mirror of
https://github.com/adambard/learnxinyminutes-docs.git
synced 2024-12-23 09:41:36 +00:00
Added modules and main()
Worth noting that this will change the diff of the parallel section quite a bit, since they became the body of the main procedure. Thus each line in intented.
This commit is contained in:
Ian Bertolacci
parent
1f6f7b7843
commit
b27d526822
@ -673,234 +673,288 @@ var copyNewTypeList = new GenericClass( realList, int );
|
||||
for value in copyNewTypeList do write( value, ", " );
|
||||
writeln( );
|
||||
|
||||
// Parallelism
|
||||
// In other languages, parallelism is typically this is done with
|
||||
// complicated libraries and strange class structure hierarchies.
|
||||
// Chapel has it baked right into the language.
|
||||
|
||||
// A begin statement will spin the body of that statement off into one new task.
|
||||
// A sync statement will ensure that the progress of the main
|
||||
// task will not progress until the children have synced back up.
|
||||
sync {
|
||||
begin { // Start of new task's body
|
||||
var a = 0;
|
||||
for i in 1..1000 do a += 1;
|
||||
writeln( "Done: ", a);
|
||||
} // End of new tasks body
|
||||
writeln( "spun off a task!");
|
||||
}
|
||||
writeln( "Back together" );
|
||||
// Modules are Chapel's way of managing name spaces.
|
||||
// The files containing these modules do not need to be named after the modules
|
||||
// (as is with Java), but files implicitly name modules.
|
||||
// In this case, this file implicitly names the 'learnchapel' module
|
||||
|
||||
proc printFibb( n: int ){
|
||||
writeln( "fibonacci(",n,") = ", fibonacci( n ) );
|
||||
}
|
||||
|
||||
// A cobegin statement will spin each statement of the body into one new task
|
||||
cobegin {
|
||||
printFibb( 20 ); // new task
|
||||
printFibb( 10 ); // new task
|
||||
printFibb( 5 ); // new task
|
||||
{
|
||||
// This is a nested statement body and thus is a single statement
|
||||
// to the parent statement and is executed by a single task
|
||||
writeln( "this gets" );
|
||||
writeln( "executed as" );
|
||||
writeln( "a whole" );
|
||||
module OurModule {
|
||||
// We can use modules inside of other modules.
|
||||
use Time;
|
||||
|
||||
// We'll use this a procedure in the parallelism section.
|
||||
proc countdown( seconds: int ){
|
||||
for i in 1..seconds by -1 {
|
||||
writeln( i );
|
||||
sleep( 1 );
|
||||
}
|
||||
}
|
||||
|
||||
// Submodule of Ourmodule
|
||||
// It is possible to create arbitrarily deep module nests.
|
||||
module ChildModule {
|
||||
proc foo(){
|
||||
writeln( "ChildModule.foo()");
|
||||
}
|
||||
}
|
||||
}
|
||||
// Notice here that the prints from each statement may happen in any order.
|
||||
|
||||
// Coforall loop will create a new task for EACH iteration
|
||||
var num_tasks = 10; // Number of tasks we want
|
||||
coforall taskID in 1..#num_tasks {
|
||||
writeln( "Hello from task# ", taskID );
|
||||
}
|
||||
// Again we see that prints happen in any order.
|
||||
// NOTE! coforall should be used only for creating tasks!
|
||||
// Using it to iterating over a structure is very a bad idea!
|
||||
|
||||
// forall loops are another parallel loop, but only create a smaller number
|
||||
// of tasks, specifically --dataParTasksPerLocale=number of task
|
||||
forall i in 1..100 {
|
||||
write( i, ", ");
|
||||
}
|
||||
writeln( );
|
||||
// Here we see that there are sections that are in order, followed by
|
||||
// a section that would not follow ( e.g. 1, 2, 3, 7, 8, 9, 4, 5, 6, ).
