The primary goal of CoSApp is to help technical departments in the design of complex systems. To do so, the framework allows the simulation of various systems representing the different parts of the final product in a common environment. The benefit is the ability for each subsystem team to carry out design study with a direct feedback at product level.

The main features are:

Butterfly effect

Couple your simulation models with CoSApp to get immediate impact on main product variables and iterate to converge on a better design.

Design guidance

All systems can share design parameters associated with an acceptable range. You can take advantage of those limited degrees of freedom without fear of breaking your collaborators' work.

Flexible simulation workflows

CoSApp solvers can be combined into versatile, customized workflows that fit specific simulation intents.

Have a look at the introduction, containing many tutorials!

This code is the property of Safran SA. It uses code coming from various open-source projects (see LICENSE file).

Citing

If you use CoSApp, please cite us!

Lac et al. (2024), CoSApp: a Python library to create, simulate and design complex systems, Journal of Open Source Software 9(94), 6292.

BibTeX entry:

@article{Lac.etal:joss2024,
    author={Étienne Lac and Guy {De Spiegeleer} and Adrien Delsalle and Frédéric Collonval and Duc-Trung Lê and Mathias Malandain},
    title={CoSApp: a Python library to create, simulate and design complex systems},
    journal={Journal of Open Source Software},
    year={2024},
    volume={9},
    number={94},
    pages={6292},
    doi={10.21105/joss.06292},
    publisher={The Open Journal}
}

Try it now!

Run a Jupyter Lab instance with binder to try out CoSApp features through examples.

History

1.3.0 (2025-09-18)

New features & API changes

Deprecation of methods NonLinearSolver.extend and RunSingleCase.extend, replaced by new methods add_problem (MR #430).
Declaring integer-valued numpy arrays no longer raises a warning (MR #428).
Harmonize solver option "history" between NonLinearSolver and Optimizer (MR #432). Optimizer option "monitored" is now deprecated, in favour of "history". Moreover, option "history" can now be set at recorder creation:
```
solver = system.add_solver(NonLinearSolver("solver"))

solver.add_recorder(DataFrameRecorder(...), history=True)
```

Bug fixes & Code improvements

Add missing initial data in solver convergence path (MR #431).
Handle zero-sized numpy arrays in mathematical algorithms (MR #433).
Fix bugs with multidimensional arrays as unknowns or transient variables (MR #434).
Fix bug on targets during mathematical problem extension (MR #435).
Fix bug on target detection during system problem assembly (MR #436).
Fix target initialization issue in implicit time drivers (MR #437).
New deprecation decorator (MR #429).
Improved type hints and general refactoring pass (MR #438).

Documentation

Updated tutorial on targets (MR #440).

1.2.0 (2025-06-13)

New features & API changes

New function cosapp.systems.batch_run and support class BatchRunner to obtain the response surface of a system over a set of test points, with multiprocessing support (MRs #423, #424).
Support of multiprocessing for System.make_surrogate (MR #422).
Removed deprecated property data for recorders (MR #421).
New method System.get_variable to obtain a variable object (containing unit, description and so on) from its contextual name in a system (MR #417).
Deprecation of function BasePort.get_details, replaced by methods get_variable and variable_dict (MR #420).
Expose protected property System.problem in the scope of method setup_run (MR #419).

Bug fixes & Code improvements

Modified call sequence in System.call_setup_run, to make sure that the system tree is setup before drivers are (MR #418).
Improved type hints and general refactoring pass (MR #425).

Documentation

Updated tutorial on multi-point design (MR #426).

1.1.0 (2025-04-28)

New features & API changes

New implicit time drivers: backward Euler and order 1-4 Backward Difference Formula (BDF) integrators (MRs #405, #415).
Add new signal system_update_signal for all time drivers, emitted at each time step (MR #406).
Improvement of driver MonteCarlo (MR #409).
Expose exception EventError in module cosapp.multimode (MR #407).

Bug fixes & Code improvements

Improved type hints and general refactoring pass (MRs #400, #408, #410, #416).
Support for polynomials with multi-dimensional coefficients in TwoPointCubicPolynomial (MR #404).

Documentation

Updated section on "Tips & Tricks" (MR #412).
Updated tutorial on time drivers (MR #415).

Dependency management

Update of the JupyterLite image (MRs #401, #402, #403, #411, #413).

1.0.1 (2025-03-24)

Bug fixes & Improvements

New transient variables dynamically added during transitions are now accounted for in time drivers (MRs #394, #396).
Bug fixes in CrankNicolson (MRs #395, #397).
Refactoring of state_io functions (MR #398).

1.0.0 (2025-03-12)

New feature: Parallel execution of drivers

The parallelization of certain drivers was implemented by Adrien Delsalle and Gaétan Laurens (MRs #330, #332, #334, #335, #339, #341, #345, #348, #353, #357, #365, #374, #390):

LinearDoE and MonteCarlo;
NonLinearSolver (computation of the Jacobian matrix in parallel).

This major feature relies on a robust serialization of systems, drivers and recorders, using either pickle or json. The serialization of all drivers, in particular, allows for the parallel execution of the drivers listed above, even when they contain sub-drivers.

