The following f90 command options were added for DIGITAL Fortran 90 Version 4.0:

• Specify the -assume byterecl option to::
  • Indicate that the OPEN statement RECL unit for unformatted files is in byte units. If you omit -assume byterecl , Compaq Fortran expects the OPEN statement RECL value for unformatted files to be in longword (four-byte) units.
  • Return the record length value for an INQUIRE by output list (unformatted files) in byte units. If you omit -assume byterecl , Compaq Fortran returns the RECL value for an INQUIRE by output list in longword (four-byte) units.
• The -check nopower option allows arithmetic calculations that result in 0**0 or a negative number raised to an integer power of type real (such as --3**3.0) to be calculated, rather than stop the program. If you omit -check nopower for such calculations, an exception occurs and the program stops (default is -check:power ).
  For example, if you specified -check:nopower , the calculation of the expression 0**0 results in 1 and the expression --3**3.0 results in --9.
• Specify -hpf_matmul to use matrix multiplication from the HPF library. Omitting the -hpf_matmul option uses inlined intrinsic code that is faster for small matrices. For nonparallel compilations, specifying -hpf_matmul to use the HPF library routine is faster for large matrices.
• The -names keyword option controls how DIGITAL Fortran 90 handles the case-sensitivity of letters in source code identifiers and external names:
  • Using -names as_is requests that Compaq Fortran distinguish between uppercase and lowercase letters in source code identifiers (treats uppercase and lowercase letters as different) and distinguish between uppercase and lowercase letters in external names.
  • Using -names lowercase (default) requests that Compaq Fortran not distinguish between uppercase and lowercase letters in source code identifiers (treats lowercase and uppercase letters as equivalent) and force all letters to be lowercase in external names.
  • Using -names uppercase requests that Compaq Fortran not distinguish between uppercase and lowercase letters in source code identifiers (treats lowercase and uppercase letters as equivalent) and force all letters to be uppercase in external names.
• The -noinclude option prevents searching for include files in the /usr/include directory. This option does not apply to the directories searched for module files or cpp files.
• The -O5 option activates both the software pipelining optimization ( -pipeline ) and the loop transform optimizations ( -transform_loops ). You can also specify -notransform_loops or -nopipeline with -O5 .
  If you also specify the -wsf option to request parallel processing, you cannot use the -O5 option.
• The -pipeline option activates the only software pipelining optimization (previously done only by -O5 ). The software pipelining optimization applies instruction scheduling to certain innermost loops, allowing instructions within a loop to "wrap around" and execute in a different iteration of the loop. This can reduce the impact of long-latency operations, resulting in faster loop execution.
  Software pipelining also enables the prefetching of data to reduce the impact of cache misses. In certain cases, software pipelining improves run-time performance (separate timings are suggested).
• The following -reentrancy keyword options specify the level of thread-safe reentrant run-time library support needed:

  Option Name	Description
  -reentrancy none	Informs the Compaq Fortran RTL that the program will not be relying on threaded or asynchronous reentrancy. Therefore the RTL need not guard against such interrupts inside the RTL. This is the default.
  -reentrancy asynch	Informs the Compaq Fortran RTL that the program may contain asynchronous handlers that could call the RTL. Therefore the RTL will guard against asynchronous interrupts inside its own critical regions.
  -reentrancy threaded	Informs the Compaq Fortran RTL that the program is multithreaded, such as those using the DECthreads library. Therefore the RTL will use thread locking to guard its own critical regions. To use the threaded libraries, also specify -threads .
  -noreentrancy	The same as -reentrancy none .

• The -S option generates a .s file, which can be assembled. This option is intended for systems running Compaq Tru64 UNIX (DIGITAL UNIX) Version 4.0 or later, which has certain new Assembler features.
  Certain complex programs that use modules or common blocks compiled with -S may not generate code completely acceptable to the Assembler.
• The -speculate keyword option supports the speculative execution optimization:
  • Use -speculate all to perform the speculative execution optimization on all routines in the program. All exceptions within the entire program will be quietly dismissed without calling any user-mode signal handler.
  • Use -speculate by_routine to perform the speculative execution optimization on all routines in the current compilation unit (set of routines being compiled), but speculative execution will not be performed for routines in other compilation units in the program.
  • Use -speculate none or -nospeculate to suppress the speculative execution optimization. This is the default.
  