|
||||
// This is because each task is taking on a chunk of the range 1..10
|
||||
// (1..3, 4..6, or 7..9) doing that chunk serially, but each task happens
|
||||
// in parallel.
|
||||
// Your results may depend on your machine and configuration
|
||||
|
||||
// For both the forall and coforall loops, the execution of the
|
||||
// parent task will not continue until all the children sync up.
|
||||
|
||||
// forall loops are particularly useful for parallel iteration over arrays.
|
||||
// Lets run an experiment to see how much faster a parallel loop is
|
||||
use Time; // Import the Time module to use Timer objects
|
||||
var timer: Timer;
|
||||
var myBigArray: [{1..4000,1..4000}] real; // Large array we will write into
|
||||
|
||||
// Serial Experiment
|
||||
timer.start( ); // Start timer
|
||||
for (x,y) in myBigArray.domain { // Serial iteration
|
||||
myBigArray[x,y] = (x:real) / (y:real);
|
||||
}
|
||||
timer.stop( ); // Stop timer
|
||||
writeln( "Serial: ", timer.elapsed( ) ); // Print elapsed time
|
||||
timer.clear( ); // Clear timer for parallel loop
|
||||
|
||||
// Parallel Experiment
|
||||
timer.start( ); // start timer
|
||||
forall (x,y) in myBigArray.domain { // Parallel iteration
|
||||
myBigArray[x,y] = (x:real) / (y:real);
|
||||
}
|
||||
timer.stop( ); // Stop timer
|
||||
writeln( "Parallel: ", timer.elapsed( ) ); // Print elapsed time
|
||||
timer.clear( );
|
||||
// You may have noticed that (depending on how many cores you have)
|
||||
// that the parallel loop went faster than the serial loop
|
||||
|
||||
// A succinct way of writing a forall loop over an array:
|
||||
// iterate over values
|
||||
[ val in myBigArray ] val = 1 / val;
|
||||
|
||||
// or iterate over indicies
|
||||
[ idx in myBigArray.domain ] myBigArray[idx] = -myBigArray[idx];
|
||||
|
||||
proc countdown( seconds: int ){
|
||||
for i in 1..seconds by -1 {
|
||||
writeln( i );
|
||||
sleep( 1 );
|
||||
|
||||
module SiblingModule {
|
||||
proc foo(){
|
||||
writeln( "SiblingModule.foo()" );
|
||||
}
|
||||
}
|
||||
}
|
||||
} // end OurModule
|
||||
|
||||
// Atomic variables, common to many languages, are ones whose operations
|
||||
// occur uninterupted. Multiple threads can both modify atomic variables
|
||||
// and can know that their values are safe.
|
||||
// Chapel atomic variables can be of type bool, int, uint, and real.
|
||||
var uranium: atomic int;
|
||||
uranium.write( 238 ); // atomically write a variable
|
||||
writeln( uranium.read() ); // atomically read a variable
|
||||
// Using OurModule also uses all the modules it uses.
|
||||
// Since OurModule uses Time, we also use time.
|
||||
use OurModule;
|
||||
|
||||
// operations are described as functions, you could define your own operators.
|
||||
uranium.sub( 3 ); // atomically subtract a variable
|
||||
writeln( uranium.read() );
|
||||
// At this point we have not used ChildModule or SiblingModule so their symbols
|
||||
// (i.e. foo ) are not available to us.
|
||||
// However, the module names are, and we can explicitly call foo() through them.
|
||||
SiblingModule.foo(); // Calls SiblingModule.foo()
|
||||
|
||||
var replaceWith = 239;
|
||||
var was = uranium.exchange( replaceWith );
|
||||
writeln( "uranium was ", was, " but is now ", replaceWith );
|
||||
// Super explicit naming.
