Doppl is a new programming language that aims providing a natural syntax for implementing parallel algorithms, designing data structures for shared memory applications and automated message passing among multiple tasks. The name is an abbreviation of `data oriented parallel programming language`.

1. DOPPL
Data Oriented Parallel Programming Language
Development Diary
Iteration #3
Covered Concepts:
Access Modifiers, Assignment Operator
Diego PERINI
Department of Computer Engineering
Istanbul Technical University, Turkey
2013-07-20
1

2. Abstract
This paper stands for Doppl language development iteration #3. In this paper, shared data
members and using assignment operator to access/copy those bindings will be introduced. An example
task group with 2 cloned tasks is used as an example program.
1. Rationale
Doppl tasks can make use of different kind of access modifiers to store its members. Previous
iteration introduced an implied one, called a private data. Private datas are copied blocks of memory
and their values may differ between tasks of the same task group. It is possible to mark a member as
non-private via access modifiers. Language operators behave differently to non-private members. This
iteration will only introduce shared members and assignment operation of a shared member for each kind
of possible scenario.
2. Shared Members
To declare a member as shared, a simple shared prefix is sufficient. Shared members only
allocate one block of memory per task group and any task can change the value. Accessing a shared
member is intrinsically mutually exclusive. No extra atomic operations are required to read and write to a
shared member.
Below is a sample task group of 2 tasks which share a single member.
#An example task group of 2 tasks
task(2) SharingMembers {
data a_private_string = string
shared data a_shared_string = string
#Examples
init: {
a_private_string = "I am private!"
a_shared_string = "I am shared!"
}
}
3. Assignment Operator and Standard Output
Assigning values to shared member and outputting values of such members rise some ambiguities
possible to be reason of common mistakes. Each ambiguity scenario is explained below in detail.
#An example task group of 2 tasks
task(2) SharingMembers {
2

3. data private_ = byte
shared data shared_ = byte
...
}
Assuming Task_A and Task_B of same task group (SharingMembers) have their
corresponding members allocated:
●
private_ = any_value #Executed on Task_A
It is a simple block copy operation. Each member have its own unique memory position
and therefore can have different values on runtime. Only private_ of Task_A is affected.
●
shared_ = any_value #Executed on Task_A
shared_ = any_value #Executed on Task_B
Both mean the exact same thing, a block copy to the shared memory location is
conducted. It is therefore considered as common practice to pick reasonable names for
shared members to prevent ambiguities.
Printing member values to standard output needs extra care since each task may have different
private member values. In order to conduct a synchronized and maintained output operation, a new kind
of messaging mechanism will be introduced in the future.
Assigning one type of value to another member type is forbidden in Doppl, thus the following
source code is not valid. Conversion rules which are subjects of another iteration will be introduced to fill
the necessity of typecasting.
data an_int = int
data a_float = float
init: {
an_int = a_float #Invalid assignment
}
4. Conclusion
Iteration #3 introduces shared task members and explains how they are allocated in the memory.
Benefits and risks of using assignment operator between different kind of members is explained.
3

4. 5. Future Concepts
Below are the concepts that are likely to be introduced in next iterations.
●
●
●
●
●
●
●
●
●
●
●
●
●
A boolean type
Arithmetic, relational, boolean and binary operators
String Concatenation
Standard input and output
if conditional and trueness
State transition operators
Primitive collections and basic collection operators
Provision operators
Tasks as members
Task and data traits
Custom data types and defining traits
Built-in traits for primitive data types
Message passing
6. License
CC BY-SA 3.0
http://creativecommons.org/licenses/by-sa/3.0/
4