===============

Pyomo CHANGELOG

===============

-------------------------------------------------------------------------------

Pyomo 5.0.1

-------------------------------------------------------------------------------

- Updating PyUtilib dependency

-------------------------------------------------------------------------------

Pyomo 5.0

-------------------------------------------------------------------------------

- Added examples used in the Pyomo book to the Pyomo software repos

- Added support for automatically generating "template expressions"

- Fix tuple flattening in the case of unhashable SimpleParam in indexes

- Deactivated solver plugins before the are returned from the SolverFactory

- Significantly simplified the polynomial_degree() logic for Pyomo4 expressions

- Updates to expression logic

- Adding a 'feasible' attribute to the TerminationCondition Enum

- Updates to ExternalFunction logic

- Renamed the component name() method to getname() and added a 'name' property

- Fix to allow creating undefined (and uninitialized) mutable params

- Added more careful checks in Set() and Param() to ensure that an abstract set

expression is not evaluated

- Added DAE examples to Pyomo

-------------------------------------------------------------------------------

Pyomo 4.4.1

-------------------------------------------------------------------------------

- Fixing PyUtilib dependency version.

-------------------------------------------------------------------------------

Pyomo 4.4

-------------------------------------------------------------------------------

- Output a warning in benders when the solver interface used to solve the

master problem does not report a solution gap

- Document DAE transformations (#28)

- Allow use of ellipsis in the middle of the indices when slicing

- The Component slicing logic now uses simple slices (`:`) for matching a

single index and the Ellipsis (`...`) for matching zero or more indices.

- Fixing Python 3 compatibility problems in pyomo.dae & dae examples.

- Support evaluating external functions in AMPL-stype shared libraries.

- Renaming "BasicExternalFunction" to "AMPLExternalFunction"

- Allowing Params to be used in setting bounds on a ContinuousSet.

- Use HTTPS with NEOS

- Allow a mutable Parameter that has not been initialized with a value to

be used in the rhs of an equality constraint. (#13)

- Updates to SolverFactor to better support functionality offered by the

'executable' keyword for SystemCallSolver.

- Updates to writers to enforce consistent output ordering in quadratic

expressions.

- Improving the error message for Constraint rules that return None

- Adding PySP solver interface to the SD solver

- Adding an implicit SP representation to PySP that uses annotations

for declaring mutable parameters as stochastic data and providing

a distribution (only tables supported for now).

- Partial fix for infinite recursion reported (#6). This will support

creating scalar (simple) components by passing a set([None]) in

as the index.

- Extending component slicing ability to nested (hierarchical) slices.

-------------------------------------------------------------------------------

Pyomo 4.3 (4.3.11381)

-------------------------------------------------------------------------------

- Removed 'nose' from required packages during installation.

- Fix to be compatible with older versions of 'six'.

-------------------------------------------------------------------------------

Pyomo 4.3 (4.3.11377)

-------------------------------------------------------------------------------

- Restructured PySP tests to hide expected exception output

- Updated pyomo_install to support jython (experimental)

- Fixed a missing reference to 'six'

- More robust management of file I/O in GLPK interface

-------------------------------------------------------------------------------

Pyomo 4.3 (4.3.11345)

-------------------------------------------------------------------------------

- Various fixes to the NEOS solver plugin and to the SOL parser for

certain NEOS solvers.

- Fixed a bug that caused an exception to occur when dynamically adding blocks

to a ConcreteModel.

- Miscellaneous fixes to PySP scripting examples.

-------------------------------------------------------------------------------

Pyomo 4.3 (4.3.11328)

-------------------------------------------------------------------------------

- Misc bug fix

-------------------------------------------------------------------------------

Pyomo 4.3 (4.3.11327)

-------------------------------------------------------------------------------

- Resolved bug in pyomo_install when pyvenv cannot be found.

- Gracefully trap BARON terminations

-------------------------------------------------------------------------------

Pyomo 4.3 (4.3.11323)

-------------------------------------------------------------------------------

- Scripts

- pyomo_install

- Added --pip-options to specify options for PIP option

- Added --index-url to specify the PyPI mirror

- Restructured this script to make it more modular

- Deprecated the --with-extras option

- Added "--venv-only" option for setting up a local python virtual

environment with no additional packages (apart from pip, setuptools, and

potentially wheel).