Example

In the example below, using the Ballistics system from the advanced time driver tutorial, we compute the initial velocity leading to a targetted end point, after an imposed flight time of two seconds. This design case implies a RungeKutta time driver, embedded into a NonLinearSolver driver. For the latter, we request a parallel computation of the Jacobian matrix by forward finite differences, using three workers.

from cosapp.drivers import NonLinearSolver, RungeKutta
from cosapp.core.numerics.solve import FfdJacobianEvaluation
from cosapp.utils.execution import ExecutionPolicy, ExecutionType

# Set test case
point = Ballistics("point")
ncpus = 3  # compute the Jacobian matrix using 3 workers

solver = point.add_driver(
    NonLinearSolver(
        "solver",
        jac=FfdJacobianEvaluation(
            execution_policy=ExecutionPolicy(ncpus, ExecutionType.MULTI_PROCESSING)
        ),
    )
)
driver = solver.add_child(RungeKutta(time_interval=(0, 2), dt=0.1, order=3))

# Set design problem: compute initial velocity that leads to a target point
solver.add_unknown("v0").add_equation("x == [10, 0, 0]")

# Define a time simulation scenario
driver.set_scenario(
    init={"x": [0, 0, 0], "v": "v0"},
    values={"point.mass": 1.5, "point.k": 0.9},
)

# Set initial guess & solve
point.v0 = np.ones(3)
point.run_drivers()

Other new features & API changes

Implementation of second-order, implicit time driver CrankNicolson (MRs #377). This driver essentially works like a nonlinear solver, solving for both transient variables and intrinsic unknowns of the system of interest. Therefore, it is highly recommended for dynamic systems containing algebraic loops or intrinsic constraints, instead of nesting a nonlinear solver inside an explicit time driver.
Detect the occurrence of multiple primary events at the same time (MR #376).
Add the possibility to filter events with a Boolean expression evaluated in a specific context, other than that of the event owner (MR #375).
Add numpy.where and logspace to the scope of evaluable expressions, used in equations and boundary conditions, e.g. (MR #382).

Bug fixes and code improvements

Bug fix in EvalString serialization (MR #383).
Bug fix in the serialization of events (MR #386).
Bug fix in MonteCarlo with a time subdriver (MRs #378, #392).
Prevent name clashes for ports and sub-systems (MR #381).
Other bug fixes (MRs #379, #380, #389).

Documentation

Add Crank-Nicolson driver in time driver tutorial (MR #385).
New tutorial on multiprocessing (MR #391).

Dependency management

Compatibility with numpy 2, with retrocompatibility with version 1 (MRs #309, #387).
Compatibility with pytest 8.3 was restored (MR #388).
The code is no longer compatible with Python 3.8, as it now contains type hints of the kind list[str] or dict[str, float] (instead of typing.List and typing.Dict), introduced in Python 3.9.

0.19.2 (2025-01-23)

Bug fixes and code improvements

Improve the system transition mechanism (MR #370).
Fix bug in event cascade resolution (MRs #371 & #372).

Maintenance and code quality

Improve type hints (MR #369).

0.19.1 (2025-01-07)

Bug fixes and code quality

Fix dealiasing bug for custom objects (MR #362).
Fix bug in ExplicitTimeDriver.set_scenario (MR #363).
Fix bug with array transients (MR #364).
Suppress unnecessary exception in PeriodicEvent.tick (MR #366).
Improve the handling of timed events (MR #367).

0.19.0 (2024-12-04)

New features & API changes

Improve the performance of unknowns and residues (MRs #350, #352, by Gaétan Laurens). In particular, this version introduces the possiblity to declare as unknown any settable attribute of an input object (that is an object contained in an input port), which until now was only possible for input port variables. Example:

from cosapp.base import System
from cosapp.drivers import NonLinearSolver
from dataclasses import dataclass

@dataclass
class Foo:
  a: float
  x: float

class SomeSystem(System):
    def setup(self):
        self.add_inward("foo", Foo(a=1.0, x=1.0))
        self.add_outward("y", 0.0)

    def compute(self):
        self.y = self.foo.a - self.foo.x**3

system = SomeSystem("system")
solver = system.add_driver(NonLinearSolver("solver"))

solver.add_unknown("foo.x")   # attribute `x` can now be manipulated by the solver
solver.add_equation("y == 0")

system.foo.a = -2.0
system.run_drivers()

import pytest, math
assert system.foo.x == pytest.approx(math.cbrt(system.foo.a))

Fix bug in TwoPointCubicInterpolator with multidimensional arrays (MR #355).

Allow filtered events in merged events (MR #356):

system.event.trigger = Event.merge(
    event_a,
    event_b.filter("x > 0"),
)

Introduction of periodic events (MR #360):

from cosapp.multimode import PeriodicTrigger

system.event_a.trigger = PeriodicTrigger(period=2.3)
system.event_b.trigger = PeriodicTrigger(period=0.25, t0=0.33)

Documentation

Add instructions on how to perform benchmarks with asv_runner in main README file (MR #358).

Maintenance and code quality

Fix import error in JupyterLite (MR #351).
Minor code refactoring (MR #354).
Use public runners for all CI jobs (MR #359).

0.18.0 (2024-10-24)

New features & API changes

Improved data recording mechanism for NonLinearSolver, to facilitate convergence path analysis (MR #312).
New driver FixedPointSolver, solving algebraic loops by fixed-point iterations (MRs #315 & #322).
New method Driver.available_options, returning the list of options available for a particular driver (MR #316).
New method System.pull_design_method, to promote sub-system design methods at parent level easily (MR #314).
Bug fix in FMU exporter (MR #324).
Bug fixes in system transition logic (MR #338).
New method System.init_mode called before each time simulation, for mode initialization (MR #347).

Documentation

Fix bad rendering of tutorial notebooks on time simulations (MR #321).
Fix bad rendering of mermaid graph in logger documentation (MR #326).
Updated tutorial on advanced time simulations and on design methods (MR #343).
Add a section on FixedPointSolver in the driver tutorial (MR #346).

