# Setting up Your Environment for Chapel¶

To get started with Chapel, there are three environment settings that are strongly recommended for effective use of the release, and a number of other optional settings that are useful for cross-compiling or overriding the default settings. To check the values of the Chapel environment variables that are set or can be inferred, run the script:

$CHPL_HOME/util/printchplenv  The setchplenv.* source scripts in the $CHPL_HOME/util/quickstart/ and $CHPL_HOME/util/ directories contain commands that set the following variables for various shells and host platforms when they are sourced from the $CHPL_HOME directory. Frequent Chapel users may want to add such settings to their shell’s dotfile(s); but for getting started the setchplenv.* scripts can be convenient.

## Optional Settings¶

### CHPL_HOST_PLATFORM¶

You can set the CHPL_HOST_PLATFORM environment variable to represent the platform on which you’re working. For standard UNIX workstations, the default is sufficient, and is equivalent to

Note

If CHPL_TARGET_PLATFORM is not set, the target platform defaults to the same value as $CHPL_HOST_PLATFORM. ### CHPL_HOST_ARCH¶ Optionally, set the CHPL_HOST_ARCH environment variable to indicate the architecture type of the current machine. Normally, the default value is sufficient. Value Description x86_64 64-bit AMD and Intel processors aarch64 64-bit ARM processors If unset, the default will be computed. The command uname -m should produce the same value as the default. ### CHPL_TARGET_ARCH¶ Optionally, set the CHPL_TARGET_ARCH environment variable to indicate the architecture type of the target machine. See the table above for CHPL_HOST_ARCH for values this might be set to. If unset, CHPL_TARGET_ARCH will be inferred. If CHPL_TARGET_CPU is native, unknown, or none then CHPL_TARGET_ARCH will be set to CHPL_HOST_ARCH. Otherwise, CHPL_TARGET_ARCH will be set based on the architecture type specified in CHPL_TARGET_CPU. ### CHPL_*_COMPILER¶ Optionally, you can set CHPL_HOST_COMPILER and/or CHPL_TARGET_COMPILER to indicate the compiler suite to use in building the sources. CHPL_HOST_COMPILER is the compiler used to build the Chapel compiler itself so that it will run on CHPL_HOST_PLATFORM. CHPL_TARGET_COMPILER is the compiler used to build the runtime libraries and generated code for CHPL_TARGET_PLATFORM. Currently supported values are as follows: Value Description allinea The Allinea ARM compiler suite – clang and clang++ clang The Clang compiler suite – clang and clang++ clang-included The Clang compiler in third-party/llvm cray-prgenv-allinea The Cray PrgEnv compiler using the Allinea backend cray-prgenv-cray The Cray PrgEnv compiler using the Cray CCE backend cray-prgenv-gnu The Cray PrgEnv compiler using the GNU backend cray-prgenv-intel The Cray PrgEnv compiler using the Intel backend cray-prgenv-pgi The Cray PrgEnv compiler using the PGI backend gnu The GNU compiler suite – gcc and g++ ibm The IBM compiler suite – xlc and xlC intel The Intel compiler suite – icc and icpc pgi The PGI compiler suite – pgcc and pgc++ The default for CHPL_*_COMPILER depends on the value of the corresponding CHPL_*_PLATFORM environment variable: Platform Compiler cray-xc, hpe-cray-ex • gnu (for CHPL_HOST_COMPILER) • cray-prgenv-$PE_ENV (for CHPL_TARGET_COMPILER, where PE_ENV is set by PrgEnv-* modules)

darwin

clang if available, otherwise gnu

pwr6

ibm

other

gnu

If CHPL_HOST_PLATFORM == CHPL_TARGET_PLATFORM and is not cray-x* or hpe-cray-ex, CHPL_TARGET_COMPILER will default to the same value as CHPL_HOST_COMPILER.

Note

Note that builds with LLVM Support (i.e. when CHPL_LLVM=bundled) will build the runtime twice: once with the compiler as described above and once with clang-included. We do this in order to avoid issues in linking objects built by different compilers.

