Difference between pages "File" and "Long"
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== Syntax == | == Syntax == | ||
| − | + | Long | |
== Semantics == | == Semantics == | ||
| − | A | + | A long 64 bit number. |
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== Example == | == Example == | ||
| − | + | var i:Long; | |
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| − | '' | + | In this example variable ''i'' is explicitly declared to be of type ''Long''. |
== Communication == | == Communication == | ||
| − | + | {{ElementTypeCommunication}} | |
[[Category:Element Types]] | [[Category:Element Types]] | ||
[[Category:Type Library]] | [[Category:Type Library]] | ||
Revision as of 00:25, 4 January 2010
Syntax
Long
Semantics
A long 64 bit number.
Example
var i:Long;
In this example variable i is explicitly declared to be of type Long.
Communication
When a variable is assigned to another, depending on where each variable is allocated to, there may be communication required to achieve this assignment. Table \ref{tab:eltypecomm} details the communication rules in the assignment \emph{assignmed variable := assigning variable}. If the communication is issued from MPMD programming style then this will be one sided. The default communication listed here is guaranteed to be safe, which may result in a small performance hit.
| Assigned Variable | Assigning Variable | Semantics |
|---|---|---|
| multiple[] | multiple[] | local assignment |
| single[on[i]] | multiple[] | individual processes write values to process i |
| multiple[] | single[on[i]] | individual processes read values from process i |
| single[on[i]] | single[on[i]] | local assignment where i==i |
| single[on[i]] | single[on[j]] | communication from j to i where i!=j |
Communication Example
var a:Int;
var b:Int :: allocated[single[on[2]]];
var p;
par p from 0 to 3 {
if (p==2) b:=p;
a:=b;
sync;
};
This code will result in each process reading the value of b from process 2 and then writing this into a. As already noted, in absence of allocation information the default of allocating to all processes is used. In this example the variable a can be assumed to additionally have the type allocated[multiple]. Note that communication groups are the same as multiple in this context and share the same semantics. All variables marked multiple are private to their containing process.
