Re: [Help-bash] slow in function creation

[Peng Yu]

On Mon, Dec 3, 2018 at 10:58 PM Peng Yu <address@hidden> wrote:
>
> On Mon, Dec 3, 2018 at 10:26 PM Peng Yu <address@hidden> wrote:
> >
> > Hi,
> >
> > I see that function creation can be much slower than typeset -F when
> > there are many functions. Why function creation can be so slow? Is
> > there a way to improve its runtime?
> >
> > I see that the typeset -F slows down ~10x from 100000 to 1000000. Is
> > 100000 approximately the bucket size of the hash storing the
> > functions?
> >
> > $ ./main.sh
> > ==> 1 <==
> > 0.008
> > 0.000
> > 1.254
> > ==> 10 <==
> > 0.009
> > 0.000
> > 1.291
> > ==> 1000 <==
> > 0.013
> > 0.007
> > 1.280
> > ==> 10000 <==
> > 0.022
> > 0.065
> > 1.296
> > ==> 100000 <==
> > 0.110
> > 1.706
> > 1.767
> > ==> 1000000 <==
> > 1.015
> > 218.159
> > 10.999
> > $ cat main.sh
> > #!/usr/bin/env bash
> > # vim: set noexpandtab tabstop=2:
> >
> > tmpfile=$(mktemp -u)
> > TIMEFORMAT=%R
> > for n in 1 10 1000 10000 100000 1000000
> > do
> >     echo "==> $n <=="
> >     time awk -v n="$n" -e 'BEGIN { for(i=1;i<n;++i) printf("function
> > f%d { :; }\n", i) }' > "$tmpfile"
> >     time source "$tmpfile"
> >     time for ((i=0;i<100000;++i))
> >     do
> >         typeset -F f0
> >     done > /dev/null
> > done
>
> An associative array has about the same runtime characteristics. I
> assume that the function table and associative uses the same
> underlying hash implementation? Is it so?
>
> $  ./main.sh
> ==> 1 <==
> 0.008
> 0.000
> 1.211
> ==> 10 <==
> 0.010
> 0.000
> 1.220
> ==> 100 <==
> 0.009
> 0.001
> 1.200
> ==> 1000 <==
> 0.012
> 0.006
> 1.191
> ==> 10000 <==
> 0.022
> 0.065
> 1.275
> ==> 100000 <==
> 0.106
> 1.996
> 2.092
> ==> 1000000 <==
> 1.186
> 336.367
> 15.847
>
> $ cat main.sh
> #!/usr/bin/env bash
> # vim: set noexpandtab tabstop=2:
>
> #set -v
> tmpfile=$(mktemp -u)
> TIMEFORMAT=%R
> for n in 1 10 100 1000 10000 100000 1000000
> do
>     echo "==> $n <=="
>     declare -A x
>     time awk -v n="$n" -e 'BEGIN { for(i=0;i<n;++i)
> printf("x[x%d]=\n", i ) }' > "$tmpfile"
>     time source "$tmpfile"
>     time for ((i=0;i<100000;++i))
>     do
>         [[ -v x[x0] ]]
>     done > /dev/null
>     unset x
> done

Here are the runtime results in a easier to read format.

--
function    1    0.008    0.001    1.113
asso_array    1    0.010    0.001    0.893
--
function    10    0.011    0.001    1.130
asso_array    10    0.010    0.001    0.883
--
function    100    0.009    0.001    1.093
asso_array    100    0.011    0.001    0.881
--
function    1000    0.010    0.007    1.135
asso_array    1000    0.010    0.006    0.900
--
function    10000    0.019    0.072    1.191
asso_array    10000    0.018    0.060    0.940
--
function    100000    0.107    2.289    1.122
asso_array    100000    0.103    2.533    0.897
--
function    1000000    1.133    219.749    0.990
asso_array    1000000    0.861    272.116    0.761

-- 
Regards,
Peng