- Fixes when installing from zip files offline.

- get-pyomo-extras.py

- Misc fixes and updates

- pyomo

- Consolidated help information within the 'pyomo help' subcommand

- Added 'pyomo install-extras' to install third-party dependencies

- pyomo.bilevel

- Major changes to get the bilevel_ld solver working

- Extended the logic in SubModel to allow for implicit declarations of

upper-level variables.

- pyomo.check

- More complete scoping checks

- pyomo.core

- Changes to allow sorted output using DataPortal objects

- Bug fix in linear dualization transformation

- Adding a mechanism to load default configuration information from a

standard location.

- Changes to allow objectives to be used inside expressions, and to

allow objectives to be sent through the solver plugins

- Updating blocks so that models can be created and populated using rule options

- Added a domain property method to IndexedVar so it cannot be treated as having

a single domain

- Added the Var() 'dense' option. This defaults to True, which defines variables

densely. But sparse variables are defined when dense==False.

- Change to define a SOS constraint over the declared index set for a variable

unless an explicit index set is provided.

- Changes to ensure that most components do not define their data densely.

- pyomo.dae

- Updates to support Python3 and current Pyomo Transformation API

- Fixed the collocation extension to reduce the degrees of freedom for certain variables

- pyomo.gdp

- Many fixes to bilinear transformation

- Fixed the Big-M estimation routine to work with constant expressions

- pyomo.neos

- Added support for ephemeral solver options, which over-ride the

options dictionary

- Fixes to enable loading of solutions from NEOS solvers

- pyomo.opt

- Sort variable names when printing results

- Many fixes to sol reader.

- pyomo.pysp

- Updates to ScenarioStructure.dat to handle a larger

class of models that can have non-uniform variable sets

in later time stages. Also updating parsing rules to

allow for more convenient variable declarations

- NodeVariables / NodeDerivedVariables can be used in

place of StageVariables / StageDerivedVariables to

declare variables on a per-node basis

- Indexed variables can be declared without bracket

notation (e.g., x[*,*] -> x)

- Single or indexed block names can be used to

conveniently declare all variables found on that

block within a node or stage

- Re-write of runef and runbenders based off of new PySP

scripting tools

- Adding option to runbenders for including one or more

scenarios in the master benders problem

- Fixes to csvsolutionwriter so that it works with

distributed PH

- Added new script (evaluate_xhat) that allows users to

evaluate SP solutions on alternate scenario trees.

- Added more extensive checking to PySP->SMPS conversion

utility (pysp2smps) to alert users when conversion fails

due to non-uniform problem structure or missing

stochastic annotations

- Added helper routine to convert a networkx directed

graph into a PySP scenario tree model

- Fixes to PH for better handling of user warmstarts

- pyomo.repn

- Updates to the NL writer to handle new expression types.

- Added an MPS writer

- pyomo.scripting

- Updated the Pyro mip server to improve its efficiency

- pyomo.solvers

- Updates to xpress plugin to use the ASL interface to xpress.

- Fixed a major issue with the gap computation in the CPLEX direct/persistent

solver plugins

- Significant speed-up of the the CPLEX persistent plugin.

- Added the 'mps' mode for various solvers.

- Changes to the Pyro solver manager to allow out-of-order results collection

-------------------------------------------------------------------------------

Pyomo 4.2 (4.2.10784)

-------------------------------------------------------------------------------

- Changes to make the --json command-line option backwards compatible.

-------------------------------------------------------------------------------

Pyomo 4.2 (4.2.10782)

-------------------------------------------------------------------------------

- pyomo.core

- Removed the 'initial' attribute from Var components.

- Removed the 'reset()' method from core components.

- Objective components now store sense for each objective.

- Added support for slicing when indexing a component.

- pyomo.dae

- Added methods to set and test the value of integral expressions

- pyomo.gdp

- Added property methods to access disjunction expressions (e.g. lower, upper)

- pyomo.opt

- Added support for ephemeral solver options that override the default

values set in the solver object.

