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Merge pull request #1183 from ian-bertolacci/master

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[Chapel] Modules, main(), range/domain/array slicing and array assignment, loop expressions, zipped iterators
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Levi Bostian 2015-08-06 08:54:25 -05:00
commit d1874637c7
1 changed files with 352 additions and 214 deletions
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@ -24,7 +24,7 @@ writeln( "World!" );
// each thing is printed right next to each other, so include your spacing! // each thing is printed right next to each other, so include your spacing!
writeln( "There are ", 3, " commas (\",\") in this line of code" ); writeln( "There are ", 3, " commas (\",\") in this line of code" );
// Different output channels // Different output channels
stdout.writeln( "This goes to standard output (just like plain writeln( ) does)"); stdout.writeln( "This goes to standard output, just like plain writeln() does");
stderr.writeln( "This goes to standard error" ); stderr.writeln( "This goes to standard error" );
// Variables don't have to be explicitly typed as long as // Variables don't have to be explicitly typed as long as
@ -285,6 +285,7 @@ for i in rangeCountBy{
} }
// Rectangular domains are defined using the same range syntax // Rectangular domains are defined using the same range syntax
// However they are required to be bounded (unlike ranges)
var domain1to10: domain(1) = {1..10}; // 1D domain from 1..10; var domain1to10: domain(1) = {1..10}; // 1D domain from 1..10;
var twoDimensions: domain(2) = {-2..2,0..2}; // 2D domain over product of ranges var twoDimensions: domain(2) = {-2..2,0..2}; // 2D domain over product of ranges
var thirdDim: range = 1..16; var thirdDim: range = 1..16;
@ -310,6 +311,18 @@ stringSet += "a"; // Redundant add "a"
stringSet -= "c"; // Remove "c" stringSet -= "c"; // Remove "c"
writeln( stringSet ); writeln( stringSet );
// Both ranges and domains can be sliced to produce a range or domain with the
// intersection of indices
var rangeA = 1.. ; // range from 1 to infinity
var rangeB = ..5; // range from negative infinity to 5
var rangeC = rangeA[rangeB]; // resulting range is 1..5
writeln( (rangeA, rangeB, rangeC ) );
var domainA = {1..10, 5..20};
var domainB = {-5..5, 1..10};
var domainC = domainA[domainB];
writeln( (domainA, domainB, domainC) );
// Array are similar to those of other languages. // Array are similar to those of other languages.
// Their sizes are defined using domains that represent their indices // Their sizes are defined using domains that represent their indices
var intArray: [1..10] int; var intArray: [1..10] int;
@ -357,6 +370,48 @@ var dict: [dictDomain] int = [ "one" => 1, "two" => 2 ];
dict["three"] = 3; dict["three"] = 3;
for key in dictDomain do writeln( dict[key] ); for key in dictDomain do writeln( dict[key] );
// Arrays can be assigned to each other in different ways
var thisArray : [{0..5}] int = [0,1,2,3,4,5];
var thatArray : [{0..5}] int;
// Simply assign one to the other.
// This copies thisArray into thatArray, instead of just creating a reference.
// Modifying thisArray does not also modify thatArray.
thatArray = thisArray;
thatArray[1] = -1;
writeln( (thisArray, thatArray) );
// Assign a slice one array to a slice (of the same size) of the other.
thatArray[{4..5}] = thisArray[{1..2}];
writeln( (thisArray, thatArray) );
// Operation can also be promoted to work on arrays.
var thisPlusThat = thisArray + thatArray;
writeln( thisPlusThat );
// Arrays and loops can also be expressions, where loop
// body's expression is the result of each iteration.
var arrayFromLoop = for i in 1..10 do i;
writeln( arrayFromLoop );
// An expression can result in nothing,
// such as when filtering with an if-expression
var evensOrFives = for i in 1..10 do if (i % 2 == 0 || i % 5 == 0) then i;
writeln( arrayFromLoop );
// Or could be written with a bracket notation
// Note: this syntax uses the 'forall' parallel concept discussed later.
var evensOrFivesAgain = [ i in 1..10 ] if (i % 2 == 0 || i % 5 == 0) then i;
// Or over the values of the array
arrayFromLoop = [ value in arrayFromLoop ] value + 1;
// Note: this notation can get somewhat tricky. For example:
// evensOrFives = [ i in 1..10 ] if (i % 2 == 0 || i % 5 == 0) then i;
// would break.
