The default file name for the executable program is a.out. You can select a different name with the -o compiler option. You should avoid giving your programs the same names as system or shell commands (such as test or cp), as you could accidentally execute the wrong command. If a name conflict does occur, you can execute the program by specifying a path name, such as ./test.
You can run a program by entering the path name and file name of an executable file along with any run-time arguments on the command line.
To suspend a running program, press the Ctrl+Z key while the program is in the foreground. Use the fg command to resume running.
To cancel a running program, press the Ctrl+C key while the program is in the foreground.
If you want to move an XL Fortran executable file to a different system for execution, you can link statically and copy the program, and optionally the run-time message catalogs. Alternatively, you can link dynamically and copy the program as well as the XL Fortran libraries if needed and optionally the run-time message catalogs. For non-SMP programs, libxlf90.so, libxlfmath.so, and libxlomp_ser.so are usually the only XL Fortran libraries needed. For SMP programs, you will usually need at least the libxlf90_r.so, libxlfmath.so, and libxlsmp.so libraries. libxlfpmt*.so and libxlfpad.so are only needed if the program is compiled with the -qautodbl option.
For a dynamically linked program to work correctly, the XL Fortran libraries and the operating system on the execution system must be at either the same level or a more recent level than on the compilation system.
For a statically linked program to work properly, the operating-system level may need to be the same on the execution system as it is on the compilation system.
There are two run-time libraries that are connected with POSIX thread support. The libxlf90_r.so library is a thread-safe version of the Fortran run-time library. The libxlsmp.so library is the SMP run-time library.
Depending on the invocation command, and in some cases, the compiler option, the appropriate set of libraries for thread support is bound in. For example:
Cmd. | Libraries Used | Include Directory |
---|---|---|
xlf90_r xlf95_r xlf_r |
/opt/ibmcmp/lib/libxlf90_r.so /opt/ibmcmp/lib64/libxlf90_r.so /opt/ibmcmp/lib/libxlsmp.so /opt/ibmcmp/lib64/libxlsmp.so |
/opt/ibmcmp/xlf/10.1/include |
To select a language for run-time messages that are issued by an XL Fortran program, set the LANG and NLSPATH environment variables before executing the program.
In addition to setting environment variables, your program should call the C library routine setlocale to set the program's locale at run time. For example, the following program specifies the run-time message category to be set according to the LC_ALL, LC_MESSAGES, and LANG environment variables:
PROGRAM MYPROG PARAMETER(LC_MESSAGES = 5) EXTERNAL SETLOCALE CHARACTER NULL_STRING /Z'00'/ CALL SETLOCALE (%VAL(LC_MESSAGES), NULL_STRING) END
Internal switches in an XL Fortran program control run-time behavior, similar to the way compiler options control compile-time behavior. You can set the run-time options through either environment variables or a procedure call within the program. You can specify XL Fortran run-time option settings by using the following environment variables: XLFRTEOPTS and XLSMPOPTS.
The XLFRTEOPTS environment variable allows you to specify options that affect I/O, EOF error-handling, and the specification of random-number generators. You can declare XLFRTEOPTS by using the following bash command format:
.-:------------------------------------------. V | >>-XLFRTEOPTS=--+---+----runtime_option_name--=----option_setting---+--+---+->< '-"-' '-"-'
You can specify option names and settings in uppercase or lowercase. You can add blanks before and after the colons and equal signs to improve readability. However, if the XLFRTEOPTS option string contains imbedded blanks, you must enclose the entire option string in double quotation marks (").
The environment variable is checked when the program first encounters one of the following conditions:
Changing the XLFRTEOPTS environment variable during the execution of a program has no effect on the program.
The SETRTEOPTS procedure (which is defined in the XL Fortran Language Reference) accepts a single-string argument that contains the same name-value pairs as the XLFRTEOPTS environment variable. It overrides the environment variable and can be used to change settings during the execution of a program. The new settings remain in effect for the rest of the program unless changed by another call to SETRTEOPTS. Only the settings that you specified in the procedure call are changed.