- pyomo.neos

- Bug fixes to get data after calling NEOS

- Resolving issues with python 3

- pyomo.scripting

- Added --pyro-host and --pyro-port options

- Added shutdown capabilities to pyro solver manager

- Collect solve time for pyro solvers

- pyomo.pysp

- Added --pyro-host and --pyro-port options to manage pyro-based execution

in a more robust manner.

- Adding utility for converting PySP models into SMPS input files (pysp2smps).

- pyomo.solver

- Resolved serious issues with python direct interfaces:

- CPLEX: constants in linear range constraints and all quadratic

constraints were being excluded from the expression.

- CPLEX and GUROBI: actually raise an exception when a nonlinear

(non-quadratic) objective or constraint expression is encountered

rather than just emitting the linear and quadratic part of the

expression to the solver. This could lead to a naive user

thinking they have solved a general nonlinear model with these

solvers.

- CPLEX and GUROBI: do not skip trivial constraints by default.

Adding I/O option 'skip_trivial_constraints' to recover this

behavior.

- CPLEX: Merging as much of CPLEXPersistent with CPLEXDirect

as possible to avoid repeating bug fixes. More should be done,

but for now CPLEXDirect is a base class for CPLEXPersistent.

- Fix to various solver plugins so that variable bounds set to

float('inf') and float('-inf') are treated the same as variable

bounds set to None.

- Updates to Pyro solver managers

- Major performance enhancements for Pyro-based solver managers.

- Tasks can be uploaded to the dispatcher in bulk.

- Workers no longer use a timeout when requesting tasks from the queue, which

was wasting CPU cycles.

- Compatibility fixes when Pyro4 is used.

- other

- Updated the get-pyomo-extras.py script to install conditional dependencies

for Pyomo (e.g. xlrd and ipython)

- Adding logic to explicitly identify metasolvers. This information is

reflected in the 'pyomo help -s' command.

- Deprecated 'pyomo.os', which was not being actively supported.

- Added the 'pyomo info' subcommand to provide information about the Python

installation.

-------------------------------------------------------------------------------

Pyomo 4.1 (4.1.10519)

-------------------------------------------------------------------------------

- Resolving bugs in NEOS solver interface due to change in solver options

management.

-------------------------------------------------------------------------------

Pyomo 4.1 (4.1.10509)

-------------------------------------------------------------------------------

- Cleanup runbenders script to make it easier to test

- Cleanup temporary files during testing.

- Fixing PyUtilib version

-------------------------------------------------------------------------------

Pyomo 4.1 (4.1.10505)

-------------------------------------------------------------------------------

- Allow the dim() method to be called without the equality operator, which

enables its use on unconstructed components

- RangeSet inherits from OrderedSimpleSet

- Added missing __slots__ declarations in set classes

-------------------------------------------------------------------------------

Pyomo 4.1 (4.1.10486)

-------------------------------------------------------------------------------

- API changes for model transformations

- Revised API for SOSConstraint, Suffix and Block components

- Optimization results are now loaded into models

- Removed explicit specification of model preprocessing

- Resolved many issues with writing and solving MPECs

- Changes to MPEC meta-solver names

- The solution output for runph has been changed to

- Pyomo subcommands can now use configuration files (e.g. pyomo solve config.json)

- New JSON/YAML format for parameter data

- Added a script to install pyomo.extras

-------------------------------------------------------------------------------

Pyomo 4.0 (4.0.9682)

-------------------------------------------------------------------------------

- Adding a more useful error message when a named objective is not

present when load-solution is invoked on a model.

- Bug fix for pickling results objects.

- Performance fix for ordered sets

- Removed StateVar from DAE examples.

- Resolving a bug that disabled pyodbc support.

- Added preliminary support for pypyodbc.

- Fix to enable sets to be initialized with a tuple

- PySP test baseline updates

- Added PySP ddsip extension.

- Removed the 'pyomo bilevel' and 'pyomo mpec' subcommands

- Re-enabled the 'import' and 'export' Pyomo data commands, which

are still deprecated.