// The reasons for this are explained in depth when discussing zipped iterators.
// Chapel procedures have similar syntax to other languages functions. // Chapel procedures have similar syntax to other languages functions.
proc fibonacci( n : int ) : int { proc fibonacci( n : int ) : int {
if ( n <= 1 ) then return n; if ( n <= 1 ) then return n;
@ -533,6 +588,19 @@ iter oddsThenEvens( N: int ): int {
for i in oddsThenEvens( 10 ) do write( i, ", " ); for i in oddsThenEvens( 10 ) do write( i, ", " );
writeln( ); writeln( );
// Iterators can also yield conditionally, the result of which can be nothing
iter absolutelyNothing( N ): int {
for i in 1..N {
if ( N < i ) { // Always false
yield i; // Yield statement never happens
}
}
}
for i in absolutelyNothing( 10 ){
writeln( "Woa there! absolutelyNothing yielded ", i );
}
// We can zipper together two or more iterators (who have the same number // We can zipper together two or more iterators (who have the same number
// of iterations) using zip() to create a single zipped iterator, where each // of iterations) using zip() to create a single zipped iterator, where each
// iteration of the zipped iterator yields a tuple of one value yielded // iteration of the zipped iterator yields a tuple of one value yielded
@ -541,6 +609,34 @@ writeln( );
for (positive, negative) in zip( 1..5, -5..-1) do for (positive, negative) in zip( 1..5, -5..-1) do
writeln( (positive, negative) ); writeln( (positive, negative) );
// Zipper iteration is quite important in the assignment of arrays,
// slices of arrays, and array/loop expressions.
var fromThatArray : [1..#5] int = [1,2,3,4,5];
var toThisArray : [100..#5] int;
// The operation
toThisArray = fromThatArray;
// is produced through
for (i,j) in zip( toThisArray.domain, fromThatArray.domain) {
toThisArray[ i ] = fromThatArray[ j ];
}
toThisArray = [ j in -100..#5 ] j;
writeln( toThisArray );
// is produced through
for (i, j) in zip( toThisArray.domain, -100..#5 ){
toThisArray[i] = j;
}
writeln( toThisArray );
// This is all very important in undestanding why the statement
// var iterArray : [1..10] int = [ i in 1..10 ] if ( i % 2 == 1 ) then j;
// exhibits a runtime error.
// Even though the domain of the array and the loop-expression are
// the same size, the body of the expression can be though of as an iterator.
// Because iterators can yield nothing, that iterator yields a different number
// of things than the domain of the array or loop, which is not allowed.
// Classes are similar to those in C++ and Java. // Classes are similar to those in C++ and Java.
// They currently lack privatization // They currently lack privatization
class MyClass { class MyClass {
@ -673,30 +769,82 @@ var copyNewTypeList = new GenericClass( realList, int );
for value in copyNewTypeList do write( value, ", " ); for value in copyNewTypeList do write( value, ", " );
writeln( ); writeln( );
// Parallelism // Modules are Chapel's way of managing name spaces.
// In other languages, parallelism is typically this is done with // The files containing these modules do not need to be named after the modules
// complicated libraries and strange class structure hierarchies. // (as in Java), but files implicitly name modules.
// Chapel has it baked right into the language. // In this case, this file implicitly names the 'learnchapel' module
// A begin statement will spin the body of that statement off into one new task. module OurModule {
// A sync statement will ensure that the progress of the main // We can use modules inside of other modules.
// task will not progress until the children have synced back up. use Time; // Time is one of the standard modules.
sync {
// We'll use this procedure in the parallelism section.
proc countdown( seconds: int ){
for i in 1..seconds by -1 {
writeln( i );
sleep( 1 );
}
}
// Submodules of OurModule
// It is possible to create arbitrarily deep module nests.
module ChildModule {
proc foo(){
writeln( "ChildModule.foo()");
}
}
module SiblingModule {
proc foo(){
writeln( "SiblingModule.foo()" );
}
}
} // end OurModule
// Using OurModule also uses all the modules it uses.
