GPU621/The Chapel Programming Language

Project Description

The Chapel is a portable, scalable, open-source modern parallel programming language designed to be productive. The Chapel is a high-level programming language that tends to be more human-readable and writable with some similarity to Python. The Chapel's performance can compete or even surpass MPI/OpenMP. This project will introduce the main functionality of Chapel programming language, compare the code and performance to C++ MPI/OpenMP, analysis the pros and cons of the Chapel.

Team Members

1. Xi Weng
2. Ivan Huang
3. Yu Li
4. eMail All

Installation

The Chapel is an open-source language that still constantly updates. The latest version as of the creation of this project is 1.23.0 released on October 15, 2020.

There is currently no official support for The Chapel Programming Language in major known IDE like Visual Studio, which is a downside compared to other languages in terms of usability.

Select one of the following options to install The Chapel Programming Language.

Pre-packaged Chapel installations are available for:

• Cray® XC™ systems
• Docker users (Requires to install Docker Engine, available on Linux, MAC, Windows 10)
• Mac OS X Homebrew users

GitHub source code download available here.

Users can also try The Chapel online here, though the version is currently stuck on Chapel 1.20.

The Chapel Programming Language

Main Functionality

//https://chapel-lang.org/docs/primers/

Language Basics

Variable:

Variables are declared with the var keyword. Variable declarations must have a type, initializer, or both.

   var myVariable1: int;

const and param can be used to declare runtime constants and compile-time constants respectively. A const must be initialized in place, but can have its value generated at runtime. A param must be known at compile time.

   const myConst: real = sqrt(myVariable2);
   param myParam = 3.14;

All three variable kinds can be qualified by the config keyword. This allows the initial value to be overridden on the command line.

   config var myVariable2: bool = false; //./variable --myVariable=true

Procedures:

A procedure groups computations that can be called from another part of the program.

   proc factorial(x: int) : int
   {
     if x < 0 then
       halt("factorial -- Sorry, this is not the gamma procedure!");
     return if x == 0 then 1 else x * factorial(x-1);
   }

Classes:

A class is a type that can contain variables and constants, called fields, as well as functions and iterators called methods. A new class type is declared using the class keyword.

   class C {
     var a, b: int;
     proc printFields() {
       writeln("a = ", a, " b = ", b);
     }
   }

The new keyword creates an instance of a class by calling an initializer.

   var foo = new C(1, 3);
   foo.printFields();

Records:

Records are similar to classes, but there are several important differences:

• classes support inheritance and virtual dispatch while records do not
• different class variables can refer to the same instance, while record variables refer to distinct memory
• copy-initialization and assignment can be implemented for records but not for classes.

Iterators

Chapel implements iterators using a function-like syntax, although the semantic behaviour of an iterator differs from that of a function in some important ways. Unlike functions, instead of returning a value, Chapel iterators typically return a sequence of values. The yield statement, legal only within iterator bodies, returns a value and temporarily suspends the execution of the code within the iterator.

As an example, the following Chapel code defines a trivial iterator that yields the first n values from the Fibonacci sequence:

   iterator fibonacci(n): integer {
      var i1 = 0, i2 = 1;
      var i = 0;
      while i <= n {
         yield i1;
         var i3 = i1 + i2;
         i1 = i2;
         i2 = i3;
         i += 1;
      }
   }

Pros and Cons of Using The Chapel

Adoption

Small Number of Contributors

References

• The Chapel Programming Language official page: https://chapel-lang.org/
• The Chapel Documentation: https://chapel-lang.org/docs/#
• Full-Length Chapel Tutorial: https://chapel-lang.org/tutorials.html
• Learn Chapel in Y Minutes: https://learnxinyminutes.com/docs/chapel/
• Specific Chapel Concepts or Features: https://chapel-lang.org/docs/primers/
• October 2018 Chapel Tutorial: https://chapel-lang.org/tmp/OctTut2018/slides.html
• The Chapel Promotional Video: https://youtu.be/2yye1yJPcsg
• The Chapel Overview Talk Video: https://youtu.be/ko11tLuchvg
• The Chapel Overview Talk Slide: https://chapel-lang.org/presentations/ChapelForHPCKM-presented.pdf