|
||||
OurModule.ChildModule.foo(); // Calls ChildModule.foo()
|
||||
|
||||
var isEqualTo = 235;
|
||||
if uranium.compareExchange( isEqualTo, replaceWith ) {
|
||||
writeln( "uranium was equal to ", isEqualTo,
|
||||
" so replaced value with ", replaceWith );
|
||||
} else {
|
||||
writeln( "uranium was not equal to ", isEqualTo,
|
||||
" so value stays the same... whatever it was" );
|
||||
}
|
||||
use ChildModule;
|
||||
foo(); // Less explicit call on ChildModule.foo()
|
||||
|
||||
sync {
|
||||
begin { // Reader task
|
||||
writeln( "Reader: waiting for uranium to be ", isEqualTo );
|
||||
uranium.waitFor( isEqualTo );
|
||||
writeln( "Reader: uranium was set (by someone) to ", isEqualTo );
|
||||
// We can declare a main procedure
|
||||
// Note: all the code above main still gets executed.
|
||||
proc main(){
|
||||
|
||||
// Parallelism
|
||||
// In other languages, parallelism is typically this is done with
|
||||
// complicated libraries and strange class structure hierarchies.
|
||||
// Chapel has it baked right into the language.
|
||||
|
||||
// A begin statement will spin the body of that statement off
|
||||
// into one new task.
|
||||
// A sync statement will ensure that the progress of the main
|
||||
// task will not progress until the children have synced back up.
|
||||
sync {
|
||||
begin { // Start of new task's body
|
||||
var a = 0;
|
||||
for i in 1..1000 do a += 1;
|
||||
writeln( "Done: ", a);
|
||||
} // End of new tasks body
|
||||
writeln( "spun off a task!");
|
||||
}
|
||||
writeln( "Back together" );
|
||||
|
||||
proc printFibb( n: int ){
|
||||
writeln( "fibonacci(",n,") = ", fibonacci( n ) );
|
||||
}
|
||||
|
||||
begin { // Writer task
|
||||
writeln( "Writer: will set uranium to the value ", isEqualTo, " in..." );
|
||||
countdown( 3 );
|
||||
uranium.write( isEqualTo );
|
||||
// A cobegin statement will spin each statement of the body into one new task
|
||||
cobegin {
|
||||
printFibb( 20 ); // new task
|
||||
printFibb( 10 ); // new task
|
||||
printFibb( 5 ); // new task
|
||||
{
|
||||
// This is a nested statement body and thus is a single statement
|
||||
// to the parent statement and is executed by a single task
|
||||
writeln( "this gets" );
|
||||
writeln( "executed as" );
|
||||
writeln( "a whole" );
|
||||
}
|
||||
}
|
||||
}
|
||||
// Notice here that the prints from each statement may happen in any order.
|
||||
|
||||
// sync vars have two states: empty and full.
|
||||
// If you read an empty variable or write a full variable, you are waited
|
||||
// until the variable is full or empty again
|
||||
var someSyncVar$: sync int; // varName$ is a convention not a law.
|
||||
sync {
|
||||
begin { // Reader task
|
||||
writeln( "Reader: waiting to read." );
|
||||
var read_sync = someSyncVar$;
|
||||
writeln( "value is ", read_sync );
|
||||
// Coforall loop will create a new task for EACH iteration
|
||||
var num_tasks = 10; // Number of tasks we want
|
||||
coforall taskID in 1..#num_tasks {
|
||||
writeln( "Hello from task# ", taskID );
|
||||
}
|
||||
// Again we see that prints happen in any order.
|
||||
// NOTE! coforall should be used only for creating tasks!
|
||||
// Using it to iterating over a structure is very a bad idea!
|
||||
|
||||
begin { // Writer task
|
||||
writeln( "Writer: will write in..." );
|
||||
countdown( 3 );
|
||||
someSyncVar$ = 123;
|
||||
// forall loops are another parallel loop, but only create a smaller number
|
||||
// of tasks, specifically --dataParTasksPerLocale=number of task
|
||||
forall i in 1..100 {
|
||||
write( i, ", ");
|
||||
}
|
||||
}
|
||||
writeln( );
|
||||
// Here we see that there are sections that are in order, followed by
|
||||
// a section that would not follow ( e.g. 1, 2, 3, 7, 8, 9, 4, 5, 6, ).
