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ES: Generalized adoption and passive roots
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@l4haie
l4haie committed Jan 31, 2025
1 parent 195b511 commit 5268fce
Showing 1 changed file with 60 additions and 72 deletions.
132 changes: 60 additions & 72 deletions src/host/c/es.c
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Original file line number Diff line number Diff line change
Expand Up @@ -16,16 +16,11 @@
/* TODO (Even-Shiloach)
* --------------------
*
* Explain my approach to adopt and why I don't set the rank of pc and stack
* to 0 (too tired rn)
*
*
* Bugs
* - Co-friend loop?
* - Fuzzy tests bugs (potentially)
*
* - [Not a priority, happens rarely] co-friend not found in remove_cofriend
* - [Not a priority] is_root should work with just `get_rank(x) == 0`
* - FIXMEs and TODOs in the code
* - Call a GC for every instruction to make sure everything is collected...
* => Do that for the bootstrap, the test suite, and fuzzy tests
Expand All @@ -40,19 +35,10 @@
* contains the ES algorithm for the paper as well...)
* - [Not a priority] ... cleanup the code
*
* Catch queue
* - Pqueue with singly linked list and no remove operation
* - Buckets with and without remove operation
* - Skip list
* - Red-black tree or some other balanced tree
* - Heap (min, binomial, fib, ...)
* - Indexed array
* - ... ???
*
* Optimizations
* - Only protect a rib if it would get deallocated otherwise
* - Redundant drop/catch (set_stack followed by set_pc)
* - Expensive drop/catch (flat closures)
* - Adoption (optimized and integrated in the co-friend traversal phase)
* - Flat closures
* - Remove PC as a root
*/


Expand All @@ -67,11 +53,6 @@
* - Primitives: apply, io, and sys
* - Missing features from the original rvm
* - ... cleanup the code
*
* Optimizations
* - ... ?
*
* ... Should also optimize mark-and-sweep and stop-and-copy a little bit
*/

// @@(location import)@@
Expand All @@ -91,16 +72,14 @@
#define UPDATE_RANKS
// )@@

// @@(feature adopt
#define ADOPT
// @@(feature es-roots
// FIXME causes a memory leak if used with adoption
#define ES_ROOTS
#define NO_ADOPT
// )@@

#define ADOPT

// @@(feature unsafe
// This is to activate some optimizations that I made that I'm not sure why they
// work (or if they really do) or if they're safe to use
#define UNSAFE
// @@(feature no-adopt
#define NO_ADOPT
// )@@

// @@(feature debug/rib-viz
Expand Down Expand Up @@ -891,8 +870,6 @@ void add_cofriend(obj x, obj cfr, int j) {
get_field(cfr, j+3) = tmp;
}

void foo(){}

void remove_cofriend(obj x, obj cfr, int k) {
// Should be named "remove_link" or something because we don't remove the
// co-friend if there exist more than one ref from cfr to x
Expand Down Expand Up @@ -1048,11 +1025,18 @@ void add_edge(obj from, obj to, int i) {

// Intuition: TODO

#ifdef NO_ADOPT

#define adopt(x) false

#else

bool adopt(obj x) {
int rank = get_rank(x);
obj cfr = get_parent(x);
while (cfr != _NULL) {
if (get_rank(cfr) < rank) {
// FIXME not sure about the second condition
if (get_rank(cfr) < rank && get_rank(cfr) > 0) {
set_parent(x, cfr, get_mirror_field(x, cfr)-3);
set_rank(x, get_rank(cfr)+1);
return 1;
Expand All @@ -1062,12 +1046,15 @@ bool adopt(obj x) {
return 0;
}

#endif

#define loosen(x) set_rank(x, -1); pq_remove(x)

void drop() {
obj x; // current "falling" rib
obj *_x;
obj cfr;

while (!Q_IS_EMPTY()) {
x = q_dequeue();
_x = RIB(x)->fields;
Expand All @@ -1078,7 +1065,7 @@ void drop() {
// making x's children "fall" along with him
for (int i = 0; i < 3; i++) {
if (IS_RIB(_x[i]) && is_parent(_x[i], x) && (!is_root(_x[i]))) {
if (get_rank(_x[i]) != -1) {
if (get_rank(_x[i]) != -1 && (!adopt(_x[i]))) {
// if we loosen here instead of when we dequeue, we can reuse the
// queue field for the priority queue
loosen(_x[i]);
Expand Down Expand Up @@ -1185,7 +1172,7 @@ void remove_edge(obj from, obj to, int i) {

// Second condition happens when we remove an edge between a node and his
// parent but the parent points to the child more than once
if (!is_root(to) && (!is_parent(to, from))) {
if (!is_root(to) && (!is_parent(to, from)) && (!adopt(to))) {
// Q_INIT(); // drop queue i.e. "falling ribs"
// PQ_INIT(); // anchors i.e. potential "catchers"
q_enqueue(to);
Expand All @@ -1208,10 +1195,10 @@ void remove_edge(obj from, obj to, int i) {


void remove_node(obj old_root) {
// FIXME assumes old_root is parentless, merge remove_or_adopt_node and
// remove_node together, no reason to have both

