Worse compression rates with ZLIB-CF?

ROOT
1

Hi all

I noticed that the change of the built-in zlib library from 6.16 to 6.18 gives worse compression rates in my use case:

Attaching file file_18.root as _file0...
(TFile *) 0x5582ad81fae0
root [1] _file0->GetCompressionAlgorithm()
(int) 1
root [2] _file0->GetCompressionFactor()
(float) 6.21950f
root [3] _file0->GetCompressionLevel()
(int) 1
root [4] _file0->GetCompressionSettings()
(int) 101

Attaching file file_16.root as _file0...
(TFile *) 0x558475539b00
root [1] _file0->GetCompressionAlgorithm()
(int) 1
root [2] _file0->GetCompressionFactor()
(float) 9.60246f
root [3] _file0->GetCompressionLevel()
(int) 1
root [4] _file0->GetCompressionSettings()
(int) 101

The files (containing a tree and a bunch of histograms) were created with the same analysis software, using 6.16.00 and 6.18.00, respectively.

The new library seems to be faster, so do we have a classic case of speed-memory conservation?

Cheers,
Dominik

2

Maybe @pcanal and @oshadura may have some ideas about it.

3

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4

@werthm sorry for a late reply, I missed this post…

Thank you for an interesting data! In general you are correct, it is a case of speed-memory trade-off, even though I was not expecting such difference in compression factor (it should be a bit smaller).

Do you have examples of both files? I will be very happy to take a look on them! Thank you in advance!

Other question, on which platform you are running ROOT with a new built-in zlib ?