A process-oriented and trajectory-based Discrete-Event Simulation
(DES) package for R. It is designed as a generic yet powerful framework. The
architecture encloses a robust and fast simulation core written in 'C++' with
automatic monitoring capabilities. It provides a rich and flexible R API that
revolves around the concept of trajectory, a common path in the simulation
model for entities of the same type. Documentation about 'simmer' is provided
by several vignettes included in this package, via the paper by Ucar, Smeets
& Azcorra (2019,
handle_unfinished() activity sets a drop-out trajectory for unfinished
arrivals, i.e., those dropped from a resource (due to preemption, resource
shrinkage or a rejected seize) or those that leave a trajectory (#178
addressing #177).release_all() and release_selected_all() activities automatically
retrieve the amount of resources seized and release it (#180 addressing #25).get_seized() and get_seized_selected() getters allow an arrival to
retrieve the amount of resources seized (#180 addressing #179).stop_if() activity sets a conditional breakpoint (#181 addressing #100).Queueing Systems vignette with a section about state-dependent
service rates.get_selected() retrieves names of selected resources via the
select() activity (#172 addressing #171).Simulator interface for adding processes and resources (#162).
The responsibility of building the objects has been moved to the caller.add_global() method to attach global attributes to a simulation
environment (#174 addressing #158).get_global() to work outside trajectories (#170 addressing #165).rollback() with an infinite amount (#173).reset() to avoid overwriting the simulation environment (#175).get_sources() and get_resources() retrieve a character vector of
source/resource names defined in a simulation environment.get_trajectory() retrieves a trajectory to which a given source is
attached.shortest-queue-available,
round-robin-available, random-available (#156). These are the same as the
existing non-available ones, but they exclude unavailable resources
(capacity set to zero). Thus, if all resources are unavailable, an error is
raised.-DRCPP_PROTECTED_EVAL (Rcpp >= 0.12.17.4) as
-DRCPP_USE_UNWIND_PROTECT (6d27671).-DBOOST_NO_AUTO_PTR (70328b6).log_ print (7c2e3b1).when_activated() convenience function to easily generate arrivals on
demand from trajectories (#161 closing #160).schedule printing (9c66285).set_attribute(global=TRUE), get_attribute(global=TRUE) and
timeout_from_attribute(global=TRUE) (#164), the *_global versions should
be used instead.simmer license has been changed to GPL >= 2.inst/include (#147 closing #145). Therefore, from now on it is possible to
extend the C++ API from another package by listing simmer under the
LinkingTo field in the DESCRIPTION file.monitor constructor enables the development of new monitoring
backends in other packages (179f656, as part of #147).log_ activity has a new argument
level which determines whether the message is printed depending on a global
log_level defined in the simmer constructor (#152).set_attribute and set_global gain a new argument to automatically
initialise new attributes (#157). Useful to update counters and indexes in a
single line, without initialisation boilerplate.-DRCPP_PROTECTED_EVAL (Rcpp >= 0.12.17.3), which provides fast
evaluation of R expressions by leveraging the new stack unwinding protection
API (R >= 3.5.0).ostream method (2b2f43e).rlang and purrr (#154).add_dataframe enables the attachment of precomputed data,
in the form of a data frame, to a trajectory. It can be used instead of (or
along with) add_generator. The most notable advantage over the latter is
that add_dataframe is able to automatically set attributes and
prioritisation values per arrival based on columns of the provided data frame
(#140 closing #123).set_source activity deprecates set_distribution(). It works both for
generators and data sources (275a09c, as part of #140).simmer()
constructor gains a new argument mon to provide different types of monitors.
