Synergy User Manual and Tutorial. - THE CORE MEMORY

Synergy User Manual and Tutorial
entries in the tuple space similar to the example above. Active tuples are created with the
eval() function. The function call:
eval(“worker”, worker());
would create a tuple entry with “worker” in the first field and spawn a new process that
will immediately call the worker() function. Passive tuples are created and added to the
tuple space with the Linda’s out() function. The function call:
out(“string”, 123, 45.678);
would create the tuple and add it to the tuple space.
Data can be either read or removed from the tuple space. A template is used to retrieve a
tuple from the tuple space by matching a pattern in the fields of a tuple’s fields. The
following conditions must be met to match a template to a tuple:
1. The template and tuple both must have the same number of fields.
2. The template and tuple both must have the same types, values, and length of all
literal values in corresponding fields.
3. The template and tuple both must have matching types and lengths of all formals
in the corresponding fields.
A read operation, using the rd() function, leaves the tuple for other processes to access.
The function call:
rd(“string”, 123, ? A);
reads a three entry tuple that has “string” as its first element and 123 as its second. The
data in the third element is placed in the A variable. The in() function gets and removes
an entry from the tuple space. The function call:
in(“string”, 123, ? A);
gets a three entry tuple that has “string” as its first element and 123 as its second. The
data in the third element is placed in the A variable and the entry is removed from the
tuple space.
Programming for a tuple space is similar to programming for shared memory because all
participating processes share it. However it is also similar to message passing because
entries are posted and taken from it. The major benefit of this system is that participants
can enter and leave the system without formerly announcing an arrival or departure.
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