pasing an array pointer and storing as a class member

[stephen b]

(apologies for cross posting from the moderated group..i'm sure you
understand)

Hello, I'm passing an array into a Constructor and hoping to use it
as
a pointer and store it as a class member for future use. So far, I'm
just causing crashes, psuedo code below:
double block[8192];
foo = MyClass(block);

////

MyClass {

public:

MyClass (double *blk) {// constructor
inBlk = blk;

}

Process {
// this method will be called periodically and
// iterate over array pointed to by inBlk
// ..which causes a crash
}

private:
double *inBlk;

}

I imagine I'm doing something stupid that I just can't see at the
moment. How might one solve this? Perhaps ideally I should create
the array within MyClass but I don't really want to right now.
Thanks
for any help,
Stephen.

[Kenneth Porter]

stephen b <ke****@audiosp illage.comwrote in news:1192294175 .091803.112560
@z24g2000prh.go oglegroups.com:

I imagine I'm doing something stupid that I just can't see at the
moment. How might one solve this? Perhaps ideally I should create
the array within MyClass but I don't really want to right now.

The code looks ok, although you don't show what Process does. Is the array
on the stack or global? (Ie. is it still in scope when you mess with it?)
What's wrong with declaring it in the class? Does something else need raw
access to it? Why not use a std::vector<dou ble>?

[Ron AF Greve]

Hi,

You are aware that the array is on the stack and shouldn't be accessed when
returning from the function (for instance by doing something like 'return
foo;' )?

Show the real code so we don't have to guess
Regards, Ron AF Greve

http://www.InformationSuperHighway.eu

"stephen b" <ke****@audiosp illage.comwrote in message
news:11******** **************@ z24g2000prh.goo glegroups.com.. .

(apologies for cross posting from the moderated group..i'm sure you
understand)

Hello, I'm passing an array into a Constructor and hoping to use it
as
a pointer and store it as a class member for future use. So far, I'm
just causing crashes, psuedo code below:
double block[8192];
foo = MyClass(block);

////

MyClass {

public:

MyClass (double *blk) {// constructor
inBlk = blk;

}

Process {
// this method will be called periodically and
// iterate over array pointed to by inBlk
// ..which causes a crash
}

private:
double *inBlk;

}

I imagine I'm doing something stupid that I just can't see at the
moment. How might one solve this? Perhaps ideally I should create
the array within MyClass but I don't really want to right now.
Thanks
for any help,
Stephen.

[stephen b]

Show the real code so we don't have to guess

Okay here is the full code.. well I stripped out a lot of stuff that
doesn't matter and removed destructors for brevity. Hopefully I
didn't miss anything else out. FilterSynth (or Synth) objects are
created at runtime (musical notes) and last for upto 5-6 seconds.

I am using arrays instead of vector<doublebe cause I found the
initialisation of many vector<double>s caused brief CPU spikes each
time an object is created. Arrays seemed less troublesome which is
important for real-time DSP stuff. I declare the arrays in
FilterSynth instead of Filter as other objects will need access to
them although I could always provide a pointer for access I guess..
Thanks for taking time.

class FIlterSynth : public Synth
{
public:

FilterSynth() {
filt = Filter(filtIn, filtOut);
}

virtual UInt32 NextBlock(UInt3 2 inNumFrames) {
// this function is called by another class.
Filter.Process( inNumFrames);
}

private:
double filtIn[8192];
double filtOut[8192];
Filter filt;

};
class Filter : public UGen
{
public:

Filter(double *inBlk, double *outBlk) {
in = inBlk;
out = outBlk;
}

void Process(UInt32 inNumFrames) {

for (UInt32 i=0; i<inNumFrames; ++i) {
// some pseudo filter code..
y0 = *(in)++ + b1 * y1 + b2 * y2;
*(out)++ = a0 * y0 + a1 * y1 + a2 * y2;
}

private:
double *in, *out;
};

curiously if I do:
Filter.Process( filtIn, FiltOut, inNumFrames);
to call:
void Process(double *in, double *out, UInt32 inNumFrames) {//etc };
and omitt
private: double *in, *out;
then all is fine.

Stephen

[arun.darra]

On Oct 14, 8:23 am, stephen b <ker...@audiosp illage.comwrote :

Show the real code so we don't have to guess

Okay here is the full code.. well I stripped out a lot of stuff that
doesn't matter and removed destructors for brevity. Hopefully I
didn't miss anything else out. FilterSynth (or Synth) objects are
created at runtime (musical notes) and last for upto 5-6 seconds.