### CHPL_TARGET_CPU¶

Optionally, set the CHPL_TARGET_CPU environment variable to indicate that the target executable should be specialized to the given architecture when using --specialize (and --fast). Valid options are:

Value

Description

native

The C compiler will attempt to detect the architecture on the machine that is compiling the target executable. This is a good choice if you will be running on the same machine that you are compiling on. If you are not, see the options below.

unknown

No specialization will be performed

none

No specialization will be performed (will not warn)

Architecture-specific values

intel

amd

arm

core2

k8

aarch64

nehalem

k8sse3

thunderx

westmere

barcelona

thunderx2t99

sandybridge

bdver1

ivybridge

bdver2

haswell

bdver3

bdver4

skylake

knl

These values are defined to be the same as in GCC 7:

If you do not want CHPL_TARGET_CPU to have any effect, you can set it to either unknown or none. Both will disable specialization, but the latter will not warn if --specialize is used.

Setting CHPL_TARGET_CPU to an incorrect value for your processor may result in an invalid binary that will not run on the intended machine. Special care should be taken to select the lowest common denominator when running on machines with heterogeneous processor architectures.

The default value for this setting will vary based on settings in your environment, in order of application these rules are:

• If CHPL_TARGET_COMPILER is cray-prgenv-* you do not need to set anything in CHPL_TARGET_CPU. One of the craype-* modules (e.g. craype-sandybridge) should be loaded to provide equivalent functionality. Once the proper module is loaded, CRAY_CPU_TARGET will have the architecture being used in it.

• If CHPL_TARGET_COMPILER is cray, pgi, or ibm, CHPL_TARGET_CPU will be set to none and no specialization will occur.

• If CHPL_COMM is set, no attempt to set a useful value will be made and CHPL_TARGET_CPU will be unknown.

• If CHPL_TARGET_PLATFORM is darwin, linux*, or cygwin* CHPL_TARGET_CPU will be native, passing the responsibility off to the backend C compiler to detect the specifics of the hardware.

