ah! I thought I had scrutinized your repos for such a thing (you usually
have quite the gems over there) but overlooked that one.
thanks.
sadly, the improvement wasn't impressive (probably a testimony to the
performances of the linux filesystem layer...)
copying the whole file's content into a []byte and building my own
reader+readerat on top of that got me the same perfs than with your libs.
now, my biggest time consumers are:
ROUTINE ======================== go-hep.org/x/hep/rootio.(*LeafD).readBasket
in /usr/lib/go/src/encoding/binary/binary.go
3.25s 3.25s (flat, cum) 18.83% of Total
. . 121:}
. . 122:
. . 123:func (bigEndian) Uint64(b []byte) uint64 {
. . 124: _ = b[7] // bounds check hint to compiler;
see golang.org/issue/14808
. . 125: return uint64(b[7]) | uint64(b[6])<<8 |
uint64(b[5])<<16 | uint64(b[4])<<24 |
3.25s 3.25s 126: uint64(b[3])<<32 | uint64(b[2])<<40 |
uint64(b[1])<<48 | uint64(b[0])<<56
. . 127:}
which compiles down to:
70ms 70ms 4f028d: ANDQ SI, BX ;
go-hep.org/x/hep/rootio.(*LeafD).readBasket rbuffer.go:307
. . 4f0290: CMPQ $0x7, DX
;binary.go:124
. . 4f0294: JBE 0x4f02e1
. . 4f0296: MOVQ 0(DI)(BX*1), DX
;binary.go:126
3.25s 3.25s 4f029a: BSWAP DX ;
go-hep.org/x/hep/rootio.(*LeafD).readBasket binary.go:126
90ms 90ms 4f029d: MOVQ DX, 0x38(SP) ;
go-hep.org/x/hep/rootio.(*LeafD).readBasket rbuffer.go:308
so probably not much to be gained here...
the profile is here:
https://cern.ch/binet/go-hep/rootio.cpu.pprof
https://cern.ch/binet/go-hep/read-data.go
(if anyone's interested in making that program as fast or even faster than
the C++ one... it's for science! :P)
-s
On Sat, Sep 16, 2017 at 2:05 PM, Jan Mercl <0xj...@gmail.com> wrote:
> On Sat, Sep 16, 2017 at 1:52 PM Sebastien Binet <seb.bi...@gmail.com>
> wrote:
>
> > Has anybody written a buffered version of an io.ReaderAt ?
>
> IIUC what's needed, you might want to try https://github.com/cznic/
> file/blob/efffc965e97bbf31b0ed00deb82fe697500f22b5/file.go#L1039
>
> --
>
> -j
>
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