// Compute a hash for objects of any type.
//
// The way it's currently implemented, two objects will have the same hash if
// all their non-address fields (all the way down) expand to the same sequence
// of scalar values. In particular, a container with all zero addresses hashes
// to 0. Hopefully this won't be an issue because we are usually hashing
// objects of a single type in any given hash table.
//
// Based on http://burtleburtle.net/bob/hash/hashfaq.html
:(before "End Primitive Recipe Declarations")
HASH,
:(before "End Primitive Recipe Numbers")
put(Recipe_ordinal, "hash", HASH);
:(before "End Primitive Recipe Checks")
case HASH: {
if (SIZE(inst.ingredients) != 1) {
raise << maybe(get(Recipe, r).name) << "'hash' takes exactly one ingredient rather than '" << to_original_string(inst) << "'\n" << end();
break;
}
break;
}
:(before "End Primitive Recipe Implementations")
case HASH: {
const reagent& input = current_instruction().ingredients.at(0);
products.resize(1);
products.at(0).push_back(hash(0, input));
break;
}
//: in all the code below, the intermediate results of hashing are threaded through 'h'
:(code)
size_t hash(size_t h, reagent/*copy*/ r) {
canonize(r);
if (is_mu_text(r)) // optimization
return hash_mu_text(h, r);
else if (is_mu_address(r))
return hash_mu_address(h, r);
else if (is_mu_scalar(r))
return hash_mu_scalar(h, r);
else if (is_mu_array(r))
return hash_mu_array(h, r);
else if (is_mu_container(r))
return hash_mu_container(h, r);
else if (is_mu_exclusive_container(r))
return hash_mu_exclusive_container(h, r);
assert(false);
}
size_t hash_mu_scalar(size_t h, const reagent& r) {
double input = is_literal(r) ? r.value : get_or_insert(Memory, r.value);
return hash_iter(h, static_cast<size_t>(input));
}
size_t hash_mu_address(size_t h, reagent& r) {
if (r.value == 0) return 0;
trace(Callstack_depth+1, "mem") << "location " << r.value << " is " << no_scientific(get_or_insert(Memory, r.value)) << end();
r.set_value(get_or_insert(Memory, r.value));
drop_from_type(r, "address");
return hash(h, r);
}
size_t hash_mu_text(size_t h, const reagent& r) {
string input = read_mu_text(get_or_insert(Memory, r.value+/*skip alloc id*/1));
for (int i = 0; i < SIZE(input); ++i) {
h = hash_iter(h, static_cast<size_t>(input.at(i)));
//? cerr << i << ": " << h << '\n';
}
return h;
}
size_t hash_mu_array(size_t h, const reagent& r) {
int size = get_or_insert(Memory, r.value);
reagent/*copy*/ elem = r;
delete elem.type;
elem.type = copy_array_element(r.type);
for (int i=0, address = r.value+1; i < size; ++i, address += size_of(elem)) {
reagent/*copy*/ tmp = elem;
tmp.set_value(address);
h = hash(h, tmp);
//? cerr << i << " (" << address << "): " << h << '\n';
}
return h;
}
size_t hash_mu_container(size_t h, const reagent& r) {
type_info& info = get(Type, get_base_type(r.type)->value);
int address = r.value;
int offset = 0;
for (int i = 0; i < SIZE(info.elements); ++i) {
reagent/*copy*/ element = element_type(r.type, i);
if (has_property(element, "ignore-for-hash")) continue;
element.set_value(address+offset);
h = hash(h, element);
//? cerr << i << ": " << h << '\n';
offset += size_of(info.elements.at(i).type);
}
return h;
}
size_t hash_mu_exclusive_container(size_t h, const reagent& r) {
const type_tree* type = get_base_type(r.type);
assert(type->value);
int tag = get(Memory, r.value);
reagent/*copy*/ variant = variant_type(r, tag);
