chore: The from and to components of the R representation of an igraph objects use ALTREP to avoid unnecessary materialization

[Antonov548]

Implement ALTREP for igraph_t_idx_from and igraph_t_idx_to (requires R 4.0)

#787

[Antonov548]

Seems need to have two different altrep classes for from and to since it's accessing different members in graph. Or change altrep to store pointer to from or to member in graph, but not to enviorement.

[krlmlr]

Two classes seem fine for me. I'll review when the checks have finished.

[krlmlr]

I was wondering how this even compiles with oldrel-4... Turns out we only need R >= 3.6, perhaps even R >= 3.5 would be sufficient.

Can you please add verbosity, triggered by an option, so that we can test materialization? Similarly to https://github.com/duckdb/duckdb/blob/85989198104c893f302e2fff6fae6bba65156af8/tools/rpkg/src/reltoaltrep.cpp#L65-L68.

[Antonov548]

I was wondering how this even compiles with oldrel-4... Turns out we only need R >= 3.6, perhaps even R >= 3.5 would be sufficient.

Yes, it interesting. I have added igraph.verbose option.

[Antonov548]

I think we can add this option to the test which is now failing: #806

[krlmlr]

Thanks. As discussed, can you please extend the logging to creation and destruction of igraph objects triggered from the R code?

[krlmlr]

R_ShowMessage() is slightly better here.

[krlmlr]

@Antonov548: can you please extend the logging to creation and destruction of igraph objects triggered from the R code?

[Antonov548]

@Antonov548: can you please extend the logging to creation and destruction of igraph objects triggered from the R code?

Added logs for such events of pointer: make, free, restore.

Also found that rigraph already has function to make logs with option verbose.

library(igraph)

igraph_options(verbose = TRUE)

g <- make_ring(3, directed = TRUE)
gs <- unserialize(serialize(g, NULL))

[krlmlr]

Thanks, great! We can work on enhancing the messages by printing which object is saved/restored, but this is good for now.

options(conflicts.policy = list(warn = FALSE))
library(igraph)

igraph_options(verbose = TRUE)

g <- make_ring(3, directed = TRUE)
#> Make graph external pointer.
#> Materializing 'from' vector.
#> Materializing 'to' vector.
gs <- unserialize(serialize(g, NULL))
gs
#> Restore graph external pointer.
#> Make graph external pointer.
#> IGRAPH 7eb8913 D--- 3 3 -- Ring graph
#> + attr: name (g/c), mutual (g/l), circular (g/l)
#> + edges from 7eb8913:
#> [1] 1->2 2->3 3->1

^{Created on 2023-05-27 with reprex v2.0.2}

[krlmlr]

Thanks!