HP Fortran for OpenVMS
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5.2.1.2 Using a Command Procedure

Some of the information obtained by using the LIB$xxxx_TIMER routines can be obtained using a command procedure. You should be aware of the following:

Before using a command procedure to measure performance, define a foreign symbol that runs the program to be measured in a subprocess. In the following example, the name of the command procedure is TIMER: 


$ TIMER :== SPAWN /WAIT /NOLOG @SYS$LOGIN:TIMER

The command procedure shown in Example 5-2 uses the F$GETJPI lexical function to measure performance statistics and the F$FAO lexical function to report the statistics. Each output line is saved as a logical name, which can be saved by the parent process if needed.

Example 5-2 Command Procedure that Measures Program Performance 

$    verify = 'f$verify(0) 
$ 
$! Get initial values for stats (this removes SPAWN overhead or the current 
$! process values). 
$ 
$ bio1 = f$getjpi (0, "BUFIO") 
$ dio1 = f$getjpi (0, "DIRIO") 
$ pgf1 = f$getjpi (0, "PAGEFLTS") 
$ vip1 = f$getjpi (0, "VIRTPEAK") 
$ wsp1 = f$getjpi (0, "WSPEAK") 
$ dsk1 = f$getdvi ("sys$disk:","OPCNT") 
$ tim1 = f$time () 
$ 
$ set noon 
$ tik1 = f$getjpi (0, "CPUTIM") 
$ set noverify 
$ 
$! User command being timed: 
$ 
$ 'p1' 'p2' 'p3' 'p4' 'p5' 'p6' 'p7' 'p8' 
$ 
$ tik2 = f$getjpi (0, "CPUTIM") 
$ 
$ bio2 = f$getjpi (0, "BUFIO") 
$ dio2 = f$getjpi (0, "DIRIO") 
$ pgf2 = f$getjpi (0, "PAGEFLTS") 
$ vip2 = f$getjpi (0, "VIRTPEAK") 
$ wsp2 = f$getjpi (0, "WSPEAK") 
$ dsk2 = f$getdvi ("sys$disk:","OPCNT") 
$ tim2 = f$time () 
$ 
$ tim  = f$cvtime("''f$cvtime(tim2,,"TIME")'-''f$cvtime(tim1,,"TIME")'",,"TIME") 
$ thun = 'f$cvtime(tim,,"HUNDREDTH") 
$ tsec = (f$cvtime(tim,,"HOUR")*3600) + (f$cvtime(tim,,"MINUTE")*60) + - 
  f$cvtime(tim,,"SECOND") 
$ 
$ bio  = bio2 - bio1 
$ dio  = dio2 - dio1 
$ pgf  = pgf2 - pgf1 
$ dsk  = dsk2 - dsk1 
$ vip  = "" 
$ if vip2 .le. vip1 then vip = "*"   ! Asterisk means didn't change (from parent) 
$ wsp  = "" 
$ if wsp2 .le. wsp1 then wsp = "*" 
$ 
$ tiks = tik2 - tik1 
$ secs = tiks / 100 
$ huns = tiks - (secs*100) 
$ write sys$output "" 
$! 
$ time$line1 ==  - 
 f$fao("Execution (CPU) sec!5UL.!2ZL   Direct I/O  !7UL   Peak working set!7UL!1AS", - 
          secs, huns, dio, wsp2, wsp) 
$ write sys$output time$line1 
$! 
$ time$line2 ==  - 
 f$fao("Elapsed (clock) sec!5UL.!2ZL   Buffered I/O!7UL   Peak virtual    !7UL!1AS", - 
                tsec, thun, bio, vip2, vip) 
$ write sys$output time$line2 
$! 
$ time$line3 == - 
 f$fao("Process ID         !AS   SYS$DISK I/O!7UL   Page faults     !7UL", - 
        f$getjpi(0,"pid"), dsk, pgf) 
$ write sys$output time$line3 
$ if wsp+vip .nes. "" then write sys$output - 
 "                                                       (* peak from parent)" 
$ write sys$output "" 
$ 
$! Place these output lines in the job logical name table, so the parent 
$! can access them (useful for batch jobs to automate the collection). 
$ 
$ define /job/nolog time$line1 "''time$line1'" 
$ define /job/nolog time$line2 "''time$line2'" 
$ define /job/nolog time$line3 "''time$line3'" 
$ 
$ verify = f$verify(verify)

This example command procedure accepts multiple parameters, which include the RUN command, the name of the executable image to be run, and any parameters to be passed to the executable image. 


