//: Addresses help us spend less time copying data around.
//: So far we've been operating on primitives like numbers and characters, and
//: we've started combining these primitives together into larger logical
//: units (containers or arrays) that may contain many different primitives at
//: once. Containers and arrays can grow quite large in complex programs, and
//: we'd like some way to efficiently share them between recipes without
//: constantly having to make copies. Right now 'next-ingredient' and 'return'
//: copy data across recipe boundaries. To avoid copying large quantities of
//: data around, we'll use *addresses*. An address is a bookmark to some
//: arbitrary quantity of data (the *payload*). It's a primitive, so it's as
//: efficient to copy as a number. To read or modify the payload 'pointed to'
//: by an address, we'll perform a *lookup*.
//:
//: The notion of 'lookup' isn't an instruction like 'add' or 'subtract'.
//: Instead it's an operation that can be performed when reading any of the
//: ingredients of an instruction, and when writing to any of the products. To
//: write to the payload of an ingredient rather than its value, simply add
//: the /lookup property to it. Modern computers provide efficient support for
//: addresses and lookups, making this a realistic feature.
//:
//: To create addresses and allocate memory exclusively for their use, use
//: 'new'. Memory is a finite resource so if the computer can't satisfy your
//: request, 'new' may return a 0 (null) address.
//:
//: Computers these days have lots of memory so in practice we can often
//: assume we'll never run out. If you start running out however, say in a
//: long-running program, you'll need to switch mental gears and start
//: husbanding our memory more carefully. The most important tool to avoid
//: wasting memory is to 'abandon' an address when you don't need it anymore.
//: That frees up the memory allocated to it to be reused in future calls to
//: 'new'.
//: Since memory can be reused multiple times, it can happen that you have a
//: stale copy to an address that has since been abandoned and reused. Using
//: the stale address is almost never safe, but it can be very hard to track
//: down such copies because any errors caused by them may occur even millions
//: of instructions after the copy or abandon instruction. To help track down
//: such issues, Mu tracks an 'alloc id' for each allocation it makes. The
//: first call to 'new' has an alloc id of 1, the second gets 2, and so on.
//: The alloc id is never reused.
:(before "End Globals")
long long Next_alloc_id = 0;
:(before "End Reset")
Next_alloc_id = 0;
//: The 'new' instruction records alloc ids both in the memory being allocated
//: and *also* in the address. The 'abandon' instruction clears alloc ids in
//: both places as well. Tracking alloc ids in this manner allows us to raise
//: errors about stale addresses much earlier: 'lookup' operations always
//: compare alloc ids between the address and its payload.
//: todo: give 'new' a custodian ingredient. Following malloc/free is a temporary hack.
:(code)
void test_new() {
run(
// call 'new' two times with identical types without modifying the
// results; you should get back different results
"def main [\n"
" 10:&:num <- new num:type\n"
" 12:&:num <- new num:type\n"
" 20:bool <- equal 10:&:num, 12:&:num\n"
"]\n"
);
CHECK_TRACE_CONTENTS(
"mem: storing 1000 in location 11\n"
"mem: storing 0 in location 20\n"
);
}
void test_new_array() {
run(
// call 'new' with a second ingredient to allocate an array of some type
// rather than a single copy
"def main [\n"
" 10:&:@:num <- new num:type, 5\n"
" 12:&:num <- new num:type\n"
" 20:num/alloc2, 21:num/alloc1 <- deaddress 10:&:@:num, 12:&:num\n"
" 30:num <- subtract 21:num/alloc2, 20:num/alloc1\n"
"]\n"
);
CHECK_TRACE_CONTENTS(
"run: {10: (\"address\" \"array\" \"number\")} <- new {num: \"type\"}, {5: \"literal\"}\n"
"mem: array length is 5\n"
// skip alloc id in allocation
"mem: storing 1000 in location 11\n"
// don't forget the extra locations for alloc id and array length