You can specify the following run-time options with the XLFRTEOPTS environment variable or the SETRTEOPTS procedure:
The library reads data from, or writes data to the file system in chunks for READ or WRITE statements, instead of piece by piece. The major benefit of buffering is performance improvement.
If you have applications in which Fortran routines work with routines in other languages or in which a Fortran process works with other processes on the same data file, the data written by Fortran routines may not be seen immediately by other parties (and vice versa), because of the buffering. Also, a Fortran READ statement may read more data than it needs into the I/O buffer and cause the input operation performed by a routine in other languages or another process that is supposed to read the next data item to fail. In these cases, you can use the buffering run-time option to disable the buffering in the XL Fortran run-time library. As a result, a READ statement will read in exactly the data it needs from a file and the data written by a WRITE statement will be flushed out to the file system at the completion of the statement.
Note: I/O buffering is always enabled for files on sequential access devices (such as pipes, terminals, sockets). The setting of the buffering option has no effect on these types of files.
If you disable I/O buffering for a logical unit, you do not need to call the Fortran service routine flush_ to flush the contents of the I/O buffer for that logical unit.
The suboptions for buffering are as follows:
In the following example, Fortran and C routines read a data file through redirected standard input. First, the main Fortran program reads one integer. Then, the C routine reads one integer. Finally, the main Fortran program reads another integer.
Fortran main program:
integer(4) p1,p2,p3 print *,'Reading p1 in Fortran...' read(5,*) p1 call c_func(p2) print *,'Reading p3 in Fortran...' read(5,*) p3 print *,'p1 p2 p3 Read: ',p1,p2,p3 end
C subroutine (c_func.c):
#include <stdio.h>
void
c_func(int *p2)
{
int n1 = -1;
printf("Reading p2 in C...\n");
setbuf(stdin, NULL); /* Specifies no buffering for stdin */
fscanf(stdin,"%d",&n1);
*p2=n1;
fflush(stdout);
}
Input data file (infile):
11111 22222 33333 44444
The main program runs by using infile as redirected standard input, as follows:
$ main < infile
If you turn on buffering=disable_preconn, the results are as follows:
Reading p1 in Fortran... Reading p2 in C... Reading p3 in Fortran... p1 p2 p3 Read: 11111 22222 33333
If you turn on buffering=enable, the results are unpredictable.
The suboptions for cpu_time_type are as follows:
The default_recl run-time option applies only in 64-bit mode. In 32-bit mode, default_recl is ignored and the record size is 32-bit.
Use default_recl when porting 32-bit programs to 64-bit mode where a 64-bit record length will not fit into the specified integer variable. Consider the following:
INTEGER(4) I OPEN (11) INQUIRE (11, RECL=i)
A run-time error occurs in the above code sample in 64-bit mode when default_recl=64, since the default record length of 2**63-1 does not fit into the 4-byte integer I. Specifying default_recl=32 ensures a default record size of 2**31-1, which fits into I.
For more information on the RECL= specifier, see the OPEN statement in the XL Fortran Language Reference.
For example, setting the iostat_end=2003std run-time option results in a different IOSTAT value from extensions being returned for the end-of-file condition
export XLFRTEOPTS=iostat_end=2003std character(10) ifl integer(4) aa(3), ios ifl = "12344321 " read(ifl, '(3i4)', iostat=ios) aa ! end-of-file condition occurs and ! ios is set to -1 instead of -2.
For more information on setting and using IOSTAT values, see the READ, WRITE, and Conditions and IOSTAT Values sections in the XL Fortran Language Reference.
Changing the number of threads available to the MATMUL and RANDOM_NUMBER intrinsic procedures can influence performance.
For example, setting the langlvl=2003std run-time option results in a run-time error message.
integer(4) aa(100) call setrteopts("langlvl=2003std") ... ! Write to a unit without explicitly ... ! connecting the unit to a file. write(10, *) aa ! The implicit connection to a file does not ... ! comform with Fortran 2003 behavior.