- Various performance enhancements to avoid iterating over list of

dictionary keys.

- Added a ComplementarityList component.

-------------------------------------------------------------------------------

Pyomo 4.0 (4.0.9629)

-------------------------------------------------------------------------------

This release rebrands Coopr as Pyomo, which reflects the fact that

users have consistently confused the Coopr software and the Pyomo

modeling language. Pyomo 4.0 includes the following significant

changes:

- Pyomo provides a single source tree replacing all Coopr packages

- The 'pyomo' command replaces the 'coopr' command

- The 'pyomo solve' subcommand replaces the former 'pyomo' command

- The 'pyomo.environ' package is now used to import core Pyomo capabilities

- Robust support for Python 3.x

The following are highlights of this release:

- Modeling

* Added a RealInterval domain

* Major rework of coopr.dae. Can now represent higher order and partial

differential equations. Also added more discretization schemes.

- Solvers

* Added preliminary support for a Benders solver

* Added support for the BARON solver

* Preliminary support for MPEC solvers, including the PATH solver

- Transformations

* Added explicit support for model transformations

* The 'pyomo solve --transform' option specified model transformations

* Created a streamline linear dual transformation

- Other

* The 'pyomo help' command documents installed capabilities

* Major rework and simplification of the 'pyomo_install' script

* Added support for parallelism using Pyro4

-------------------------------------------------------------------------------

Pyomo 3.5.8787

-------------------------------------------------------------------------------

- pyomo.opt 2.12.2

pyomo.core 3.6.4

pyomo.pysp 3.5.5

pyomo.solvers 3.2.1

-------------------------------------------------------------------------------

Pyomo 3.5.8748

-------------------------------------------------------------------------------

- pyomo.pysp 3.5.4

-------------------------------------------------------------------------------

Pyomo 3.5.8734

-------------------------------------------------------------------------------

- PyUtilib 4.7.3336

-------------------------------------------------------------------------------

Pyomo 3.5.8716

-------------------------------------------------------------------------------

- pyomo.core 3.6.3

pyomo.pysp 3.5.3

-------------------------------------------------------------------------------

Pyomo 3.5.8706

-------------------------------------------------------------------------------

- pyomo.util 2.0.4

pyomo.core 3.6.2

-------------------------------------------------------------------------------

Pyomo 3.5.8690

-------------------------------------------------------------------------------

- pyomo.neos 1.1.2

pyomo.opt 2.12.1

pyomo.core 3.6.1

pyomo.pysp 3.5.2

- Added the pyomo_install script

-------------------------------------------------------------------------------

Pyomo 3.5.8669

-------------------------------------------------------------------------------

- PyUtilib 4.7.3311

pyomo.util 2.0.3

-------------------------------------------------------------------------------

Pyomo 3.5.8663

-------------------------------------------------------------------------------

- PyUtilib 4.7.3305

pyomo.util 2.0.2

pyomo.environ 1.0.1

-------------------------------------------------------------------------------

Pyomo 3.5.8648

-------------------------------------------------------------------------------

- PyUtilib 4.7.3301

pyomo.age 1.1.4

pyomo.bilevel 1.0

pyomo.util 2.0.1

pyomo.dae 1.2

pyomo.environ 1.0

pyomo.gdp 1.2

pyomo.util 2.8.2

pyomo.mpec 1.0

pyomo.neos 1.1.1

pyomo.openopt 1.1.3

pyomo.opt 2.12

pyomo.os 1.0.4

pyomo.core 3.6

pyomo.pysos 2.0.9

pyomo.pysp 3.5.1

pyomo.solvers 3.2

pyomo.sucasa 3.0

-------------------------------------------------------------------------------

Pyomo 3.4.7842

-------------------------------------------------------------------------------

- pyomo.dae 1.1

pyomo.gdp 1.1.1

pyomo.util 2.8.1

pyomo.openopt 1.1.2

pyomo.opt 2.11

pyomo.os 1.0.3

pyomo.plugins 3.1

pyomo.core 3.5

pyomo.pysp 3.4

-------------------------------------------------------------------------------

Pyomo 3.3.7114

-------------------------------------------------------------------------------

- pyomo.age 1.1.3

pyomo.util 1.0.1

