Reduce ratios of user / elapsed times in examples

[mpadge]

CRAN rejects current submission attempts because most examples generate "CPU time > 2.5 times elapsed times." These are the "user" and "elapsed" times in proc.time/system.time. These ratios seem to be anomalously high because of the data.table filtering calls in timetable construction.

[mpadge]

The above commits implement data.table's "fast sub-selection" syntax, and only make things much worse:

library (gtfsrouter)
packageVersion ("gtfsrouter")
#> [1] '0.1.0.8'
day <- route_pattern <- NULL
quiet <- FALSE
berlin_gtfs_to_zip ()
#> [1] "/tmp/Rtmp0oVroZ/vbb.zip"
f <- file.path (tempdir (), "vbb.zip")
gtfs <- extract_gtfs (f)
#> ▶ Unzipping GTFS archive✔ Unzipped GTFS archive  
#> ▶ Extracting GTFS feed✔ Extracted GTFS feed 
#> ▶ Converting stop times to seconds✔ Converted stop times to seconds 
#> ▶ Converting transfer times to seconds✔ Converted transfer times to seconds
test <- function (gtfs) {
    from <- "Innsbrucker Platz"
    to <- "Alexanderplatz"
    start_time <- 12 * 3600 + 120

    route <- gtfs_route (gtfs, from = from, to = to, start_time = start_time)
}
pt0 <- proc.time ()
test (gtfs)
#> Day not specified; extracting timetable for friday
pt1 <- proc.time ()
timing <- pt1 - pt0
print (timing)
#>    user  system elapsed 
#>   0.323   0.005   0.065
cli::cli_h2 (paste0 ("ratio: ", round (timing [1] / timing [3], digits = 1)))
#> 
#> ── ratio: 5 ──

^{Created on 2023-06-30 with reprex v2.0.2}

So data.table is definitely the issue here, and all examples are simply going to have to be switched off to get this update on CRAN.

[mpadge]

Solution: data.table::setDTthreads(1L) in all examples.