Main Features of Vnano Engine, and Examples

Here we introduce main features of Vnano Engine, with example code of apps.

Calculate Expressions

Vnano Engine is an interpreter for processing scripts, but it is also available for calculating expressions. Probably there are many times you want to calculate expressions than scripts, so Let's start this guide from: how to calculate expressions.

The following is an example application, calculating an expression inputted by the user:

Note that, in the input content to Vnano Engine, regardless of whether it is an expression or a script, a semicolon ";" is required at the end of each lines. So in the above example, it appends ";" at the end of an expression, before passing it to Vnano Engine.

How to compile and run is:

When you have executed the above "ExampleApp2", it requests you to input the expression to be calculated. So input as follows:

Then the expression will be calculated by using the Vnano Engine, and the result will be displayed as:

Also, you can input script code instead of an expression as:

The result is:

For more details, see Execute Scripts.

Please note that, when you execute scripts, we strongly recommend to remove the line of:

If the above option is enabled, all numeric literals (including integer literals) are handled as float-type values. It should be a cause of confusion. By the way, above option does not affect to contents of library scripts.

Also, for the list and details of available option items, see the page: Specifications of Vnano Engine.

Access to Fields/Methods of a Java Class (Plug-in)

You can connect fields and methods of any class to Vnano Engine, and can access to them from an expression/script runs on the engine.

For example:

Let's compile and run:

Then input the following expression:

Now the value of x is 3.4 and f(x) = x * 5.6, so we should get the result of 1.2 + (3.4 * 5.6) = 20.24. The actual result is:

Also, when you want to connect all methods/fields belong to a class/instance, simply pass the class/instance to "connectPlugin" method:

As a result of the above, you can access to "x" and "f(x)" from scripts/expression as completely the same as the previous way, in addition, you also can accsess to them with specifing the namespace "AnyNamespace." at heads of their names. It is helpful when you want to connect multiple instances of the same class (assign a unique namespace for each instance).

Define a (Plug-in) Class Providing Methods/Fields as Another File

Like as "AnyClass" in Example2, we call a class providing fields/methods to Vnano Engine as a "plug-in". (In addition, sometimes we call fields/methods provided by plug-ins as "external variables/functions", to distinguish from internally declared variables/functions in scripts.)

In previous example, we defined "AnyClass" plug-in as an inner class of "ExampleApp3". If you want, you can define it as another file in any package:

You can simply import and use it in usual way:

The result is the same as the previous example.

Specify Plug-ins to be Loaded, by a List File

The previous example requires to decide "which plug-ins should be loaded/connected" before when the application is compiled. However, sometimes you may want to make it customizable by users. It becomes little complex than previous examples, but Let's try to do it.

An example plug-in class "ExamplePlugin1.java" is included in "plugin" folder:

Compile it as follows:

In addition, create a text file (list file) "VnanoPluginList.txt" in "plugin" folder, and in there list-up compiled plug-ins to be loaded, as follows:

where lines starts with "#" will be ignored.

On the command-line mode, the above list file will be referred by default. On the other hand, when you use Vnano Engine on you applications, it is necessary to specify the list file explicitly, as we do in the following example.

Now you are all set. Let's load plug-ins dynamically and connect them to Vnano Engine:

Let's compile and run:

Input the expression:

And you can get the result:

Advanced Steps About Plug-ins (Standard Plug-ins, Less-Overhead Interfaces, etc.)

A fundamental set of plug-ins are officially provided as "Vnano Standard Plug-ins":

• Source Code Repository of Vnano Standard Plug-Ins
• Specification Documents of Vnano Standard Plug-Ins

Basic I/O functions, math and statistical functions, and so on are provided by the above standard plug-ins, so you are not required to implement them by yourself.

Also, interfaces for developing less-overhead plug-ins are provided:

• Source Code Repository of Vnano Plug-in Interfaces
• Documents of Vnano Plug-in Interfaces

When you develop a plug-in which is very frequently accessed from scripts, and you want to make it as faster as possible, consider to use above interfaces.

Execute Scripts

Instead of an expression, you can execute script code written in C-like language. The name of the scripting language is "Vnano". For details of syntax and language features of Vnano, see the following page:

• Vnano as a Language

Let's execute a Vnano script:

When "executeScript(script)" method has executed a script, it returns: the value of the expression statement (if exists) at the last line in the script. So we will get the value of the variable "sum", when we run the above Example4.

Compile the above example and run:

And you can get the result:

This value equals to the summation from 1 to 100 ( = 100 * 101 / 2 ), so we have gotten the correct result.

Load Library Scripts

Vnano (as a scripting language) supports declarations of variables and functions.

So sometimes you may want to make a script in there utility functions and variables are declared, for using them in other scripts. We call such script providing variables/functions for other scripts, as a "library script".

An example of a library script is:

To load the above library, create a text file "lib/VnanoLibraryList.txt" and in there list-up library scripts:

where lines starts with "#" will be ignored.

On the command-line mode, the above list file will be referred by default. On the other hand, when you use Vnano Engine on you applications, it is necessary to specify the list file explicitly as:

How to compile and run is:

The result is:

As declared in "lib/ExampleLibrary1.vnano", the value of x is 3.4 and f(x) = x * 5.6, so we should get the result of 1.2 + (3.4 * 5.6) = 20.24. Hence the above result is correct.

Option Settings

As we already seen in ExampleApp2, you can modify some behaviour of Vnano Engine by option settings.