pyomo.dae 1.0

pyomo.gdp 1.1

pyomo.util 2.7.2

pyomo.openopt 1.1

pyomo.opt 2.10

pyomo.os 1.0.2

pyomo.plugins 3.0

pyomo.core 3.4

pyomo.pysos 2.0.8

pyomo.pysp 3.3

pyomo.sucasa 2.1

-------------------------------------------------------------------------------

Pyomo 3.2.6148

-------------------------------------------------------------------------------

- pyomo.opt 2.9.1

pyomo.core 3.3.2

-------------------------------------------------------------------------------

Pyomo 3.2.6124

-------------------------------------------------------------------------------

- pyomo.core 3.3.1

-------------------------------------------------------------------------------

Pyomo 3.2.6091

-------------------------------------------------------------------------------

- pyomo.gdp 1.0.4

pyomo.openopt 1.0.3

pyomo.opt 2.9

pyomo.plugins 2.11

pyomo.core 3.3

pyomo.pysos 2.0.7

pyomo.pysp 3.2

pyomo.sucasa 2.0.6

-------------------------------------------------------------------------------

Pyomo 3.1.5746

-------------------------------------------------------------------------------

- pyomo.age 1.1.2

pyomo.gdp 1.0.3

pyomo.util 2.7

pyomo.openopt 1.0.2

pyomo.opt 2.8

pyomo.os 1.0.1

pyomo.plugins 2.9

pyomo.core 3.1

pyomo.pysp 3.1

-------------------------------------------------------------------------------

Pyomo 3.1.5409

-------------------------------------------------------------------------------

- Made the imports of pyomo.opt services more robust to the failure of

individual services.

- Minor performance improvement

- Fixing import error when ordereddict is not available.

-------------------------------------------------------------------------------

Pyomo 3.1.5362

-------------------------------------------------------------------------------

- Bug fix for Python 2.7 installation.

-------------------------------------------------------------------------------

Pyomo 3.1.5325

-------------------------------------------------------------------------------

The following are highlights of this release:

- Solvers

* Interfaces for OpenOpt solvers

* Many solver interface improvements

* A solver checker to validate solver interfaces

* Improved support for SOS constraints (cplex, gurobi)

* PH supports nonlinear models

* PH-specific solver servers

- Modeling

* Changes in rule semantics to limit rule return values

* Changes in the expected order of rule arguments

* Constant sums or products can now be used as constraint bounds

* Added full support for the !ConstraintList modeling component.

- Usability enhancements

* New 'pyomo' command has subcommands that consolidate Pyomo scripting

* Added support to connect to databases with ODBC

* Added comprehensive support for set expressions

* Comprehensive rework of blocks and connectors for modular modeling

* Made JSON the default results format

- Other

* Efficiency improvements in model generation, memory, runtime, etc.

* Preliminary support for black-box applications

* Deprecated modeling syntax in Pyomo 3.0 is no longer legal

-------------------------------------------------------------------------------

Pyomo 3.0.4362

-------------------------------------------------------------------------------

- Solvers

* More sophisticated logic for solver factory to find ASL and OS solvers

* Various solver interface improvements

* New Solver results object for efficient representation of variable values

* New support for asynchronous progressive hedging

- Modeling

* Changes in rule semantics to limit rule return values

* Changes in the expected order of rule arguments

* Constant sums or products can now be used as constraint bounds

* Added full support for the ConstraintList modeling component.

- Usability enhancements

* More explicit output from runph and runef commands

* Added support in runef to write the extensive form in NL format

* Add controls for garbage collection in PH

- Other

* Efficiency improvements in generation of NL and LP files.

* Significant efficiency improvements in parsing of Pyomo Data Files.

* More robust MS Windows installer (does not use virtual python environment)

-------------------------------------------------------------------------------

Pyomo 2.5.3978

-------------------------------------------------------------------------------

- Performance improvements in Pyomo

- Bug fix when updating a results object that contains suffix data.