Maintenance and code quality

Improved type hints for drivers (MR #318).
Updated JupyterLite image (MR #313).
Add new test on swap_system (MR #342).
Various updates of CI/CD settings (MRs #317, #319 #320, #336, #337).
Various test improvements (MRs #340, #342).

0.17.0 (2024-06-18)

New features & API changes

A JupyterLite image including CoSApp is now available in the main README file (MR #300).
Fix a bug with primary event initialization (MR #293).

Improved API for partial connections: name mappings can now be given as lists mixing variable names and dictionaries, which is convenient when most variable names are identical, and only a few differ (MRs #294, #295 & #306). Example:

from cosapp.base import System

class SomeSystem(System):
    def setup(self):
        foo = self.add_child(Foo('foo'), pulling=['a', 'b', {'c': 'c_foo'}])
        bar = self.add_child(Bar('bar'))

        self.connect(foo, bar, ['x', 'y', {'z': 'v'}])

New utility function cosapp.tools.views.show_tree displaying the hierarchical tree of a system similar to a folder tree in a filesystem (MRs #296-#298).

Bug fixes and code quality

New attribute Residue.variables providing the names of the variables involved in the residue (MR #299).
Minor bug fix in Newton-Raphson algorithm (MR #303).
Fix bad markdown rendering of systems (MR #292).
Improved type hints throughout the code (MR #307).
Other improvements (MRs #291, #301, #302, #304, #305, #307, #308).

Maintenance

Pin dependency to numpy v1, until full migration to v2 (MR #310).

0.16.0 (2024-04-18)

Bug fixes and code quality

Primary events triggered within the same time step are now correctly captured (MR #287). A bug persists when several primary events occur at the exact same time, though, as only one will be retained.
Fix bug preventing events from occurring during the first time step of a simulation (MR #288).
Fix a bug causing recorders to crash when inspecting ports with properties (MR #282).
Algebraic and time-dependent problems are now dissociated (MR #284). As a consequence, invoking self.problem.clear() during transitions, for instance, no longer affects time-dependent unknowns such as transients.
Fix ambiguous warning message raised by RunSingleCase (MR #279).
Various refactoring passes (MRs #283 and #286).

Maintenance

Updated description inside the conda recipe (MR #276).
Pin pytest version due to a bug in version 8.1 (MR #280).
Add a "Citing" section in the main README file (MR #281).
The module parser was updated (MR #285).
Force sphinx < 7.3 in the documentation building environment, owing to an incompatibility with sphinx-mdinclude (MR #289). This is a temporary patch until root cause is fixed.

0.15.4 (2024-02-28)

Bug fixes and code quality

Fix bug raised in NonLinearSolver for systems with rates (MR #268).
Minor refactoring pass (MR #274).

Maintenance

Drop Python 3.8 support and add Python 3.11 test pipeline (MR #270).
Update installation and contribution guidelines (MR #270).
Update dependency list (MRs #269 and #270).

JOSS article

Publication of an article on CoSApp in the Journal of Open-Source Software, referenced to version 0.15.4 (MR #271).

0.15.3 (2023-12-19)

Bug fixes and code quality

Fix minor bug in NonLinearSolver (MR #261).
Fix incorrect return type hints in System (MR #259).
Improve support for read-only properties in system getters and setters (MR #264).

Maintenance

Remove deprecated dependency for compatibility with Python 3.12 (MR #258).
Force pythonfmu < 0.6.3 in dependency list, to prevent a crash during tests (MR #262). Temporary fix until root cause is identified.

0.15.2 (2023-10-14)

Bug fixes

Fix crash with VisJs rendering of sub-systems (MR #252).
Fix minor bug in EvalString (MR #253).
Fix bad synchronization of mode variables during transitions (MR #254).
Improve error message when pulling variables with different roles (MR #255).
Fix TypeError when passing pulling argument as a tuple in System.add_child (MR #256).

0.15.1 (2023-09-18)

New features & API changes

The representation of MathematicalProblem objects now indicates the number of unknowns and equations, for a better readability (MR #249).
Optional argument execution_index in System.add_child and Driver.add_child can now take a negative value, with a behaviour following that of list.insert (MR #250).

Bug fixes and code quality

Add missing field "time" in ExplicitTimeRecorder.event_data, when no recorder is set (MR #245).
Fix bug with recorders inspecting systems with iterators (MRs #246 and #247).
Fix bug with NonLinearSolver with NumPy array residues (MR #248).
Fix initialization bug of targets involving expressions (MR #249).

0.15.0 (2023-07-20)

New features & API changes

Suppression of default RunSingleCase subdriver runner in NonLinearSolver drivers (MR #239).
Enable target initialization in multi-point design problems (MR #233).
New utility function swap_system to replace on the fly a subsystem by another System instance (MR #238).

Bug fixes and code quality

Refactor driver Optimizer (MR #240).
Various bug fixes (MRs #234, #235, #241).

Documentation

New tutorial on swap_system (MR #243).
General update of tutorials (MRs #232 and #242).

0.14.1 (2023-06-08)

Bug fixes and code quality

Fix incorrect output file name in cosapp.tools.parse_module (MR #229).
Refactoring pass (MR #230).

Documentation

Upgrade documentation build stack (MRs #224 and #226).
Fix bad rendering of ports and systems (MRs #227 and #228).

0.14.0 (2023-05-17)

New features & API changes

Improved performance, through a revised clean/dirty mechanism (MR #215).

