Difference between revisions of "Par"

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(Created page with '== Syntax == par p from a to b<br> {<br> par body<br> };<br> == Semantics == The parallel equivalent of the for loop, each iteration will execute concurrently on different pro…')
 
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== Semantics ==
 
== Semantics ==
  
The parallel equivalent of the for loop, each iteration will execute concurrently on different processes. This allows the programmer to write code MPMD style, with the limitation that bounds ''a'' and ''b'' must be known during compilation. All (variable sharing) communication in a par loop is performed using one sided communication, whereas variable sharing SPMD style is performed using synchronous communication for performance reasons.
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The parallel equivalent of the for loop, each iteration will execute concurrently on different processes. This allows the programmer to write code MPMD style, with the limitation that bounds ''a'' and ''b'' must be known during compilation. Variables declared to be multiply allocated within parallel scope, such as a par block, will automatically be allocated just to the subgroup of processes within that scope.<br><br>
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''Note:'' There is no guarantee as to the ranks of the processes involved within a par block and such as block will be distributed over the ranks which are most appropriate at that time.
  
 
== Example ==
 
== Example ==
  
  var p;
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  #include <io>
par p from 0 to 10
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function void main() {
{
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    var p;
    print["Hello from process ",p,"\n"];
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    par p from 0 to 9 {
 +
      print("Hello world\n");
 +
    };
 
  };
 
  };
  
The code fragment will spawn 11 processes (0 to 10 inclusive) and each will display a message.
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The code fragment will involve 10 processes (0 to 9 inclusive) and each will display a ''Hello world'' message.
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''Since: Version 0.41b''
  
 
[[Category:Parallel]]
 
[[Category:Parallel]]

Latest revision as of 15:44, 15 April 2019

Syntax

par p from a to b
{
par body
};

Semantics

The parallel equivalent of the for loop, each iteration will execute concurrently on different processes. This allows the programmer to write code MPMD style, with the limitation that bounds a and b must be known during compilation. Variables declared to be multiply allocated within parallel scope, such as a par block, will automatically be allocated just to the subgroup of processes within that scope.

Note: There is no guarantee as to the ranks of the processes involved within a par block and such as block will be distributed over the ranks which are most appropriate at that time.

Example

#include <io>
function void main() {
   var p;
   par p from 0 to 9 {
      print("Hello world\n");
   };
};

The code fragment will involve 10 processes (0 to 9 inclusive) and each will display a Hello world message.

Since: Version 0.41b