jobergum
commented
3 months ago | Query Cell Type | Document Cell Type | nDCG@5 | Latency | Score | Rank-Profile |
|---|---|---|---|---|---|
| float | float | 54.4 | x | sum of max dotproducts | full |
| float | float (unpacked from int8 to 0,1) | 52.4 | x | sum of max dotproducts | binary |
| float | float (unpacked from int8 scaled to -1,1) | 52.4 | x | sum of max dotproducts | binary-sign |
| int8 | int8 | 48.7 | x | sum of max partial inverted hamming | binary-hamming2 |
| int8 | int8 | 49.8 | x | sum of max full inverted hamming | binary-hamming |
| int8 | int8 | 34.86 | x | binary dotproduct | binary-dotproduct |
Where binary-hamming is defined as
sum(
reduce(
1/(1+ sum(hamming(query(qt), attribute(binary_embedding)),v)
),
max, patch
),
querytoken
)Where we find the hamming distance for the entire 128 dim vector and covert that to a similarity score by 1/(1 + hamming_full_vector) instead of sum over each cell. This is also easier to optimize, and scores better than the initial suggestion which sums each cell score.
Full schema with rank-profiles referenced in the above table.
schema pdf_page {
document pdf_page {
field id type string {
indexing: summary | attribute
}
field embedding type tensor<bfloat16>(patch{}, v[128]) {
indexing: attribute
}
field binary_embedding type tensor<int8>(patch{}, v[16]) {
indexing: attribute
}
}
rank-profile full {
inputs {
query(qt) tensor<float>(querytoken{}, v[128])
}
function max_sim() {
expression {
sum(
reduce(
sum(
query(qt) * cell_cast(attribute(embedding), float), v
),
max, patch
),
querytoken
)
}
}
first-phase {
expression {
max_sim
}
}
}
rank-profile binary inherits full {
function max_sim() {
expression {
sum(
reduce(
sum(
query(qt) * unpack_bits(attribute(binary_embedding)), v
),
max, patch
),
querytoken
)
}
}
first-phase {
expression {
max_sim
}
}
}
rank-profile binary-hamming {
inputs {
query(qt) tensor<int8>(querytoken{}, v[16])
}
function max_sim() {
expression {
sum(
reduce(
1/(1+ sum(
hamming(query(qt), attribute(binary_embedding)),v
)),
max, patch
),
querytoken
)
}
}
first-phase {
expression {
max_sim
}
}
}
rank-profile binary-dotproduct {
inputs {
query(qt) tensor<int8>(querytoken{}, v[16])
}
function max_sim() {
expression {
sum(
reduce(
sum(
unpack_bits(query(qt)) * unpack_bits(attribute(binary_embedding)), v
),
max, patch
),
querytoken
)
}
}
first-phase {
expression {
max_sim
}
}
}
rank-profile binary-sign inherits full {
function max_sim() {
expression {
sum(
reduce(
sum(
query(qt) * (2*unpack_bits(attribute(binary_embedding)) -1), v
),
max, patch
),
querytoken
)
}
}
first-phase {
expression {
max_sim
}
}
}
rank-profile binary-hamming2 {
inputs {
query(qt) tensor<int8>(querytoken{}, v[16])
}
function max_sim() {
expression {
sum(
reduce(
sum(
1/(1+hamming(query(qt), attribute(binary_embedding))),v
),
max, patch
),
querytoken
)
}
}
first-phase {
expression {
max_sim
}
}
}
}```
havardpe
Multi-vector MaxSim is increasingly important and we have optimizations for float cell precision, but I think we should also consider optimize for int8 with hamming as it approximates the dotproduct for normalized vectors.
It can help scale both ColBert and ColPali.
The following documents proton query latency for a query
where trueranking 500 documents using the schema below (one thread per search) and ranking accuracy on the DocVQA benchmark.Schema with rank-profiles referenced above. Note that without the
cell_castfrom bfloat16 in thefullprofile, it is much slower (8-10x).