Possibility to add a contextual description to sub-systems and ports of a system, as well as sub-drivers (MR #216). This feature is useful for automatic documentation tools, and has been included in the Markdown representation of systems (also used in function cosapp.tools.display_doc). Example:

from cosapp.base import System
from my_module import FlowPort

class MySystem(System):
    def setup(self):
        self.add_input(FlowPort, "fl_in1", desc="Primary inlet flow port")
        self.add_input(FlowPort, "fl_in2", desc="Secondary inlet flow port")

        self.add_output(FlowPort, "fl_out")

New hook function _parse_module_config, returning pre-defined settings for cosapp.tools.parse_module (MR #218). This allows module maintainers to simply call

from cosapp.tools import parse_module
import my_module

parse_module(my_module)

instead of, e.g.,

parse_module(
    my_module,
    ctor_config={
        "ComplexSystem1": [
            dict(n=1, foo=0.5),
            dict(n=2, foo=0.1),
        ],
        "ComplexSystem2": [
            dict(xi=0.0, __alias__="ComplexSystem2_a"),
            dict(xi=1.0, __alias__="ComplexSystem2_b"),
        ],
    },
    excludes=["Foo*", "*Bar?"],
)

provided my_module._parse_module_config() returns a dictionary specifying the values of ctor_config, excludes, etc.

Make SolverResults a dataclass, for easier handling of NonLinearSolver.results, e.g. (MR #220).
Expose attribute problem in system setup (MR #221). Previously, problem was only exposed in method System.transition.

Bug fixes and code quality

Fix bug in NonLinearSolver log message (MR #214).
Add missing JSON file in PyPI and conda packages, preventing the use of cosapp.tools.parse_module (MR #219).

Documentation

Illustrate port and sub-system description in tutorials (MR #215).

0.13.1 (2023-04-03)

Bug fixes and code quality

Update test baseline to pass in a Python 3.11 environment (MR #200).
Creation of a dummy system factory, mostly for tests (MR #201).
Improve clean/dirty mechanism (MR #202) and fix incorrect clean/dirty status with surrogate models (MR #205).
Fix bug in function cosapp.tools.display_doc for classes with setup arguments (MR #208).
Various code quality improvements (MRs #211, #212).

Documentation

Note: extensive use of self-documenting f-strings (introduced in Python 3.8) has made tutorials incompatible with Python 3.7.

Updated tutorials (MRs #203, #206, #207, #210).
The image used in binder is now based on Python 3.10 (MR #204).

Module parser

New function parse_module in cosapp.tools collecting all system and port classes within a Python module. This parser, generating a JSON file containing the description of all CoSApp symbols, is primarily meant to be used for constructional GUI applications, developed separately (MRs #192 & #209).

0.13.0 (2023-02-09)

Python 3.10 support

The code is now tested for Python 3.8, 3.9 and 3.10. Support of Python 3.7 is thus officially dropped, although no version-specific Python code was introduced in this version of CoSApp.

New features & API changes

Module connectors moved from cosapp.core to cosapp.ports (MR #189).
New "direct" (with no unit conversion) connector classes PlainConnector, CopyConnector and DeepCopyConnector, in cosapp.ports.connectors (MR #188).
New method MathematicalProblem.is_empty(), equivalent to shape == (0, 0) (MR #186).
Improved VisJs graph rendering, by limiting node size for long system names (MR #184).

New utility functions get_state and set_state in cosapp.utils, for quick system data recovery (MR #193):

from cosapp.utils import get_state, set_state

s = SomeSystem('s')
# ... many design steps, say

# Save state in local object
designed = get_state(s)

s.drivers.clear()
s.add_driver(SomeDriver('driver'))

try:
    s.run_drivers()
except:
    # Recover previous state
    set_state(s, designed)

Functions radians, degrees and arctan2/atan2 have been added to the scope of EvalString objects, and can therefore be used in equations, e.g. (MR #178).
Recorders can now record constant properties (MR #181).
Deprecation of System.get_unsolved_problem in favour of new method assembled_problem (MR #174).

Inner off-design problem of systems is now exposed as attribute problem, but only within the transition method (MR #174). This allows users to add or remove off-design constraints during event-driven transitions, while keeping this property inaccessible the rest of the time.

from cosapp.base import System
from math import sin, cos

class SomeSystem(System):
    def setup(self):
        self.add_inward('x', 0.0)
        self.add_inward('y', 0.0)
        self.add_outward('z', 0.0)
        a = self.add_event('event_a', trigger='x > y')
        b = self.add_event('event_b', trigger='x < y')
    
    def compute(self):
        self.z = cos(self.x) * sin(self.y)

    def transition(self):
        offdesign = self.problem
        if self.event_a.present:
            offdesign.clear()
            offdesign.add_equation('z == 0.5').add_unknown('x')
        if self.event_b.present:
            offdesign.clear()

Bug fixes and code quality

Fix serialization bugs for systems with setup parameters (MR #180) and None variables (MR #172).
Bug fix on event time calculation involving array transients (MR #177).
Bug fix on possible name conflicts in connector storage (MR #173).
Fix inconsistent behaviour of System.add_child when a pulling error is raised (MR #197).
Various code quality improvements (MRs #175, #185, #186, #187, #190, #191, #194).

Documentation

Updated time driver tutorial (MR #182).
Updated Tips & Tricks (MR #196).
Other updates (MRs #176, #195, #198).

0.12.3 (2022-09-21)

New features & API changes

Improved user experience:
- Auto-completion for dynamically added attributes of systems (ports, subsystems, inwards, outwards, events...) and drivers (sub-drivers) (MRs #164 and #166);
- Improved representation of mathematical problems, in particular for loop equations and multi-point design problems (MRs #159, #160 and #163).
New method System.new_problem to facilitate the creation of dynamic design methods, e.g. (MR #162).