$ TIMER RUN PROG_TEST
$ 
$! User command being timed: 
$ 
$ RUN PROG_TEST.EXE; 
 
Execution (CPU) sec   45.39   Direct I/O        3   Peak working set   2224 
Elapsed (clock) sec   45.96   Buffered I/O     18   Peak virtual      15808 
Process ID         20A00999   SYS$DISK I/O      6   Page faults          64

If your program displays a lot of text, you can redirect the output from the program. Displaying text increases the buffered I/O count. Redirecting output from the program will change the times reported because of reduced screen I/O.

For More Information:

About system-wide tuning and suggestions for other performance enhancements on OpenVMS systems, see the HP OpenVMS System Manager's Manual, Volume 2: Tuning, Monitoring, and Complex Systems.

5.2.2 Performance and Coverage Analyzer (PCA)

To generate profiling information, you can use the optional Performance and Coverage Analyzer (PCA) tool.

Profiling helps you identify areas of code where significant program execution time is spent; it can also identify those parts of an application that are not executed (by a given set of test data).

PCA has two components:

PCA works with related DECset tools LSE and the Test Manager. PCA provides a callable routine interface, as well as a command-line and DECwindows Motif graphical windowing interface. The following examples demonstrate the character-cell interface.

When compiling a program for which PCA will record and analyze data, specify the /DEBUG qualifier on the FORTRAN command line: 


$ FORTRAN /DEBUG TEST_PROG.F90

On the LINK command line, specify the PCA debugging module PCA$OBJ using the Linker /DEBUG qualifier: 


$ LINK /DEBUG=SYS$LIBRARY:PCA$OBJ.OBJ TEST_PROG

When you run the program, the PCA$OBJ.OBJ debugging module invokes the Collector and is ready to accept your input to run your program under Collector control and gather the performance or coverage data: 


$ RUN TEST_PROG
PCAC>

You can enter Collector commands, such as SET DATAFILE, SET PC_SAMPLING, GO, and EXIT.

To run the Analyzer, type the PCA command and specify the name of a performance data file, such as the following: 


$ PCA TEST_PROG
PCAA>

You can enter the appropriate Analyzer commands to display the data in the performance data file in a graphic representation.

For More Information:

5.3 Data Alignment Considerations

The HP Fortran compiler aligns most numeric data items on natural boundaries to avoid run-time adjustment by software that can slow performance.

A natural boundary is a memory address that is a multiple of the data item's size (data type sizes are described in Table 8-1). For example, a REAL (KIND=8) data item aligned on natural boundaries has an address that is a multiple of 8. An array is aligned on natural boundaries if all of its elements are.

All data items whose starting address is on a natural boundary are naturally aligned. Data not aligned on a natural boundary is called unaligned data.

Although the HP Fortran compiler naturally aligns individual data items when it can, certain HP Fortran statements (such as EQUIVALENCE) can cause data items to become unaligned (see Section 5.3.1).

Although you can use the FORTRAN command /ALIGNMENT qualifier to ensure naturally aligned data, you should check and consider reordering data declarations of data items within common blocks and structures. Within each common block, derived type, or record structure, carefully specify the order and sizes of data declarations to ensure naturally aligned data. Start with the largest size numeric items first, followed by smaller size numeric items, and then nonnumeric (character) data.

5.3.1 Causes of Unaligned Data and Ensuring Natural Alignment

Common blocks (COMMON statement), derived-type data, and Compaq Fortran 77 record structures (STRUCTURE and RECORD statements) usually contain multiple items within the context of the larger structure.

The following declaration statements can force data to be unaligned:

To avoid unaligned data in a common block, derived-type data, or record structure (extension), use one or both of the following:

Other possible causes of unaligned data include unaligned actual arguments and arrays that contain a derived-type structure or Compaq Fortran 77 record structure.

When actual arguments from outside the program unit are not naturally aligned, unaligned data access will occur. HP Fortran assumes all passed arguments are naturally aligned and has no information at compile time about data that will be introduced by actual arguments during program execution.

For arrays where each array element contains a derived-type structure or Compaq Fortran 77 record structure, the size of the array elements may cause some elements (but not the first) to start on an unaligned boundary.

Even if the data items are naturally aligned within a derived-type structure without the SEQUENCE statement or a record structure, the size of an array element might require use of the FORTRAN /ALIGNMENT qualifier to supply needed padding to avoid some array elements being unaligned.

If you specify /ALIGNMENT=RECORDS=PACKED (or equivalent qualifiers), no padding bytes are added between array elements. If array elements each contain a derived-type structure with the SEQUENCE statement, array elements are packed without padding bytes regardless of the FORTRAN command qualifiers specified. In this case, some elements will be unaligned.

When /ALIGNMENT=RECORDS=NATURAL is in effect (default), the number of padding bytes added by the compiler for each array element is dependent on the size of the largest data item within the structure. The compiler determines the size of the array elements as an exact multiple of the largest data item in the derived-type structure without the SEQUENCE statement or a record structure. The compiler then adds the appropriate number of padding bytes.