// todo: move this error to container definition time
if (has_property(variant, "ignore-for-hash"))
raise << get(Type, type->value).name << ": /ignore-for-hash won't work in exclusive containers\n" << end();
variant.set_value(r.value + /*skip tag*/1);
h = hash(h, variant);
return h;
}
size_t hash_iter(size_t h, size_t input) {
h += input;
h += (h<<10);
h ^= (h>>6);
h += (h<<3);
h ^= (h>>11);
h += (h<<15);
return h;
}
void test_hash_container_checks_all_elements() {
run(
"container foo [\n"
" x:num\n"
" y:char\n"
"]\n"
"def main [\n"
" 1:foo <- merge 34, 97/a\n"
" 3:num <- hash 1:foo\n"
" return-unless 3:num\n"
" 4:foo <- merge 34, 98/a\n"
" 6:num <- hash 4:foo\n"
" return-unless 6:num\n"
" 7:bool <- equal 3:num, 6:num\n"
"]\n"
);
// hash on containers includes all elements
CHECK_TRACE_CONTENTS(
"mem: storing 0 in location 7\n"
);
}
void test_hash_exclusive_container_checks_all_elements() {
run(
"exclusive-container foo [\n"
" x:bar\n"
" y:num\n"
"]\n"
"container bar [\n"
" a:num\n"
" b:num\n"
"]\n"
"def main [\n"
" 1:foo <- merge 0/x, 34, 35\n"
" 4:num <- hash 1:foo\n"
" return-unless 4:num\n"
" 5:foo <- merge 0/x, 34, 36\n"
" 8:num <- hash 5:foo\n"
" return-unless 8:num\n"
" 9:bool <- equal 4:num, 8:num\n"
"]\n"
);
// hash on containers includes all elements
CHECK_TRACE_CONTENTS(
"mem: storing 0 in location 9\n"
);
}
void test_hash_can_ignore_container_elements() {
run(
"container foo [\n"
" x:num\n"
" y:char/ignore-for-hash\n"
"]\n"
"def main [\n"
" 1:foo <- merge 34, 97/a\n"
" 3:num <- hash 1:foo\n"
" return-unless 3:num\n"
" 4:foo <- merge 34, 98/a\n"
" 6:num <- hash 4:foo\n"
" return-unless 6:num\n"
" 7:bool <- equal 3:num, 6:num\n"
"]\n"
);
// hashes match even though y is different
CHECK_TRACE_CONTENTS(
"mem: storing 1 in location 7\n"
);
}
//: These properties aren't necessary for hash, they just test that the
//: current implementation works like we think it does.
void test_hash_of_zero_address() {
run(
"def main [\n"
" 1:&:num <- copy null\n"
" 2:num <- hash 1:&:num\n"
"]\n"
);
CHECK_TRACE_CONTENTS(
"mem: storing 0 in location 2\n"
);
}
//: This is probably too aggressive, but we need some way to avoid depending
//: on the precise bit pattern of a floating-point number.
void test_hash_of_numbers_ignores_fractional_part() {
run(
"def main [\n"
" 1:num <- hash 1.5\n"
" 2:num <- hash 1\n"
" 3:bool <- equal 1:num, 2:num\n"
"]\n"
);
CHECK_TRACE_CONTENTS(
"mem: storing 1 in location 3\n"
);
}
void test_hash_of_array_same_as_string() {
run(
"def main [\n"
" 10:num <- copy 3\n"
" 11:num <- copy 97\n"
" 12:num <- copy 98\n"
" 13:num <- copy 99\n"
" 2:num <- hash 10:@:num/unsafe\n"
" return-unless 2:num\n"
" 3:text <- new [abc]\n"
" 4:num <- hash 3:text\n"
" return-unless 4:num\n"
" 5:bool <- equal 2:num, 4:num\n"
"]\n"
);
CHECK_TRACE_CONTENTS(
"mem: storing 1 in location 5\n"
);
}
void test_hash_ignores_address_value() {
run(
"def main [\n"
" 1:&:num <- new number:type\n"
" *1:&:num <- copy 34\n"
" 2:num <- hash 1:&:num\n"
" 3:&:num <- new number:type\n"
" *3:&:num <- copy 34\n"
" 4:num <- hash 3:&:num\n"
" 5:bool <- equal 2:num, 4:num\n"
"]\n"
);
// different addresses hash to the same result as long as the values the point to do so
CHECK_TRACE_CONTENTS(
"mem: storing 1 in location 5\n"
);
}
void test_hash_container_depends_only_on_elements() {
run(
"container foo [\n"
" x:num\n"
" y:char\n"
"]\n"
"container bar [\n"
" x:num\n"