Documentation

Updated tutorials (MRs #169 and #170).

Bug fixes and code quality

Bug fix on unknown dealiasing (MR #157).
Bug fix on port variable export (MR #158).
Bug fix on system serialization (MR #161).
Bug fix on subsystem read-only constants (MR #167).
Various code quality improvements (MRs #154, #155, #162, #168).

0.12.2 (2022-05-26)

New features & API changes

Automatic tolerance in NonLinearSolver (MRs #148 and #152).
Optimizer.set_objective is deprecated, in favour of set_minimum and set_maximum (MR #150).
Loop residues are no longer normalized (MR #151).
Improved type hints for ports, systems and drivers, in functions whose return type depends on arguments, such as System.add_child, add_driver, etc. (MR #145).

Documentation

Updated tutorials (MRs #144, #147 and #154).

Bug fixes and code quality

Fix inconsistent behaviour of recorders (MR #143).
Fix bug on event initialization (MR #146).
Fix bad markdown formatting of ports occurring in jupyterlab 3.4 (MR #149).
Fix failed test caused by a regression in pytest 7.1 (MR #142).

0.12.1 (2022-02-25)

New features & API changes

Simplification of driver Optimizer:

Suppression of sub-driver runner (MR #136). This change introduces new methods set_objective, add_unknowns and add_constraints in driver Optimizer.
Optimization constraints are now declared with human-readable expressions in Optimizer.add_constraints (MR #138).

Before:

from cosapp.drivers import Optimizer

s = SomeSystem('s')
optim = s.add_driver(Optimizer('optim'))

optim.runner.set_objective('cost')
optim.runner.add_unknown(['a', 'b', 'p_in.x'])
# Enter constraints as non-negative expressions:
optim.runner.add_constraints([
    "b - a",  # b >= a
    "a",      # a >= 0
    "1 - a",  # a <= 1
])
optim.runner.add_constraints(
    "p_out.y",
    inequality = False,  # p_out.y == 0
)

s.run_drivers()

After:

optim.set_objective('cost')
optim.add_unknown(['a', 'b', 'p_in.x'])
optim.add_constraints(
    "b >= a",
    "0 <= a <= 1",
    "p_out.y == 0",
)

New, convenient iterators and setters for ports (MR #137):

from cosapp.base import Port, System

class XyzPort(Port):
    def setup(self):
        self.add_variable('x')
        self.add_variable('y')
        self.add_variable('z')

class SomeSystem(System):
    def setup(self):
        self.add_input(XyzPort, 'p_in')
        self.add_output(XyzPort, 'p_out')
    
    def compute(self):
        self.p_out.set_from(self.p_in)  # assign values from `p_in`
        self.p_out.z = 0.0

s = SomeSystem('s')
# Multi-variable setter `set_values`
s.p_in.set_values(x=1, y=-0.5, z=0.1)

s.run_once()
# Dict-like (key, value) iterator `items`:
for varname, value in s.p_out.items():
    print(f"p_out.{varname} = {value})

Documentation

Updated tutorials on ports (MR #139) and on optimization (MR #140).

Bug fixes and code quality

Fix bug in Jacobian computation for negative perturbations (MR #129).
Fix bug in RunOnce and RunSingleCase recorders with hold=False (MR #130).
Resolve input aliasing in time driver scenarios (MR #135).
Fix bugs with events (MRs #123, #126, #128).
Discard empty connectors, and send a warning (MR #132).
Other code quality improvements (MRs #127, #131, #133, #134).

0.12.0 (2022-01-17)

New features

Implementation of multimode systems and hybrid continuous/discrete time solver (MRs #100, #103, #105-#108, #110-#121):
- Possibility to declare events and mode variables in systems.
- New method System.transition describing system transition upon the occurrence of events.
- Event detection in ExplicitTimeDriver.
Possibility to specify a stop criterion in time simulation scenarios (MR #107).

Documentation

New tutorial on hybrid time simulations and multimode systems (MRs #116 and #120).
Updated build config file following up a bug fix in github.com/readthedocs (MR #109).

0.11.8 (2021-11-24)

New features & API evolutions

New module cosapp.base (MR #96) containing base classes for user-defined classes (in particular, Port, System and Driver). Also contains BaseConnector, base class for custom connectors (see "User-defined and peer-to-peer connectors" below), as well as CoSApp-specific exceptions ScopeError, UnitError and ConnectorError. Note: Port, System and Driver can still be imported from cosapp.ports, cosapp.systems and cosapp.drivers, respectively.
Public API cosapp.base.SurrogateModel to define custom surrogate models used in System.make_surrogate (MR #97). Pre-defined models have been moved to module cosapp.utils.surrogate_models.
System-to-system connections (MR #94).

class LegacyPortToPort(System):
    def setup(self):
        a = self.add_child(ModelA('a'))
        b = self.add_child(ModelB('b'))

        # Explicit port-to-port connections
        self.connect(a.p_in, b.p_out)
        self.connect(a.outwards, b.inwards, {'y': 'x'})

class Alternative(System):
  """Same as `LegacyPortToPort`, with alternative connection syntax"""
    def setup(self):
        a = self.add_child(ModelA('a'))
        b = self.add_child(ModelB('b'))

        # Alternative syntax: connect systems, with port or variable mapping
        self.connect(a, b, {'p_in': 'p_out', 'y': 'x'})

User-defined and peer-to-peer connectors (MR #87 and MR #98).