  The speculative execution optimization reduces instruction latency stalls to improve run-time performance for certain programs or routines. This optimization evaluates conditional code (including exceptions) and moves instructions that would otherwise be executed conditionally to a position before the test, so they are executed unconditionally.
  Speculative execution does not support some run-time error checking, since exception and signal processing (including SIGSEGV, SIGBUS, and SIGFPE) is conditional. When the program needs debugging or while testing for errors, use -speculate none (default).
• Specifying -threads requests that the linker use threaded libraries. This is usually used with -reentrancy threaded .
• The -transform_loops option supports a group of optimizations that improve the performance of the memory system and can apply to multiple nested loops. The loops chosen for loop transformation optimizations are always counted loops (counted loops include DO or IF loops, but not uncounted DO WHILE loops). In certain cases, loop transformation improves run-time performance (separate timings are suggested).
• Specify -nowsf_main to indicate that the HPF global routine being compiled will be linked with a main program that was not compiled with -wsf .

For more information on f90 command options, see the Compaq Fortran User Manual for Tru64 UNIX and Linux Alpha Systems, Chapter 3, or f90(1).

In addition to the f90 command-line options, the following new or changed features were added for Version 4.0:

• The random_number intrinsic (as of Version 4.0) uses two separate congruential generators together to produce a period of approximately 10**18, and produces real pseudorandom results with a uniform distribution in (0,1). It accepts two integer seeds, the first of which is reduced to the range [1, 2147483562]. The second seed is reduced to the range [1, 2147483398]. This means that the generator effectively uses two 31-bit seeds.
  The new algorithm behaves differently from one provided prior to Version 4.0 in the following ways:
  • Both seeds are active and contribute to the random number being produced.
  • If the given seeds are not in the ranges given above, they will be reduced to be in those ranges.
  • The sequences of random numbers produced by the new generator will be different from the sequences produced by the old generator.
  
  For more information on the algorithm, see:
  • Communications of the ACM vol 31 num 6 June 1988, entitled Efficient and Portable Combined Random Number Generators by Pierre L'ecuyer
  • Springer-Verlag New York, N. Y. 2nd ed. 1987, entitled A Guide to Simulation by Bratley, P., Fox, B. L., and Schrage, L. E.
  
  For an example program, see Section 1.11.4.
• The implementation of the MATMUL intrinsic procedure was changed for this release. Previously the compiler called a routine in the scalar HPF library to perform the operation. As of this release, the compiler generates optimized inline code for the MATMUL intrinsic with a significant increase in the performance when the size of the array arguments are small.
  To use previous implementation of the MATMUL intrinsic (routine in the scalar HPF library), specify -hpf_matmul .
• The cDEC$ ALIAS directive
  The cDEC$ ALIAS directive is now supported in the same manner as in Compaq Fortran 77. This directive provides the ability to specify that the external name of an external subprogram is different than the name by which it is referenced in the calling subprogram.
  This feature can be useful when porting code between OpenVMS and UNIX systems where different routine naming conventions are in use.
  For more information on the cDEC$ ALIAS directive, see the Compaq Fortran User Manual for Tru64 UNIX and Linux Alpha Systems.
• The cDEC$ ATTRIBUTES directive
  The cDEC$ ATTRIBUTES directive lets you specify properties for data objects and procedures. These properties let you specify how data is passed and the rules for invoking procedures. This directive is intended to simplify mixed language calls with Compaq Fortran routines written in C or Assembler.
  For more information on the cDEC$ ATTRIBUTES directive, see Compaq Fortran User Manual for Tru64 UNIX and Linux Alpha Systems.
• An additional math library allows use of optimizations for a series of square root calculations.
  The library file libm_4sqrt ships on the DIGITAL Fortran 90 Version 4.0 kit (and DIGITAL Fortran 77 Version 4.0). These optimizations improve run-time performance when a series of square root calculations occur within a counted loop.
• Enhanced support for the FORALL statement and construct
  The FORALL construct now allows the following statements in the forall body:
  • Pointer assignment statement
  • FORALL statement or construct (nested FORALL)
  • WHERE statement or construct
  