// Since OurModule uses Time, we also use time.
use OurModule;
// 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()
// Super explicit naming.
OurModule.ChildModule.foo(); // Calls ChildModule.foo()
use ChildModule;
foo(); // Less explicit call on ChildModule.foo()
// We can declare a main procedure
// Note: all the code above main still gets executed.
proc main(){
// Parallelism
// In other languages, parallelism is typically 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 begin { // Start of new task's body
var a = 0; var a = 0;
for i in 1..1000 do a += 1; for i in 1..1000 do a += 1;
writeln( "Done: ", a); writeln( "Done: ", a);
} // End of new tasks body } // End of new tasks body
writeln( "spun off a task!"); writeln( "spun off a task!");
} }
writeln( "Back together" ); writeln( "Back together" );
proc printFibb( n: int ){ proc printFibb( n: int ){
writeln( "fibonacci(",n,") = ", fibonacci( n ) ); writeln( "fibonacci(",n,") = ", fibonacci( n ) );
} }
// A cobegin statement will spin each statement of the body into one new task // A cobegin statement will spin each statement of the body into one new task
cobegin { cobegin {
printFibb( 20 ); // new task printFibb( 20 ); // new task
printFibb( 10 ); // new task printFibb( 10 ); // new task
printFibb( 5 ); // new task printFibb( 5 ); // new task
@ -707,100 +855,90 @@ cobegin {
writeln( "executed as" ); writeln( "executed as" );
writeln( "a whole" ); writeln( "a whole" );
} }
}
// 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 );
} }
} // Notice here that the prints from each statement may happen in any order.
// Atomic variables, common to many languages, are ones whose operations // Coforall loop will create a new task for EACH iteration
// occur uninterupted. Multiple threads can both modify atomic variables var num_tasks = 10; // Number of tasks we want
// and can know that their values are safe. coforall taskID in 1..#num_tasks {
// Chapel atomic variables can be of type bool, int, uint, and real. writeln( "Hello from task# ", taskID );
var uranium: atomic int; }
uranium.write( 238 ); // atomically write a variable // Again we see that prints happen in any order.
writeln( uranium.read() ); // atomically read a variable // NOTE! coforall should be used only for creating tasks!
// Using it to iterating over a structure is very a bad idea!
// operations are described as functions, you could define your own operators. // forall loops are another parallel loop, but only create a smaller number
uranium.sub( 3 ); // atomically subtract a variable // of tasks, specifically --dataParTasksPerLocale=number of task
writeln( uranium.read() ); 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
var replaceWith = 239; // For both the forall and coforall loops, the execution of the
var was = uranium.exchange( replaceWith ); // parent task will not continue until all the children sync up.
writeln( "uranium was ", was, " but is now ", replaceWith );
var isEqualTo = 235; // forall loops are particularly useful for parallel iteration over arrays.
if uranium.compareExchange( isEqualTo, replaceWith ) { // 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
// The bracket style loop-expression described
// much earlier implicitly uses a forall loop.
[ val in myBigArray ] val = 1 / val; // Parallel operation
// 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, writeln( "uranium was equal to ", isEqualTo,
" so replaced value with ", replaceWith ); " so replaced value with ", replaceWith );
} else { } else {
writeln( "uranium was not equal to ", isEqualTo, writeln( "uranium was not equal to ", isEqualTo,
" so value stays the same... whatever it was" ); " so value stays the same... whatever it was" );
} }
sync { sync {
begin { // Reader task begin { // Reader task
writeln( "Reader: waiting for uranium to be ", isEqualTo ); writeln( "Reader: waiting for uranium to be ", isEqualTo );
uranium.waitFor( isEqualTo ); uranium.waitFor( isEqualTo );
@ -812,13 +950,13 @@ sync {
countdown( 3 ); countdown( 3 );
uranium.write( isEqualTo ); uranium.write( isEqualTo );
} }
} }
// sync vars have two states: empty and full. // sync vars have two states: empty and full.
