GNU UPC
A Unified Parallel C (UPC)
Compilation and Execution Environment
Based on the GNU C Compiler (GCC)

.upc     UPC source; preprocess, compile, assemble
.upci    Preprocessed UPC; compile, assemble
.h       Preprocessor file; not usually named on command line
.c,.i,.s C, preprocessed C, and assembler source files, and are processed by the C compiler and assembler. The resulting object files can be linked with UPC source code.

.o      Object file
.a      Archive file

Linking is always the last stage unless you use one of the -c, -S, or -E options to avoid linking (or unless compilation errors stop the whole process). For the link stage, all .o files corresponding to source files, -l libraries, unrecognized filenames (including named .o object files and .a archives) are passed to the linker in command-line order.  

OPTIONS

Information Options

-v

Language Options

-fupc-threads-n
-x upc

Debugging Options

-g

Optimization Options

-O1, -O2, -O3

INFORMATION OPTIONS

-v

Identifies the version of UPC currently in use, with a path name to a specification file that is in the same directory as include directories and other version-specific directories and files. Can be invoked without a source file name. When invoked with files, gives include and library directory paths in the order that they are searched.

LANGUAGE OPTIONS

-fupc-threads-n

Compile for n threads. The special symbol THREADS will be set to n and can be used both in data declarations (as a constant for array dimensions) and in expressions. On each thread the special symbol MYTHREAD refers to the thread number.

DEBUGGING OPTIONS

-g

Produce symbolic debugging information

OPTIMIZATION OPTIONS

-O2

This optimization level is one of GCC's standard options. It is especially important for UPC because it enables instruction scheduling, which increases performance dramatically for distributed data access. Nearly all supported optimizations that do not involve a space-speed tradeoff are performed. Loop unrolling and function inlining are not done, for example.

EXECUTION (RUNTIME) OPTIONS

The number of THREADS in an UPC application can be specified statically at compile-time, or dynamically at execution time. In the static compilation environment THREADS is a constant, and can be used freely in contexts where a constant is required by the C language specification (for example in an array declaration). In a dynamic compilation environment, the value of THREADS is given at runtime, and THREADS can be used in array declarations only if the array is qualified as shared and in contexts where one and only one of the shared array's dimensions is specified as an integral multiple of THREADS.

<UPC_program> [-fupc-threads-n] [-fupc-heap-n[K|M|G]] [program-specific-arguments and switches]

If the UPC program was not compiled with the -fupc-threads-n option, then the number of THREADS must be specified explicitly on the command line when the program is executed. The UPC runtime recognizes the -fupc-threads-n command line switch, and establishes the number of parallel execution threads given by the value `n'. Generally, `n' should not exceed the number of physical central processing units. The implementation-imposed maximum value of `n' is 256.

The size of the heap used by the UPC program is established with the specificaion of the -fupc-heap-n command line switch. The value of `n' is the size of the heap available to each thread, specified in bytes. A suffix of `K', indicates that the value `n' is expressed in kilobytes (2^10 bytes); a suffix of `M' indicates that `n' is expressed in megabytes (2^20 bytes); and `G' indicates the value is given in gigabytes (2^30 bytes). If the -fupc-heap-n switch is not supplied, then the runtime system will choose a default heap size of 1 megabyte per thread.

The UPC runtime will remove all switches that begin with the prefix -fupc- and that immediately follow the UPC program name on the command line, before calling the UPC program's `main()' routine.

FILES

file.upc           UPC source file
file.upci          preprocessed UPC source file
file.c             C source file
file.h             C header (preprocessor) file
file.i             preprocessed C source file
file.s             assembly language file
file.o             object file
a.out              link edited output
TMPDIR/cc*         temporary files
LIBDIR/cpp         preprocessor
LIBDIR/cc1upc      compiler for UPC
LIBDIR/cc1         compiler for C
LIBDIR/collect2    linker front end needed on some machines
LIBDIR/libupc.a    UPC runtime library
LIBDIR/libgcc.a    GCC subroutine library
/lib/crt[01n].o    start-up routine
/lib/libc.a        standard C library, see
intro(3)
/usr/include       standard directory for #include files
LIBDIR/include     standard gcc directory for #include files

SEE ALSO

Introduction to UPC and Language Specification, William W. Carlson et al., LLNL, CCS-TR-99-157, May 13, 1999

UPC Language Specifications Tarek A. El-Ghazawi et al, February 25, 2001

The GNU UPC Mailing List is an electronic forum for discussing news announcements, bug reports, planned developments, and other topics of interest to GNU UPC developers and users.  

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