import numpy
from copy import deepcopy
from cosapp.base import Port, System, BaseConnector

class DeepCopyConnector(BaseConnector):
  """User-defined deep-copy connector"""
    def transfer(self) -> None:
        source, sink = self.source, self.sink

        for target, origin in self.mapping.items():
            value = getattr(source, origin)
            setattr(sink, target, deepcopy(value))

class CustomPort(Port):
    def setup(self):
        self.add_variable('x', 0.0)
        self.add_variable('y', 1.0)

    class Connector(BaseConnector):
      """Connector for peer-to-peer connections"""
        def transfer(self) -> None:
            source, sink = self.source, self.sink
            sink.x = source.y
            sink.y = -source.x

class MyModel(System):
    def setup(self):
        self.add_input(CustomPort, 'p_in')
        self.add_output(CustomPort, 'p_out')

        self.add_inward('entry', numpy.identity(3))
        self.add_outward('exit', numpy.zeros_like(self.entry))

class Assembly(System):
    def setup(self):
        a = self.add_child(MyModel('a'))
        b = self.add_child(MyModel('b'))

        self.connect(a, b, {'exit', 'entry'}, cls=DeepCopyConnector)
        self.connect(a.p_in, b.p_out)  # will use CustomPort.Connector

Documentation

Updated tutorials (MR #102).
- Include latest API evolutions in tutorials on ports and systems.
- New tutorial on user-defined connectors.
- New section on user-defined surrogate models.

Bug fixes and code quality

Simplify loop resolution (MR #77, #101).
Improve connector transfer (MR #99).
Update binder settings, to take advantage of prebuilt plotly extension for jupyter lab (MR #95).
Other code quality improvements (MR #76, #82, #90).

0.11.7 (2021-09-21)

New features

Possibility to define unknowns and equations at solver level (MR #65). Minor API evolution facilitating the definition of nonlinear problems and of multi-point design problems.

engine = Turbofan('engine')
solver = engine.add_driver(NonLinearSolver('solver'))

# Add design points:
takeoff = solver.add_child(RunSingleCase('takeoff'))
cruise = solver.add_child(RunSingleCase('cruise'))

# Unknowns defined at solver level regarded as *design* unknowns
solver.add_unknown(['fan.diameter', 'core.turbine.inlet.area'])

# Local off-design equations can be directly defined at case level
takeoff.add_equation('thrust == 1.2e5')
cruise.add_equation('Mach == 0.8')

New recursive iterator tree() for systems and drivers, yielding all elements in a composite tree (MR #68).

head = CompositeSystem('head')

bottom_to_top = [s.name for s in head.tree()]
top_to_bottom = [s.name for s in head.tree(downwards=True)]

Visitor pattern for composite collections of systems, drivers and ports (MR #68).

from cosapp.patterns.visitor import Visitor, send as send_visitor

class DataCollector(Visitor):
    def __init__(self):
        self.data = {}

    def visit_system(self, system):
        key = system.full_name()
        self.data.setdefault(key, {})
        self.data[key]['children'] = [
            child.name for child in system.children.values()
        ]
        send_visitor(self, system.inputs.values())

    def visit_port(self, port):
        # specify what to do with a port

    def visit_driver(self, driver):
        # specify what to do with a driver

head = CompositeSystem('head')
collector = DataCollector()

send_visitor(collector, head.tree())
print(collector.data)

Documentation

New tutorials, and new "Tips & Tricks" notebook (MR #71).

Bug fixes and code quality

Improved tests on clean/dirty status (MR #66).
Bug fix in tutorial notebook on validation (MR #67).
Code quality improvements (MR #69).
Make System.exec_order a view on System.children dictionary keys, rather than an independent attribute (MR #70). Execution order can still be specified, via a dedicated setter for exec_order.
Fix solver bugs occurring when system structure changes (MR #73).

0.11.6 (2021-06-25)

Bug fixes and code quality

Resolve unknown aliasing for pulled input variables (MR #58).
Resolve bugs and issues related to add_target (MR #61).
Fix wrong comparison of Jacobian matrix jac is None after converting it as a numpy array (MR #56).
Set transparent background in PortMarkdownFormatter (MR #59).
Other code quality improvements (MR #55, #57, #60).

0.11.5 (2021-05-07)

New features

New binder container, allowing anyone to run interactively the tutorials used in the online documentation (MR #30 and #36).
Deferred equations to set targets:

New method add_target, defining a deferred equation on on a target variable (MR #48). In effect, add_target creates an equation whose right-hand side is evaluated dynamically prior to each execution of the nonlienar solver.

In the example below, the feature is illustrated in design mode. Outward z is a function of two independent variables x and y. When design method 'target_z' is activated, the actual value of z, set interactively, is used as a target value, with unknown y:

class SystemWithTarget(System):
    def setup(self):
        self.add_inward('x', 1.0)
        self.add_inward('y', 1.0)
        self.add_outward('z', 1.0)

        # Define design problem with a target on `z`
        design = self.add_design_method('target_z')
        design.add_unknown('y').add_target('z')

    def compute(self):
        self.z = self.x * self.y**2

s = SystemWithTarget('s')

solver = s.add_driver(NonLinearSolver('solver', tol=1e-9))
# Activate design method 'target_z': outward `z` becomes a target
solver.runner.design.extend(s.design_methods['target_z'])

s.x = 0.5
s.y = 0.5
s.z = 2.0  # set target
s.run_drivers()
assert s.y == pytest.approx(2)  # solution of x * y**2 == 2
assert s.z == pytest.approx(2)

s.z = 4.0  # dynamically set new target
s.run_drivers()
assert s.y == pytest.approx(np.sqrt(8))  # solution of x * y**2 == 4
assert s.z == pytest.approx(4)

Targets can be also be declared in off-design mode, by calling self.add_target(...) in System.setup.