// If you read an empty variable or write a full variable, you are waited // If you read an empty variable or write a full variable, you are waited
// until the variable is full or empty again // until the variable is full or empty again
var someSyncVar$: sync int; // varName$ is a convention not a law. var someSyncVar$: sync int; // varName$ is a convention not a law.
sync { sync {
begin { // Reader task begin { // Reader task
writeln( "Reader: waiting to read." ); writeln( "Reader: waiting to read." );
var read_sync = someSyncVar$; var read_sync = someSyncVar$;
@ -830,12 +968,12 @@ sync {
countdown( 3 ); countdown( 3 );
someSyncVar$ = 123; someSyncVar$ = 123;
} }
} }
// single vars can only be written once. A read on an unwritten single results // 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 // 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. var someSingleVar$: single int; // varName$ is a convention not a law.
sync { sync {
begin { // Reader task begin { // Reader task
writeln( "Reader: waiting to read." ); writeln( "Reader: waiting to read." );
for i in 1..5 { for i in 1..5 {
@ -849,24 +987,24 @@ sync {
countdown( 3 ); countdown( 3 );
someSingleVar$ = 5; // first and only write ever. someSingleVar$ = 5; // first and only write ever.
} }
} }
// Heres an example of using atomics and a synch variable to create a // Heres an example of using atomics and a synch variable to create a
// count-down mutex (also known as a multiplexer) // count-down mutex (also known as a multiplexer)
var count: atomic int; // our counter var count: atomic int; // our counter
var lock$: sync bool; // the mutex lock var lock$: sync bool; // the mutex lock
count.write( 2 ); // Only let two tasks in at a time. count.write( 2 ); // Only let two tasks in at a time.
lock$.writeXF( true ); // Set lock$ to full (unlocked) lock$.writeXF( true ); // Set lock$ to full (unlocked)
// Note: The value doesnt actually matter, just the state // Note: The value doesnt actually matter, just the state
// (full:unlocked / empty:locked) // (full:unlocked / empty:locked)
// Also, writeXF() fills (F) the sync var regardless of its state (X) // Also, writeXF() fills (F) the sync var regardless of its state (X)
coforall task in 1..#5 { // Generate tasks coforall task in 1..#5 { // Generate tasks
// Create a barrier // Create a barrier
do{ do{
lock$; // Read lock$ (wait) lock$; // Read lock$ (wait)
}while count.read() < 1; // Keep waiting until a spot opens up }while ( count.read() < 1 ); // Keep waiting until a spot opens up
count.sub(1); // decrement the counter count.sub(1); // decrement the counter
lock$.writeXF( true ); // Set lock$ to full (signal) lock$.writeXF( true ); // Set lock$ to full (signal)
@ -877,30 +1015,31 @@ coforall task in 1..#5 { // Generate tasks
count.add( 1 ); // Increment the counter count.add( 1 ); // Increment the counter
lock$.writeXF( true ); // Set lock$ to full (signal) lock$.writeXF( true ); // Set lock$ to full (signal)
} }
// we can define the operations + * & | ^ && || min max minloc maxloc // we can define the operations + * & | ^ && || min max minloc maxloc
// over an entire array using scans and reductions // over an entire array using scans and reductions
// Reductions apply the operation over the entire array and // Reductions apply the operation over the entire array and
// result in a single value // result in a single value
var listOfValues: [1..10] int = [15,57,354,36,45,15,456,8,678,2]; var listOfValues: [1..10] int = [15,57,354,36,45,15,456,8,678,2];
var sumOfValues = + reduce listOfValues; var sumOfValues = + reduce listOfValues;
var maxValue = max reduce listOfValues; // 'max' give just max value var maxValue = max reduce listOfValues; // 'max' give just max value
// 'maxloc' gives max value and index of the 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 // Note: We have to zip the array and domain together with the zip iterator
var (theMaxValue, idxOfMax) = maxloc reduce zip(listOfValues, var (theMaxValue, idxOfMax) = maxloc reduce zip(listOfValues,
listOfValues.domain); 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 // Scans apply the operation incrementally and return an array of the
// value of the operation at that index as it progressed through the // value of the operation at that index as it progressed through the
// array from array.domain.low to array.domain.high // array from array.domain.low to array.domain.high
var runningSumOfValues = + scan listOfValues; var runningSumOfValues = + scan listOfValues;
var maxScan = max scan listOfValues; var maxScan = max scan listOfValues;
writeln( runningSumOfValues ); writeln( runningSumOfValues );
writeln( maxScan ); writeln( maxScan );
} // end main()
``` ```
Who is this tutorial for? Who is this tutorial for?