// @@(location gc-start)@@
if (CFR(old_root) != _NULL) {
set_rank(old_root, get_rank(CFR(old_root))+1);
}
q_enqueue(old_root);
set_rank(old_root, -1); // loosen without removing
drop();
Expand All @@ -1226,13 +1213,7 @@ void remove_node(obj old_root) {

void remove_or_adopt_node(obj old_root) {
// @@(location gc-start)@@
if (CFR(old_root) != _NULL) {
if (adopt(old_root)) {
return;
} else {
set_rank(old_root, get_rank(CFR(old_root))+1);
}
}
if (adopt(old_root)) return;
q_enqueue(old_root);
set_rank(old_root, -1); // loosen without removing
drop();
Expand Down Expand Up @@ -1369,19 +1350,34 @@ void set_field(obj src, int i, obj dest) { // write barrier
void set_sym_tbl(obj new_sym_tbl) {
obj old_sym_tbl = symbol_table;
symbol_table = new_sym_tbl;
remove_root(old_sym_tbl);
#ifdef ES_ROOTS
if (IS_RIB(symbol_table)) set_rank(symbol_table, 0);
#endif

update_ranks(symbol_table);

#ifdef NO_ADOPT
remove_root(old_sym_tbl);
#else
if (IS_RIB(old_sym_tbl)) {
if (get_parent(old_sym_tbl) == _NULL) {
remove_node(old_sym_tbl);
} else {
remove_or_adopt_node(old_sym_tbl);
}
}
#endif
}

void set_stack(obj new_stack) {
obj old_stack = stack;
stack = new_stack;
// if (IS_RIB(stack)) set_rank(stack, 0);

#ifdef ES_ROOTS
if (IS_RIB(stack)) set_rank(stack, 0);
#endif
if (IS_RIB(stack)) update_ranks(stack);

#ifdef ES_ROOTS
if (IS_RIB(stack)) {
obj *_stack = RIB(stack)->fields;
for (int i = 0; i < 3; i++) {
Expand All @@ -1396,36 +1392,29 @@ void set_stack(obj new_stack) {
}
}
}
// AFAIK the only time where the old stack is reachable from... anything
// if when we have a closure, in which case it won't be deallocated so
// there's no point in doing the whole drop and catch phases...
// This is 10x time faster on programs with big boy recursion like `fib`
// but it causes some occasional memory leak (see the 3 tests that breaks).
// Potentially useless if we have flat closures
#ifdef UNSAFE
if (IS_RIB(old_stack) && get_parent(old_stack) == _NULL) remove_root(old_stack);
#endif
#ifdef NO_ADOPT
remove_root(old_stack);
#else
#ifdef ADOPT
if (IS_RIB(old_stack)) {
if (get_parent(old_stack) == _NULL) {
remove_node(old_stack);
} else {
remove_or_adopt_node(old_stack);
}
}
#else
remove_root(old_stack);
#endif
#endif
}

void set_pc(obj new_pc) {
obj old_pc = pc;
pc = new_pc;
// set_rank(pc, 0);

#ifdef NO_ADOPT
set_rank(pc, 0);
#endif
update_ranks(pc);

#ifdef ES_ROOTS
obj *_pc = RIB(pc)->fields;
for (int i = 0; i < 3; i++) {
if (IS_RIB(_pc[i])) {
Expand All @@ -1438,16 +1427,17 @@ void set_pc(obj new_pc) {
}
}
}
#ifdef ADOPT
#endif
#ifdef NO_ADOPT
remove_root(old_pc);
#else
if (IS_RIB(old_pc)) {
if (get_parent(old_pc) == _NULL) {
remove_node(old_pc);
} else {
remove_or_adopt_node(old_pc);
}
}
#else
remove_root(old_pc);
#endif
}

Expand Down Expand Up @@ -1557,7 +1547,6 @@ obj pop() {
TEMP5 = tos;
add_edge(null_rib, tos, 0);
}
// if (IS_RIB(tos)) set_rank(tos, 0);
set_stack(CDR(stack));
return tos;
}
Expand Down Expand Up @@ -1694,9 +1683,10 @@ void push2(obj car, obj tag) {
}
}
}

add_ref(new_rib, car, 0);
add_ref(new_rib, tag, 2);

// FIXME are these redundant now?
/* add_ref(new_rib, car, 0); */
/* add_ref(new_rib, tag, 2); */

alloc = (obj *)tmp;
}
Expand Down Expand Up @@ -2159,9 +2149,6 @@ void run() { // evaluator
break;
}
case INSTR_HALT: { // halt
//printf("deallocation count = %d\n", d_count);
/* viz_heap("graph.dot"); */
/* viz_heap(); */
gc();
vm_exit(0);
}
Expand Down Expand Up @@ -2352,6 +2339,7 @@ void decode() {
obj c = TAG_RIB(alloc_rib(TAG_NUM(i), n, NUM_0));
SET_TAG(c, TOS); // c->fields[2] = TOS;
SET_CAR(stack, c); // TOS = TAG_RIB(c);
// SET_CAR(stack, TAG_RIB(alloc_rib(TAG_NUM(i), n, TOS))); // TOS = TAG_RIB(c);
#ifdef REF_COUNT
DEC_COUNT(CDR(c)); // n
DEC_COUNT(TOS); // c
Expand Down

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