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HP MPE/iX 6.x Operating System Coding for Performance and Optimization

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Coding for Performance and Optimization

The MPE/iX Optimizer modies code to use mac hine resources ecien tly, using less space and running faster. It impro ves code, but does not alter the algorithm used in code. Coding for good performance requires recognition of the following facts:

Coding practices alter performance.

Mismatches exist between programming languages and most arc hitectures.

Coding techniques can enhance or inhibit optimization opportunities.

Coding for optimization pro vides the follo wing methods of optimizing a program at the source code level:

Reduces or avoids aliasing

Uses optimal data t ypes

Identies common subexpressions

Reduces procedure calls Avoids non-nativ e alignment

Reduce Aliasing

The compiler must generate explicit loads and stores when programs use aliasing with pointers. If you specify that the poin ter does not change (for example, b y using WITH in HP Pascal/iX), you can eliminate some loads and stores. Th us, more optimization (suc h as using registers) can occur. Figure 5-1 sho ws an example of reducing aliasing.

Figure 5-1. Reducing Aliasing

Use Optimal Data Types

Examples of optimal data t ypes are 8-bit character and 32-bit in teger. For detailed information refer to the appropriate man ual in the Language Series.

5-4 Optimizing a Program

Contents

900 Series HP 3000 Computer Systems Hewlett-PackardCompany 3000 Hanover Street Palo Alto, CA 94304 U.S.A Printing History Page Preface Organization of this Man ual Conventions Conventions (continued) Contents Page Page Page Page Page Figures Page Tables Page OVERVIEW Introduction to the HP MPE Operating Systems Page Page 900 Series Migration Object Code Translator Native Mode Compilers HP C/iX COBOL II/XL HP Pascal/iX MPE/iX Features MPE/iX Information Management Page MPE/iX Transaction Management F acility DEBUG MPE/iX User Interface MPE/iX System Performance Native Mode System Components Terminal Keyboard Layouts Giving Commands to MPE/iX Page Location of a parameter in the list is signican t Each parameter is separated b y a comma (,) For example: The characteristics of a k eyword parameter list are: Location of a parameter in the list is not signican t Page A User-DenedCommand (UDC) le is a text le that con tains one or more command NOBREAK , which disables the BREAK k ey for UDC execution A parameter without a default v alue is required to execute the UDC Break Mode Page Echo On/Off Accounting Structure Ov erview Amount of CPU time Elapsed connect time Disc space used User Figure 1-7shows an example of sev eral users on an accoun t Group Following is an example of a logon to the group PR OJ1: File Specifications lename/lockword Session and Batch Modes Page Converting Data Files from MPE V/E to MPE/iX Page Page Page Data Communications Local Area Network (LAN) Remote File Access Calling standard MPE/iX File System in trinsics Remote Terminal Access Remote Data Base Access Page Page Utilities and Tools Programmatic Access to the Command Interpreter Concatenating Strings and String Substitution purges les ACCT1, ACCT2, . . . , ACCT9 Expression Evaluation Using Job Control Words (JCWs) JCW commands and in trinsics denes a variable named X as a JCW with value 99. The statemen t: and the initial value remains unchanged JCWs with reserv ed-wordprexes and numeric values are: Help Facility Toolset/XL Useful Tools Report Generation Tools Three modules are in tegrated with the HP Visor in terface Page Editor SORT-MERGE/XL DISCFREE FCOPY/XL Page Page Program Development Writing a Program Compiling a Program Compiler Output Compiler Operation A relocatable object module on MPE/iX corresponds to a relocatable binary module (RBM) on MPE V/E, with the follo wing exceptions: A relocatable object module can con tain zero, one, or sev eral procedures Compiled code (mac hine instructions) for all procedures in the source le Information on data v ariables to be used External references (resources required to run the program) :CCXL :COB85XL :FTNXL :PASXL Linking a Program Resolve references among the relocatable object modules Page Page Page Page Loading and Running a Program Using Executable Libraries :RUN prog; XL = " xlib1[,xlib2][,xlib3] Searching Executable Libraries The following guidelines apply to searc hing executable libraries (XLs): Run-timelibraries can appear only once in the :RUN command System Libraries Processes using the same object module share code, global data, and binding Cannot use UNSAT procedures Mixing Execution Modes Virtual Memory and Demand Paging LMAP: Load MAP File name and type of le (program or library) Load-timeBinding Sequence Running a Program Multi-programmingEnvironment Error Detection Run-timeErrors What is the cause or source What is the mechanism of the abort What information is pro vided to help trace and correct the problem What are typical abort situations Typical Causes of Program Aborts File Information Display (Tombstone) Actual physical and operational le c haracteristics Information on the last error for the le and the last HPFOPEN or FOPEN error Control Codes (JCWs) Page Page User-definedJCWs Available to each process in the same session or job Have names dierent from JCW or CIERROR Using a User-definedJCW The following job shows an example of using a user-denedJCW HP Link Editor/XL Page Common Uses of HP Link Editor/XL Linking a Relocatable Object File Comparison of HP Link Editor/XL and MPE V/E Segmenter How HP Link Editor/XL Works Files Used by HP Link Editor/XL Page HP Link Editor/XL Commands Using an Indirect File Starting and Ending HP Link Editor/XL Creating an Executable Program File Page Comparison of Executable and Relocatable Libraries Using a Relocatable Library Using an Executable Library Page Optimizing a Program Optimizer Levels Use of MPE/iX Optimizer with Languages Optimizer Assumptions Coding for Performance and Optimization Page Instructions Required for Operations on Simple Data Types These examples assume the follo wing characteristics are true: Unoptimized code Well aligned operands No range or overow checking Reduce Procedure Calls Expand Small Procedures In-line Extract Procedure Calls from Loops Avoid Non-nativeAlignment Figure 5-8sho ws an example of a voiding non-native alignment Page Page File System Records and Files in the File System The File System , and access Use of device characteristics :FILE command Disc File Storage File Directory Structure Page When you specify a le domain using HPFOPEN , you should open only disc les with the domain option set to NEW. Device les can be opened with the domain option set to NEW (to maintain compatibility with MPE V/E), but a warning is returned in the status parameter Any le can be deleted when closed. This is the default for a NEW le Delete the previous cop y of the le before the run Rename the existing le b y using FRENAME For examples of changing domains, refer to Accessing Files Programmer's Guide Refer to it from a command or program Transfer it during I/O File Designators The two types of MPE/iX le designators are: Formal le designator Actual le designator filename [/lockword][.groupname][.accountname] HPFOPEN option (Item #38), the le privilege option , when used to set a Page Page System Files System-denedles are: Page Input/Output Sets Passed Files Searching File Directories Finding Files You can use the the follo wing commands to see le and le equation lists: :LISTEQ command for curren t le equations Types of Operations Allowed on Files les) are PERMANENT les. To maintain compatibility with MPE V/E, device les can be opened with the domain option set to NEW, but a warning is returned in the status parameter Page Page Using Files at Run Time Hierarchy of File Overrides Record Structure Page Specifying a Record Size File Structure File Codes Creating a File Specify the le with the :FILE command Deleting Files Renaming Files Saving Temporary Files newlereference Listing File Characteristics File names and structure of permanen t disc les Number of records in the le Number of extents Maximum number of extents Records per block Record Selection and Data Transfer Page Data Transfer Control Operations FSPACE , provides spacing. It mo ves the record poin ter backward or forward FPOINT , provides pointing. It resets the record poin ter FCONTROL , provides rewinding. It resets the record poin ter to record Reading from a File Other specialized read in trinsics are READX and FREADLABEL Writing to a File FWRITEDIR writes a specic logical record from a program to a disc le Updating a File Using Mapped Access to a File Standard disc les with v ariable-lengthrecord formats KSAM les (with COPY mode enabled) The following le types cannot be opened for mapped access: Relative I/O (RIO) les Sharing a File Page Maintaining File Security Page Page Page The default securit y at account, group, and le lev els are as follo ws: Account level Group level File level At the group level, the MPE/iX Securit y System recognizes six access modes: Page 3.Listing ACDs 4.Copying ACDs 5.Modifying ACDs 6.Deleting ACDs 7.Migrating A CDs Page Data Management Data Management Subsystems KSAM/V The KSAMUTIL command BUILD requires the follo wing parameters: Data le name Key le name One or more key types, with corresponding k ey location, and k ey size FCOPY (KSAM Options) Load a KSAM le by copying data from an MPE/iX or a KSAM le in to a KSAM le Page Page ALLBASE/SQL HP SQL Page Concurrency Recovery Database Creation Database Restructuring HP SQL provides dynamic restructuring for the following cases: Expanding table capacities Altering securit y designations Adding columns Page TurboIMAGE/XL Data Base Page Page TurboIMAGE/XL and QUERY/V PARM=3 if both DBSTEXT and DBSLIST have been equated to actual le designators DBUTIL Create a database Purge a database Erase a data set Page Access data Information and status Logging 1.Run DBUNLOAD , specifying the old database 2.Use the DBUTIL command PURGE to purge the old database QUERY/V Page TurboIMAGE DBchange/V DICTDBA DICTDBU DICTDBL Page Index