@ -908,18 +1047,15 @@ Who is this tutorial for?
This tutorial is for people who want to learn the ropes of chapel without having to hear about what fiber mixture the ropes are, or how they were braided, or how the braid configurations differ between one another. This tutorial is for people who want to learn the ropes of chapel without having to hear about what fiber mixture the ropes are, or how they were braided, or how the braid configurations differ between one another.
It won't teach you how to develop amazingly performant code, and it's not exhaustive. It won't teach you how to develop amazingly performant code, and it's not exhaustive.
Refer to the [language specification](http://chapel.cray.com/language.html) and the [library documentation](http://chapel.cray.com/docs/latest/) for more details. Refer to the [language specification](http://chapel.cray.com/language.html) and the [module documentation](http://chapel.cray.com/docs/latest/) for more details.
Occasionally check back here and on the [Chapel site](http://chapel.cray.com) to see if more topics have been added or more tutorials created. Occasionally check back here and on the [Chapel site](http://chapel.cray.com) to see if more topics have been added or more tutorials created.
### What this tutorial is lacking: ### What this tutorial is lacking:
* Modules and standard modules * Exposition of the standard modules
* Multiple Locales (distributed memory system) * Multiple Locales (distributed memory system)
* ```proc main(){ ... }```
* Records * Records
* Whole/sliced array assignment
* Range and domain slicing
* Parallel iterators * Parallel iterators
Your input, questions, and discoveries are important to the developers! Your input, questions, and discoveries are important to the developers!
@ -940,26 +1076,28 @@ Chapel can be built and installed on your average 'nix machine (and cygwin).
[Download the latest release version](https://github.com/chapel-lang/chapel/releases/) [Download the latest release version](https://github.com/chapel-lang/chapel/releases/)
and its as easy as and its as easy as
1. ```tar -xvf chapel-1.11.0.tar.gz``` 1. `tar -xvf chapel-1.11.0.tar.gz`
2. ```cd chapel-1.11.0``` 2. `cd chapel-1.11.0`
3. ```make``` 3. `make`
4. ```source util/setchplenv.bash # or .sh or .csh or .fish``` 4. `source util/setchplenv.bash # or .sh or .csh or .fish`
You will need to `source util/setchplenv.EXT` from within the Chapel directory (`$CHPL_HOME`) every time your terminal starts so its suggested that you drop that command in a script that will get executed on startup (like .bashrc). You will need to `source util/setchplenv.EXT` from within the Chapel directory (`$CHPL_HOME`) every time your terminal starts so its suggested that you drop that command in a script that will get executed on startup (like .bashrc).
Chapel is easily installed with Brew for OS X Chapel is easily installed with Brew for OS X
1. ```brew update``` 1. `brew update`
2. ```brew install chapel``` 2. `brew install chapel`
Compiling Code Compiling Code
-------------- --------------
Builds like other compilers: Builds like other compilers:
```chpl myFile.chpl -o myExe``` `chpl myFile.chpl -o myExe`
Notable arguments: Notable arguments:
* ``--fast``: enables a number of optimizations and disables array bounds checks. Should only enable when application is stable. * `--fast`: enables a number of optimizations and disables array bounds checks. Should only enable when application is stable.
* ```--set <Symbol Name>=<Value>```: set config param <Symbol Name> to <Value> at compile-time * `--set <Symbol Name>=<Value>`: set config param `<Symbol Name>` to `<Value>` at compile-time.
* `--main-module <Module Name>`: use the main() procedure found in the module `<Module Name>` as the executable's main.
* `--module-dir <Directory>`: includes `<Directory>` in the module search path.