  Please note that each statement in the FORALL body is executed completely before execution begins on the next FORALL body statement.
  The compiler now correctly defines the scope of a FORALL subscript name to be the scope of the FORALL construct. That is, the subscript name is valid only within the scope of the FORALL. Its value is undefined on completion of the FORALL construct.
• OPTIONS statement options can now be abbreviated (for compatibility with DIGITAL Fortran 77).
• The -vms option now supports use of /LIST or /NOLIST in an INCLUDE statement (for compatibility with DIGITAL Fortran 77).
• To improve run-time performance, new optimizations are now available and certain improvements have been made, including:
  • Certain intrinsic procedures specific to Fortran 90 (not available in FORTRAN-77)
  • Subprogram calls with array arguments
  • New command-line options that activate new optimizations, including the loop transformation optimizations ( -transform_loops or -O5 ) and the speculative execution optimization ( -speculate keyword ). The software pipelining optimization is now activated by using -pipeline or -O5 .
• Variable formats expressions (VFEs) are now allowed in quoted strings.
• Invalid formats in quoted strings are now detected at compile-time rather than run-time.

For more information on compatibility with DIGITAL Fortran 77, see the revised Compaq Fortran User Manual for Tru64 UNIX and Linux Alpha Systems, Appendix A.

2.3 New Features in Version 2.0

New features for Version 2.0 include the LOC intrinsic function. LOC returns the internal address of its argument (same as the built-in function %LOC).

In addition, the Compaq Ladebug debugger has added support for Compaq Fortran language features (see Section 1.11.8.1).

2.4 New Features in Version 1.3

New features for Version 1.3 include the f90 command options that support the Compaq Parallel Software Environment.

To request parallel execution, specify the -wsf or -wsf nn option . This compiles the program to run in parallel using the Compaq Parallel Software Environment product. The optional nn parameter specifies the number of processors on which the program is intended to execute. If not specified, the program will be compiled to execute on any number of processors. More efficient code is generated when nn is specified.

If you specify the -wsf or -wsf nn option to request parallel execution, you can also use the following related options:

• The -assume nozsize option assumes there are no zero-sized array sections.
• The -nearest_neighbor or -nearest_neighbor nn option enables or disables the nearest neighbor parallel optimization. The optional nn parameter specifies the width of the shadow edge to use. If you omit nn, it is set to 1.
• The -pprof string option allows parallel profiling of an application. Valid characters for string are s for sampling or i for interval. This option must be used with the -non_shared option (as well as -wsf or -wsf nn ). This option must not be used with the -p1 option.
• The -show wsfinfo option includes information about statements which cause interprocessor communication to be generated or are serialized in the listing file.

Other Version 1.3 new features include the following:

• Support for the DIGITAL Fortran 77 pointers (CRAY® style). This is an extension to the Fortran 95/90 and FORTRAN-77 standards. For more information, see the DEC Fortran Language Reference Manual and Section 1.11.5.
• Bit constants with a trailing B or Z or leading X (a Compaq Fortran extension) are now supported for compatibility with Compaq Fortran 77:

  i = '001'B k = '0ff'Z j = X'00f'

• The SYSTEM_CLOCK intrinsic procedure has been extended to allow integer arguments of any KIND rather than the default integer KIND . This allows the use of INTEGER*8 arguments to obtain a higher degree of magnitude and accuracy in timings (1,000,000 counts per second). For example:

  integer*8 count,count_max,count_rate call system_clock(count,count_rate,count_max)

