Discussion:
Simplicity proposal - Jets?
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JOSE FEMENIAS CAÑUELO via bitcoin-dev
2017-11-01 10:34:40 UTC
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Hi,

I am trying to follow this Simplicity proposal and I am seeing all over references to ‘jets’, but I haven’t been able to find any good reference to it.
Can anyone give me a brief explanation and or a link pointing to this feature?
Thanks
The plan is that discounted jets will be explicitly labeled as jets in the
commitment. If you can provide a Merkle path from the root to a node that
is an explicit jet, but that jet isn't among the finite number of known
discounted jets,
Russell O'Connor via bitcoin-dev
2017-11-03 01:10:42 UTC
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Hi Jose,

Jets are briefly discussed in section 3.4 of
https://blockstream.com/simplicity.pdf

The idea is that we can recognize some set of popular Simplicity
expressions, and when the Simplicity interpreter encounters one of these
expressions it can skip over the Simplicity interpreter and instead
directly evaluate the function using specialized C or assembly code.

For example, when the Simplicity interpreter encounters the Simplicity
expression for ECDSA verification, it might directly call into libsecp
rather than continuing the ECDSA verification using interpreted Simplicity.

HTH.


On Nov 2, 2017 18:35, "JOSE FEMENIAS CAÑUELO via bitcoin-dev" <
bitcoin-***@lists.linuxfoundation.org> wrote:

Hi,

I am trying to follow this Simplicity proposal and I am seeing all over
references to ‘jets’, but I haven’t been able to find any good reference to
it.
Can anyone give me a brief explanation and or a link pointing to this
feature?
Thanks

On 31 Oct 2017, at 22:01, bitcoin-dev-***@lists.linuxfoundation.org
wrote:

The plan is that discounted jets will be explicitly labeled as jets in the
commitment. If you can provide a Merkle path from the root to a node that
is an explicit jet, but that jet isn't among the finite number of known
discounted jets,
Adán Sánchez de Pedro Crespo via bitcoin-dev
2017-11-03 08:46:16 UTC
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Oops. That makes much more sense than what I said. Thanks a lot for the
clarification.
Post by Russell O'Connor via bitcoin-dev
Hi Jose,
Jets are briefly discussed in section 3.4 of
https://blockstream.com/simplicity.pdf
The idea is that we can recognize some set of popular Simplicity
expressions, and when the Simplicity interpreter encounters one of these
expressions it can skip over the Simplicity interpreter and instead
directly evaluate the function using specialized C or assembly code.
For example, when the Simplicity interpreter encounters the Simplicity
expression for ECDSA verification, it might directly call into libsecp
rather than continuing the ECDSA verification using interpreted Simplicity.
HTH.
On Nov 2, 2017 18:35, "JOSE FEMENIAS CAÑUELO via bitcoin-dev"
Hi,
I am trying to follow this Simplicity proposal and I am seeing all
over references to ‘jets’, but I haven’t been able to find any good
reference to it.
Can anyone give me a brief explanation and or a link pointing to this feature?
Thanks
Post by Russell O'Connor via bitcoin-dev
On 31 Oct 2017, at 22:01,
The plan is that discounted jets will be explicitly labeled as jets in the
commitment.  If you can provide a Merkle path from the root to a
node that
is an explicit jet, but that jet isn't among the finite number of known
discounted jets,
_______________________________________________
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<https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev>
_______________________________________________
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--
Adán Sánchez de Pedro Crespo
CTO, Stampery Inc.
San Francisco - Madrid
Hampus Sjöberg via bitcoin-dev
2017-11-03 12:59:46 UTC
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Thank you for your answer, Russel.

When a code path takes advantage of a jet, does the Simplicity code still
need to be publicly available/visible in the blockchain? I imagine that for
big algorithms (say for example EDCA verification/SHA256 hashing etc), it
would take up a lot of space in the blockchain.
Is there any way to mitigate this?

I guess in a softfork for a jet, the Simplicity code for a jet could be
defined as "consensus", instead of needed to be provided within every
script output.
When the Simplicity interpretor encounters an expression that has a jet, it
would run the C/Assembly code instead of interpreting the Simplicity code.
By formal verification we would be sure they match.

