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    lehins commented #122
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Man of Letters
@man_of_letters:mozilla.org
[m]
openblas is not the standard one
Alexey Kuleshevich
@lehins:matrix.org
[m]
I've tried it on ubuntu and compiling against openblas did do multi core as well
Man of Letters
@man_of_letters:mozilla.org
[m]
you need a flag to hmatrix to use it, too
are we talking past each other? I meant ibgsl0-dev, liblapack-dev and libatlas-base-dev and no hmatrix flag is
"standard"
openblas and the openblas flag is "special " :)
Alexey Kuleshevich
@lehins:matrix.org
[m]
Man of Letters
@man_of_letters:mozilla.org
[m]
ASAIK, openblas is multicore, standard is not
thank you for the data, though
Alexey Kuleshevich
@lehins:matrix.org
[m]
All I can say is my htop is maxed out :D
Man of Letters
@man_of_letters:mozilla.org
[m]
yes
so, withiout this flag, it would probably be as you described earlier: massive faster
Alexey Kuleshevich
@lehins:matrix.org
[m]
Oh without that flag hmatrix is doooog slow
Man of Letters
@man_of_letters:mozilla.org
[m]
oh, I didn't know the difference is so huge; much slower than just from lack of multicore? I mean single-core performance much slower, too?
Alexey Kuleshevich
@lehins:matrix.org
[m]
The first time I tried it I could not believe that I am that good
Man of Letters
@man_of_letters:mozilla.org
[m]
haha
Alexey Kuleshevich
@lehins:matrix.org
[m]
Orders of magnitude
Man of Letters
@man_of_letters:mozilla.org
[m]
TIL
Alexey Kuleshevich
@lehins:matrix.org
[m]
I take it back. Compiling without an openblas makes hmatrix just a little bit slower. I don't remember how I got "orders of magnitude" difference, but in my defence it has been a while since I looked at it:
benchmarking HMatrix/MxM Double - (500x800 X 800x500)/Par
time                 9.140 ms   (4.980 ms .. 12.18 ms)
                     0.527 R²   (0.349 R² .. 0.651 R²)
mean                 4.794 ms   (2.775 ms .. 6.977 ms)
std dev              5.082 ms   (3.646 ms .. 5.969 ms)
variance introduced by outliers: 98% (severely inflated)

benchmarking HMatrix/MxM Float - (500x800 X 800x500)/Par
time                 6.678 ms   (4.953 ms .. 8.027 ms)
                     0.743 R²   (0.519 R² .. 0.907 R²)
mean                 6.208 ms   (5.417 ms .. 6.890 ms)
std dev              1.838 ms   (1.391 ms .. 2.718 ms)
variance introduced by outliers: 94% (severely inflated)

benchmarking Massiv/MxM P Double - (500x800 X 800x500)/Par
time                 6.874 ms   (6.559 ms .. 7.147 ms)
                     0.991 R²   (0.987 R² .. 0.995 R²)
mean                 7.485 ms   (7.157 ms .. 8.063 ms)
std dev              1.246 ms   (789.7 μs .. 1.867 ms)
variance introduced by outliers: 79% (severely inflated)

benchmarking Massiv/MxM P Float - (500x800 X 800x500)/Par
time                 6.783 ms   (6.671 ms .. 6.896 ms)
                     0.997 R²   (0.993 R² .. 0.999 R²)
mean                 6.832 ms   (6.766 ms .. 6.933 ms)
std dev              238.9 μs   (168.5 μs .. 365.5 μs)
variance introduced by outliers: 16% (moderately inflated)
Man of Letters
@man_of_letters:mozilla.org
[m]
almost 3 times slower, but you said previously it was on how many cores? 16? and this one is on a single core, I presume? a bit strange...
Alexey Kuleshevich
@lehins:matrix.org
[m]
No, during benchmark it used all cores too.
Man of Letters
@man_of_letters:mozilla.org
[m]
OTOH, "variance introduced by outliers: 98% (severely inflated)" makes it very suspect
Alexey Kuleshevich
@lehins:matrix.org
[m]

98% (severely inflated)

taht's normal for multi core benchmarks

Man of Letters
@man_of_letters:mozilla.org
[m]
oh, ok
Alexey Kuleshevich
@lehins:matrix.org
[m]
There is always a lot of noise
Man of Letters
@man_of_letters:mozilla.org
[m]
thanks again for the measurements
I think I was confused about multicore when run not with openblas, probably because I'm running with -N1 (actually, even without -threaded) --- that may be why it's single core for me
Alexey Kuleshevich
@lehins:matrix.org
[m]
My pleasure. I just got this computer so it is really fun for me to see how much faster all of the benchmarks have gotten 😀
Man of Letters
@man_of_letters:mozilla.org
[m]
while, presumably, openblas can parallelize even with -N1 (not tested)
Alexey Kuleshevich
@lehins:matrix.org
[m]
In the matter of fact hmatrix doesn't care about RTS flags like -N since it uses parallelization on C side
Man of Letters
@man_of_letters:mozilla.org
[m]
well, that's strange then, because I swear my hmatrix doesn't use many cores
(not openblas flag set)
though it probably uses SIMD, etc.
Alexey Kuleshevich
@lehins:matrix.org
[m]
From what I've seen online it is either controlled either by the env variable or som eruntime setting
Man of Letters
@man_of_letters:mozilla.org
[m]
oh, ok, again good to know
Alexey Kuleshevich
@lehins:matrix.org
[m]
Man of Letters
@man_of_letters:mozilla.org
[m]
I have an ancient Ubuntu, so probably the default flags are different
^^^ that link is openblas, though
we talking results without openblas now, right?
Alexey Kuleshevich
@lehins:matrix.org
[m]
Yeah, I don't really use any of that stuff aside from benchmarks for massiv. So I am no expert on openblas
Oh sorry, you are right

we are talking results without openblas now, right?

openblas or blas

Cause it seems hmatrix uses either or:

        if flag(openblas)
            if !flag(disable-default-paths)
                extra-lib-dirs:     /usr/lib/openblas/lib
            extra-libraries:    openblas
        else
            extra-libraries:    blas lapack
Man of Letters
@man_of_letters:mozilla.org
[m]
yes, either-or
I read in blas/lapack docs that they are strictly single core and my experience confirms it, but there must be other versions in new Ubuntus for which it doesn't apply any more or perhaps it stopped applying long ago, but now they have different default setting and run multicore
Alexey Kuleshevich
@lehins:matrix.org
[m]
Yeah, I can definitely confirm that without openblas flag in hmatrix it still uses all cores
Man of Letters
@man_of_letters:mozilla.org
[m]
ta
man_of_letters:mozilla.org @man_of_letters:mozilla.org fixes his docs
Alexey Kuleshevich
@lehins:matrix.org
[m]

I read in blas/lapack docs that they are strictly single core and my experience confirms it, but there must be other versions in new Ubuntus for which it doesn't apply any more or perhaps it stopped applying long ago, but now they have different default setting and run multicore

Ok, so this is exactly where I got my impression that massiv was much faster than hmatrix without an openblas flag on my older computer whre I used Ubuntu

I think I was comparing single core hmatrix to multicore massiv