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PPTX Merging Is Extremely Slow

I am starting with a blank presentation and then merging specific slides from multiple ppts into the blank one. It approximately takes 8-10 seconds for merging 1 slide.

Java Configuration:
java version “15.0.2” 2021-01-19
Java™ SE Runtime Environment (build 15.0.2+7-27)
Java HotSpot™ 64-Bit Server VM (build 15.0.2+7-27, mixed mode, sharing)

Aspose Configuration:

System Configuration:
OS: Windows 10
Storage: 1TB

I have performed an exhaustive time analysis and it either takes around 10-15 seconds in creating the presentation object or in cloning the slide.

p_new = new Presentation();
SlideCollection slds = p_new.getSlides();

Welcome to our community! Thank you for the issue description. To my regret, I cannot use your code example containing the unknown symbols (p, v, i). Could you please share a comprehensive code snippet for checking the issue?

Please find the entire code below. The slowness in merging is present irrespective of the deck I use.

package aspose20;
import java.io.IOException;
import java.util.concurrent.TimeUnit;
import java.util.stream.IntStream;

import com.aspose.slides.Presentation;
import com.aspose.slides.SaveFormat;
import com.aspose.slides.ISlideCollection;

public class MergeSlide {
public static void main(String args[]) throws IOException {
System.out.println(“Merging Started!”);
Presentation p_new = new Presentation();
ISlideCollection slds = p_new.getSlides();

   //Any File location
   String file1 = "C:\\data\\deck1.pptx";
   String file2 = "C:\\data\\deck2.pptx";
   String[] inputs = {file1, file2};

// Index of slides to merge
    int deck1[] = new int[]{75, 17};
    int deck2[] = new int[]{15, 6}
    int [][] pptarr = {deck1, deck2};
    boolean test;
    long startTimefi = System.nanoTime();
    for(int p_no = 0; p_no < inputs.length; p_no++) {
	long startTime = System.nanoTime();
	Presentation p = new Presentation(inputs[p_no]);
    long endTime = System.nanoTime();
   System.out.println("Reading "+TimeUnit.SECONDS.convert((endTime - startTime), TimeUnit.NANOSECONDS) + " s"); 
for (int index = 0; index< p.getSlides().size(); index = index+1) {
             // Merge slides from source to target
	final Integer innersc = new Integer(index);
	// Check if this slide is to be merged
            test  = IntStream.of(pptarr[p_no]).anyMatch(x -> x == innersc);
	startTime = System.nanoTime();
	endTime = System.nanoTime();
	System.out.println("Merging "+TimeUnit.SECONDS.convert((endTime - startTime), TimeUnit.NANOSECONDS) + " s"); 

long endTimefi = System.nanoTime();
System.out.println("Took “+TimeUnit.SECONDS.convert((endTimefi - startTimefi), TimeUnit.NANOSECONDS) + " s”);
// Save the presentation
p_new.save(“merged-presentation.pptx”, SaveFormat.Pptx);
System.out.println(“Merging Done!” + p_new.getSlides().size());


Thank you for the code example. It will take me a while to investigate the issue. Thank you for your patience.

Please share your test files (deck1.pptx and deck2.pptx).

Please find the decks over here:

Few points to note:

  1. It works slow irrespective of the deck being used.
  2. I ran it on AWS t2.micro ec2 instance and it works pretty fast, bringing down 10 seconds per slide to around 3.5 seconds per slide on an average.

Thank you for the file samples. I reproduced the problem and received the same results for some slides. I have logged the issue in our tracking system with ID SLIDESJAVA-38482 for further investigation. You will be notified about any progress.

Our development team has investigated the issue. This behavior occurs when the first slide is loaded because we are loading internal caches, etc. Please take a look at the following experimental results on our end:

Merging slide 75: 7 s
Merging slide 75: 0 s
Merging slide 75: 1 s
Merging slide 17: 1 s
Merging slide 17: 1 s

As you can see, when loading the slide a second time, the timing has greatly improved. Our development team investigated our code and found no bottlenecks that could be improved.