|
||||
// This is because each task is taking on a chunk of the range 1..10
|
||||
// (1..3, 4..6, or 7..9) doing that chunk serially, but each task happens
|
||||
// in parallel.
|
||||
// Your results may depend on your machine and configuration
|
||||
|
||||
// single vars can only be written once. A read on an unwritten single results
|
||||
// in a wait, but when the variable has a value it can be read indefinitely
|
||||
var someSingleVar$: single int; // varName$ is a convention not a law.
|
||||
sync {
|
||||
begin { // Reader task
|
||||
writeln( "Reader: waiting to read." );
|
||||
for i in 1..5 {
|
||||
var read_single = someSingleVar$;
|
||||
writeln( "Reader: iteration ", i,", and the value is ", read_single );
|
||||
// For both the forall and coforall loops, the execution of the
|
||||
// parent task will not continue until all the children sync up.
|
||||
|
||||
// forall loops are particularly useful for parallel iteration over arrays.
|
||||
// Lets run an experiment to see how much faster a parallel loop is
|
||||
use Time; // Import the Time module to use Timer objects
|
||||
var timer: Timer;
|
||||
var myBigArray: [{1..4000,1..4000}] real; // Large array we will write into
|
||||
|
||||
// Serial Experiment
|
||||
timer.start( ); // Start timer
|
||||
for (x,y) in myBigArray.domain { // Serial iteration
|
||||
myBigArray[x,y] = (x:real) / (y:real);
|
||||
}
|
||||
timer.stop( ); // Stop timer
|
||||
writeln( "Serial: ", timer.elapsed( ) ); // Print elapsed time
|
||||
timer.clear( ); // Clear timer for parallel loop
|
||||
|
||||
// Parallel Experiment
|
||||
timer.start( ); // start timer
|
||||
forall (x,y) in myBigArray.domain { // Parallel iteration
|
||||
myBigArray[x,y] = (x:real) / (y:real);
|
||||
}
|
||||
timer.stop( ); // Stop timer
|
||||
writeln( "Parallel: ", timer.elapsed( ) ); // Print elapsed time
|
||||
timer.clear( );
|
||||
// You may have noticed that (depending on how many cores you have)
|
||||
// that the parallel loop went faster than the serial loop
|
||||
|
||||
// A succinct way of writing a forall loop over an array:
|
||||
// iterate over values
|
||||
[ val in myBigArray ] val = 1 / val;
|
||||
|
||||
// or iterate over indicies
|
||||
[ idx in myBigArray.domain ] myBigArray[idx] = -myBigArray[idx];
|
||||
|
||||
proc countdown( seconds: int ){
|
||||
for i in 1..seconds by -1 {
|
||||
writeln( i );
|
||||
sleep( 1 );
|
||||
}
|
||||
}
|
||||
|
||||
begin { // Writer task
|
||||
writeln( "Writer: will write in..." );
|
||||
countdown( 3 );
|
||||
someSingleVar$ = 5; // first and only write ever.
|
||||
// Atomic variables, common to many languages, are ones whose operations
|
||||
// occur uninterupted. Multiple threads can both modify atomic variables
|
||||
// and can know that their values are safe.
|
||||
// Chapel atomic variables can be of type bool, int, uint, and real.
|
||||
var uranium: atomic int;
|
||||
uranium.write( 238 ); // atomically write a variable
|
||||
writeln( uranium.read() ); // atomically read a variable
|
||||
|
||||
// operations are described as functions, you could define your own operators.