-------------------------------------------------------------------------------

Pyomo 2.5.3890

-------------------------------------------------------------------------------

- Solvers

* MIP solver interface updates to use appropriate objective names

* Added support for suffixes in GUROBI solver interface

* Improved diagnostic analysis of PH solver for the extensive form

- Usability enhancements

* Improved robustness of pyomo_install

* Fixed Pyomo installation problem when using easy_install

* Added a script to launch the PyomoAge GUI.

* LP files now are written with the true objective name

* Rework of pyomo command line to create a concise output

* Many efficiency improvements during model generation!

* Many improvements to diagnostic output and error handling

* Expressions like "model.p > 1" can now be used within generation rules

- Modeling

* Added support for generalized disjunctive programs (in pyomo.gdp)

* Constraints can now be specified in "compound" form: lb <= expr <= ub

* Significant robustness enhancements for model expressions

* Improved error handling for constraint generation

- Other

* Python 2.5 is deprecated due to performance issues

* Python versions 2.6 and 2.7 are supported

* New MS Windows installer is now available

-------------------------------------------------------------------------------

Pyomo 2.4.3307

-------------------------------------------------------------------------------

- Solvers

- Various fixes for Gurobi and CPLEX

- Reorganized OS services in pyomo.os

- Usability enhancements

- Improved robustness of pyomo_install

- Default install of pyomo_install from PyPI

-------------------------------------------------------------------------------

Pyomo 2.4.3261

-------------------------------------------------------------------------------

- Updating dependencies for Pyomo.

-------------------------------------------------------------------------------

Pyomo 2.4.3209

-------------------------------------------------------------------------------

- Patch fix for pyomo.colin

-------------------------------------------------------------------------------

Pyomo 2.4.3199

-------------------------------------------------------------------------------

- Modeling

- Concrete models are now supported

- Nonlinear modeling extensions using the AMPL NL problem format

- Add support for immutable versus mutable parameters.

- Support for SOS1 and SOS2 constraints

- Data Integration

- Can now import data from relational databases

- Solvers

- Better support for Gurobi solver

- Direct CPLEX solver interface

- Interface to ipopt and nonlinear solvers via asl (just to be clear)

- ASL solver interface can now be specified with the form

--solver=asl:PICO

- Usability enchancements

- Numerous bug fixes.

- Updated messages to provide clearer indication of modeling errors

-------------------------------------------------------------------------------

Pyomo 2.3.2581

-------------------------------------------------------------------------------

- A preliminary Gurobi solver interface

- Extended syntax for data command files:

'include' command to load other data command files

'import' command to load data from other sources

namespaces to next data declarations

- The pyomo_install script can install packages from Coin Bazaar

- New conversion scripts to generate LP or NL files from Pyomo models

- Solvers now extract standard suffix information

- Various fixes to PySP solvers

-------------------------------------------------------------------------------

Pyomo 2.0

-------------------------------------------------------------------------------

- Reorganization of Pyomo into separate packages:

- pyomo.opt 2.0

- pyomo.util 2.0

- pyomo.plugins 2.0

- pyomo.core 2.0

- pyomo.pysos 2.0

- pyomo.sucasa 2.0

-------------------------------------------------------------------------------

Pyomo 1.2

-------------------------------------------------------------------------------

- OPT

- Added explicit support for a symbol_map, which is used to coordinate

the symbols used in a converted problem with the symbols used in the

original problem.

- PYOMO

- Fixed bug in logic associated with index validation in ProductSets.

- Changed the set ord() method to be 1-based

- Added presolve diagnostics.

- SUCASA

- Added draft SUCASA user manual.

- PYSP

- Modified PH to support parallelism with Pyro.

- Introduced the PH scripts, with many options that an end-user

might want to try out.

- Added a convergence criterion to PH based on the # of free

discrete variables.

- Flushed out PYSP 1.1 documentation.

- Updated/improved timing reports and output in PH.

- Setup binary quadratic term linearization.

- Setup PH checkpointing using pickle.

- Added 48-scenario test case for forestry problem.

- Added PH option to specify a user-defined PH extension.

