[Scilab-users] HDF5 save is super slow

[amonmayr at laas.fr]

Hello,

I tried your code in 5.5.1 and the last nightly-build of 6.0: I see a 
slowdown of around 175 between old save in 5.5.1 and new (and only) save 
in 6.0.
It's really related to the data structure, because we use hdf5 
read/write a lot here and did not experience significant slowdowns using 
6.0.
I think the overhead might come to the translation of your fairly 
complex variable (a long array of tlist) in the corresponding hdf5 
structure.
In the old save, this translation was not necessary.
Maybe you could try to save your data in a different way.
For example:
3) you could save each element of "filters" in a separate file.
2) you could bypass save and directly write your data in a hdf5 file by 
using h5open(), h5write() directly. It means you need to write your own 
load() for your custom file format. But this way, you can try to find 
the best way to layout your data in hdf5 format.
3) in addition to 2) you could try to save each entry of your "filters" 
array as one dataset in a given hdf5 file.

Did you search on bugzilla whether this bug was already submitted?
Could you try to report it?


Antoine

Le 15/10/2018 à 10:11, Arvid Rosén a écrit :
>
> /////////////////////////////////
>
> N = 4;
>
> n = 10000;
>
> filters = list();
>
> for i=1:n
>
>   G=syslin('c', rand(N,N), rand(N,1), rand(1,N), rand(1,1));
>
>   filters($+1) = G;
>
> end
>
> tic();
>
> save('filters.dat', filters);
>
> ts1 = toc();
>
> tic();
>
> save('filters.dat', 'filters');
>
> ts2 = toc();
>
> printf("old save %.2fs\n", ts1);
>
> printf("new save %.2fs\n", ts2);
>
> printf("slowdown %.1f\n", ts2/ts1);
>
> /////////////////////////////////
>

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