|
||||
uranium.sub( 3 ); // atomically subtract a variable
|
||||
writeln( uranium.read() );
|
||||
|
||||
var replaceWith = 239;
|
||||
var was = uranium.exchange( replaceWith );
|
||||
writeln( "uranium was ", was, " but is now ", replaceWith );
|
||||
|
||||
var isEqualTo = 235;
|
||||
if uranium.compareExchange( isEqualTo, replaceWith ) {
|
||||
writeln( "uranium was equal to ", isEqualTo,
|
||||
" so replaced value with ", replaceWith );
|
||||
} else {
|
||||
writeln( "uranium was not equal to ", isEqualTo,
|
||||
" so value stays the same... whatever it was" );
|
||||
}
|
||||
}
|
||||
|
||||
// Heres an example of using atomics and a synch variable to create a
|
||||
// count-down mutex (also known as a multiplexer)
|
||||
var count: atomic int; // our counter
|
||||
var lock$: sync bool; // the mutex lock
|
||||
sync {
|
||||
begin { // Reader task
|
||||
writeln( "Reader: waiting for uranium to be ", isEqualTo );
|
||||
uranium.waitFor( isEqualTo );
|
||||
writeln( "Reader: uranium was set (by someone) to ", isEqualTo );
|
||||
}
|
||||
|
||||
count.write( 2 ); // Only let two tasks in at a time.
|
||||
lock$.writeXF( true ); // Set lock$ to full (unlocked)
|
||||
// Note: The value doesnt actually matter, just the state
|
||||
// (full:unlocked / empty:locked)
|
||||
// Also, writeXF() fills (F) the sync var regardless of its state (X)
|
||||
begin { // Writer task
|
||||
writeln( "Writer: will set uranium to the value ", isEqualTo, " in..." );
|
||||
countdown( 3 );
|
||||
uranium.write( isEqualTo );
|
||||
}
|
||||
}
|
||||
|
||||
coforall task in 1..#5 { // Generate tasks
|
||||
// Create a barrier
|
||||
do{
|
||||
lock$; // Read lock$ (wait)
|
||||
}while count.read() < 1; // Keep waiting until a spot opens up
|
||||
// sync vars have two states: empty and full.
|
||||
// If you read an empty variable or write a full variable, you are waited
|
||||
// until the variable is full or empty again
|
||||
var someSyncVar$: sync int; // varName$ is a convention not a law.
|
||||
sync {
|
||||
begin { // Reader task
|
||||
writeln( "Reader: waiting to read." );
|
||||
var read_sync = someSyncVar$;
|
||||
writeln( "value is ", read_sync );
|
||||
}
|
||||
|
||||
begin { // Writer task
|
||||
writeln( "Writer: will write in..." );
|
||||
countdown( 3 );
|
||||
someSyncVar$ = 123;
|
||||
}
|
||||
}
|
||||
|
||||
// single vars can only be written once. A read on an unwritten single results
|
||||
// in a wait, but when the variable has a value it can be read indefinitely
|
||||
var someSingleVar$: single int; // varName$ is a convention not a law.
|
||||
sync {
|
||||
begin { // Reader task
|
||||
writeln( "Reader: waiting to read." );
|
||||
for i in 1..5 {
|
||||
var read_single = someSingleVar$;
|
||||
writeln( "Reader: iteration ", i,", and the value is ", read_single );
|
||||
}
|
||||
}
|
||||
|
||||
begin { // Writer task
|
||||
writeln( "Writer: will write in..." );
|
||||
countdown( 3 );
|
||||
someSingleVar$ = 5; // first and only write ever.
|
||||
}
|
||||
}
|
||||
|
||||
// Heres an example of using atomics and a synch variable to create a
|
||||
// count-down mutex (also known as a multiplexer)
|
||||
var count: atomic int; // our counter
|
||||
var lock$: sync bool; // the mutex lock
|
||||
|
||||
count.write( 2 ); // Only let two tasks in at a time.