"mem: storing 7 in location 30\n"
);
}
void test_dilated_reagent_with_new() {
run(
"def main [\n"
" 10:&:&:num <- new {(& num): type}\n"
"]\n"
);
CHECK_TRACE_CONTENTS(
"new: size of '(& num)' is 2\n"
);
}
//: 'new' takes a weird 'type' as its first ingredient; don't error on it
:(before "End Mu Types Initialization")
put(Type_ordinal, "type", 0);
:(code)
bool is_mu_type_literal(const reagent& r) {
return is_literal(r) && r.type && r.type->name == "type";
}
:(before "End Primitive Recipe Declarations")
NEW,
:(before "End Primitive Recipe Numbers")
put(Recipe_ordinal, "new", NEW);
:(before "End Primitive Recipe Checks")
case NEW: {
const recipe& caller = get(Recipe, r);
if (inst.ingredients.empty() || SIZE(inst.ingredients) > 2) {
raise << maybe(caller.name) << "'new' requires one or two ingredients, but got '" << to_original_string(inst) << "'\n" << end();
break;
}
// End NEW Check Special-cases
const reagent& type = inst.ingredients.at(0);
if (!is_mu_type_literal(type)) {
raise << maybe(caller.name) << "first ingredient of 'new' should be a type, but got '" << type.original_string << "'\n" << end();
break;
}
if (SIZE(inst.ingredients) > 1 && !is_mu_number(inst.ingredients.at(1))) {
raise << maybe(caller.name) << "second ingredient of 'new' should be a number (array length), but got '" << type.original_string << "'\n" << end();
break;
}
if (inst.products.empty()) {
raise << maybe(caller.name) << "result of 'new' should never be ignored\n" << end();
break;
}
if (!product_of_new_is_valid(inst)) {
raise << maybe(caller.name) << "product of 'new' has incorrect type: '" << to_original_string(inst) << "'\n" << end();
break;
}
break;
}
:(code)
bool product_of_new_is_valid(const instruction& inst) {
reagent/*copy*/ product = inst.products.at(0);
// Update NEW product in Check
if (!product.type || product.type->atom || product.type->left->value != Address_type_ordinal)
return false;
drop_from_type(product, "address");
if (SIZE(inst.ingredients) > 1) {
// array allocation
if (!product.type || product.type->atom || product.type->left->value != Array_type_ordinal)
return false;
drop_from_type(product, "array");
}
reagent/*local*/ expected_product(new_type_tree(inst.ingredients.at(0).name));
return types_strictly_match(product, expected_product);
}
void drop_from_type(reagent& r, string expected_type) {
assert(!r.type->atom);
if (r.type->left->name != expected_type) {
raise << "can't drop2 " << expected_type << " from '" << to_string(r) << "'\n" << end();
return;
}
// r.type = r.type->right
type_tree* tmp = r.type;
r.type = tmp->right;
tmp->right = NULL;
delete tmp;
// if (!r.type->right) r.type = r.type->left
assert(!r.type->atom);
if (r.type->right) return;
tmp = r.type;
r.type = tmp->left;
tmp->left = NULL;
delete tmp;
}
void test_new_returns_incorrect_type() {
Hide_errors = true;
run(
"def main [\n"
" 1:bool <- new num:type\n"
"]\n"
);
CHECK_TRACE_CONTENTS(
"error: main: product of 'new' has incorrect type: '1:bool <- new num:type'\n"
);
}
void test_new_discerns_singleton_list_from_atom_container() {
Hide_errors = true;
run(
"def main [\n"
" 1:&:num <- new {(num): type}\n" // should be '{num: type}'
"]\n"
);
CHECK_TRACE_CONTENTS(
"error: main: product of 'new' has incorrect type: '1:&:num <- new {(num): type}'\n"
);
}
void test_new_with_type_abbreviation() {
run(
"def main [\n"
" 1:&:num <- new num:type\n"
"]\n"
);
CHECK_TRACE_COUNT("error", 0);
}
void test_new_with_type_abbreviation_inside_compound() {
run(
"def main [\n"
" {1: (address address number), raw: ()} <- new {(& num): type}\n"
"]\n"
);
CHECK_TRACE_COUNT("error", 0);
}
void test_equal_result_of_new_with_null() {
run(
"def main [\n"
" 1:&:num <- new num:type\n"
" 10:bool <- equal 1:&:num, null\n"
"]\n"
);
CHECK_TRACE_CONTENTS(
"mem: storing 0 in location 10\n"
);
}
//: To implement 'new', a Mu transform turns all 'new' instructions into
//: 'allocate' instructions that precompute the amount of memory they want to
//: allocate.
//: Ensure that we never call 'allocate' directly, and that there's no 'new'
//: instructions left after the transforms have run.
