JavaScript Performance Slow – Not Utilizing Full CPU?

Question

Hello all. I have a script performance question I was hoping someone could help with.
I’ve developed a folder level JavaScript for Acrobat that does a great detail of linking and annotation for a certain kind of PDF book that we produce where I work.   The script works, however the performance is quite slower than I would expect.  On some of the larger books I run the script on it takes hours to complete.    I did suspect my code for a while and optimized it as much as possible.  I noticed later though that while the script is running Acrobat only utilizes a maximum of about 12 percent of the CPU (12 percent of one core).   I would think this number would be much higher.  Has anyone else experienced this? Is there a way around it?  
Craig

Answer 1

JavaScript is an interpretive language or each line of  code is reprocessed each time it is asked to be rerun. When a PDF form is opened all of the JavaScript is processed from plain text through a syntax check, and common actions being converted into tokens for faster running. Also functions are converted into tokens for reuse.
So gains in processing times are achieved by determining the best place to place code like using the on blur action for processing a field process that only has to occur when a field value changes  like testing a value and issuing a waring versus running a full calculation for that same action.
When any field used within a calculation is modified, all calculations are reprocessed when ever one of those fields is changed. Another way to improve performance is to create a function  or a predefined process that may have some input values, performs a specific task. and may return a result. So if I have a calculation like computing elapsed time between 2 time values on a time sheet rather than coding the conversion of the time strings to a number, performing calculation and formatting the result for each day, I could define a function that uses the 2 time values, computes the difference and returns the formatted result. Since the function has been syntax checked and tokenized it will run faster on each call for each day.
It is also possible to combine the calculation for many fields into one larger calculation in one form field and it is even possible to call a user defined function within another user defined function so one eliminates the repeated initialization for the code for each field.
If one is adding fields with JavaScript and adding calculation actions, it is best to turn off the the doc's calculate property while adding the fields since each new added field will trigger a recalculation as each field is added. Just remember to turn it back on at the end. This should have no affect when adding annotations or searching for words.
If you are having to search through the PDF for each word, then there is a lot of overhead. I have noticed with such scripts that the first use takes significantly longer than the next call as long as Acrobat is not closed. This maybe due to the use of virtual memory by the computer and the code I use is in the RAM from the first call and not the virtual swap file for the second call of the process.
You might also get faster processing by using the Action/Batch processing of Acrobat Professional.