Javascript within OPL CPLEX

With very popular Python, Java and C# you can either model directly with CPLEX or call OPL. With very popular Javascript, it's different. Javascript is part of OPL CPLEX.

Optimization (Prescriptive analytics, Operations Research, Decision Optimization) is doing more with less. Which is why most of the time, this makes sense. In a few posts I tried to show the way:

• Low barrier to entry to Optimization
• Should we use a dedicated modeling language or a general purpose language ?

Then I gave some tricks and examples but nothing happened, well not much. Then came 2018 and I tried a very simple story.

This got some impact and got translated into 23 languages (English included) because this was very simple. In Freakonomics, Nobel Prize 2017 Richard Thaler said : "If you want to get people to do something, make it easy. Remove the barriers."

In most examples I have shared and the IBM Research Ponder This I have solved I have focused on the 2 engines within CPLEX and the modeling part within OPL.

But here I will spend more time on the scripting part either called ILOGscript, ECMA or javascript. As an interpreted language this is not as fast as OPL modeling part but this language that is part of OPL is very useful. Plus Javascript is a very common and standard language, which is very good for OPL CPLEX adoption.

Javascript is behind node.js, typescript and many other dialects like the one in OPL.

In OPL we can use scripting for preprocessing and postprocessing,for flow control, but also within the data file .dat to process data.

Some simple examples:

• Hello world

• call any external program like python or anything else

• call java with IloOplCallJava
• call many models in parallel
• flow control can be successful or fail

Within scripting you can use

• arrays and its methods
• constraints
• dates
• decision variables and expressions
• interval decision variables

• sequence

• eval (evaluate) a string
• functions with any number of arguments
• .js files
• maths functions

• objects
• opl name space

• range
• sets
• strings
• typeof
• IloCplex object

• IloCP object

• IloOplFile to crawl files

You can do any kind of computation:

• prime numbers

And use the debugger from the IDE

And let's not forget codeassist that is available in both the CPLEX IDE and WatsonStudio in CloudPakForData

In the IDE you can also run any new scripts after running the model and that helps when running the model again takes time. We call this interactive scripting.

Through external python call you can get any file from the web to your machine.

What else ?

• Get local environment variables
• Get CPLEX version
• lazy evaluation
• export tuple set to csv file
• import tuple set from csv file
• turn minimize into maximize

• turn a tuple set into a flat tuple set

• split a string with values into an array

In Scripting you may use brute force too. For the zoo example, brute force in scripting even if not as efficient as brute force in the OPL modeling part

NB:

Scripting is much slower than OPL modeling part. So not to be used in huge loops. Here some figures with OPL and python.

1. OPL computation : 14.652
2. OPL scripting : 109.809
3. python expression :?12.402294158935547
4. python loop :?17.183008909225464