HELP (Программа GPSS), страница 4

The Random Numbers Page

Figure 2—16. The Random Numbers Page of the Settings Notebook

The Random Numbers Page lets you control the internal Random Number Streams of the simulation and the external numbering of child objects.

To keep naming of objects unique, GPSS World adds a sequence number to the names of newly created child objects. The number to be used for the next sequence number is kept here, in the Settings of the parent object. To change it just modify the Child Object Sequence Numberfield.

The Random Number Streams groupbox contains the remaining settings on the page. They determine which GPSS Random Number Stream is to be used for the purpose of resolving Time Ties, time randomization in GENERATE and ADVANCE Blocks, and Next Block in TRANSFER Blocks.

The Time Tiesentry field allows you to specify that when imminent events occur at the same time, the next event is to be selected randomly. To do so, place the Entity Number of the Random Number Generator to be used in the Time Ties entry field. If you use a value of 0, time ties will not be randomized. A fuzz value of one part per billion is used in the equality criterion for real time values.

The GENERATEBlocks entry field allows you to specify which Random Number Generator is to be used when a GENERATE Block calculates an interarrival time from Operands A and B. If you specify a nonpositive number, Random Number Generator number 1 is used.

The ADVANCEBlocks entry field allows you to specify which Random Number Generator is to be used when an ADVANCE Block calculates a delay time from Operands A and B. If you specify a nonpositive number, Random Number Generator number 1 is used.

The TRANSFERBlocks entry field allows you to specify which Random Number Generator is to be used when a TRANSFER Block selects a probabilistic destination Block. If you specify a nonpositive number, Random Number Generator number 1 is used.

The Function Keys Page

Figure 2—17. The Function Keys Page of the Settings Notebook

You can enter GPSS Statements into the fields on this page to load them into Function Keys, and/or you can change the tabstops of a Model Object.

When a Simulation Object is selected all you have to do to send the loaded GPSS Statement is to press the Function Key. Using an INCLUDE Statement permits you to send a Statement list of any complexity, including PLUS Procedures and Experiment definitions.

The Model Tabstops section allows you to set the tabstops of Model Objects. This may be desirable when you use the Block Creation Dialogs which themselves use tabs in the Block Statements they create. Tabstops are disabled for Simulation or Report Objects. Tabstops must be nonzero and strictly increasing from the first (leftmost) to the last. You can specify the tabstops in either of two units: characters or twips. There are 1440 twips in an inch (approximately 567 in a centimeter).

The Expressions Page

Figure 2—18. The Expressions Page of the Settings Notebook

When you open an Expression Window or a Plot Window on a Simulation Object, you must specify the expression to be watched as well as a name to be used as a label. This page allows you to save complex expressions with the Simulation Object. Then, when you open a Window using the expression, you can select it from a list instead of having to retype it.

Both the Expression Window and the Plot Window give you a chance to save expressions currently in use in the window. You can do this by

SELECT Edit / Expression Window

and

SELECT Edit / Plot Window

And then selecting the expression and

CLICK ON Memorize

Alternately, you can type the label and expression into this page of the Settings Notebook. The effect is the same. You will now be able to bring back the labeled expression simply by selecting it.

2.3. Controlling a Session

Normal installation of GPSS World places a line in your operating system's Start / Programs Menu that you click on to start the program. Alternately, you can create a shortcut to GPSS World and place it on your personal computer's "desktop", or anywhere you like. Simply drag the GPSS World icon from the Start / Programs menu.

You can open an object in GPSS World Session merely by double-clicking on it. When you run GPSS World the first time, it registers the file types and extensions of GPSS World with the Windows operating system. This allows Windows to associate GPSS World with any of its Object files. Thereafter you can double click on any of the file icons to start a GPSS World Session.

2.3.1. Using the Main Window

Once you have started a Session you can control it using your mouse and the keyboard. You can choose menu items by clicking with your mouse, by using menu mnemonic keys, and by using accelerator keys. Many interactions require you to type information using the keyboard, and the set of Functions Keys on your keyboard can be loaded with any Commands you choose. As described in the previous section, you edit the Settings of an object in order to load Commands into the Function Keys.