|
||||
lock$.writeXF( true ); // Set lock$ to full (unlocked)
|
||||
// Note: The value doesnt actually matter, just the state
|
||||
// (full:unlocked / empty:locked)
|
||||
// Also, writeXF() fills (F) the sync var regardless of its state (X)
|
||||
|
||||
coforall task in 1..#5 { // Generate tasks
|
||||
// Create a barrier
|
||||
do{
|
||||
lock$; // Read lock$ (wait)
|
||||
}while count.read() < 1; // Keep waiting until a spot opens up
|
||||
|
||||
count.sub(1); // decrement the counter
|
||||
lock$.writeXF( true ); // Set lock$ to full (signal)
|
||||
count.sub(1); // decrement the counter
|
||||
lock$.writeXF( true ); // Set lock$ to full (signal)
|
||||
|
||||
// Actual 'work'
|
||||
writeln( "Task #", task, " doing work." );
|
||||
sleep( 2 );
|
||||
// Actual 'work'
|
||||
writeln( "Task #", task, " doing work." );
|
||||
sleep( 2 );
|
||||
|
||||
count.add( 1 ); // Increment the counter
|
||||
lock$.writeXF( true ); // Set lock$ to full (signal)
|
||||
}
|
||||
count.add( 1 ); // Increment the counter
|
||||
lock$.writeXF( true ); // Set lock$ to full (signal)
|
||||
}
|
||||
|
||||
// we can define the operations + * & | ^ && || min max minloc maxloc
|
||||
// over an entire array using scans and reductions
|
||||
// Reductions apply the operation over the entire array and
|
||||
// result in a single value
|
||||
var listOfValues: [1..10] int = [15,57,354,36,45,15,456,8,678,2];
|
||||
var sumOfValues = + reduce listOfValues;
|
||||
var maxValue = max reduce listOfValues; // 'max' give just max value
|
||||
// we can define the operations + * & | ^ && || min max minloc maxloc
|
||||
// over an entire array using scans and reductions
|
||||
// Reductions apply the operation over the entire array and
|
||||
// result in a single value
|
||||
var listOfValues: [1..10] int = [15,57,354,36,45,15,456,8,678,2];
|
||||
var sumOfValues = + reduce listOfValues;
|
||||
var maxValue = max reduce listOfValues; // 'max' give just max value
|
||||
|
||||
// 'maxloc' gives max value and index of the max value
|
||||
// Note: We have to zip the array and domain together with the zip iterator
|
||||
var (theMaxValue, idxOfMax) = maxloc reduce zip(listOfValues,
|
||||
listOfValues.domain);
|
||||
// 'maxloc' gives max value and index of the max value
|
||||
// Note: We have to zip the array and domain together with the zip iterator
|
||||
var (theMaxValue, idxOfMax) = maxloc reduce zip(listOfValues,
|
||||
listOfValues.domain);
|
||||
|
||||
writeln( (sumOfValues, maxValue, idxOfMax, listOfValues[ idxOfMax ] ) );
|
||||
writeln( (sumOfValues, maxValue, idxOfMax, listOfValues[ idxOfMax ] ) );
|
||||
|
||||
// Scans apply the operation incrementally and return an array of the
|
||||
// value of the operation at that index as it progressed through the
|
||||
// array from array.domain.low to array.domain.high
|
||||
var runningSumOfValues = + scan listOfValues;
|
||||
var maxScan = max scan listOfValues;
|
||||
writeln( runningSumOfValues );
|
||||
writeln( maxScan );
|
||||
// Scans apply the operation incrementally and return an array of the
|
||||
// value of the operation at that index as it progressed through the
|
||||
// array from array.domain.low to array.domain.high
|
||||
var runningSumOfValues = + scan listOfValues;
|
||||
var maxScan = max scan listOfValues;
|
||||
writeln( runningSumOfValues );
|
||||
writeln( maxScan );
|
||||
}
|
||||
```
|
||||
|
||||
Who is this tutorial for?
|
||||
|
||||
Loading…
Reference in New Issue
Block a user