Spillings change ?

[OlivierBBB]

I updated the spillings.toml file and noticed that quite a number of spillings values changed, typically by 1, even with older (mostly?) stable modules, while some changed drastically (e.g. HUB and TXN_DATA)

module key	old spilling	new spilling	down by 1
ADD	2	1	true
BIN	16	15	true
BIN_REFERENCE_TABLE	0	0
BLAKE_MODEXP_DATA	∅	1
BLOCK_DATA	6	6
BLOCK_HASH	1	1
EC_DATA	12	11	true
EUC	1	1
EXP	5	5
EXT	8	7	true
GAS	∅	1
HUB	2	12
INSTRUCTION_DECODER	0	0
LOG_DATA	1	1
LOG_INFO	5	5
MMIO	∅	0
MMU	10	10
MOD	8	7	true
MUL	9	8	true
MXP	4	3	true
OOB	5	5
RLP_ADDR	7	7
RLP_TXN	7	7
RLP_TXN_RCPT	7	7
ROM	2	1	true
ROM_LEX	1	1
SHAKIRA_DATA	∅	1
SHF	16	15	true
SHF_REFERENCE_TABLE	0	0	true
STP	4	4
TRM	7	7
TXN_DATA	15	8
WCP	16	15	true

Question. Did something change in the spillings computation to explain the above ?

[DavePearce]

Did something change in the spillings computation to explain the above ?

Well, that is a question. Certainly there have been changes which could affect spillage. For example, using range constraints for enforcing byte@prove instead of how it was done before is something that could affect spillage. However, I cannot easily tell if that explains what is happening in this case.

Still, I can investigate this and come back with a proper answer.

[OlivierBBB]

I don't think this warrants an "investigation" per se, unless the spillings fail (which AFAIK we will only know once we connect to the prover.) I'm mostly curious if this is a change for which we have an explanation 🙂

[DavePearce]

@OlivierBBB We just need to be sure its not the cause of any failures. To be fair, I think the ones we are currently investigating are not related, as these do not require padding to trigger.

[OlivierBBB]

@DavePearce it's unclear currently if this is the source of errors. To give you context @DavePearce I applied the above and @powerslider suddenly has failing tests. Some (previously successful) test expects the EXT module to contain 9 rows. This test now fails as the trace now contains 8 rows for some reason. 8 is the value I would have expected since the arithmetization does not incorporate a padding row, padding is added later.

Note. The EXT module lost 1 spilling row ☠️ ...

That is: we are unsure whether the spillings could affect the line-count.

[DavePearce]

it's unclear currently if this is the source of errors.

@OlivierBBB Well, the issues that came out from Leo's tests run could all be recreated using corset check. Since that doesn't use padding, those issues don't seem related to this.

However, what I understand from what you are saying above is that there is at least one issue which might be.