dealt with will generally be larger. Smaller
+*min*s result in shorter, more frequent garbage collections.
+
+*exh?* tells whether or not this garbage collection should be
+"exhaustive". It is optional, a `FALSE` by default. The difference
+between normal and exhaustive "copying" garbage collections is whether
+certain kinds of storage that require complicated treatment (for
+example, associations) are reclaimed. An exhaustive garbage collection
+occurs every eighth time that the "copying" algorithm is used, or when
+`GC` is called with this argument true, or when a normal garbage
+collection cannot satisfy the storage request.
+
+*ms-freq* gives the number of times the "mark-sweep" algorithm should
+be used hereafter for every time the normal "copying" algorithm is
+used. Giving `0` for *ms-freq* means never to use the "mark-sweep"
+algorithm, and giving `<CHTYPE <MIN> FIX>` means (effectively) always
+to use it. The "mark-sweep" algorithm uses considerably less processor
+time than the "copying" algorithm, but it never shrinks the
+free-storage pool, and in fact the pool can become fragmented. The
+"mark-sweep" algorithm could be useful in a program system (such as
+the compiler) where the size of the pool rarely changes, but objects
+are created and thrown away continuously.
22.6. BLOAT
-----------
`READ`ing large `STRING`s, and calling routines within the
interpreter and compiled programs)
-Arguments on the second line are also `FIX` and optional, but they set
-garbage-collection parameters permanently, as follows:
+Arguments on the second line above are also `FIX` and optional, but
+they set garbage-collection parameters permanently, as follows:
- *min*: as for `GC`
- *plcl*: number of slots for `LVAL`s added when the space for
22.8. GC-MON
------------
- <GC-MOND pred>
+ <GC-MON pred>
("garbage-collector monitor") determines whether or not the
interpreter will hereafter print information on the terminal when a
Two `SUBR`s, described next, use only part of the garbage-collector
algorithm, in order to find all pointers to an object. `GC-DUMP` and
`GC-READ`, as their names imply, also use part in order to translate
-between Muddle objects and binary representation thereof.
+between Muddle objects and binary representations thereof.
### 22.9.1. SUBSTITUTE
the "wrong" one, after `OBLIST`s have been in the wrong state. This is
more or less the way `ATOM`s are impurified. It is also useful for
unlinking `RSUBR`s. `SUBSTITUTE` returns *old* as a favor: unless you
-hang onto *old* at that point, it will be garbage-collected.
+hang onto *old* at that point, it will be garbage.
22.9.2 PURIFY
-------------
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