Greetings
Hampus

2017-11-03 2:10 GMT+01:00 Russell O'Connor via bitcoin-dev <
Post by Russell O'Connor via bitcoin-dev
Hi Jose,
Jets are briefly discussed in section 3.4 of https://blockstream.com/
simplicity.pdf
The idea is that we can recognize some set of popular Simplicity
expressions, and when the Simplicity interpreter encounters one of these
expressions it can skip over the Simplicity interpreter and instead
directly evaluate the function using specialized C or assembly code.
For example, when the Simplicity interpreter encounters the Simplicity
expression for ECDSA verification, it might directly call into libsecp
rather than continuing the ECDSA verification using interpreted Simplicity.
HTH.
On Nov 2, 2017 18:35, "JOSE FEMENIAS CAÑUELO via bitcoin-dev" <
Hi,
I am trying to follow this Simplicity proposal and I am seeing all over
references to ‘jets’, but I haven’t been able to find any good reference to
it.
Can anyone give me a brief explanation and or a link pointing to this feature?
Thanks
The plan is that discounted jets will be explicitly labeled as jets in the
commitment. If you can provide a Merkle path from the root to a node that
is an explicit jet, but that jet isn't among the finite number of known
discounted jets,
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
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Mark Friedenbach via bitcoin-dev
2017-11-03 16:19:39 UTC
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To reiterate, none of the current work focuses on Bitcoin integration, and many architectures are possible.

However the Jets would have to be specified and agreed to upfront for costing reasons, and so they would be known to all validators. There would be no reason to include anything more then the identifying hash in any contract using the jet.
Post by Hampus Sjöberg via bitcoin-dev
Thank you for your answer, Russel.
When a code path takes advantage of a jet, does the Simplicity code still need to be publicly available/visible in the blockchain? I imagine that for big algorithms (say for example EDCA verification/SHA256 hashing etc), it would take up a lot of space in the blockchain.
Is there any way to mitigate this?
I guess in a softfork for a jet, the Simplicity code for a jet could be defined as "consensus", instead of needed to be provided within every script output.
When the Simplicity interpretor encounters an expression that has a jet, it would run the C/Assembly code instead of interpreting the Simplicity code. By formal verification we would be sure they match.
Greetings
Hampus
Post by Russell O'Connor via bitcoin-dev
Hi Jose,
Jets are briefly discussed in section 3.4 of https://blockstream.com/simplicity.pdf
The idea is that we can recognize some set of popular Simplicity expressions, and when the Simplicity interpreter encounters one of these expressions it can skip over the Simplicity interpreter and instead directly evaluate the function using specialized C or assembly code.
For example, when the Simplicity interpreter encounters the Simplicity expression for ECDSA verification, it might directly call into libsecp rather than continuing the ECDSA verification using interpreted Simplicity.
HTH.
Hi,
I am trying to follow this Simplicity proposal and I am seeing all over references to ‘jets’, but I haven’t been able to find any good reference to it.
Can anyone give me a brief explanation and or a link pointing to this feature?
Thanks
The plan is that discounted jets will be explicitly labeled as jets in the
commitment. If you can provide a Merkle path from the root to a node that
is an explicit jet, but that jet isn't among the finite number of known
discounted jets,
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
Adán Sánchez de Pedro Crespo via bitcoin-dev
2017-11-03 16:42:38 UTC
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If I did understand it right, you don't need to publish the Simplicity
code for the "jetable" expression.

That's the whole point of MAST. Each Simplicity expression can be
identified by its MAST root (the Merkle root of all branches in its
Abstract Syntax Tree).

Imagine you want to write a Simplicity script that is roughly equivalent
to P2PKH. Regardless of directly writing such script or using a higher
level smart contract language, you won't likely write for yourself the
part in which you compute the hash of the public key. Instead, you are
expected to include some external library providing hash functions or at
least copy and paste such function into your code.

As everyone is expected to use the same, let's say, RIPEMD160
implementation, it doesn't matter how you included such function in your
program. The point is that once you build the MAST for your program,
such function will be completely replaced by its MAST root---which is
nothing but a hash.

