-SimGrid (3.28.1) NOT RELEASED YET (v3.29 expected September 22. 2021, 19:21 UTC)
-
-New features:
- - Non-linear resource sharing: allows to dynamically change the resource
- capacity. Users can change this capacity by setting a callback which will
- be called when SimGrid is sharing the resource between the active
- activities. An activity can be a task running, a read/write IO operation or a
- communication flow.
- - Callback signature: double (double capacity, int n_activities): given the
- current resource's capacity and number of activities running on it,
- returns the new capacity.
- - Note that this callback is in the critical path of the system solve and
- should not take long to execute.
- - Examples:
- - Disk: examples/cpp/io-degradation
- - Link: examples/cpp/network-nonlinear
- - CPU: examples/cpp/exec-cpu-nonlinear
- - Dynamic factors for CPU and disk: similarly to dynamic network factors,
- allows the user to set a callback which can affect the progress of activities
- (multiplicative factor applied when updating the amount of work remaining).
- - Example: examples/cpp/exec-cpu-factors
+SimGrid (3.29) October 7. 2021
+
+The "Ask a stupid question" release.
+
+We wish that every user ask one question about SimGrid to celebrate.
+On Mattermost, Stack Overflow or using the issues tracker.
+
+
+New modeling features:
+ - Non-linear resource sharing, modeling resources whose performance heavily degrades with contention:
+ - The total capacity may be updated dynamically through a callback
+ and depends mainly on the number of concurrent flows.
+ - Examples (both cpp and python): io-degradation, network-nonlinear, exec-cpu-nonlinear
+
+ - Dynamic factors: model variability in the speed of activities
+ - Each action can now have a factor that affects its progression.
+ This multiplicative factor is applied when updating the amount of work
+ remaining, thereby an activity with factor=0.5 only uses half of the
+ instantaneous power/bandwidth it is allocated and will appear twice
+ slower than what it actually consumes.
+ - This can be used to model a overhead (e.g., there is a 20 bytes
+ header in a 480 bytes TCP packet so the factor 0.9583) but the novelty
+ is this factor can now easily be adjusted depending on activity's and
+ resources characteristics.
+ - This existed for network (e.g., the effective bandwidth depends
+ on the message in SMPI piecewise-linear network model) but it is now
+ more general (the factor may depend on the source and destination and
+ thus account to different behaviors for intra-node communications and
+ extra-node communications) and is available for CPUs (e.g., if you
+ want to model an affinity as in the "Unrelated Machines" problem in
+ scheduling) and disks (e.g., if you want to model a stochastic
+ capacity) too.
+ - For that, resources can be provided with a callback that computes
+ the activity factor when creating the action.
+ - Example: examples/cpp/exec-cpu-factors
+ - The same mechanism is also available for the latency, which
+ allows to easily introduce complex variability patterns.