• When it is passed an INTEGER (KIND=4) value, the SYSTEM_CLOCK intrinsic procedure now returns a value in terms of 10,000 instead of 1,000,000 counts per second.
• Debugging support has been enhanced to allow breakpoints on CONTINUE, GOTO, and RETURN statements. Before Version 1.3, breakpoints could not be set on a CONTINUE statement and only on certain GOTO and RETURN statements.
• The following DIGITAL Fortran 90 cDEC$ directives are now supported:
  • cDEC$ IDENT specifies a string that identifies the object file.
  • cDEC$ OPTIONS and cDEC$ END_OPTIONS controls alignment of fields in common blocks, record structures, and most derived-type structures.
  • cDEC$ PSECT modifies certain attributes of a common block, including the [NO]MULTILANGUAGE attribute for compatibility with DIGITAL Fortran 77.
  • cDEC$ TITLE and cDEC$ SUBTITLE specifies strings for the title and subtitle of a listing file header.
• Any number raised to a floating point 2.0 (x ** 2.0) is now transformed to (x ** 2) for compatibility with DIGITAL Fortran 77.
• The Bessel function 3f library (jacket) routines are now supported (see bessel(3f))
• The following f90 command options were added for Version 1.3:
  • The -fuse_xref option requests that DIGITAL Fortran 90 generate a data file that the DEC FUSE Database Manager uses to create a cross-reference database file. This improves the performance of the DEC FUSE Call Graph Browser and Cross-Referencer that use the database file for their operations.
  • The -inline speed and -inline size options have been added in place of -inline automatic to provide more control over procedure inlining:
    Use -inline size (same as -inline space ) to inline procedures that will likely improve run-time performance where inlining will not significantly increase program size. This option is meaningful only at optimization levels -O1 and higher.
    Use -inline speed to inline procedures that will likely improve run-time performance where inlining may significantly increase program size. Using -inline speed often results in larger executable program sizes (than -inline size ). This type of inlining occurs automatically with the -O4 or -O5 optimization levels. This option is meaningful only at optimization levels -O1 and higher.
    Other -inline xxxx options include -inline none , -inline manual , and -inline all (see Section 2.5).
  • The -ladebug option includes additional symbolic information in the object file for the DIGITAL Ladebug debugger (see ladebug(1). This option enables Ladebug to print and assign to dynamic arrays using standard Fortran syntax, including array sections.
  • The -show map option includes a symbol map in the listing file (also specify -V ).
  • The -version option displays DIGITAL Fortran 90 version number information.

For more complete product information, see the Compaq Fortran documentation and the f90(1) reference (man) page.

2.5 New Features in Version 1.2

DIGITAL Fortran 90 Version 1.2 contains the following changes since Version 1.1:

• Support for REAL (KIND=16) (or REAL*16) X_float (extended precision) data type and its associated intrinsics (a DIGITAL Fortran extension). For more information see Section 1.11.
• Support for variable format expressions (VFEs), a DIGITAL Fortran extension (see Section 1.11).
• Support for OPTIONS statements, which allow you to specify command-line options in your source files. The OPTIONS statement is a DIGITAL Fortran extension.
• Intrinsic procedures FP_CLASS and IMAG (a DIGITAL Fortran extension).
• STATIC and AUTOMATIC declaration attributes and statements (a DIGITAL Fortran extension).
• The following f90 command options were added for Version 1.2:
  • The -convert fgx and -convert fdx options allow conversion of unformatted OpenVMS Alpha DIGITAL Fortran 77 data files. Similarly, the FDX and FGX keywords are recognized for the OPEN statement CONVERT keyword and the FORT_CONVERTn environment variable names.
    Specifying -convert fdx indicates the data contains::
    • Little endian integer format (INTEGER declarations of the appropriate size)
    • REAL*4 and COMPLEX*8 data in VAX F_float format
    • REAL*8 and COMPLEX*16 data in VAX D_float format
    • REAL*16 data in native X_float format
    
    Specifying -convert fgx indicates the data contains:
    • Little endian integer format (INTEGER declarations of the appropriate size)
    • REAL*4 and COMPLEX*8 data in VAX F_float format
    • REAL*8 and COMPLEX*16 data in VAX G_float format
    • REAL*16 data in native X_float format
  • The -double_size 128 option specifies that DOUBLE PRECISION declarations are implemented as extended precision REAL (KIND=16) data rather than double precision REAL (KIND=8) data.
  • The -real_size 128 and -r16 options allow a REAL declaration to be interpreted using the REAL (KIND=16) data type.
  • The -inline xxxxx options can be used to specify the type of inlining done independent of the -On option (optimization level) specified:
    • To prevent inlining of procedures (except statement functions), use -inline none or -inline manual .
      This is the type of inlining done with -O0 , -O1 , -O2 , or -O3 .
    • The -inline automatic option was replaced at Version 1.3 with -inline size and -inline speed (see Section 2.4), allowing more control over inlining.
    • To inline every call that can possibly be inlined while generating correct code, including: statement functions, procedures that Compaq Fortran thinks will improve run-time performance, and any other procedures that can possibly be inlined while generating correct code (certain recursive routines cannot be inlined), use -inline all . This option is meaningful only at optimization levels -O1 and higher.
  • The -gen_feedback option requests additional profiling information needed for feedback file use. You can use -gen_feedback with any optimization level up to -O3 (to avoid inlining procedures). If you omit a -On option, the -gen_feedback option changes the default optimization level to -O0 .
    A typical command-line sequence to create a feedback file ( profsample.feedback ) follows:

