ASCEND overview - Revision history

Jpye: /* Example of a simple model in ASCEND */

2026-03-14T09:06:30Z

Example of a simple model in ASCEND

← Older revision		Revision as of 09:06, 14 March 2026
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	In ASCEND, models are written in a special-purpose modelling language that combines declarative ''variables'' and ''equations'' with procedural ''methods''. The following simple model calculates the mass of water in a tank:		In ASCEND, models are written in a special-purpose modelling language that combines declarative ''variables'' and ''equations'' with procedural ''methods''. The following simple model calculates the mass of water in a tank:

	<source lang="~~a4c~~">REQUIRE "atoms.a4l";		<source lang="ascend">REQUIRE "atoms.a4l";

	MODEL tank;		MODEL tank;

Jpye: /* Solvers and integrators */

2026-02-15T09:14:38Z

Solvers and integrators

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	* [[ODE]] and [[DAE]] problems, where the behaviour of a time-varying system is to be studied (see [[LSODE]], [[IDA]])		* [[ODE]] and [[DAE]] problems, where the behaviour of a time-varying system is to be studied (see [[LSODE]], [[IDA]])
	* [[Conditional_modelling\|Conditional models]], where the applicable equations depend on the value or values of other variables in the model (see [[CMSlv]])		* [[Conditional_modelling\|Conditional models]], where the applicable equations depend on the value or values of other variables in the model (see [[CMSlv]])
			* [[LP Solvers]] (including MIP solvers), where equations are linear, possibly with some variables required to be boolean/integer (see [[HiGHS]])

	The ASCEND GUI allows you to load a model then select a suitable 'solver' or 'integrator' according to the type of problem that you have. Several solvers are already included with ASCEND, and the API allows you to write new solvers without having to dig into the innards of ASCEND.		The ASCEND GUI allows you to load a model then select a suitable 'solver' or 'integrator' according to the type of problem that you have. Several solvers are already included with ASCEND, and the API allows you to write new solvers without having to dig into the innards of ASCEND.

Jpye at 06:21, 21 January 2018

2018-01-21T06:21:21Z

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	ASCEND does enough things to be genuinely useful for engineers, students and scientists, and has an active user group. It was first written around 1978, and has been through several re-writes over that time. Its 'compiler' (which converts the input file into a tree structure containing variables, submodels, and equations) as well as its solvers have been the subject of several PhDs and many features in ASCEND have since been incorporated into commercial simulation programs. Development of ASCEND continues in exciting new directions however. We are working on adding new solvers as well as improving ASCEND's support for solving ODEs and DAEs.		ASCEND does enough things to be genuinely useful for engineers, students and scientists, and has an active user group. It was first written around 1978, and has been through several re-writes over that time. Its 'compiler' (which converts the input file into a tree structure containing variables, submodels, and equations) as well as its solvers have been the subject of several PhDs and many features in ASCEND have since been incorporated into commercial simulation programs. Development of ASCEND continues in exciting new directions however. We are working on adding new solvers as well as improving ASCEND's support for solving ODEs and DAEs.

	If you are interested in contributing to ASCEND, please see our [[Development Activities]] page and also our list of [[Student Projects]]~~. We have participated in the 2009 and 2010 Google Summer of Code programmes, and hope to participate in~~ [[~~GSOC2011~~]]~~, so you might even be able to get paid!~~		If you are interested in contributing to ASCEND, please see our [[Development Activities]] page and also our list of [[Student Projects]] for [[GSOC]].

	[[Category:Documentation]]		[[Category:Documentation]]

Jpye at 01:40, 11 July 2015

2015-07-11T01:40:51Z

← Older revision		Revision as of 01:40, 11 July 2015
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	__NOTOC__		__NOTOC__
	ASCEND is a system for '''solving systems of equations''', aimed at engineers and scientists. It allows you to '''build up complex models''' as as systems constructed from simpler '''sub-models'''. Using ASCEND it is simple to ~~'''~~play around~~'''~~ with your model, examine its behaviour, and work out how it can best be solved. You can '''easily change which variables are fixed''' and which are to be solved, and you can examine the way in which the model is being solved.		ASCEND is a system for '''solving systems of equations''', aimed at engineers and scientists. It allows you to '''build up complex models''' as as systems constructed from simpler '''sub-models'''. Using ASCEND it is simple to play around with your model, examine its behaviour, and work out how it can best be solved. You can '''easily change which variables are fixed''' and which are to be solved, and you can examine the way in which the model is being solved.

