In order to reduce the traffic on this thread, please only use this thread to report issues with new VM; we’re also starting to collect a list of popular places to do a player-facing beta test, so if you’d like the new VM to be enabled on desktop clients and server, please let me know what your place is; we expect to enable the VM for these individual places next week after the release.
If you have feature requests for Lua, you can use the feature request forum category.
Idk if this is off-topic or not, but the new vm has been enabled in the first game: https://www.roblox.com/games/1720015937/Space-Mining-Simulator
Thought I’d let everyone know /shrug
(fflags log useful)
I tested the new Lua VM with an implementation of SHA-256, utilizing the upcoming bit32 library.
Using an input of 260 KB, this is how long it took to compute their hashes:
1.2972564697266
0.17563724517822
These results are quite astonishing! I can’t wait for this to go live!
This is just a cleaned up version of an implementation I found on GitHub Gist.
local band = bit32.band
local bnot = bit32.bnot
local bxor = bit32.bxor
local rrotate = bit32.rrotate
local rshift = bit32.rshift
local primes =
{
0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5,
0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,
0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,
0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3,
0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5,
0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
}
local function toHex(str)
local result = str:gsub('.', function (char)
return string.format("%02x", char:byte())
end)
return result
end
local function toBytes(value, length)
local str = ""
for i = 1, length do
local rem = value % 256
str = string.char(rem) .. str
value = (value - rem) / 256
end
return str
end
local function readInt32(buffer, index)
local value = 0
for i = index, index + 3 do
value = (value * 256) + string.byte(buffer, i)
end
return value
end
local function digestBlock(msg, i, hash)
local digest = {}
for j = 1, 16 do
digest[j] = readInt32(msg, i + (j - 1) * 4)
end
for j = 17, 64 do
local v = digest[j - 15]
local s0 = bxor(rrotate(v, 7), rrotate(v, 18), rshift(v, 3))
v = digest[j - 2]
digest[j] = digest[j - 16] + s0 + digest[j - 7] + bxor(rrotate(v, 17), rrotate(v, 19), rshift(v, 10))
end
local a, b, c, d, e, f, g, h = unpack(hash)
for i = 1, 64 do
local s0 = bxor(rrotate(a, 2), rrotate(a, 13), rrotate(a, 22))
local maj = bxor(band(a, b), band(a, c), band(b, c))
local t2 = s0 + maj
local s1 = bxor(rrotate(e, 6), rrotate(e, 11), rrotate(e, 25))
local ch = bxor(band(e, f), band(bnot(e), g))
local t1 = h + s1 + ch + primes[i] + digest[i]
h, g, f, e, d, c, b, a = g, f, e, d + t1, c, b, a, t1 + t2
end
hash[1] = band(hash[1] + a)
hash[2] = band(hash[2] + b)
hash[3] = band(hash[3] + c)
hash[4] = band(hash[4] + d)
hash[5] = band(hash[5] + e)
hash[6] = band(hash[6] + f)
hash[7] = band(hash[7] + g)
hash[8] = band(hash[8] + h)
end
local function sha256(msg)
do
local extra = 64 - ((#msg + 9) % 64)
local len = toBytes(8 * #msg, 8)
msg = msg .. '\128' .. string.rep('\0', extra) .. len
assert(#msg % 64 == 0)
end
local hash =
{
0x6a09e667,
0xbb67ae85,
0x3c6ef372,
0xa54ff53a,
0x510e527f,
0x9b05688c,
0x1f83d9ab,
0x5be0cd19,
}
for i = 1, #msg, 64 do
digestBlock(msg, i, hash)
end
local result = ""
for i = 1, 8 do
local value = hash[i]
result = result .. toBytes(value, 4)
end
return toHex(result)
end
------------------------------------------------------------------
local input = string.rep(".", 26e4)
local now = tick()
local result = sha256(input)
print(tick() - now)
print(result)
------------------------------------------------------------------
Where did you enable the bit32 library? I want to use that for something I made a while back, but was too clunky and slow to be of any use. Asking here in case others want to know how to.
It’s currently disabled via an FFlag (specifically FFlagLuaBit32), likely because it’s not available everywhere yet. If you enable that flag (you can DM me if you want help with that as this is a public thread), you should be able to access it in Studio.
Not really. The new lua is supposed to be faster, and without you editing any code.
That depends. A lot of people use next in loops instead of pairs, but the optimization only covers pairs. Localizing variables speeds up the old VM greatly when global functions have to be called a lot, but now doing that disables the optimization as well.
I feel like many people coming from other Lua scenes will find it confusing why their carefully optimized code runs worse than some random stuff a child could write.
Also, while everyone says that next and other stuff will run just as fast, nobody considers the reason why they were chosen over something else in the first place.
I had an enormous module for custom pathfinding for high number of units that would apply the same result to all of them by using a slightly modified flow-field algorithm. It worked pretty well, but still slower than a frame, so I had to distribute the iterations over multiple frames to maintain acceptable experience. Now that we have this, I have to rewrite the entire code as there were A LOT of localized variables, usage of custom hashtables (avoiding the use of next) and so on.
This has been stated many times already, but ok, here were go again. You don’t need to rewrite code.
If you have code that runs slower than it does in old VM, you can report this as a bug. If you have code that doesn’t run as fast as you’d like, we can look at what the performance problems are. If your code has a performance problem with for loops due to use of next or localized pairs, we can implement an optimization for this. As stated before, all code we’ve looked at so far doesn’t do either of these.
Do the places have to be “popular” or?
If not then I’d love for my development universe to have this to ensure this works for my upcoming game as early as possible!
Here is the Universe ID: 1012447630
I’m waiting to be added to the beta program so I can test this on a soon to be released game.
I’m extremely excited to try this out, is it cool if I post a load of my results from some of my heavy game scripts here when I can via tick() functions?
I’m not sure if this is off-topic, but will bit32 be enabled at or around the same time as the new VM?
He means it’s up to you to analyze the performance of your game between the old and new Lua VM and see if there’s any sign of obvious performance downgrade, then report it here. They won’t look at your game themselves.
You can index unassigned globals without error:
print(a.a)--nil
a=nil print(a.a)--error
bit32 is independent and will be enabled once all mobile clients are updated with the new version so that it’s safe to use.
Thanks! That’s a bug, we’ll take a look.
With the new vm coming, is there any chance to get the bit operators/metamethods added along with the library?
What metamethods are you talking about? Wrt bit operators, bit32 library should be sufficient I think.
That would require modifying the bit32 library as lua 5.3 has bitwise operators, so it’s not done through functions. The bit32 was imported from lua 5.2 which has no bitwise metamethods, so the functions will have to be modified to call them.
Though it shouldn’t be hard as we already have tostring() calling the __tostring method.