Documentation

Updated tutorials on System, Driver, and design methods (MR #41).
Typo fix and improvements in time driver tutorial (MR #33)

Bug fixes, minor improvements and code quality

Report variable name in unit-related Connector warning message (MR #32).
Automatically include field time in DataFrame recorders attached to a time driver (MR #34).
Bug fix in MonteCarlo driver (MR #37).
Replace conda by mamba in CI scripts (MR #39).
Revamp markdown and JS rendering of systems and ports (MR #40 and #43, #47 and #51).
Fix bug in rate type inference (MR #44).
Other code quality improvement (MR #35, #38, #42, #46, #50, #52, #53).

0.11.4 (2021-03-08)

New features

Recorders: It is now possible to add evaluable expressions in recorders (MR #27):

point = PointMass('point')
driver = point.add_driver(RungeKutta(order=3, time_interval=(0, 2), dt=0.01))

recorder = driver.add_recorder(recorders.DataFrameRecorder(
    includes=['x', 'a', 'norm(v)']),  # norm(v) will be recorded in DataFrame
    period=0.1,
)

Documentation

New tutorial on SystemSurrogate (MR #15).

Bug fixes, minor improvements and code quality

Initialization bug in time simulations (MR #23).
Bug in nonlinearity estimation in NumericalSolver (MR #22).
Do not raise ArithmeticError when an unknown is declared several time (MR #18).
Suppress deprecation warnings raised by numpy (MR #20 and #24).
Suppress undue warning raised by numpy in NonLinearSolver (MR #19).
Fix incompatibility between pandas and xlrd (MR #21).
Other code quality improvement (MR #16, #17, #26, #27).

0.11.3 (2020-12-16)

New features

Surrogate models: It is now possible to create a surrogate model at any system level with new method System.make_surrogate (MR #3 and #12):

plane = Aeroplane('plane')  # system with subsystems engine1 and engine2

# Say engine systems have one input parameter `fuel_rate`
# and possibly several outputs, and many sub-systems

# Create training schedule for input data
doe = pandas.DataFrame(
    # loads of input data
    columns=['fuel_rate', 'fan.diameter', ..]  # input names
)
plane.engine1.make_surrogate(doe)  # generates output data and train model

plane.run_once()  # executes the surrogate model of `engine1` instead of original compute()

# dump model to file
plane.engine1.dump_surrogate('engine.bin')
# load model into `engine2`:
plane.engine2.load_surrogate('engine.bin')

# deactivate surrogate model on demand
plane.engine1.active_surrogate = plane.engine2.active_surrogate = False

Bug fixes, minor improvements and code quality

Add several US-common unit conversions (MR #2).
New method to export cosapp system structure into a dictionary (MR #5)
Make recorders capture port and system properties (MR #8).
Fix Module/System naming bug: 'inwards' and 'outwards' are allowed as Module/System names (MR #9).
Broad code quality improvement (MR #11).
- Replace typing.NoReturn by None when appropriate.
- Rewording pass, typo and error fixes in tutorial notebooks.
- Suppress a DeprecationWarning raised by numpy in class Variable.
- Reformat many strings as Python f-strings, for clarity.
- Symplify many occurrences of str.join() for just two elements.

Global rewording of tutorial notebooks, including a few error fixes.

0.11.2 (2020-09-28)

First open-source version. No major code change; mostly updates of license files, URLs in docs, and CI scripts.

0.11.1 (2020-07-22)

Features

Add the possibility to set boundary condition of transient simulation from interpolate profile.
Add the possibility to prescribe a maximum step for transient variables.

Bugs and code quality

Bug fix in RunOnce driver, preventing undue call to run_once method.
Bug fix in AssignString: force copy for numpy arrays.
New tutorial for advanced features of time simulations in CosApp.

0.11.0 (2020-05-12)

Features

Improve documentation at various places, add documentation about the cosapp packages structure and sequence diagram for transient simulation.
Add a advanced logger feature for CoSApp simulations.
Update FMU export to PythonFMU 0.6.0
New method System.add_property allowing users to create read-only properties.

Bugs and code quality

Suppress deprecation warnings raised by external dependencies.
Fix bug in AssignString with arrays, AssignString of the kind 'x = [0, 1, 2]' won't change variable x into an array of integers, if x is declared as an array of floats.
Fix TimeStackUnknown not able to stack transient variables defined on a children System or with partially pulled transient variable.
Fix the bug related to the initialization of rate attributes in systems.

0.10.2 (2020-04-21)

Features

[BETA] Export CoSApp System as FMU

Bugs and code quality

Apply Broyden correction on Jacobian matrix for iteration without Jacobian update
Support varying time step
Fix time not being set before setup_run are called.
Fix reference for residues in IterativeConnector (it equals 1. now)
Drop pyhamcrest for pytest

0.10.1 (2020-01-15)

Features

Time varying boundary conditions are now possible:

system = MySystem('something')  # system with transient variables x and v
driver = system.add_driver(RungeKutta(time_interval=(0, 2), dt=0.01, order=3))

driver.set_scenario(
    init = {'x': 0.5, 'v': 0},  # initial conditions
    values =
    {
        'omega': 0.7,
        'F_ext': '0.6 * cos(omega * t)'  # explicit time-dependency
    }
)

Bugs and code quality

Fix various bug on the transient simulation front
Correct implementation of step limitation in the Newton-Raphson solver
Using a logger at DEBUG level will now display the call stack through the systems and drivers
Rework of the Python evaluable string to be more efficient

0.10.0 (2019-10-23)

Introduce continuous time simulations with dedicated time drivers (see TimeDriver notebook in tutorials).
Suppress notion of (un)freeze; all variables are considered as known, unless explicitly declared as unknowns.
Drivers no longer use ports.
Connectors are now stored by parent system.
Migrate to pytest.

