A. IF BLOCKS AND DO LOOPS

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1 IF BLOCKS AND DO LOOPS Overview A. IF BLOCKS AND DO LOOPS A.1 Overview GAMBIT allows you to use IF blocks and DO loops as part of a set of journalfile commands. IF blocks and DO loops allow you to customize journal files in order to facilitate the creation and/or meshing of GAMBIT models. For example, you can use DO loops to construct, locate, and orient multiple copies of a single entity type. The following sections of this appendix describe the general syntax and use of GAMBIT IF blocks and DO loops Fluent, Inc. All rights reserved. A-1

2 IF Blocks IF BLOCKS AND DO LOOPS A.2 IF Blocks A.2.1 General Syntax The general syntax of a GAMBIT IF block is as follows: IF COND (X) [ ] where X represents a logical expression and the square brackets ([]) indicate that the statement and its associated are optional. (For a description of valid logical expressions, see Appendix B, Section B.3.2.) When GAMBIT encounters an IF block, it evaluates the expression, X, and executes selected blocks of subsequent commands depending on whether the expression is true or false. The following table describes the action that results from the evaluation of a GAMBIT IF block expression (X). X True False Action GAMBIT executes the block of commands that exists between the IF and commands. If the IF block does not contain an command, GAMBIT executes the entire block of commands between the IF and commands. GAMBIT skips to the next command at the same nesting level. If the IF block does not contain an command, GAMBIT skips to the command that follows the command. NOTE: GAMBIT IF,, and statements are not case-sensitive. For example, the following block of commands constitutes a valid GAMBIT IF block: if cond ($q.eq. 5) volume create sphere radius ($q*3) endif A Fluent, Inc. All rights reserved.

3 IF BLOCKS AND DO LOOPS IF Blocks A.2.2 Example As an example of the use of GAMBIT IF blocks, consider the following block of commands: IF COND ($a.gt. 5) volume create sphere radius ($a/2) volume create brick width 1 height 1 depth 1 GAMBIT interprets the IF block as follows: A.2.3 Nested IF Blocks If the parameter a is greater than 5, create a sphere of radius 2.5. If the parameter a is less than or equal to 5, create a unit cube. GAMBIT IF blocks can contain any number of nested IF blocks. For example, the following structure constitutes a valid general use of nested IF blocks: IF COND (X(1)) IF COND (X(2)) IF COND (X(3)) IF COND (X(4)) where the X(i) represent distinct logical expressions Fluent, Inc. All rights reserved. A-3

4 DO Loops IF BLOCKS AND DO LOOPS A.3 DO Loops A.3.1 General Syntax The general syntax of any GAMBIT DO loop is as follows: DO PARA "$p" [ INIT i ] COND (X) [ INCR n ] ENDDO where the brackets ([]) indicate that the keywords INIT and INCR and their associated parameters are optional. The DO-loop parameters shown above are defined as follows. Parameter $p i X n Definition Loop control variable. NOTE: The loop control variable must constitute an existing parameter that is, a parameter that has been previously defined. (For a description of the definition and use of GAMBIT parameters see Section ) An arithmetic expression that provides the initial value for $p when loop execution begins. (Default = 1.) A logical expression used to terminate loop execution. The loop terminates when the expression X evaluates as false. NOTE: For a description of valid logical expressions, see Appendix B, Section B.3.2. An arithmetic expression that defines the amount by which $p is incremented after each execution of the DO loop. (Default = 1.) NOTE: The value of n is evaluated only once at the initialization of the DO loop. NOTE: GAMBIT DO-loop statements are not case-sensitive. For example, the following block of commands constitutes a valid DO loop do para "$x" init 3 cond ($x.le. 5) volume create brick width $x height ($x*2.5) enddo A Fluent, Inc. All rights reserved.

5 IF BLOCKS AND DO LOOPS DO Loops A.3.2 DO-Loop Operations When GAMBIT encounters a DO loop, it executes the following sequence of operations. Step Operation 1 Evaluate i and n. 2 Initialize $p to the value of i. 3 Evaluate X: If X evaluates as false, skip to the command that follows the ENDDO command. If X does not evaluate as false, execute the commands that exist between the DO command and the ENDDO command. 4 Increment $p by n. 5 Go to Step 3. A.3.3 Example As an example of a GAMBIT DO loop, consider the following block of commands: $Tmp = 2 do para "$Z" init 6 cond ($Z.le. 24) incr ($Tmp*3) volume create sphere radius $Z enddo If you execute the command block shown above, GAMBIT creates four spheres with radii 6, 12, 18, and Fluent, Inc. All rights reserved. A-5

6 DO Loops IF BLOCKS AND DO LOOPS A.3.4 BREAK and NEXT GAMBIT allows you to control DO loop operation by means of two additional commands: BREAK NEXT The BREAK and NEXT commands operate as follows: A.3.5 Nested DO Loops If GAMBIT encounters a BREAK command, it skips immediately to the command that follows the ENDDO command. If GAMBIT encounters a NEXT command, it skips any commands that exist between the NEXT command and the ENDDO command but continues execution of the DO loop. GAMBIT allows you to nest DO loops within other DO loops. The only restriction that GAMBIT imposes on the nesting of DO loops is that each nested loop must be completely contained within the outer loop. A Fluent, Inc. All rights reserved.

4. GAMBIT MENU COMMANDS

GAMBIT MENU COMMANDS 4. GAMBIT MENU COMMANDS The GAMBIT main menu bar includes the following menu commands. Menu Item File Edit Solver Help Purposes Create, open and save sessions Print graphics Edit and/or