- Fixes to PH proximal term linearization.

- Created windows-friendly versions of core PYSP scripts.

- Plugins

- Switched default CBC input file format to CPLEXLP

- General

- Added a Pyomo 'getting started' manual.

- Reorganized Pyomo package to use the 'pyomo' namespace. The pyomo.util

package was renamed pyomo.opt.

- Added documentation on how to create/install plugins in Pyomo.

- Added documentation for using pyomo_install.

- Reworked pyomo_install to be created with the pyutilib.virtualenv script

vpy_create.

- Misc edits due to the PyUtilib reorg.

-------------------------------------------------------------------------------

Pyomo 1.1

-------------------------------------------------------------------------------

- OPT

- Reorganized pyomo.opt to rely on plugins for most of its core

functionality.

- Changed the default output for PICO to be LP format, rather than

.NL. This avoids issues with name-mapping that we haven't resolved yet.

- Updated LP writer to not output integer/binary status for variables

that aren't referenced in the model.

- In LP output format, modified constraint names to be "suffixed"

with the index in the same fashion as variables. The suffix is "None"

if the constraint is a singleton. Will help debug models during

development/prototyping.

- For MIPs, added "slack" suffix to solutions and modified CPLEX solver

interface to populate the suffix accordingly.

- Improvement of the factory mechanism used to launch optimizers;

solvers can be passed options during construction.

- The CPLEX LP format assumes default variable bounds equal to 0 and

+inf. These conflict with the more sane defaults in Pyomo, which are

-inf and +inf. This leads to all kinds of silent, incorrect behavior

in terms of getting very strange solutions where you are expecting a

straightforward solve. The cpxlp writer was changed to always output

bounds for variables, which is the safest route in any case.

- Added a facility for managing asynchronous events. In particular,

this facility has been setup to support the application of Pyomo

solvers with subclasses of the AsynchronousSolverManager.

- Created a distributed solver manager that uses the Pyro

RPC package.

- Rework of MIP solver interfaces for CPLEX, GLPK, PICO and CBC.

- Using an explicit temporary file when launching the shell command

subprocess, to avoid a buffer overflow.

- A rework of the logic in shellcmd.py to segregate the solution

into preprocess/solve/postprocess. This facilitates a fine-grain

parallelization of just the IP solve, using Pyro.

- If a variable name has the format x(1,a) or x[3,4,5] then create a

dictionary attribute 'x' in the SolverResults object, which maps the

tuple values to the corresponding value.

For example:

results.solution().variable.add('x(1,a)')

print results.solution().variable.x[1,'a']

- A change in the converter semantics. Now, the convert returns a

tuple of filenames. In most cases, this is a singleton tuple. But

in some important cases this is a non-singleton tuple (e.g. AMPL

*.mod/*.dat files).

- PYOMO

- Reworked Pyomo's management of components to use plugins.

- Adding two new components BuildCheck and BuildAction. Their

usage is similar, but their expected use is a it

different. BuildAction allows for the injection of arbitrary build

actions during construction of the model, while BuildCheck is used

to test conditions and generate exceptions when the build process

goes awry.

- There is also a subtle change to the Param component. The following

is now legal:

def f(model):

return 1.3

model.x = Param(initialize=f)

That is, when the Param object does not have an explicit index,

then no index is passed to an initializer function (as is expected).

- Adding 'summation', a function that computes multi-vector

product sums:

sum_i x[i]*y[i]*z[i]

- Adding automatic computation of variable bounds based on the domain.

If the domain set supports simple bounds, then they will be used to

initialize the bounds of a variable.

- Adding logic to ignore the generation of constraints if the

constructor rule returns either 'None' or '0'.

- Changed default domain of a Param to be Any, to be consistent with Set.

- Rework of Pyomo to enable preprocessor actions to manage all

post-instance-generation activities. This includes a simple preprocessor

plugin, which simply applies preprocessor actions in an order specified

by the action-specific ranks. The problem writers are no longer

responsible for how preprocessor actions take place.