For instance, if a structure contains an 8-byte floating-point number followed by a 3-byte character variable, each element contains five bytes of padding (16 is an exact multiple of 8). However, if the structure contains one 4-byte floating-point number, one 4-byte integer, followed by a 3-byte character variable, each element would contain one byte of padding (12 is an exact multiple of 4).

For More Information:

On the FORTRAN command /ALIGNMENT qualifier, see Section 5.3.4.

5.3.2 Checking for Inefficient Unaligned Data

During compilation, the HP Fortran compiler naturally aligns as much data as possible. Exceptions that can result in unaligned data are described in Section 5.3.1.

Because unaligned data can slow run-time performance, it is worthwhile to:

There are two ways unaligned data might be reported:

For More Information:

On the /WARNINGS qualifier, see Section 2.3.51.

5.3.3 Ordering Data Declarations to Avoid Unaligned Data

For new programs or when the source declarations of an existing program can be easily modified, plan the order of your data declarations carefully to ensure the data items in a common block, derived-type data, record structure, or data items made equivalent by an EQUIVALENCE statement will be naturally aligned.

Use the following rules to prevent unaligned data:

Using the suggested data declaration guidelines minimizes the need to use the /ALIGNMENT qualifier to add padding bytes to ensure naturally aligned data. In cases where the /ALIGNMENT qualifier is still needed, using the suggested data declaration guidelines can minimize the number of padding bytes added by the compiler.

5.3.3.1 Arranging Data Items in Common Blocks

The order of data items in a COMMON statement determines the order in which the data items are stored. Consider the following declaration of a common block named X: 


LOGICAL (KIND=2) FLAG 
INTEGER          IARRY_I(3) 
CHARACTER(LEN=5) NAME_CH 
COMMON /X/ FLAG, IARRY_I(3), NAME_CH

As shown in Figure 5-1, if you omit the appropriate FORTRAN command qualifiers, the common block will contain unaligned data items beginning at the first array element of IARRY_I.

Figure 5-1 Common Block with Unaligned Data

As shown in Figure 5-2, if you compile the program units that use the common block with the /ALIGNMENT=COMMONS=STANDARD qualifier, data items will be naturally aligned.

Figure 5-2 Common Block with Naturally Aligned Data

Because the common block X contains data items whose size is 32 bits or smaller, you can specify the /ALIGNMENT=COMMONS qualifier and still have naturally aligned data. If the common block contains data items whose size might be larger than 32 bits (such as REAL (KIND=8) data), specify /ALIGNMENT=COMMONS=NATURAL to ensure naturally aligned data.

If you can easily modify the source files that use the common block data, define the numeric variables in the COMMON statement in descending order of size and place the character variable last. This provides more portability, ensures natural alignment without padding, and does not require the FORTRAN command /ALIGNMENT=COMMONS=NATURAL (or equivalent) qualifier: 


LOGICAL (KIND=2) FLAG 
INTEGER          IARRY_I(3) 
CHARACTER(LEN=5) NAME_CH 
COMMON /X/ IARRY_I(3), FLAG, NAME_CH

As shown in Figure 5-3, if you arrange the order of variables from largest to smallest size and place character data last, the data items will be naturally aligned.

Figure 5-3 Common Block with Naturally Aligned Reordered Data

When modifying or creating all source files that use common block data, consider placing the common block data declarations in a module so the declarations are consistent. If the common block is not needed for compatibility (such as file storage or Compaq Fortran 77 use), you can place the data declarations in a module without using a common block.

5.3.3.2 Arranging Data Items in Derived-Type Data

Like common blocks, derived-type data may contain multiple data items (members).

Data item components within derived-type data will be naturally aligned on up to 64-bit boundaries, with certain exceptions related to the use of the SEQUENCE statement and FORTRAN qualifiers. See Section 5.3.4 for information about these exceptions.

HP Fortran stores a derived data type as a linear sequence of values, as follows:

Consider the following declaration of array CATALOG_SPRING of derived-type PART_DT: 


MODULE DATA_DEFS 
  TYPE PART_DT 
    INTEGER           IDENTIFIER 
    REAL              WEIGHT 
    CHARACTER(LEN=15) DESCRIPTION 
  END TYPE PART_DT 
  TYPE (PART_DT) CATALOG_SPRING(30) 
  . 
  . 
  . 
END MODULE DATA_DEFS

As shown in Figure 5-4, the largest numeric data items are defined first and the character data type is defined last. There are no padding characters between data items and all items are naturally aligned. The trailing padding byte is needed because CATALOG_SPRING is an array; it is inserted by the compiler when the /ALIGNMENT=RECORDS=NATURAL qualifier (default) is in effect.

Figure 5-4 Derived-Type Naturally Aligned Data (in CATALOG_SPRING : ( ,))

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