By default, monitoring is performed in-memory, as usual. Additionally,
monitoring can be offloaded to disk through monitor_delim and monitor_csv,
which produce flat delimited files. But more importantly, the C++ interface
has been refactorised to enable the development of new monitoring backends
(#146 closing #119).until=Inf for the run method (3e6aae9, as part of #140).branch and clone now accept lists of trajectories, in the same way as
join, so that there is no need to use do.call (#142).continue (present in seize and branch) is recycled if only
one value is provided but several sub-trajectories are defined (#143).timeout_from_attribute() activity makes it easier to set a timeout based
on an attribute (#129).set_attribute(), set_prioritization(), set_capacity() and
set_queue_size() get a new argument mod which, if set to "+" or "*",
modifies the corresponding value instead of substituting it. This makes it
easier to increment, decrement or scale one of these values (#130).*_selected() versions for the already available resource getters:
get_capacity(), get_queue seize(), get_server_count() and
get_queue_count() (#134).trap() after a send() (#135).create_trajectory() and onestep() (#117).get_mon_resources()'s data argument. It was there for historical
reasons and probably nobody was using it (851d34b).set_attribute() (and set_global() by extension) can set multiple
attributes at once by providing vectors of keys and values (or functions
returning such keys and/or values). get_attribute() (and get_global()
by extension) can retrieve multiple keys (#122).stepn() method deprecates onestep() (e452975).ostream after formatting (9ff11f8).set_capacity() (#125).progress callback in run() (#103).get_name() retrieves the arrival name.get_attribute() retrieves an attribute by name. The old method of
retrieving them by providing a function with one argument is deprecated in
favour of get_attribute(), and will be removed in version 3.7.x.get_prioritization() retrieves the three prioritization values
(priority, preemptible, restart) of the active arrival.set_global() and get_global(),
equivalent to set_attribute(global=TRUE) and get_attribute(global=TRUE)
respectively.Rcpp::DataFrame instead of Rcpp::List (#104).make_resetable() (c596f73).trap()'s handler cloning and associated test (#91).select()'s policy also when resources is a function (#92).rollback()'s default behaviour to times=Inf, i.e., infinite loop (#95).timeout() returns a missing value (#96 and #97).[<- and [[<- (#88).rep() S3 method for trajectories (7fa515e).simmer.plot package (on CRAN) already covers these features among others.Suggests are not installed (e40e5b6).every parameter to the from_to() convenience function (9d68887).[ and [[, for trajectories (1847898). Think
about trajectories as lists of activities and these operators will do (almost)
everything you expect. As a side effect, the generics head() and tail()
automatically work with trajectories also as expected.length() method to obtain the number of first-level activities in a
trajectory (f86375a). Useful in combination with the subsetting operators.create_trajectory() has been deprecated in favor of trajectory() (76c1317).plot_resource_usage(), plot_resource_utilization(),
plot_evolution_arrival_times() and plot_attributes() have been deprecated
and will be removed in the next release in order to minimise dependencies
(5b43f2b). We plan to release a new package on CRAN covering these features
and new ones.get_head(),
get_tail(), print_activity(), get_next_activity(), get_prev_activity()
(f86375a). These methods were only useful for development purposes and nobody
should be using them. And it was never a good idea to directly expose external
pointers.renege_if() activity triggers reneging upon reception of a signal
broadcasted with send() (#84).trap() (bb2aa46).set_attribute() (#82).set_queue_size() with queue_size_strict=TRUE: arrivals were
not being dropped (#83).set_capacity() with a preemptive resource when the old value was
Inf: arrivals were not being preempted (63beb2c).trap() printed information.set_capacity() and set_queue_size() become activities (#77). Just like
seize() and release(), they have the associated set_capacity_selected()
and set_queue_size_selected() for a joint use together with select().activate() and deactivate() activities allow an arrival to start or
stop a generator, respectively, from inside a trajectory (#80).set_trajectory() and set_distribution() activities allow an arrival
to install a new trajectory or distribution, respectively, in a generator
from inside a trajectory (#80).send(), trap(), untrap() and wait() can be used to send signals, wait
for signals, trap them and launch asynchronous handlers.log_() activity simply prints messages for debugging purposes (eaa4554).seize() and seize_selected() (1c8c3bb).get_mon_arrivals(ongoing = TRUE) (#73).as<>() calls (ec4e51a).run(until) runs the simulation exactly until until, instead of until
the first event scheduled at a time >= until (e7264f6).priority, preemptible, restart) has been moved from
seize() to add_generator() (#69). This leads to a more natural
interpretation of prioritization values as attributes of arrivals from the
same generator, rather than attributes of a seize(). Still, prioritization
values can be redefined dynamically from inside a trajectory with the new
activity set_prioritization().post.seize and reject sub-trajectories in seize() and
seize_selected() (#49). This feature allows us to fine-tune what happens to
an arrival if it cannot seize a resource: instead of getting dropped, it may
execute a given sub-trajectory.clone() and synchronize() activities (#71). clone() implements the
workflow pattern in which an entity is processed in multiple parallel threads.