Before you begin, you should familiarize yourself with the Main Menu. A quick overview is presented above, in Section 2.2.2. Many of the Main Menu items are disabled and appear gray until they can be used. As you open and create GPSS World Objects, the valid menu commands will become enabled as appropriate.

Using The Main Menu

Although all the GPSS World Objects have small menus on their own windows, most actions start in the Main Menu. All menus are used in a similar fashion. Some menu sequences result in the creation of a Dialog Window containing several controls such as buttons and entry fields. Entry fields normally require you to use the keyboard to type in additional information.

To initiate the menu actions, you have three choices. First, you can simply use the mouse to click on the succession of menu items. Second you can press the a key to activate the menu, and then press the underlined (i.e. the mnemonic) letter in each menu item, in sequence. Third, if the lowest level menu item has an accelerator key listed to the right of the item name in the menu, you can simply press that combination of keys to begin the action, if it is enabled.

The Accelerator Keys

Accelerator keys are key combinations that immediately enter a menu command into GPSS World. Usually, they are listed just to the right of the menu item they effect. They are enabled only when their associated menu item is. To activate an accelerator key, hold down all keys in the combination except the last, then press the last key, then release all keys.

GPSS World Hot Keys

Hot keys are quick ways to send GPSS World Commands to a Simulation Object. They are:

b+a+S - Create Simulation b+a+R - Retranslate b+a+L - Repeat Last Command

b+a+C - CONTINUE b+a+H - HALT b+a+1 - STEP 1

Text View Navigation Keys

Navigation Keys let you jump to specific locations in a Text View. They are:

b+a+B - Next Bookmark b+a+G - Go To Line b+a+N - Next Error b+a+P - Previous Error b+a

+F - Find / Replace

Text Editing Accelerators

Editing is faster using Text Edit Accelerators instead of menu selection. These keys are:

b+Z - Insert Line b+D - Delete Line b+I - Undo

b+C - Copy to Clipboard b+X - Cut to Clipboard b+V - Paste from Clipboard

also,

b+h - Copy to Clipboard j+c - Cut to Clipboard j+h - Paste from Clipboard

General Accelerators

There are several other general purpose keys. They are:

b+O - File Open b+S

 - File Save b+P - File Print

a+q - Next Pane j+q  - Previous Pane

Online Help

The l key opens the GPSS World Help System any time it is pressed. You can then explore the contents and index of the "Windows Help" form of the GPSS World Reference Manual.

In addition, if a menu item or control is selected, l will open context sensitive help on that topic. Or, if the cursor is embedded in a GPSS World keyword, such as a Command Name, in a Text View, if you press the l key, you will open the online Reference manual to information on that topic.

Error Messages

When an operation cannot be completed, GPSS World displays an Error Message in a dialog box or a Text Window. Most messages are intended to be self-explanatory. Even so, a further explanation of each message can be found in Chapter 14 of this manual.

Using Text Windows

The Text Windows of all GPSS World Objects have text editing capabilities. You can enter text into a Text Window by opening a file, by typing, or by pasting from the clipboard. Text can be modified in a variety of ways.

There are two place-marking indicators that you can use when a Text View has the input focus. In a Text View, the mouse pointer is the I-beam icon that travels as you move the mouse. The cursor, or insertion point, is the flashing vertical line in the text window that marks the text insertion point. Text you type is placed at the insertion point indicated by the cursor.

The editing operations available are:

Move the cursor to the position of the mouse pointer by clicking mouse button 1.

Move the cursor by arrow keys in the keypad.

Move the cursor and scroll using the { and } keys.

Move the cursor to the beginning and end of a text line by pressing g and d , respectively.

Scroll using the scroll bars of the Text Window.

Break a text line with e or f .

Delete selected text with c .

Undo last edit with Edit / Undo .

Delete line with cursor with Edit / Delete Line

Insert new line after cursored line with Edit / Insert Line .

Selection operationsinclude

Select word by double click on button 1.

Swipe select by click and hold button 1, move mouse, release button 1.

Extended select by j + click mouse button 1 to select from cursor to mouse pointer.

Clipboard operationsinclude

· Cut selected text by Edit / Cut. Delete text and place copy in clipboard. You may also use the key combination b + X.

· Copy selected text by Edit / Copy. Copy text to clipboard. You may also use the key combination b + C.