:(before "End Primitive Recipe Checks")
case ALLOCATE: {
raise << "never call 'allocate' directly'; always use 'new'\n" << end();
break;
}
:(before "End Primitive Recipe Implementations")
case NEW: {
raise << "no implementation for 'new'; why wasn't it translated to 'allocate'? Please save a copy of your program and send it to Kartik.\n" << end();
break;
}
:(after "Transform.push_back(check_instruction)") // check_instruction will guard against direct 'allocate' instructions below
Transform.push_back(transform_new_to_allocate); // idempotent
:(code)
void transform_new_to_allocate(const recipe_ordinal r) {
trace(101, "transform") << "--- convert 'new' to 'allocate' for recipe " << get(Recipe, r).name << end();
for (int i = 0; i < SIZE(get(Recipe, r).steps); ++i) {
instruction& inst = get(Recipe, r).steps.at(i);
// Convert 'new' To 'allocate'
if (inst.name == "new") {
if (inst.ingredients.empty()) return; // error raised elsewhere
inst.operation = ALLOCATE;
type_tree* type = new_type_tree(inst.ingredients.at(0).name);
inst.ingredients.at(0).set_value(size_of(type));
trace(102, "new") << "size of '" << inst.ingredients.at(0).name << "' is " << inst.ingredients.at(0).value << end();
delete type;
}
}
}
//: implement 'allocate' based on size
:(before "End Globals")
extern const int Reserved_for_tests = 1000;
int Memory_allocated_until = Reserved_for_tests;
int Initial_memory_per_routine = 100000;
:(before "End Reset")
Memory_allocated_until = Reserved_for_tests;
Initial_memory_per_routine = 100000;
:(before "End routine Fields")
int alloc, alloc_max;
:(before "End routine Constructor")
alloc = Memory_allocated_until;
Memory_allocated_until += Initial_memory_per_routine;
alloc_max = Memory_allocated_until;
trace(Callstack_depth+1, "new") << "routine allocated memory from " << alloc << " to " << alloc_max << end();
:(before "End Primitive Recipe Declarations")
ALLOCATE,
:(before "End Primitive Recipe Numbers")
put(Recipe_ordinal, "allocate", ALLOCATE);
:(before "End Primitive Recipe Implementations")
case ALLOCATE: {
// compute the space we need
int size = ingredients.at(0).at(0);
int alloc_id = Next_alloc_id;
Next_alloc_id++;
if (SIZE(ingredients) > 1) {
// array allocation
trace(Callstack_depth+1, "mem") << "array length is " << ingredients.at(1).at(0) << end();
size = /*space for length*/1 + size*ingredients.at(1).at(0);
}
int result = allocate(size);
// initialize alloc-id in payload
trace(Callstack_depth+1, "mem") << "storing alloc-id " << alloc_id << " in location " << result << end();
put(Memory, result, alloc_id);
if (SIZE(current_instruction().ingredients) > 1) {
// initialize array length
trace(Callstack_depth+1, "mem") << "storing array length " << ingredients.at(1).at(0) << " in location " << result+/*skip alloc id*/1 << end();
put(Memory, result+/*skip alloc id*/1, ingredients.at(1).at(0));
}
products.resize(1);
products.at(0).push_back(alloc_id);
products.at(0).push_back(result);
break;
}
:(code)
int allocate(int size) {
// include space for alloc id
++size;
trace(Callstack_depth+1, "mem") << "allocating size " << size << end();
//? Total_alloc += size;
//? ++Num_alloc;
// Allocate Special-cases
// compute the region of memory to return
// really crappy at the moment
ensure_space(size);
const int result = Current_routine->alloc;
trace(Callstack_depth+1, "mem") << "new alloc: " << result << end();
// initialize allocated space
for (int address = result; address < result+size; ++address) {
trace(Callstack_depth+1, "mem") << "storing 0 in location " << address << end();
put(Memory, address, 0);
}
Current_routine->alloc += size;
// no support yet for reclaiming memory between routines
assert(Current_routine->alloc <= Current_routine->alloc_max);
return result;
}
//: statistics for debugging
//? :(before "End Globals")
//? int Total_alloc = 0;
//? int Num_alloc = 0;
//? int Total_free = 0;
//? int Num_free = 0;
//? :(before "End Reset")
//? if (!Memory.empty()) {
//? cerr << Total_alloc << "/" << Num_alloc
//? << " vs " << Total_free << "/" << Num_free << '\n';
//? cerr << SIZE(Memory) << '\n';
//? }
//? Total_alloc = Num_alloc = Total_free = Num_free = 0;
:(code)
void ensure_space(int size) {
if (size > Initial_memory_per_routine) {
cerr << "can't allocate " << size << " locations, that's too much compared to " << Initial_memory_per_routine << ".\n";