The user can define a different sub-trajectory for each clone. With
synchronize(), multiple parallel clones converge and are synchronized: only
one continues (the first or the last to arrive), and the others are removed.batch() and separate() activities (#45). They can be used to implement
a rollercoaster process: batch() collects a number of arrivals before they
can continue processing as a block, and separate() splits a previousl
established batch.renege_in() and renege_abort() activities (#58). They can be used to
set or unset a timer after which the arrival will abandon.branch()'s option returns 0, the arrival skips the branch()
and continues to the next activity instead of throwing an index out of range
error (#70).every() (#65) and branch()'s
deprecated argument merge (#57).join() activity to concatenate trajectories (#50).queue_size_strict to add_resource() to guarantee the queue
size limit with preemption (#59).select(), seize_selected() and release_selected() activities (#52).leave() activity (#63).end_time - start_time. All
versions 3.2.x are affected by this bug.preemptible in the documentation of seize() and
force preemptible to be equal or greater than priority (#53).branch()'s merge parameter name to continue. The old name is
deprecated (#57).match.arg() in multiple-choice arguments (#55).branch() backwards linking and count (#56).release() in two steps to deal properly with capacity changes at
the same point in time (#64).every() is deprecated due to #65.capacity and queue_size can change over time following a user-defined
scheduling, which can be generated with the new function schedule().?peek.plot_resource_usage() (8da9b97).merge=TRUE (#46).until=Inf is allowed now (f47baa9).t=3, queue=2 meant that, until t=3, the queue had
2 customers, and at t=3 the system changed (because of a new arrival or
a new departure). The idea was to keep the values and time vectors aligned
(see #28). But from this moment on, the resources are monitored after
changing the status of the system. This is more consistent with what a user
would expect, and more consistent with the behaviour of other related R
functions (e.g., see stepfun(), from the stats package). Wrapping up and
from now on, t=3, queue=2 means that some event happened at t=3 whose
immediate and subsequent result was a queue with 2 customers.preemptive=TRUE. Arrivals in the server can be preempted on
a preempt_order="fifo" or preempt_order="lifo" basis. Each seize() has
three basic properties:
priority: already present in previous versions.preemptible: another seize() with a priority value greater than this
may preempt the present seize().restart: whether the current task (a timeout() activity, for instance)
should be restarted if the arrival is preempted.show_activity() and show_trajectory().every(), to() and from_to() convenience functions (8e524cd).plot_resource_usage() (6b034a7).testthat (#41).branch() activity now provides attributes to its option function, as
the other activities (#42).plot_*() functions (#44).get_mon_arrivals() returned the start/activity/end times
per arrival for the whole trajectory. This behaviour remains, but additionally,
get_mon_arrivals(per_resource = TRUE) returns these times per resource, so
that it is possible to retrieve queueing/system times per resource.get_mon_*() functions accept a single simulation environment as well as a
list of environments representing several replications (5ee2725). A new column
(replication) in the resulting data frame indicates the corresponding
replication number.set_attribute() activity (#16).rollback() activity (#17 and #22).self visibly, instead of invisibly (#35).at() and from() convenience functions (29cccd2 and 7cfdd90).add_skip_event() function to implement a more flexible and user-friendly
branching method.n arrivals beforehand,
this release leverages the concept of generator of arrivals, which is faster
and more flexible. At the same time, the concept of trajectory as a chain of
activities is implemented entirely in C++ internally. Our tests show that
simmer is even faster than SimPy when it comes to simulate queueing networks.