For performing the option settings, create a Map<String, Object> storing the option values, with option names as keys. We refer to this Map as the "option map". Then, pass the option map to "setOptionMap(...)" method of the VnanoEngine instance.

For example:

The above example assumes that Vnano Engine is used for calculating expressions on calculator apps (On such apps, its depeloper may want to restrict integer operations, to avoid confusion about behaviour of so called integer-division).

About all available option items and their details, see Specifications of Vnano Engine.

Permission Settings

Some plug-ins and libraries perform actions which sometimes app-developers or users want to restrict it, depends on situations. For example, file-reading/writing/overwriting and so on. Sometimes users/developers want to allow it, and sometimes they want to deny it.

Vnano Engine is equipped with a permission-based mechanism for such situation. Plug-ins (or libraries using them) request Vnano Engine to allow an actions like above, and then the engine decides whether allow/deny it, depends on settings, or by asking users. We refer this process as "permission request", and settings for controlling it as "permission settings".

For performing the permission settings, create a Map<String, String> storing the setting values, with the names of the permission items as keys. We refer to this Map as the "permission map". Then, pass the permission map to "setPermissionMap(...)" method of the VnanoEngine instance.

For example:

About all available permission items and their details, see Specifications of Vnano Engine.

Also, on the command-line mode which we will introduce in the latter section, use --permission option for switching permission settings, from some choices:

In the above example, we specify "askAll", for asking users to decide whether allow/deny a permission request when it is requested, for every permission items. You can also specify "denyAll" or "allowAll" for denying/allowing every permission requests, or "balanced" for using the permission settings considering balance between userbility and protectividy. For details, see the explanation by --help option.

By the way, when you are developing your original plug-in, sometimes you may want to ask users to decide whether your plug-in shoud do some process or don't (e.g.: file-overwriting). Hence, you may want to support the permission controlling mechanism shown in this section, by your original plug-in. For supporting the mechanism, implement plug-in interfaces such as XNCI1, and request permissions to Vnano Engine by calling requestPermission(...) method of the engine connector interface, which is passed when the plug-in is intialized.

Supporting this mechanism by your original plug-ins is good way, because app-developpers and users can integratedly control whether allow/deny actions through the mecanism. For example, as an opposite way, imagine the situation that each plug-in has a permission setting for file-overwriting independently, or each plug-in asks an user to decide whether overwrites something independently. It should be difficult to manage them for app-developers/users, especially when many plug-ins are used.

Command-Line Mode

In addition to the embedded use in apps, you can directly execute a Vnano script file on a command line terminal, by using "command-line mode" of Vnano Engine. It may be helpful for debugging scripts/plug-ins when you are developing them.

The following is an example of Vnano script:

Let's execute it as:

As the above, when a script is specified as an argument, "Vnano.jar" works in the command-line mode, and executes the specified script. The result is:

As the above example script, on the command-line mode, "output" function is provided by default for the convenience.

Please note that, it is NOT provided by default when you execute scripts by using "executeScript" method of Vnano Enginem, embedded in your Java applications.

We recommend to introduce Vnano Standard Plug-ins if you use this command-line mode frequently. How to:

And then copy & paste "vnano-standard-plugin/plugin" folder to "vnano/plugin" folder, and rename "VnanoPluginList_AllStandards.txt" in the folder to "VnanoPluginList.txt" (it will be referred by default on the command-line mode).

If you have succeeded to introduce standard plug-ins, following script should run without any errors:

Now you can use all features of all standard plug-ins, on the command-line mode. Also, some practical example scripts are code argive in this website. Now you should able to execute all of them.

For more details of the command-line mode, specify --help option.

Performance Benchmarking / Analysis

Vnano Engine focuses on processing speed, assuming use in data-analysis / calculation software. In the repository, benchmarking scripts for measuring processing speed of Vnano Engine are included in "benckmark" folder.

For measuring the performance of scalar (non-array) operations of 64-bit floating point (FP64) numbers:

The result is (depends on you environment):

where [MFLOPS] is a unit of operating speed of floating point numbers. 1MFLOPS represents the speed that 1 million of operations are performed in 1 second. The above score means that, on Vnano Engine, about 700 millions of FP64 operations have performed in 1 second (measured on a mid-range laptop PC).

For measuring the performance of vector (array) operations of 64-bit floating point (FP64) numbers:

The result is (depends on you environment):

where [GFLOPS] is also a unit of operating speed of floating point numbers. 1GFLOPS represents the speed that 1 billion of operations are performed in 1 second. Hence the above result means that, on Vnano Engine, about 15 billions of FP64 operations have performed in 1 second. Note that, performances of vector operations are greatly depend on the size of operand vectors, and cache size of your CPU.

Also, when you do performance tuning of your practical scripts, the command-line option "--perf all" may be helpful:

An example of result is:

On the result of "Instruction Execution Frequency" section, if the total propotions of arithmetic operations (ADD, SUB, MUL, DIV, REM, NEG) and external function calls (CALLX) and MOV instructions are enough high, the script is well optimized.

In the contrast, if JMP/JMPN or LT/GT/EQ/GEQ/LEQ have large proportions, it means that "if/else" statements or small loops are being bottolnecks in your scripts, so maybe you can improve performance by modifying its processing flow.

Specifications

For detailed specifications of methods, options and so on of Vnano Engine, see the page: Specifications of Vnano Engine.

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