Good afternoon,
I'm working with gatk and more specifically with the Haplotypecaller function in order to create the GVCF files and I've seen that it takes quite a lot of time. I'm a bit in a rush and I would like to speed up the process, but I did not find useful information about it. Here is my code: 

    java -jar ~/softwares/GATKK/gatk/gatk-package-4.1.7.0-local.jar HaplotypeCaller --reference Pmuralis_1.0.fa --input run2_mergeandaligned.bam --output run2_4096_mergeandaligned.g.vcf -ERC GVCF

The only thing that seems to improve a bit the process is if I add `-Xmx4096m` to the beginning, like this:

    java -Xmx4096m -jar ~/softwares/GATKK/gatk/gatk-package-4.1.7.0-local.jar HaplotypeCaller --reference Pmuralis_1.0.fa --input run2_mergeandaligned.bam --output run2_4096_mergeandaligned.g.vcf -ERC GVCF

Another thing I noticed is this message:

    20:58:54.759 INFO  IntelPairHmm - Available threads: 20
    20:58:54.759 INFO  IntelPairHmm - Requested threads: 4

As in my server I have 20 cores but the process is just taking 4. I think I solved it adding `-native-pair-hmm-threads 20` but it didn't speed up the process...
Let's see if somebody knows about java and can help me! 

Thank you very much!
> . I'm a bit in a rush and I would like to speed up the process, but I did not find useful information about it. 


split by chromosome using option `-L` and run in parallel.
