Changelog • heumilkr

heumilkr (development version)

clarke_wright(): Return value changed: instead of returning a single data.frame() a list of three data.frame()s is returned now that makes it easier to interpret the result.
cvrplib_ls() now returns a data.frame() instead of a simple vector.
“cvrplib_instance” objects, including the bundled data sets: the field optimum is renamed to best_known_cost, since CVRPLIB provides best known solutions that are not necessarily proven optima.
cvrplib_download() now raises an error if a solution file exists but can not be downloaded, instead of silently setting the value to NA.

cvrplib_download() now accepts a vector of qualifiers and returns a named list of instances in that case. The list of available instances is only requested once. A single qualifier still returns the instance itself.
clarke_wright() now supports negative demands: sites with negative demand are treated as “backhaul” points, i.e. they deliver goods back to the depot. Sites with positive and negative demands can be visited in any order within a run, as long as the load stays within the vehicle capacity at every point of the run. Negative demands that exceed vehicle capacities are split across multiple runs, like positive demands.
clarke_wright() has gained a large runtime speedup compared to the previous version: for 500 sites the run time drops from about 6 seconds to about 0.007 seconds in our benchmarks. The actual speedup depends on input characteristics and grows with the number of sites. In return, large problems need more memory: the savings between sites now take about 8 * n^2 bytes for n sites instead of half of that.
clarke_wright(): Results are now deterministic, also in case of tied savings. Run identifiers follow the order of run creation.

clarke_wright(): Fractional vehicle capacities are not truncated to integers anymore. Previously this caused unnecessary splits of demand, and capacities below 1 never terminated.
clarke_wright(): Fix a crash with sites of zero demand.
clarke_wright(): The load of visits now always refers to the load after the visit, also for sites whose demand is split across multiple runs.
plot(), autoplot(): Fix errors and misplaced visits for solutions with sites whose demand is split across multiple runs.
milkr_saving(): The naive cost now includes the additional round trips of sites whose demand is split across multiple runs. Previously the saving could become negative.
cvrplib_download(), clarke_wright_cvrplib(): Instances defined by an explicit distance matrix (including E-n13-k4 and E-n31-k7 in cvrplib_E) got corrupted distances, since coordinates were derived from them incorrectly. The matrix is now kept in the new field distances and used by the solver, and the coordinates in pos are NA for those instances.
cvrplib_ls(), cvrplib_download(): Upstream website has changed. Fix malfunctioning functions by adjusting webscraping accordingly.

CRAN release: 2025-04-24

clarke_wright(): The default argument of restrictions is changed from NULL to an empty data frame. Passing restrictions = NULL now fails.

clarke_wright():
- Vehicle restrictions are now correctly applied if two tours are linked whose end points do not have vehicle restrictions maintained, but the tours include other edges with vehicle restrictions.
- R session does not crash anymore due to integer overflow issues in certain circumstances.
plot()/autoplot():
- Plotting of a milk run result with a single site now also works.
- The functions do have reference pages now.

CRAN release: 2024-04-01

Add the cvrp_*() function family for handling CVRPLIB data.
New vignette with performance benchmarks: vignette("clarke_wright_performance").

clarke_wright() does not crash R anymore when passing NA values to the distances argument: it stops gracefully instead.

CRAN release: 2024-01-10