Optionally, set the CHPL_MAKE environment variable to indicate the GNU-compatible make utility that you want the compiler back-end to invoke when compiling the generated C code. If not set, this will default to a value based on $CHPL_HOST_PLATFORM: platform make utility cygwin*, darwin make linux32, linux64 gmake if available, otherwise make other gmake ### CHPL_MODULE_PATH¶ Optionally, set the CHPL_MODULE_PATH environment variable to provide a list of directories to be added to the Module Search Paths. The value of this environment variable should be a colon-separated list of directory paths. The module search path is used to satisfy ‘use’ statements in the Chapel program. The complete search path can be displayed using the compiler option --print-search-dirs. It will also include the compiler’s standard module search paths, those introduced by the -M flag on the command line and directories containing the .chpl files named explicitly on the compiler command line. ### CHPL_LOCALE_MODEL¶ Optionally, set the CHPL_LOCALE_MODEL environment variable to indicate the locale model you want to use. Current options are: Value Description flat top-level locales are not further subdivided numa top-level locales are further subdivided into sublocales, each one a NUMA domain If unset, CHPL_LOCALE_MODEL defaults to flat. See Locale Models for more information about locale models. ### CHPL_TASKS¶ Optionally, set the CHPL_TASKS environment variable to indicate what tasking layer you want to use to implement intra-locale parallelism (see Chapel Tasks for more information on this option). Current options are: Value Description qthreads use Sandia’s Qthreads package fifo use POSIX threads If CHPL_TASKS is not set it defaults to qthreads in all cases except for a few specific configurations in which it defaults to fifo: • target platform is cygwin* • target platform is netbsd* Note Note that the Chapel util/quickstart/setchplenv.* source scripts set CHPL_TASKS to fifo to reduce build-time and third-party dependences, while the util/setchplenv.* versions leave it unset, resulting in the behavior described just above. See Chapel Tasks for more information about executing using the various CHPL_TASKS options. ### CHPL_COMM¶ Optionally, set the CHPL_COMM environment variable to indicate what communication layer you want to use to implement inter-locale communication. Current options are: Value Description none only supports single-locale execution gasnet use the GASNet-based communication layer ofi use the libfabric-based communication layer ugni Cray-specific native communication layer If unset, CHPL_COMM defaults to none in most cases. On Cray XC systems it defaults to ugni. On Cray CS systems it defaults to gasnet. See Multilocale Chapel Execution for more information on executing Chapel programs using multiple locales. See Using Chapel with libfabric for more information about the ofi communication layer. See Using Chapel on Cray Systems for more information about Cray-specific runtime layers. ### CHPL_MEM¶ Optionally, the CHPL_MEM environment variable can be used to select a memory management layer. Current options are: Value Description cstdlib use the standard C malloc/free commands jemalloc use Jason Evan’s memory allocator If unset, CHPL_MEM defaults to jemalloc for most configurations. If the target platform is cygwin* it defaults to cstdlib Note Certain CHPL_COMM settings (e.g. ugni, gasnet segment fast/large, ofi with the gni provider) register the heap to improve communication performance. Registering the heap requires special allocator support that not all allocators provide. Currently only jemalloc is capable of supporting configurations that require a registered heap. ### CHPL_LAUNCHER¶ Optionally, the CHPL_LAUNCHER environment variable can be used to select a launcher to get your program up and running. See Chapel Launchers for more information on this variable’s default and possible settings. ### CHPL_ATOMICS¶ Optionally, the CHPL_ATOMICS environment variable can be used to select an implementation for atomic operations in the runtime. Current options are: Value Description cstdlib implement atomics with C standard atomics (from C11) intrinsics implement atomics with target compiler intrinsics locks implement atomics with mutexes If CHPL_ATOMICS is not set, it defaults to cstdlib when the target compiler is gnu, clang, allinea, clang-included, or cray. It defaults to intrinsics when the target compiler is intel. It defaults to locks when the target compiler is pgi. See the Chapel Language Specification for more information about atomic operations in Chapel or Runtime Support for Atomics for more information about the runtime implementation. ### CHPL_TIMERS¶ Optionally, the CHPL_TIMERS environment variable can be used to select an implementation for Chapel’s timers. Current options are: generic use a gettimeofday()-based implementation If unset, CHPL_TIMERS defaults to generic ### CHPL_GMP¶ Optionally, the CHPL_GMP environment variable can select between no GMP support, using the GMP distributed with Chapel in third-party, or using a system GMP. Current options are: Value Description system use a system install of GMP (#include gmp.h, -lgmp) none do not build GMP support into the Chapel runtime bundled use the GMP distribution bundled with Chapel in third-party gmp deprecated - use bundled instead If unset, Chapel will attempt to build GMP using CHPL_TARGET_COMPILER (noting that the bundled version may not be supported by all compilers). Based on the outcome, Chapel will default to: Value Description bundled if the build was successful system if unsuccessful and CHPL_TARGET_PLATFORM is cray-x* none otherwise Note Note that the Chapel util/quickstart/setchplenv.* source scripts set CHPL_GMP to none while the util/setchplenv.* versions leave it unset, resulting in the behavior described just above. ### CHPL_HWLOC¶ Optionally, the CHPL_HWLOC environment variable can select between no hwloc support or using the hwloc package distributed with Chapel in third-party. Value Description none do not build hwloc support into the Chapel runtime bundled use the hwloc distribution bundled with Chapel in third-party hwloc deprecated - use bundled instead If unset, CHPL_HWLOC defaults to bundled if CHPL_TASKS is qthreads. In all other cases it defaults to none. In the unlikely event the bundled hwloc distribution does not build successfully, it should still be possible to use qthreads. To do this, manually set CHPL_HWLOC to none and rebuild (and please file a bug with the Chapel team.) Note that building without hwloc will have a negative impact on performance. ### CHPL_REGEXP¶ Optionally, the CHPL_REGEXP environment variable can be used to enable regular expression operations as defined in Regexp. Current options are: Value Description re2 use the re2 distribution in third-party none do not support regular expression operations If unset, Chapel will attempt to build RE2 using CHPL_TARGET_COMPILER (noting that the bundled version may not be supported by all compilers). Based on the outcome, Chapel will default to: Value Description re2 if the build was successful none otherwise Note Note that the Chapel util/quickstart/setchplenv.