To obtain support for items that are part of the Fortran 95 standard and are available in XL Fortran (such as namelist comments), you must specify one of the following suboptions:
The following example contains a Fortran 95 extension (the file specifier is missing from the OPEN statement):
program test1
call setrteopts("langlvl=95std")
open(unit=1,access="sequential",form="formatted")
10 format(I3)
write(1,fmt=10) 123
end
Specifying langlvl=95std results in a run-time error message.
The following example contains a Fortran 95 feature (namelist comments) that was not part of Fortran 90:
program test2 INTEGER I LOGICAL G NAMELIST /TODAY/G, I call setrteopts("langlvl=95std:namelist=new") open(unit=2,file="today.new",form="formatted", & & access="sequential", status="old") read(2,nml=today) close(2) end today.new: &TODAY ! This is a comment I = 123, G=.true. /
If you specify langlvl=95std, no run-time error message is issued. However, if you specify langlvl=90std, a run-time error message is issued.
The err_recovery setting determines whether any resulting errors are treated as recoverable or severe.
You can only use multiple connections within the same program for files on random-access devices, such as disk drives. In particular, you cannot use multiple connections within the same program for:
To avoid the possibility of damaging the file, keep the following points in mind:
In your program, you can now specify multiple OPEN statements that contain different values for the UNIT parameters but the same value for the FILE parameters. For example, if you have a symbolic link called mytty that is linked to TTY device /dev/tty, you can run the following program when you specify the multconnio=tty option:
PROGRAM iotest OPEN(UNIT=3, FILE='mytty', ACTION="WRITE") OPEN(UNIT=7, FILE='mytty', ACTION="WRITE") END PROGRAM iotest
Fortran preconnects units 0, 5, and 6 to the same TTY device. Normally, you cannot use the OPEN statement to explicitly connect additional units to the TTY device that is connected to units 0, 5, and 6. However, this is possible if you specify the multconnio=tty option. For example, if units 0, 5, and 6 are preconnected to TTY device /dev/tty, you can run the following program if you specify the multconnio=tty option:
PROGRAM iotest ! /dev/pts/2 is your current tty, as reported by the 'tty' command. ! (This changes every time you login.) CALL SETRTEOPTS ('multconnio=tty') OPEN (UNIT=3, FILE='/dev/pts/2') WRITE (3, *) 'hello' ! Display 'hello' on your screen END PROGRAM
With namelist=old, the nonstandard NAMELIST format is not considered an error by the langlvl=95std, langlvl=90std, or langlvl=2003std setting.
The following examples set the cnverr run-time option to yes and the xrf_messages option to no.
# Basic format XLFRTEOPTS=cnverr=yes:xrf_messages=no export XLFRTEOPTS # With imbedded blanks XLFRTEOPTS="xrf_messages = NO : cnverr = YES" export XLFRTEOPTS
As a call to SETRTEOPTS, this example could be:
CALL setrteopts('xrf_messages=NO:cnverr=yes') ! Name is in lowercase in case -U (mixed) option is used.
The XLSMPOPTS environment variable allows you to specify options that affect SMP execution. The OpenMP environment variables, OMP_DYNAMIC, OMP_NESTED, OMP_NUM_THREADS, and OMP_SCHEDULE, allow you to control the execution of parallel code. For details on using these, see XLSMPOPTS and OpenMP environment variables.
By default, the libxlopt library is linked with any application you compile with XL Fortran. However, if you are using a third-party Basic Linear Algebra Subprograms (BLAS) library or want to ship a binary that includes ESSL routines, you must specify these using the XL_BLAS_LIB environment variable. For example, if your own BLAS library is called libblas, set the environment variable as follows:
export XL_BLAS_LIB=/usr/lib/libblas.aWhen the compiler generates calls to BLAS routines, the ones defined in the libblas library will be used at runtime instead of those defined in libxlopt.
Use the XL_NOCLONEARCH to instruct the program to only execute the generic code, where generic code is the code that is not versioned for an architecture. The XL_NOCLONEARCH environment variable is not set by default; you can set it for debugging purposes in your application. (See also the -qipa=clonearch option.)