API Changes

Ports:
- add_variable("x", units="m", types=Number) => add_variable("x", unit="m", dtype=Number)
- freeze => removed
- unfreeze => replaced by add_unknown in Systems and Drivers
- connect_to => replaced by connect at system level
Systems:
- time_ref is no longer an argument of method compute:
  
  def compute(self, time_ref): => def compute(self):
- Create a new connection between a.in1 and b.out:
  
  self.a.in1.connect_to(self.b.out) => self.connect(self.a.in1, self.b.out)
- add_residues => add_equation
- set_numerical_default => Pass keyword to add_unknown
- add_inward("x", units="m", types=Number) => add_inward("x", unit="m", dtype=Number)
- add_outward("x", units="m", types=Number) => add_outward("x", unit="m", dtype=Number)
Drivers:
- add_unknowns(maximal_absolute_step, maximal_relative_step, low_bound, high_bound) => add_unknown(max_abs_step, max_rel_step, lower_bound, upper_bound)
- add_equations => add_equation
- Equations are now represented by a unique string, instead of two strings (left-hand-side, right-hand-side):
  
  add_equations("a", "b") => add_equation("a == b")
  
  add_equations([("x", "2 * y + 1"), ("a", "b")]) => add_equation(["x == 2 * y + 1", "a == b"])
- For NonLinearSolver:
  
  fatol and xtol => tol
  
  maxiter => max_iter
- For Optimizer:
  
  ftol => tol
  
  maxiter => max_iter

0.9.6 (2019-10-10)

More correction for VISjs viewer and System HTML representation

0.9.5 (2019-09-25)

Correct D3 & VISjs Viewers

0.9.4 (2019-09-25)

Introduce an optional environment variable COSAPP_CONFIG_DIR

0.9.3 (2019-07-25)

API Changes

MonteCarlo:
- Montecarlo => MonteCarlo
- Montecarlo.add_input_vars => MonteCarlo.add_random_variable
- Montecarlo.add_response_vars => MonteCarlo.add_response
MonteCarlo has been improved by using Sobol random generator
Viewers code on System is moved in a subpackage of cosapp.tools
Residue reference is now calculated only once
Various bug fix

0.9.2 (2019-07-01)

In nonlinear solver, store LU factorization of the Jacobian matrix, rather than its inverse.
Minor refactoring of the core source code, with no API changes

0.9.1 (2019-04-23)

Create Variable class to manage variable attributes
watchdog is now optional
Configuration is now inside a folder $HOME/.cosapp.d
API changes:
- get_latest_solution => save_solution
- load_solver_solution => load_solution
Various bug fix

0.9.0 (2019-03-04)

This release introduces lots of API changes:

Core ports and unit are available in cosapp.ports
Core systems are available in cosapp.systems
Core drivers are available in cosapp.drivers
Core recorders are available in cosapp.recorders
Core tools are available in cosapp.tools
Core notebook tools are available in cosapp.notebook (! this is now a separated package)
data have been renamed in inwards and add_data in add_inward
locals have been renamed in outwards and add_locals in add_outward
BaseRecorder.record_iteration renamed in BaseRecorder.record_state

Huge code refractoring: cosapp is now a Python namespace.
cosapp.notebook has been moved to an independent package cosapp_notebook. But it is still accessible from cosapp.notebook.
Introduce Signal / Slot pattern to connect to internal event (implementation from signalslot, included in cosapp.core.signal)
- Module.setup_ran: Signal emitted after the call_setup_run execution
- Module.computed: Signal emitted after the full compute stack (i.e.: _postcompute)
- Module.clean_ran: Signal emitted after the call_clean_run execution
- BaseRecorder.state_recorded: Signale emitted after the record_state execution

0.8.0 (2018-10-26)

Add Jacobian partial matrix update
Add numerical features to variables to ease convergence control
Add monitoring of solver residues
Add restoration of solver result for initialization
Rework residues and unknowns handling (remove virtual port and pulling port)
Rework optimizer to be more homogeneous with non-linear solver
Improve linear Monte Carlo computation time
Improve data viewer for non-linear solver
Create viewer for Monte Carlo
Add dropdown widget for enum variables

0.7.0 (2018-09-17)

Add helper functions to present solver evolutions
Add new d3 visualization of systems

0.6.0 (2018-08-14)

Implement clean-dirty policy
Restore compatibility with Python 3.4
Display influence matrix

0.5.0 (2018-07-20)

Simplify drivers structure, all actions for a case are supported by a single class RunSingleCase
Add support for vector variables; they can be partially (un)frozen and are handled correctly by the solver.
Add MonteCarlo driver
Add recording data capability

0.4.0 (2018-06-15)

System and Driver have now a common ancestor Module => Driver variables are now stored as data or locals
Add visualization of System connections based on N2 graph (syntax: cosapp.viewmodel(mySystem))

0.3.0 (2018-04-05)

API changes: System.add_driver and Driver.add_child take now an instance of Driver

Add external code caller System
Add validation range attributes on variables
Add variable visibility
Add metamodel training and DoE generator
Add helper function to list inputs and outputs variables of a System

0.2.0 (2018-03-01)

Stabilization of the user API

0.1.0 (2018-01-02)

First release.

Keywords

cosapp

system simulation

system design

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