NOTE: These preprocessors are very much tailored to the needs of the

NL and LP writers. We need to figure out a mechanism to tailoring

preprocessors to specific target solvers (e.g. tailoring preprocessing

for the NL writer, or tailoring preprocessing for MILP models).

_ The Constraint and Objective classes were reworked to integrate

their data into a single _data dictionary. This simplified

the management of id and label information.

- Extending the Constraint(model.A, rule=f) constructor semantics. This

change allows the rule to return a dictionary when the constraint is

indexed by one or more sets.

- A revision to Pyomo semantics. Now, expressions are not evaluated

when performing arithemetic operations (plus, times, etc).

- A major rework of how component attributes are managed for

NumericValue objects and subclasses of this class. This was driven

by the desire to add the Var.declare_attribute() method, which declares

attributes for variables (which are akin to ampl suffix's).

Most of these changes were motivated by inconsistencies that were

observed within Pyomo, and the desire to better protect declared

attributes. Now, attributes are stored with names that are unlikely

to be used by end-users or other Pyomo developers. Also, declared

attributes can now only be referenced directly. Thus, you cannot

refer to x._value, but instead you must use x.value.

- Reworked the way that 'empty' objectives and constraints are dealt

with. By default, objectives and constraints with expr/body

values of None are provided, which facilitates some aspects of

preprocessing. But this triggered exceptions, which are now disabled.

- Reworked how the '_equality' constraint attribute is managed. This is

now in the ConstraintData class, which required various changes.

- Changed the pprint output for equality constraints to make it clear

that both the upper and lower bounds are equal for these constraints.

- Fixed bug in the definition of parameter names. When using a rule

to define parameter values, the parameter name now reflex the index

values for the parameter.

- Major change of NumericalValue subclass semantics. The 'value' data

member is not supported for expressions, constraints and objectives.

These classes need to use the call method. This simplifies the

logic in their getattr/setattr methods.

- Various code optimizations to improve the runtime performance of Pyomo.

- A major rework of the Pyomo core to eliminates the use

of getattr and setattr methods. Removing these led to a 1/3 reduction

in runtime for some largish p-median test problems. This change

has had the following impact on Pyomo functionality:

. No validation that values assigned to parameters or variables are valid

. Cannot set all suffixes simultaneously

. Cannot set lower/upper bounds simultaneously

. No validation that suffixes are valid when their value is set

Also, this effort led to a rework of the Param and Var classes. These

are now segregated between Element and Array classes (similar to the

Set class). This led to further optimizations of the logic in these

classes. Unfortunately, it also led to the use of the _VarBase and

_ParamBase in the PyomoModel to index components.

- Changed order in which parameters are validated. Validation needs

to occur after parameters are set. This is due to the semantics of

the validation function: we want to allow the validation function to

refer to the value as if it were set.

- Depricating the use of the expression factory for algebraic expression

types. These are now launched directly from the generate_expression()

function.

- Adding support for specifing options when launching solvers. For example:

results = self.pico.solve(currdir+"bell3a.mps", options="maxCPUMinutes=0.1")

- The value 'None' is accepted by all NumValue objects, and this

indicates that the object has not been initialized.

- ParamValue objects print their name, rather than their value.

- Resolving an issue loading boolean data from a *.dat file. Now,

all true/false strings are changed to True/False values.

- Rework of Pyomo to use the SolverManagerFactory. The default

behavior is to use the 'serial' manager, which does local solves,

but this supports extensibility for other solvers.

- SUCASA

- Added an option to terminate SUCASA after the AMPL script is

generated, but before PICO is called. This allows the AMPL script

to be applied separately.

- Rework of the files generated by SUCASA. Before, SUCASA generated

three files:

. app_milp.h/app_milp.cpp Define the derived MILP classes

. app_extras.cpp Used to define the methods specialized by the user

Now, SUCASA generates five files:

. app_sucasa.h/app_sucasa.cpp Define the derived MILP classes

. app_milp.h/app_milp.cpp Define a MILP from the code in *_sucasa.* files.

. app_extras.cpp Used to define the methods specialized by the user

The result, is that SUCASA now generates two derived solvers. BUT, the

one that is exposed to the user can be customized without impacting