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HP OpenVMS Systems Documentation |
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HP Fortran for OpenVMS
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The /DOUBLE_SIZE qualifier allows you to specify the data size for floating-point DOUBLE PRECISION data declarations. The qualifier has the following form:
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/DOUBLE_SIZE=
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To request that all DOUBLE PRECISION declarations, constants, functions, and intrinsics use the REAL (KIND=16) extended-precision data rather than REAL (KIND=8) double-precision data, specify /DOUBLE_SIZE=128. REAL (KIND=16) data is stored in memory using X_float format.
If you omit /DOUBLE_SIZE=128, the size of DOUBLE PRECISION declarations is REAL (KIND=8) or 64-bit double-precision data (default is /DOUBLE_SIZE=64). To select the floating-point format used in memory for 64-bit REAL (KIND=8) data, use the /FLOAT qualifier.
On the /FLOAT qualifier, see Section 2.3.22.
2.3.18 /ERROR_LIMIT --- Limit Compiler Messages
The /ERROR_LIMIT qualifier specifies the maximum number of error-level or fatal-level compiler errors allowed for a given compilation unit (one or more files specified on the FORTRAN command line that create a single object file).
The qualifier has the following form:
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/ERROR_LIMIT[=nn] or /NOERROR_LIMIT |
If you specify /ERROR_LIMIT=n, the compilation can have up to n - 1 errors without terminating the compilation. When the error limit is reached, compilation is terminated.
If you specify /NOERROR_LIMIT, there is no limit on the number of errors that are allowed.
By default, execution of the compiler is terminated when 30 error (E-level) and fatal (F-level) messages are detected (default is /ERROR_LIMIT=30).
When the error limit is surpassed, only compilation of the current comma-list element is terminated; the compiler will proceed to compile any other comma-list element. For example, consider the following:
$ FORTRAN A,B,C |
If comma-list element A has more than 30 E- or F-level errors, its compilation is terminated, but the compiler proceeds to compile elements B and C.
A list of files separated by plus signs (+) form a single compilation unit. In the following example, compilation of the plus-sign separated files A, B, or C stops when the total of E- or F-level errors for all three files exceeds 30:
$ FORTRAN A+B+C |
Specifying /ERROR_LIMIT=0 is equivalent to specifying /ERROR_LIMIT=1 (compilation terminates when the first error-level or fatal-level error occurs).
On compiler diagnostic messages, see Section 2.6.
2.3.19 /EXTEND_SOURCE --- Line Length for Fixed-Form Source
Specify /EXTEND_SOURCE to request that the compiler increase the length of HP Fortran statement fields to column 132 for fixed-form source files, instead of column 72 (the default). It is ignored for free-form source files.
You can also specify this qualifier by using the OPTIONS statement. The default in either case is /NOEXTEND_SOURCE.
To request warning messages for truncated fixed-form source lines, specify /WARNINGS=TRUNCATED_SOURCE.
The /F77 qualifier requests that the compiler use FORTRAN-77 (and thus Fortran 90/95) interpretation rules for those statements that have different meanings in older versions of the Fortran standards. The default is /F77.
If you specify /NOF77, the compiler uses the FORTRAN 66 (FORTRAN IV) interpretation. This means, among other things, that:
Specifying /FAST changes the defaults for certain qualifiers, usually improving run-time performance. The new defaults are:
The /FLOAT qualifier specifies the floating-point data format to be used in memory for REAL or COMPLEX data. For performance reasons, consider specifying the same floating-point memory format as the floating-point format used by unformatted files the program will access if the data falls within the acceptable range.
Figure 2-1 shows the FORTRAN command qualifiers used to specify the floating-point format used in memory and in an unformatted file. Because REAL (KIND=16) (same as REAL*16) data is always in X_float format on OpenVMS I64 and Alpha systems, the /FLOAT keyword specifies the format for REAL (KIND=4), COMPLEX (KIND=4), REAL (KIND=8), and COMPLEX (KIND=8) data (or equivalent declarations).
Figure 2-1 Specifying the Format of Numeric Data for Unformatted Files
To specify the floating-point format (such as big endian) for all unformatted files opened by the program, use the /CONVERT qualifier. To allow the same program to use different floating-point formats, you must use the predefined logical names or the OPEN CONVERT keyword to specify the format for specific unit numbers, as described in Chapter 9.