This way, when the Simplicity interpreter (the BitMachine) bumps into
the hash, it can look for it in a predefined jets dictionary and find
the binary for a precompiled, formally proven implementation of a
function that is perfectly equivalent to the original Simplicity code.
Post by Hampus Sjöberg via bitcoin-dev
Thank you for your answer, Russel.
When a code path takes advantage of a jet, does the Simplicity code
still need to be publicly available/visible in the blockchain? I imagine
that for big algorithms (say for example EDCA verification/SHA256
hashing etc), it would take up a lot of space in the blockchain.
Is there any way to mitigate this?
I guess in a softfork for a jet, the Simplicity code for a jet could be
defined as "consensus", instead of needed to be provided within every
script output.
When the Simplicity interpretor encounters an expression that has a jet,
it would run the C/Assembly code instead of interpreting the Simplicity
code. By formal verification we would be sure they match.
Greetings
Hampus
2017-11-03 2:10 GMT+01:00 Russell O'Connor via bitcoin-dev
Hi Jose,
Jets are briefly discussed in section 3.4 of
https://blockstream.com/simplicity.pdf
<https://blockstream.com/simplicity.pdf>
The idea is that we can recognize some set of popular Simplicity
expressions, and when the Simplicity interpreter encounters one of
these expressions it can skip over the Simplicity interpreter and
instead directly evaluate the function using specialized C or
assembly code.
For example, when the Simplicity interpreter encounters the
Simplicity expression for ECDSA verification, it might directly call
into libsecp rather than continuing the ECDSA verification using
interpreted Simplicity.
HTH.
On Nov 2, 2017 18:35, "JOSE FEMENIAS CAÑUELO via bitcoin-dev"
Hi,
I am trying to follow this Simplicity proposal and I am seeing
all over references to ‘jets’, but I haven’t been able to find
any good reference to it.
Can anyone give me a brief explanation and or a link pointing to
this feature?
Thanks
Post by Russell O'Connor via bitcoin-dev
On 31 Oct 2017, at 22:01,
The plan is that discounted jets will be explicitly labeled as
jets in the
commitment.  If you can provide a Merkle path from the root to
a node that
is an explicit jet, but that jet isn't among the finite number of known
discounted jets,
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
<https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev>
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
<https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev>
_______________________________________________
bitcoin-dev mailing list
https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
--
Adán Sánchez de Pedro Crespo
CTO, Stampery Inc.
San Francisco - Madrid
Adán Sánchez de Pedro Crespo via bitcoin-dev
2017-11-03 00:45:40 UTC
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Hi everyone,

I agree that the paper could use some more details on the rationale
behind "jets". After a couple of reads, I think I can "ELI5 them":

As far as I understand, jets are a smart optimization that makes complex
Simplicity contracts way cheaper to compute (ideally, comparable to
Script or EVM).

For this purpose, jets leverage the most important element of the
Simplicity Bit Machine: the frames stack.

In a Simplicity program, every expression or sub-expression can be
thought of as a pure function that when applied on a certain initial
read frame, results in the active write frame having a different value.
This happens deterministically and without any side effects.

So, if the Simplicity interpreter finds some expression whose result
when applied upon a certain read frame is already known (because it has
already been executed or it was somehow precomputed), it doesn't need to
execute such expression step-by-step once again. Instead, it just need
to write the known result to the active write frame.

The paper suggests that at all times the interpreter knows the result of
applying many common operations on all possible combinations of inputs
in the range of 8 to 256 bits. In other words, the interpreter won't
need to calculate "123 + 321" or compare "456 > 654 because the results
of those expressions will be already known to it. These are stupid
examples, but the savings are real for hash functions internals,
elliptic curve calculations or even validation of signatures.

As said before, this can help making Simplicity programs lighter on CPU
usage, but it has many other benefits too:

+ Jets can replicate the behavior of complex chunks of Simplicity code
with the guarantee that they can't introduce side effects.

+ Interpreter-bundled jets are formally proven. The more a Simplicity
program relies on jets, the more it benefits from their safety. When
proving the soundness of your program, you can just ignore the jets,
assume they are valid and focus on your own logic.

The paper also suggests that different sets of jets could make up
different single purpose dialects, just like domain-specific languages
bring richer vocabulary and semantics to the bare syntax and grammar of
general-purpose languages.

I hope Russel or Mark can correct me if I got something totally wrong. I
must admit I really like this proposal and hereby declare myself a huge
fan of their work :)
--
Adán Sánchez de Pedro Crespo
CTO, Stampery Inc.
San Francisco - Madrid
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