Data-parallel hello world¶
This program uses Chapel’s data parallel features to create a parallel hello world program that utilizes multiple cores on a single locale (compute node).
The following configuration constant indicates the number of
messages to print out. The default can be overridden on the
config const numMessages = 100;
Next, we use a data-parallel forall-loop to iterate over a
range representing the number of messages to print. By default,
forall-loops will typically be executed cooperatively by a number
of tasks proportional to the hardware parallelism on which the loop
is running. Ranges like
1..numMessages are always local to the
current task’s locale, so this forall-loop will execute using the
number of local processing units or cores.
Because the messages are printed within a parallel loop, they may be displayed in any order. The writeln() procedure protects against finer-grained interleaving of the messages themselves.
forall msg in 1..numMessages do writeln("Hello, world! (from iteration ", msg, " of ", numMessages, ")");
For further examples of using data parallelism, refer to the data parallel primer examples.