Re: [Pdl-general] set pointer to data (PP)
Hi Ed,
thank you. I have made some progress but getting data from a cv:Mat to a
PDL is a mystery still. If you could look at the code I would appreciate
it. I have a valid pointer to the data, either in C or perl, but how to
make a piddle use that as it's dataref is beyond me.
Ingo
On 3/15/22 21:50, Ed . wrote:
Hi Ingo,
Glad you’re making progress!
The problem you’re having here is that you’re somewhat mixing your
metaphors. For now, PDL mainly uses SVs for storing data. The “datasv”
member of the struct points at the data SV, and the “data” member is
set to point at its PV. Within e.g. the readdata function, a local C
variable for the data pointer of ndarray “m” is created called
“m_datap”, which gets updated during broadcasting. The “$P(m)” macro
in PP expands to “m_datap”.
As you may now appreciate, assigning to that is not going to have any
long-term effect once the function returns. You’re going to need a
different approach. One that will operate somewhat, but isn’t the
correct answer, is to assign to “$PDL(m)->data” instead. But you’re
going to need to do memory-management properly, otherwise you’ll get
segfaults and/or leak memory.
A more direct way to achieve the aim, staying with the SV model, is to
enhance your MatWrapper Perl object (using XS) to be able to return
its data (and dimensions as well), and make your get_data be pure-Perl
that extracts dims, types and data from the MatWrapper in Perl-land,
and uses PDL methods setdims, set_datatype, and get_dataref/upd_data
to create an ndarray.
Best regards,
Ed
*From: *Ingo Schmid <mailto:ingo...@gmx.at>
*Sent: *15 March 2022 19:52
*To: *perldl <mailto:pdl-general@lists.sourceforge.net>
*Subject: *[Pdl-general] set pointer to data (PP)
Hi,
I would like to update the pointer to piddle data. I've got a C function
void * getData(MatWrapper * mw);
that returns the pointer to opencv Mat data. I declare the piddle $m
with the right size and data type in PMCode. Now, I can successfully say
void * data = getData($COMP(mw));
$P(m)=data;
and print the right numbers in C.
printf("m (48,48) %f\n",$m(k=>48,l=>48)); # 50.842896 - correct.
However, after returning to perl, $m(48,48) is 0 and get_dataref shows
the wrong datdress. What's the trick to make this permanent?
Ingo
==
pp_def ('get_data',
Pars=>'[o] m(k,l);',
OtherPars=>'MatWrapper * mw',
Code=>pp_line_numbers(__LINE__,
'
PDL_Indx ks = $SIZE(k);
PDL_Indx ls = $SIZE(l);
int x = cols($COMP(mw),-1);
int y = rows($COMP(mw),-1);
printf ("x %d : ks %d / y %d : ls %d ",x,ks,y,ls);
if ((x == ks) && (y == ls))
{
void * dat;
dat = getData($COMP(mw));
$P(m)=dat;
} else {
$CROAK("Matrix size does not match!\n");
}
printf("m (48,48) %f\n",$m(k=>48,l=>48));
'),
PMCode=>pp_line_numbers(__LINE__,
'
sub get_data {
my ($mw,$p) = @_;
unless (ref ($p) =~ "PDL") {
say "rows $mw->rows";
$p=zeroes(float,$mw->cols,$mw->rows);
}
_get_data_int($p,$$mw);
say "(get_data) 48,48: ",$p->slice("48","48");
$p->upd_data;
say "(get_data) 48,48: ",$p->slice("48","48");
$p->transpose;
}
',),
Doc=><<"EOD",
=head2 set_data - update data of a Mat object. Size and type should match.
EOD
);
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Re: [Pdl-general] set pointer to data (PP)
Hi Ingo,
Glad you’re making progress!
The problem you’re having here is that you’re somewhat mixing your metaphors.
For now, PDL mainly uses SVs for storing data. The “datasv” member of the
struct points at the data SV, and the “data” member is set to point at its PV.
Within e.g. the readdata function, a local C variable for the data pointer of
ndarray “m” is created called “m_datap”, which gets updated during
broadcasting. The “$P(m)” macro in PP expands to “m_datap”.
As you may now appreciate, assigning to that is not going to have any long-term
effect once the function returns. You’re going to need a different approach.
One that will operate somewhat, but isn’t the correct answer, is to assign to
“$PDL(m)->data” instead. But you’re going to need to do memory-management
properly, otherwise you’ll get segfaults and/or leak memory.
A more direct way to achieve the aim, staying with the SV model, is to enhance
your MatWrapper Perl object (using XS) to be able to return its data (and
dimensions as well), and make your get_data be pure-Perl that extracts dims,
types and data from the MatWrapper in Perl-land, and uses PDL methods setdims,
set_datatype, and get_dataref/upd_data to create an ndarray.
Best regards,
Ed
From: Ingo Schmid<mailto:ingo...@gmx.at>
Sent: 15 March 2022 19:52
To: perldl<mailto:pdl-general@lists.sourceforge.net>
Subject: [Pdl-general] set pointer to data (PP)
Hi,
I would like to update the pointer to piddle data. I've got a C function
void * getData(MatWrapper * mw);
that returns the pointer to opencv Mat data. I declare the piddle $m with the
right size and data type in PMCode. Now, I can successfully say
void * data = getData($COMP(mw));
$P(m)=data;
and print the right numbers in C.
printf("m (48,48) %f\n",$m(k=>48,l=>48)); # 50.842896 - correct.
However, after returning to perl, $m(48,48) is 0 and get_dataref shows the
wrong datdress. What's the trick to make this permanent?
Ingo
==
pp_def ('get_data',
Pars=>'[o] m(k,l);',
OtherPars=>'MatWrapper * mw',
Code=>pp_line_numbers(__LINE__,
'
PDL_Indx ks = $SIZE(k);
PDL_Indx ls = $SIZE(l);
int x = cols($COMP(mw),-1);
int y = rows($COMP(mw),-1);
printf ("x %d : ks %d / y %d : ls %d ",x,ks,y,ls);
if ((x == ks) && (y == ls))
{
void * dat;
dat = getData($COMP(mw));
$P(m)=dat;
} else {
$CROAK("Matrix size does not match!\n");
}
printf("m (48,48) %f\n",$m(k=>48,l=>48));
'),
PMCode=>pp_line_numbers(__LINE__,
'
sub get_data {
my ($mw,$p) = @_;
unless (ref ($p) =~ "PDL") {
say "rows $mw->rows";
$p=zeroes(float,$mw->cols,$mw->rows);
}
_get_data_int($p,$$mw);
say "(get_data) 48,48: ",$p->slice("48","48");
$p->upd_data;
say "(get_data) 48,48: ",$p->slice("48","48");
$p->transpose;
}
',),
Doc=><<"EOD",
=head2 set_data - update data of a Mat object. Size and type should match.
EOD
);
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