Software Transactional Memory

An implementation of software transaction memory (STM) using the TL2 algorithm. It aims to create atomic, consistent, and isolated access to memory as transactions (similar to database transactions).

While it cannot outperform handcrafted concurrent algorithms, it outperforms basic implementations such as placing a lock over a large portion of code. Additionally, STMs provide a generic interface allowing to integrate it in non-concurrent algorithms in a rather mechanical way.

This repository provides a C interface for a generic word-based STM. See source code for information about call invariants.

constexpr size_t word_size = 8;
// create a managed region of memory of size 1000 bytes and word size 8 bytes
auto region = tm_create(1024, word_size);
// start of the region memory
auto start = tm_start(region);

// start a transaction
while (true) {
	// all transaction operations return booleans indicating whether a transaction can continue
	bool ok;
	uint64_t value;

	// start transaction
	auto tx = tm_begin(region);

	// read first word in memory region
	ok = tm_read(region, tx, start, word_size, &value);
	if (!ok) continue;

	// write to the second word in memory region
	ok = tm_write(region, tx, &value, word_size, start + word_size);
	if (!ok) continue;

	// finish transaction
	ok = tm_end(region, tx);
	if (ok) break;
}

tm_destroy(region);