The qualifier has the following form:
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/FLOAT=
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The OpenVMS Alpha instruction set does not support D_float computations, and the OpenVMS I64 instruction set does not support D_float, F_float or G_float computations. As a result, any data stored in those formats is converted to a native format for arithmetic computations and then converted back to its original format. On Alpha systems, the native format used for D_float is G_float. On I64 systems, S_float is used for F_float data, and T_float is used for D_float and G_float data. This means that for programs that perform many floating-point computations, using D_float data on Alpha systems is slower than using G_float or T_float data. Similarly, using D_float, F_float, or G_float data on I64 systems is slower than using S_float or T_float data. Additionally, due to the conversions involved, the results might differ from native VAX D_float, F_float, and G_float computations and results. |
You should not mix floating data type formats in routines that pass single-precision or double-precision quantities among themselves.
D_FLOAT
Specifies that the memory format for REAL (KIND=4) and COMPLEX (KIND=4) data is VAX F_float and that the memory format for REAL (KIND=8) and COMPLEX (KIND=8) data is VAX D_float. Same as the obsolete qualifier /NOG_FLOATING.Due to the considerations noted above, we do not recommend use of the /FLOAT=D_FLOAT qualifier unless a program must use unformatted data files in D_float format. If range and accuracy constraints permit the use of the other REAL (KIND=8) data types, consider converting existing unformatted files that contain D_float data to another format, such as G_float on Alpha systems, or T_float on Alpha or I64 systems (see Chapter 9).
G_FLOAT
Specifies that the memory format for single precision REAL (KIND=4) and COMPLEX (KIND=4) data is VAX F_float and that the memory format for double precision REAL (KIND=8) and COMPLEX (KIND=8) data is VAX G_float. Same as the obsolete qualifier /G_FLOATING.The default on Alpha systems is /FLOAT=G_FLOAT.
Due to the considerations noted above, on I64 systems we do not recommend use of the /FLOAT=G_FLOAT qualifier unless a program must use unformatted data files in G_float format. If range and accuracy constraints permit it, consider converting existing unformatted files that contain G_float data to T_float (see Chapter 9).
IEEE_FLOAT
Specifies that the memory format for single precision REAL (KIND=4) and COMPLEX (KIND=4) data is IEEE S_float and the memory format for double precision REAL (KIND=8) and COMPLEX (KIND=8) is IEEE T_float.The default on I64 systems is /FLOAT=IEEE_FLOAT. If possible, this default should be used, because it provides the greatest performance and accuracy on I64.
Specifying /FLOAT=IEEE_FLOAT allows the use of certain IEEE exceptional values. When you specify /FLOAT=IEEE_FLOAT, you should be aware of the /CHECK=FP_EXCEPTIONS, /CHECK=FP_MODE, /IEEE_MODE, and /ROUNDING_MODE qualifiers.
Because REAL (KIND=16) (same as REAL*16) and COMPLEX (KIND=16) (same as COMPLEX*32) data is always in X_float format on I64 and Alpha systems, operations that use REAL (KIND=16) and COMPLEX (KIND=16) data may encounter certain exceptional values even when /FLOAT=IEEE_FLOAT is not used.
Section 2.3.11 (/CHECK=FP_EXCEPTIONS)
Section 2.3.11 (/CHECK=FP_MODE) (I64 only)
Section 2.3.24 (/IEEE_MODE)
Section 2.3.40 (/ROUNDING_MODE)
The /GRANULARITY qualifier controls the size of data that can be safely accessed from different threads. You do not need to specify this option for local data access by a single process, unless asynchronous write access from outside the user process might occur. The default is /GRANULARITY=QUADWORD.
The qualifier has the following form:
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/GRANULARITY=
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Data that can be written from multiple threads must be declared as VOLATILE (so it is not held in registers). To ensure alignment in common blocks, derived types, and record structures, use the /ALIGNMENT qualifier.
BYTE
Requests that all data (one byte or greater) can be accessed from different threads sharing data in memory. This option will slow run-time performance.LONGWORD
Ensures that naturally aligned data of four bytes or greater can be accessed safely from different threads sharing access to that data in memory. Accessing data items of three bytes or less and unaligned data may result in data items written from multiple threads being inconsistently updated.QUADWORD
Ensures that naturally aligned data of eight bytes can be accessed safely from different threads sharing data in memory. Accessing data items of seven bytes or less and unaligned data may result in data items written from multiple threads being inconsistently updated. This is the default.
The /IEEE_MODE qualifier specifies the arithmetic exception handling used for floating-point calculations, such as for exceptional values. On Alpha systems, it also controls the precision of exception reporting (like /SYNCHRONOUS_EXCEPTIONS (Alpha only)).
Exceptional values are associated with IEEE arithmetic and include Infinity (+ and -) values, Not-A-Number (NaN) values, invalid data values, and denormalized numbers (see Section 8.4.8).