    % f90 -gen_feedback -o profsample -O3 profsample.f90 % pixie profsample % profsample.pixie % prof -pixie -feedback profsample.feedback profsample

  • The -feedback option now works with -cord or separately without -cord to specify a previously-created feedback file. For example:

    % f90 -feedback profsample.feedback -o profsample -O3 profsample.f90

    
    The feedback file provides the compiler with actual execution information, which the compiler can use to perform such optimizations as inlining function calls.
    The same optimization level ( -On option) must be specified for the f90 command with the -gen_feedback option and the f90 command with the -feedback name option.
    You can use the feedback file as input to the f90 compiler and cord , as follows:

    % f90 -cord -feedback profsample.feedback -o profsample -O3 profsample.f90

  • The -tune keyword option selects processor-specific instruction tuning for implementations of the Alpha architecture. Regardless of the setting of -tune keyword , the generated code will run correctly on all implementations of the Alpha architecture. Tuning for a specific implementation can improve run-time performance; it is also possible that code tuned for a specific target may run slower on another target.
    Choose one of the following:
    • To generate and schedule code that will execute well for both types of chips, use -tune generic . This provides generally efficient code for those cases where both types of chips are likely to be used. If you do not specify any -tune keyword option, -tune generic is used (default).
    • To generate and schedule code optimized for the type of chip in use on the system being used for compilation, use -tune host .
    • To generate and schedule code optimized for the 21064, 20164A, 21066, and 21068 implementations of the Alpha chip, use -tune ev4 .
    • To generate and schedule code optimized for the 21164 implementation of the Alpha chip, use -tune ev5 .
  • The -check noformat option disables the run-time message (number 61) associated with format mismatches. It also requests that the data item be formatted using the specified descriptor, unless the length of the item cannot accommodate the descriptor (for example, it is still an error to pass an INTEGER (KIND=2) item to an E edit descriptor). Using -check noformat allows such format mismatches as a REAL (KIND=4) item formatted with an I edit descriptor.
    If you omit the -vms option, the default is -check noformat .
    If you specify -vms and omit -check noformat , -check format is used.
  • The -check output_conversion option disables the run-time message (number 63) associated with format truncation. The data item is printed with asterisks. Error number 63 occurs when a number could not be output in the specified format field length without loss of significant digits (format truncation).
    If you omit the -vms option, the default is -check nooutput_conversion .
    If you specify -vms and omit -check nooutput_conversion , -check output_conversion is used.
  • The -vms option now sets defaults for -check output_conversion and -check format .

For more complete product information, see the Compaq Fortran documentation and the f90(1) reference (man) page.

2.6 New Features in Version 1.1

DIGITAL Fortran 90 Version 1.1 contains the following changes since Version 1.0:

• The following f90 command options were added for Version 1.1:
  • The -check bounds option generates additional code to detect out-of-bounds subscripts for array operations and character substring expressions at run-time. Use this option for debugging purposes.
  • The -idir option specifies an additional directory to be searched for files specified with an INCLUDE statement or module files. For Version 1.0, this option specified an additional directory searched for module files only.
  • The -warn argument_checking option issues a warning message about argument mismatches between the calling and the called procedure when both program units are compiled together.
• The fsplit command now accepts DIGITAL Fortran 90 free-form source files (see fsplit(1)). For example:

  % fsplit -f90 -free bigfile.f90

For more complete product information, see the Compaq Fortran documentation and the f90(1) reference (man) page.