exit(1);
}
if (Current_routine->alloc + size > Current_routine->alloc_max) {
// waste the remaining space and create a new chunk
Current_routine->alloc = Memory_allocated_until;
Memory_allocated_until += Initial_memory_per_routine;
Current_routine->alloc_max = Memory_allocated_until;
trace(Callstack_depth+1, "new") << "routine allocated memory from " << Current_routine->alloc << " to " << Current_routine->alloc_max << end();
}
}
void test_new_initializes() {
Memory_allocated_until = 10;
put(Memory, Memory_allocated_until, 1);
run(
"def main [\n"
" 1:&:num <- new num:type\n"
"]\n"
);
CHECK_TRACE_CONTENTS(
"mem: storing 0 in location 10\n"
"mem: storing 0 in location 11\n"
"mem: storing 10 in location 2\n"
);
}
void test_new_initializes_alloc_id() {
Memory_allocated_until = 10;
put(Memory, Memory_allocated_until, 1);
Next_alloc_id = 23;
run(
"def main [\n"
" 1:&:num <- new num:type\n"
"]\n"
);
CHECK_TRACE_CONTENTS(
// initialize memory
"mem: storing 0 in location 10\n"
"mem: storing 0 in location 11\n"
// alloc-id in payload
"mem: storing alloc-id 23 in location 10\n"
// alloc-id in address
"mem: storing 23 in location 1\n"
);
}
void test_new_size() {
run(
"def main [\n"
" 10:&:num <- new num:type\n"
" 12:&:num <- new num:type\n"
" 20:num/alloc1, 21:num/alloc2 <- deaddress 10:&:num, 12:&:num\n"
" 30:num <- subtract 21:num/alloc2, 20:num/alloc1\n"
"]\n"
);
CHECK_TRACE_CONTENTS(
// size of number + alloc id
"mem: storing 2 in location 30\n"
);
}
void test_new_array_size() {
run(
"def main [\n"
" 10:&:@:num <- new num:type, 5\n"
" 12:&:num <- new num:type\n"
" 20:num/alloc1, 21:num/alloc2 <- deaddress 10:&:num, 12:&:num\n"
" 30:num <- subtract 21:num/alloc2, 20:num/alloc1\n"
"]\n"
);
CHECK_TRACE_CONTENTS(
// 5 locations for array contents + array length + alloc id
"mem: storing 7 in location 30\n"
);
}
void test_new_empty_array() {
run(
"def main [\n"
" 10:&:@:num <- new num:type, 0\n"
" 12:&:num <- new num:type\n"
" 20:num/alloc1, 21:num/alloc2 <- deaddress 10:&:@:num, 12:&:num\n"
" 30:num <- subtract 21:num/alloc2, 20:num/alloc1\n"
"]\n"
);
CHECK_TRACE_CONTENTS(
"run: {10: (\"address\" \"array\" \"number\")} <- new {num: \"type\"}, {0: \"literal\"}\n"
"mem: array length is 0\n"
// one location for array length and one for alloc id
"mem: storing 2 in location 30\n"
);
}
//: If a routine runs out of its initial allocation, it should allocate more.
void test_new_overflow() {
Initial_memory_per_routine = 3; // barely enough room for point allocation below
run(
"def main [\n"
" 10:&:num <- new num:type\n"
" 12:&:point <- new point:type\n" // not enough room in initial page
"]\n"
);
CHECK_TRACE_CONTENTS(
"new: routine allocated memory from 1000 to 1003\n"
"new: routine allocated memory from 1003 to 1006\n"
);
}
void test_new_without_ingredient() {
Hide_errors = true;
run(
"def main [\n"
" 1:&:num <- new\n" // missing ingredient
"]\n"
);
CHECK_TRACE_CONTENTS(
"error: main: 'new' requires one or two ingredients, but got '1:&:num <- new'\n"
);
}
//: a little helper: convert address to number
:(before "End Primitive Recipe Declarations")
DEADDRESS,
:(before "End Primitive Recipe Numbers")
put(Recipe_ordinal, "deaddress", DEADDRESS);
:(before "End Primitive Recipe Checks")
case DEADDRESS: {
// primary goal of these checks is to forbid address arithmetic
for (int i = 0; i < SIZE(inst.ingredients); ++i) {
if (!is_mu_address(inst.ingredients.at(i))) {
raise << maybe(get(Recipe, r).name) << "'deaddress' requires address ingredients, but got '" << inst.ingredients.at(i).original_string << "'\n" << end();
goto finish_checking_instruction;
}
}
if (SIZE(inst.products) > SIZE(inst.ingredients)) {
raise << maybe(get(Recipe, r).name) << "too many products in '" << to_original_string(inst) << "'\n" << end();
break;
}
for (int i = 0; i < SIZE(inst.products); ++i) {
if (!is_real_mu_number(inst.products.at(i))) {
raise << maybe(get(Recipe, r).name) << "'deaddress' requires number products, but got '" << inst.products.at(i).original_string << "'\n" << end();
goto finish_checking_instruction;
}
}
break;
}
:(before "End Primitive Recipe Implementations")
case DEADDRESS: {
products.resize(SIZE(ingredients));
for (int i = 0; i < SIZE(ingredients); ++i) {
products.at(i).push_back(ingredients.at(i).at(/*skip alloc id*/1));
}
break;
}