On Sat, Mar 25, 2023 at 6:40 PM Jakub Narębski [off-list ref] wrote:

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Abhradeep promised[1] that he'd include some performance work in his
next version of that series. I think the main things we'd be interested
in are:

  - Does using Roaring provide a file-size advantage over
    EWAH-compressed bitmaps?

I modified JGit to write Roaring bitmaps instead of EWAH bitmaps. The
resulting difference in file sizes are small, and actually favor EWAH:

$ ls -l {ewah-repos,roaring-repos}/*.git/objects/pack/*.bitmap
-r--r----- 1 hanwen primarygroup 26257386 Jul 31 15:04
ewah-repos/android-pfb.git/objects/pack/pack-b14c35ec7fc3bb20884abe51a81c832be5983fdc.bitmap
-r--r----- 1 hanwen primarygroup 27621579 Jul 31 15:20
roaring-repos/android-pfb.git/objects/pack/pack-b14c35ec7fc3bb20884abe51a81c832be5983fdc.bitmap

-r--r----- 1 hanwen primarygroup  1037356 Jul 31 14:46
ewah-repos/gerrit.git/objects/pack/pack-fe46c7f96a2910f5775a2ff3bef7e4fa0e779f91.bitmap
-r--r----- 1 hanwen primarygroup  1242608 Jul 31 14:45
roaring-repos/gerrit.git/objects/pack/pack-fe46c7f96a2910f5775a2ff3bef7e4fa0e779f91.bitmap

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