	After looking through this brief introduction to what ASCEND is all about, you might want to look at the [[ASCEND history]], a more detailed list of [[ASCEND capabilities]], see some [[worked examples]], find out about [[ASCEND_Users_and_Friends\|the developers]] or look at more detailed [[:Category:Documentation\|documentation]].		After looking through this brief introduction to what ASCEND is all about, you might want to look at the [[ASCEND history]], a more detailed list of [[ASCEND capabilities]], see some [[worked examples]], find out about [[ASCEND_Users_and_Friends\|the developers]] or look at more detailed [[:Category:Documentation\|documentation]].

Jpye at 06:23, 11 September 2014

2014-09-11T06:23:48Z

Jpye: /* More complex models */

2013-04-09T23:29:55Z

More complex models

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	END power_station;</source>		END power_station;</source>

	This model makes use of several sub-parts such as 'pump_simple' and so on, which are defined in another file called 'rankine.a4c' pointed to via the [[REQUIRE]] statement (see {{src\|models/johnpye/rankine.a4c}} for the full code). More documentation [[Category:Syntax\|about the syntax]] is available.		This model makes use of several sub-parts such as 'pump_simple' and so on, which are defined in another file called 'rankine.a4c' pointed to via the [[REQUIRE]] statement (see {{src\|models/johnpye/rankine.a4c}} for the full code). More documentation [[:Category:Syntax\|about the syntax]] is available, or you can look at our other models in this area of [[energy system modelling]].

	Using this style of modular model, it is possible to build and test simple component models, then 'wire them up' into more complex models. This is something that is very difficult to do with standard spreadsheet models as commonly used by engineers. With a library of standard component models at your disposal, you can get working sooner on the complex problems which you have before you.		Using this style of modular model, it is possible to build and test simple component models, then 'wire them up' into more complex models. This is something that is very difficult to do with standard spreadsheet models as commonly used by engineers. With a library of standard component models at your disposal, you can get working sooner on the complex problems which you have before you.

Jpye: /* Example of a simple model in ASCEND */

2012-03-26T22:56:14Z

Example of a simple model in ASCEND

← Older revision		Revision as of 22:56, 26 March 2012
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	== Example of a simple model in ASCEND ==		== Example of a simple model in ASCEND ==

	In ASCEND, models are written in a special-purpose modelling language that combines declarative ''variables'' and ''equations'' with procedural ''methods''. The following simple ~~method~~ calculates the mass of water in a tank:		In ASCEND, models are written in a special-purpose modelling language that combines declarative ''variables'' and ''equations'' with procedural ''methods''. The following simple model calculates the mass of water in a tank:

	<source lang="a4c">REQUIRE "atoms.a4l";		<source lang="a4c">REQUIRE "atoms.a4l";

Jpye: Reverted edits by Chenhongjuan (Talk) to last revision by Jpye

2011-07-12T06:05:11Z

Reverted edits by Chenhongjuan (Talk) to last revision by Jpye

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Chenhongjuan at 05:30, 12 July 2011

2011-07-12T05:30:48Z

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Jpye: Reverted edits by Fatihaktepe (Talk) to last revision by Jpye

2011-05-17T14:57:22Z

Reverted edits by Fatihaktepe (Talk) to last revision by Jpye

← Older revision		Revision as of 14:57, 17 May 2011
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	If you are interested in contributing to ASCEND, please see our [[Development Activities]] page and also our list of [[Student Projects]]. We have participated in the 2009 and 2010 Google Summer of Code programmes, and hope to participate in [[GSOC2011]], so you might even be able to get paid!		If you are interested in contributing to ASCEND, please see our [[Development Activities]] page and also our list of [[Student Projects]]. We have participated in the 2009 and 2010 Google Summer of Code programmes, and hope to participate in [[GSOC2011]], so you might even be able to get paid!
	~~[http://www.gizemhavaifisek.com havai fişek]~~
	~~[http://www.gizemhavaifisek.com balon]~~
	~~[http://www.gizemhavaifisek.com konfeti]~~
	~~[http://www.antalyaprefabrik.gen.tr antalya prefabrik]~~
	~~[http://www.prefabrikantalya.org prefabrik antalya]~~
	[[Category:Documentation]]		[[Category:Documentation]]