Use the /IEEE_MODE qualifier to control:
This qualifier only applies to arithmetic calculations when:
The qualifier has the following form:
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/IEEE_MODE=
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The default on I64 systems is /IEEE_MODE=DENORM_RESULTS.
The default on Alpha systems is /IEEE_MODE=FAST.
You should choose the value for the /IEEE_MODE qualifier based on the floating-point semantics your application requires, not on possible performance benefits. |
FAST
Specifies that the program should stop if any exceptional values are detected. This is the default.When the program encounters or calculates any exceptional values (infinity (+ or --), NaN, or invalid data) in a calculation, the program stops and displays a message.
Denormalized values calculated in an arithmetic expression are set to zero. Denormalized values encountered as variables in an arithmetic expression (including constant values) are treated as invalid data (an exceptional value), which stops the program.
On Alpha systems, exceptions are not reported until one or more instructions after the instruction that caused the exception. To have exceptions reported at the instruction that caused the exception when using /IEEE_MODE=FAST, also specify /SYNCHRONOUS_EXCEPTIONS (Alpha only).
UNDERFLOW_TO_ZERO
Specifies that the program should continue if any exceptional values are detected and set calculated denormalized (underflow) values to zero.When the program encounters an exceptional value (infinity (+ or --), NaN, invalid data) in an arithmetic expression, the program continues. It also continues when the result of a calculation is an exceptional value.
Calculated denormalized values are set to zero (0). This prevents the denormalized number from being used in a subsequent calculation (propagated).
Exceptions are reported at the instruction that caused the exception (same as /SYNCHRONOUS_EXCEPTIONS (Alpha only)). This allows precise run-time reporting of exceptions for those programs that generate exceptional values, but this slows program run-time performance.
Using UNDERFLOW_TO_ZERO allows programs to handle exceptional values, but does not propagate numbers in the denormalized range.
To request run-time messages for arithmetic exceptions, specify the /CHECK=FP_EXCEPTIONS qualifier.
DENORM_RESULTS
Specifies that the program should continue if any exceptional values are detected and leave calculated denormalized values as is (allows underflow).When the program encounters an exceptional value (infinity (+ or --), NaN, invalid data) in an arithmetic expression, the program continues. It also continues when the result of a calculation is an exceptional value.
Calculated denormalized values are left as denormalized values. When a denormalized number is used in a subsequent arithmetic expression, it requires extra software-assisted handling and slows performance. A program that generates denormalized numbers will be slower than the same program compiled using /IEEE_MODE=UNDERFLOW_TO_ZERO.
Exceptions are reported at the instruction that caused the exception (same as /SYNCHRONOUS_EXCEPTIONS (Alpha only)). This allows precise run-time reporting of exceptions for those programs that generate exceptional values, but this slows program run-time performance.
Using DENORM_RESULTS allows programs to handle exceptional values, including allowing underflow of denormalized numbers.
To request run-time messages for arithmetic exceptions, specify the /CHECK=FP_EXCEPTIONS qualifier. To request run-time messages for only those arithmetic exceptions related to denormalized numbers, specify the /CHECK=UNDERFLOW qualifier.
The /INCLUDE qualifier specifies one or more additional directories for the HP Fortran compiler to search for:
If the INCLUDE statement specifies an explicit device and/or directory, only that directory is searched.
If you omit /INCLUDE, the compiler searches in the current directory for module files and either the current directory or the directory containing the source file specified on the FORTRAN command line for include files or text libraries:
The order of directory searching follows:
If you do not specify /INCLUDE or /NOINCLUDE, the compiler searches first in the current directory (or directory where the source file resides) and then the directory specified by FORT$INCLUDE (if defined).
To request that the compiler only search in the current directory (or directory where the source file resides), specify /NOINCLUDE. This prevents the compiler from searching the FORT$INCLUDE directory. If you use /NOINCLUDE, you cannot specify /INCLUDE.
To request that the compiler only search in the directory specified by FORT$INCLUDE, specify /INCLUDE=FORT$INCLUDE.
To control the searching for text libraries (not included files or modules), you can also use the logical name FORT$LIBRARY.
Like other OpenVMS logical names, it can specify the location for your process only or for multiple processes (including system-wide).
To specify the additional directories DISKA:[PROJ_MODULE.F90] and DISKB:[F_COMMON.F90] with the /INCLUDE qualifier, use a single /INCLUDE qualifier, as follows:
$ FORTRAN PROJ_M.F90 /INCLUDE=(DISKA:[PROJ_MODULE.F90],DISKB:[F_COMMON.F90]) |
If you specify multiple directories, the order of the directories (and their devices) in the /INCLUDE qualifier determines the directory search order.
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