# 2. The Computation Tool ( Web version )

### 2.2. Options

• GENERATION LEVELS: The computation proceeds by levels, beginning with the starting compounds, which is level 0. Every level is the result of the applications of the rules to the one immediately preceding it. The GENERATION LEVELS option allows the user to establish at which level the program should start determining if the formula of the searched compounds has been found and at which level the computation should stop. The syntax is <lower>-<upper> (number, dash, number). The program looks for the searched product only beginning at level <lower>, which makes the execution faster. When the level <upper> is reached the program stops. For example 2-1 means start to check at 2 but stop at 1, said otherwise go to level 1 without ever checking. 2-2 means go to 2 and check the generated compounds of level 2. Of course the generation resumes by selecting continue under MAIN.
• RULE APPLICATION BOUND: Sets the maximum number of products generated by the application to a formula of a reaction step rule. If left empty, there is no bound. The rules in the list of rules are numbered in the order they are appended, beginning with 0. The Graphic Composer allows to view a rule from the list given its number.

Every rule includes a pattern and describes a movement of the bonds and of the charges. Whenever there is a match for the pattern in a formula the rule is applied. This option has been introduced to limit the number of applications of a rule and reduce the time the program spends at the rule looking for matches. By entering a number the application for all rules is limited to that number. By entering nothing all applications for all rules are processed. If the limit should depend on the rule, the following complete syntax can be used:

[n0:]b0,...,[nK:]bK
The expression above sets the maximum number of formulas generated by means of rule n0,...,nK to b0,...,bK respectively. No limit is set for the rules not among n0,...,nK. The number of the rule is optional. If it does not appear the maximum number is set for all rules. For example
5,3:2,0:1
sets the maximum to 5 for all rules except for rule 3 and 0, which can generate at most 2 respectively 1 product. With the designation
0,21:8,28:8,1:8,5:8
every rule should be applied 0 times (not applied) with the exception of rules 21, 28, 1 and 5 that should be applied at most 8 times.
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