← Older revision		Revision as of 06:23, 11 September 2014
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	This model can be loaded into ASCEND, usually just by double-clicking the file, then solved by hitting the 'solve' button, with the following result:		This model can be loaded into ASCEND, usually just by double-clicking the file, then solved by hitting the 'solve' button, with the following result:

	[[Image:simple-tank-~~example~~.png\|thumb\|400px\|none\|The simple <tt>tank</tt> model, loaded and solved in ASCEND.]]		[[Image:simple-tank-example1.png\|thumb\|400px\|none\|The simple <tt>tank</tt> model, loaded and solved in ASCEND.]]

	This is a very simple model: there is much more that ASCEND can do. For example, '''without editing the above model file''', one can use the GUI to 'fix' the volume and diameter of the tank and solve instead for the height, with just a couple of clicks, then resolve for a new tank volume of 200 L:		This is a very simple model: there is much more that ASCEND can do. For example, '''without editing the above model file''', one can use the GUI to 'fix' the volume and diameter of the tank and solve instead for the height, with just a couple of clicks, then resolve for a new tank volume of 200 L:

	[[Image:simple-~~tank2~~.png\|thumb\|400px\|none\|You can easily 'free' and 'fix' variables to solve the same model for a different set of unknowns.]]		[[Image:simple-tank21.png\|thumb\|400px\|none\|You can easily 'free' and 'fix' variables to solve the same model for a different set of unknowns.]]

	For models like this, ASCEND can quickly show you how it's solving the equation, using a simple graph representation:		For models like this, ASCEND can quickly show you how it's solving the equation, using a simple graph representation:

	[[Image:solve-~~order~~.png\|thumb\|400px\|none\|For small models, ASCEND can generate a graphical representation of the solution process, useful when debugging.]]		[[Image:solve-order1.png\|thumb\|400px\|none\|For small models, ASCEND can generate a graphical representation of the solution process, useful when debugging.]]

	Simple models like this can be useful and quite efficient ways to inspect the behaviour of simple systems of equations. They can also be useful as quick 'calculators': they can be loaded, the known variables typed in, and the solved results quickly seen.		Simple models like this can be useful and quite efficient ways to inspect the behaviour of simple systems of equations. They can also be useful as quick 'calculators': they can be loaded, the known variables typed in, and the solved results quickly seen.
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	ASCEND provides a way to keep tables of 'observed' values and plot relationships between variables:		ASCEND provides a way to keep tables of 'observed' values and plot relationships between variables:

	[[Image:~~observer~~.png\|thumb\|700px\|none\|The 'observer' tab allows results for a set of scenarios to be calculated and stored, and then plotted.]]		[[Image:observer1.png\|thumb\|700px\|none\|The 'observer' tab allows results for a set of scenarios to be calculated and stored, and then plotted.]]

	Note that ASCEND is dealing with [[units of measurement]] clearly and transparently. In ASCEND you never have to worry about 'getting the units right' because it understands how to convert between different units like in, ft, cm, m, km for length and L, m³ etc for volume.		Note that ASCEND is dealing with [[units of measurement]] clearly and transparently. In ASCEND you never have to worry about 'getting the units right' because it understands how to convert between different units like in, ft, cm, m, km for length and L, m³ etc for volume.
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	ASCEND can show you the model structure as 'viewed' by the solver. For example, using [[QRSlv]], the simple Rankine-cycle model has the following lower-triangular [[incidence matrix]] structure, which indicates that no iterative solving is needed:		ASCEND can show you the model structure as 'viewed' by the solver. For example, using [[QRSlv]], the simple Rankine-cycle model has the following lower-triangular [[incidence matrix]] structure, which indicates that no iterative solving is needed:

	[[Image:rankine-~~incidence~~.png\|thumb\|400px\|none]]		[[Image:rankine-incidence1.png\|thumb\|400px\|none]]

	See [[Solvers]] and [[Dynamic modelling]] for more information.		See [[Solvers]] and [[Dynamic modelling]] for more information.