" y:char\n"
"]\n"
"def main [\n"
" 1:foo <- merge 34, 97/a\n"
" 3:num <- hash 1:foo\n"
" return-unless 3:num\n"
" 4:bar <- merge 34, 97/a\n"
" 6:num <- hash 4:bar\n"
" return-unless 6:num\n"
" 7:bool <- equal 3:num, 6:num\n"
"]\n"
);
// containers with identical elements return identical hashes
CHECK_TRACE_CONTENTS(
"mem: storing 1 in location 7\n"
);
}
void test_hash_container_depends_only_on_elements_2() {
run(
"container foo [\n"
" x:num\n"
" y:char\n"
" z:&:num\n"
"]\n"
"def main [\n"
" 1:&:num <- new number:type\n"
" *1:&:num <- copy 34\n"
" 2:foo <- merge 34, 97/a, 1:&:num\n"
" 5:num <- hash 2:foo\n"
" return-unless 5:num\n"
" 6:&:num <- new number:type\n"
" *6:&:num <- copy 34\n"
" 7:foo <- merge 34, 97/a, 6:&:num\n"
" 10:num <- hash 7:foo\n"
" return-unless 10:num\n"
" 11:bool <- equal 5:num, 10:num\n"
"]\n"
);
// containers with identical 'leaf' elements return identical hashes
CHECK_TRACE_CONTENTS(
"mem: storing 1 in location 11\n"
);
}
void test_hash_container_depends_only_on_elements_3() {
run(
"container foo [\n"
" x:num\n"
" y:char\n"
" z:bar\n"
"]\n"
"container bar [\n"
" x:num\n"
" y:num\n"
"]\n"
"def main [\n"
" 1:foo <- merge 34, 97/a, 47, 48\n"
" 6:num <- hash 1:foo\n"
" return-unless 6:num\n"
" 7:foo <- merge 34, 97/a, 47, 48\n"
" 12:num <- hash 7:foo\n"
" return-unless 12:num\n"
" 13:bool <- equal 6:num, 12:num\n"
"]\n"
);
// containers with identical 'leaf' elements return identical hashes
CHECK_TRACE_CONTENTS(
"mem: storing 1 in location 13\n"
);
}
void test_hash_exclusive_container_ignores_tag() {
run(
"exclusive-container foo [\n"
" x:bar\n"
" y:num\n"
"]\n"
"container bar [\n"
" a:num\n"
" b:num\n"
"]\n"
"def main [\n"
" 1:foo <- merge 0/x, 34, 35\n"
" 4:num <- hash 1:foo\n"
" return-unless 4:num\n"
" 5:bar <- merge 34, 35\n"
" 7:num <- hash 5:bar\n"
" return-unless 7:num\n"
" 8:bool <- equal 4:num, 7:num\n"
"]\n"
);
// hash on containers includes all elements
CHECK_TRACE_CONTENTS(
"mem: storing 1 in location 8\n"
);
}
//: An older version that supported only strings.
//: Hash functions are subtle and easy to get wrong, so we keep the old
//: version around and check that the new one is consistent with it.
void test_hash_matches_old_version() {
run(
"def main [\n"
" 1:text <- new [abc]\n"
" 3:num <- hash 1:text\n"
" 4:num <- hash_old 1:text\n"
" 5:bool <- equal 3:num, 4:num\n"
"]\n"
);
CHECK_TRACE_CONTENTS(
"mem: storing 1 in location 5\n"
);
}
:(before "End Primitive Recipe Declarations")
HASH_OLD,
:(before "End Primitive Recipe Numbers")
put(Recipe_ordinal, "hash_old", HASH_OLD);
:(before "End Primitive Recipe Checks")
case HASH_OLD: {
if (SIZE(inst.ingredients) != 1) {
raise << maybe(get(Recipe, r).name) << "'hash_old' takes exactly one ingredient rather than '" << to_original_string(inst) << "'\n" << end();
break;
}
if (!is_mu_text(inst.ingredients.at(0))) {
raise << maybe(get(Recipe, r).name) << "'hash_old' currently only supports texts (address array character), but got '" << inst.ingredients.at(0).original_string << "'\n" << end();
break;
}
break;
}
:(before "End Primitive Recipe Implementations")
case HASH_OLD: {
string input = read_mu_text(ingredients.at(0).at(/*skip alloc id*/1));
size_t h = 0 ;
for (int i = 0; i < SIZE(input); ++i) {
h += static_cast<size_t>(input.at(i));
h += (h<<10);
h ^= (h>>6);
h += (h<<3);
h ^= (h>>11);
h += (h<<15);
}
products.resize(1);
products.at(0).push_back(h);
break;
}