· Paste to cursor by Edit / Paste . Insert a copy of text from clipboard. You may also use the key combination b + V.

Other operations using keyboard accelerators are described above.

You can change the font of text in a Text View. First select the text, then

CHOOSE Edit / Font

This will open the Font Dialog, where you can specify typeface, size, and character type for the selected text. GPSS World uses Courier as the default font. It has the advantage of being a monospaced font with uniform character widths. This has the advantage of easy column alignment in GPSS Statements.

2.3.2. Building Models

The physical process of model development starts with the creation of a Model Object that contains Model Statements written by you. Model Statements are defined in Chapters 6, 7, and 8 of this manual. Often it's easiest to begin building a simulation by modifying an existing model. The Samples folder is rich source of small GPSS World Model Objects.

Model Statements can exist in additional Text Objects (.txt) as well as the primary Model Object (.gps), permitting you to share code across projects. Although there's only one Model Object in a simulation, there can be many Text Objects. These are connected to the Model Object with INCLUDE Statements, which take the name of the Text Object file (.txt) as an argument.

Model development begins by opening a Text View of the Model Object. A complete set of text editing operations is available for modifying and adding Model Statements. If you prefer, the use of the Block Input Menu and one or more Block Creation Dialogs makes it relatively easy to correctly specify the Blocks Statements in your Model. Each Block Statement is inserted in a line following that of the flashing insertion point in the Model Object. Online Help guides you all the way and syntax errors are prevented.

A model must be Translated in order to Create a Simulation Object. The Translation is started via the Command / Create Simulation item in the main menu of the Model Window. The Translator determines if there are syntax errors in the model. If so, a circular queue of error messages is created so that the errors can be found and corrected easily. If no errors are found, the resulting simulation automatically sent to the Simulation Object, replacing any that already existed. When the Simulation Object receives a simulation, it immediately performs all embedded Commands in the order encountered by the Translator.

INCLUDE Commands

You can use an INCLUDE Command anywhere in a Model except in a PLUS Procedure. Normally, they are used in Model Objects to incorporate statements from one or more Text Objects. INCLUDE Statements can be nested to a depth of 5, but they cannot be used inside a PLUS Procedure.

The syntax of the INCLUDE Command is:

INCLUDE "FileSpec"

Where you replace the italicized word FileSpec with your file specification, including extension (normally .txt), and enclose it in double quotes. The default directory is that of the Model Object.

INCLUDE Commands have other uses, as well. You can type an INCLUDE Command as a Custom Interactive Command. This causes a whole file of Model Statements to be Translated and sent to the Simulation Object. An INCLUDE Command can be loaded into a function key, just like any other GPSS Command. In this manner a single keystroke can initiate a complex Command File or PLUS Procedure redefinition.

Before you use a file in an INCLUDE Command, you should Translate it by itself to remove syntax errors. To do so, copy its Model Statements to the clipboard, open a new temporary Model Object, paste into it from the clipboard, and Translate it using Command / Create Simulation. This allows you to correct any Syntax Errors easily before combining the Text Object into a more complicated model.

Translating Models

Simulation Objectsbegin as Translated Model Objects. When you Translate a model by selecting Command / Create Simulation, the GPSS World Translator checks for syntax errors, creates a simulation, and sends it to a newly created Simulation Object. If successful, Translation activates all the Interactive Commands and Simulation Windows, so that the state of the newly created simulation can be monitored and controlled. After that, you can send any Model Statement to the existing simulation for processing.

GPSS World features a new high performance Model Translatorthat is hundreds of times faster than its predecessor. The largest models are Translated in no more than a few seconds. When the Translator detects one or more errors in the model, it creates a circular list of error messagesthat can be accessed from the Text View of the Model Object. You can traverse the error list quickly using the Search / Next Error or Search / Previous Error menu commands. Both have keyboard mnemonics and accelerators. Each stop in the list places the error message in the Status Line of the Main Window and places the insertion point in the Model Text View just before the syntactical element that caused the error. It's then a simple matter to correct each error and move to the next.

If an error occurs in an INCLUDEd Text Object, and you cannot find it easily, you can paste those statements into a new temporary Model Object and Translate it by itself. It is best to place only tested statements into an Include-file.