* source scripts set CHPL_REGEXP to 'none while the util/setchplenv.* versions leave it unset, resulting in the behavior described just above. ### CHPL_AUX_FILESYS¶ Optionally, the CHPL_AUX_FILESYS environment variable can be used to request runtime support for certain filesystems. Value Description none only support traditional Linux filesystems lustre enable I/O improvements specific to Lustre filesystems If unset, CHPL_AUX_FILESYS defaults to none. ### CHPL_LLVM¶ Optionally, the CHPL_LLVM environment variable can be used to enable support for the LLVM back-end to the Chapel compiler (see LLVM Support) or to support extern blocks in Chapel code via the Clang compiler (see C Interoperability). Current options are: Value Description bundled use the llvm/clang distribution in third-party llvm deprecated - use bundled instead system find a compatible LLVM in system libraries; note: the LLVM must be a version supported by Chapel none do not support llvm/clang-related features If unset, CHPL_LLVM defaults to bundled if you’ve already installed llvm in third-party and none otherwise. Chapel currently supports LLVM 11.0. Note We have had success with this procedure to install LLVM 11.0 dependencies on Ubuntu. First, follow the instructions at https://apt.llvm.org that explain how to place the appropriate lines into /etc/apt/sources.list.d/llvm-toolchain.list and retrieve the archive signature, then do the following. apt-get install llvm-11-dev llvm-11 llvm-11-tools clang-11 libclang-11-dev libedit-dev  ### CHPL_UNWIND¶ Optionally, the CHPL_UNWIND environment variable can be used to select an unwind library for stack tracing. Current options are: Value Description bundled use the libunwind bundled with Chapel in third-party libunwind deprecated - use bundled instead system assume libunwind is already installed on the system none don’t use an unwind library, disabling stack tracing If unset, CHPL_UNWIND defaults to none ### CHPL_LIB_PIC¶ Optionally, the CHPL_LIB_PIC environment variable can be used to build position independent or position dependent code. This is intended for use when Calling Chapel Code from Other Languages, especially when Using Your Library in Python or when building with --dynamic. Current options are: Value Description pic build position independent code none build position dependent code If unset, CHPL_LIB_PIC defaults to none ## Character Set¶ Chapel works with the Unicode character set with UTF-8 encoding and the traditional C collating sequence. Users are responsible for making sure that they are running Chapel in a suitable environment. For example, for en_US locale, the following environment variables should be set: LANG=en_US.UTF-8 LC_COLLATE=C LC_ALL=""  Note Other character sets may be supported in the future. ## Compiler Command Line Option Defaults¶ Most of the compiler’s command line options support setting a default value for the option via an environment variable. To see a list of the environment variables that support each option, run the compiler with the --help-env flag. For boolean flags and toggles, setting the environment variable to any value selects that flag. ## Chapel Configuration File¶ The Chapel configuration file is a file named either chplconfig or .chplconfig that can store overrides of the inferred environment variables listed as a result of executing printchplenv. ### Syntax¶ Below are the valid forms of syntax for Chapel configuration files. All other usages will result in a syntax error. Definitions Users can define variables with the following format: CHPL_ENV=value  Above, the default value of CHPL_ENV will be overridden to be value. All white space is stripped away from definitions. Ignored Lines Any lines containing nothing or only white space will be ignored. Comments, which are denoted by the # character, similar to bash or python, are also ignored. ### Example¶ Below is an example of a Chapel configuration file with comments: # ~/.chplconfig # Default to multi-locale CHPL_COMM=gasnet CHPL_TASKS=qthreads # Use Qthreads # System GMP is available on these machines CHPL_GMP=system  To confirm the configuration file is written correctly, you can run printchplenv --all --overrides, which will show a list of variables that are currently being overridden. Values followed by a + have been overridden by the Chapel configuration file, whereas values followed by a * have been overridden by an environment variable. ### Generating Configuration Files¶ To generate a configuration file based on the current configuration, use printchplenv or ./configure. When using printchplenv, run it with the --simple format flag to get a format compatible with Chapel configuration files. The --overrides filter flag can be used to print only the variables currently overridden by either environment variables or Chapel configuration file. For example, to save the current overrides into a Chapel configuration file: printchplenv --all --simple --overrides > ~/.chplconfig  The printchplenv --all --simple flag can be used to print all the variables of the current configuration. For example: printchplenv --all --simple > ~/.chplconfig  For more information on using printchplenv, see the printchplenv -h output. Alternatively, the ./configure script will generate a chplconfig file. See Installing Chapel. ### Search Paths and File Names¶ Though you can put your Chapel configuration file anywhere by setting the $CHPL_CONFIG environment variable to its enclosing directory, you can also place it in your $HOME or $CHPL_HOME directory and Chapel will be able to find it.

The search priority for Chapel configuration files is as follows:

1. $CHPL_CONFIG 2. $HOME (~/)

3. $CHPL_HOME When both a chplconfig and .chplconfig are present, the visible chplconfig will be prioritized. Only a single chplconfig file will be used. That is, as soon as a valid Chapel configuration file is found, the definitions of that file are used. Note The $CHPL_CONFIG variable is the path to the enclosing directory - not the full path including chplconfig itself.

### Variable Priority¶

Variable precedence goes in the following order:

1. Explicit compiler flags: chpl --env=value

2. Environment variables: CHPL_ENV=value

3. Chapel configuration file: ~/.chplconfig

4. Inferred environment variables: printchplenv