I am using arrays instead of vector<doublebe cause I found the
initialisation of many vector<double>s caused brief CPU spikes each
time an object is created. Arrays seemed less troublesome which is
important for real-time DSP stuff. I declare the arrays in
FilterSynth instead of Filter as other objects will need access to
them although I could always provide a pointer for access I guess..
Thanks for taking time.

class FIlterSynth : public Synth
{
public:

FilterSynth() {
filt = Filter(filtIn, filtOut);
}

virtual UInt32 NextBlock(UInt3 2 inNumFrames) {
// this function is called by another class.
Filter.Process( inNumFrames);
}

private:
double filtIn[8192];
double filtOut[8192];
Filter filt;

};

class Filter : public UGen
{
public:

Filter(double *inBlk, double *outBlk) {
in = inBlk;
out = outBlk;
}

void Process(UInt32 inNumFrames) {

for (UInt32 i=0; i<inNumFrames; ++i) {
// some pseudo filter code..
y0 = *(in)++ + b1 * y1 + b2 * y2;
*(out)++ = a0 * y0 + a1 * y1 + a2 * y2;
}

private:
double *in, *out;

};

curiously if I do:
Filter.Process( filtIn, FiltOut, inNumFrames);
to call:
void Process(double *in, double *out, UInt32 inNumFrames) {//etc };
and omitt
private: double *in, *out;
then all is fine.

Stephen

there are 2 thing that i feel are wrong in ur code:

First:
filt = Filter(filtIn, filtOut);

if u want to have a class member variable (not pointer) pls use member
wise initialization
Second i dont know how are u using

Filter.Process( inNumFrames);

class-name.function-name();

could u pls change this to

filt.Process(in NumFrames);

[stephen b]

there are 2 thing that i feel are wrong in ur code:

First:
filt = Filter(filtIn, filtOut);

if u want to have a class member variable (not pointer) pls use member
wise initialization

i'm not sure what you mean by member wise initialization in this
context?

Second i dont know how are u using

Filter.Process( inNumFrames);

class-name.function-name();

could u pls change this to

filt.Process(in NumFrames);

okay well spotted that was a typo.. really I am doing
filt.Process(in NumFrames);

Stephen.

[=?UTF-8?B?RXJpayBXaWtzdHLDtm0=?=]

On 2007-10-14 20:34, stephen b wrote:

>there are 2 thing that i feel are wrong in ur code:

First:
filt = Filter(filtIn, filtOut);

if u want to have a class member variable (not pointer) pls use member
wise initialization

i'm not sure what you mean by member wise initialization in this
context?

Instead of having a constructor like this:

FilterSynth() {
filt = Filter(filtIn, filtOut);
}

you should use an initialisation-list to initialise filt, like this:

FilterSynth() : filt(filtIn, filtOut)
}
}

--
Erik Wikström

[BobR]

stephen b wrote in message...

>
I am using arrays instead of vector<doublebe cause I found the
initialisation of many vector<double>s caused brief CPU spikes each
time an object is created.

I'm curious. How did you initialize the vectors?

Arrays seemed less troublesome which is
important for real-time DSP stuff.

I think it's the opposite. :-}

I declare the arrays in
FilterSynth instead of Filter as other objects will need access to
them although I could always provide a pointer for access I guess..
Thanks for taking time.

class FIlterSynth : public Synth { public:
FilterSynth() {
filt = Filter(filtIn, filtOut);
}

If this is your class constructor, the names should match: 'FIlterSynth' vs.
'FilterSynth'.

>
virtual UInt32 NextBlock(UInt3 2 inNumFrames) {
// this function is called by another class.
Filter.Process( inNumFrames);
}

private:
double filtIn[8192];
double filtOut[8192];
Filter filt;
};

class Filter : public UGen { public:

Filter(double *inBlk, double *outBlk) {
in = inBlk;
out = outBlk;
}

This is why I'm asking about your vector inits, you should use class
initialization lists:

Filter( double *inBlk, double *outBlk )
: in( inBlk ), out( outBlk ){} // note the colon

>
void Process(UInt32 inNumFrames) {

for (UInt32 i=0; i<inNumFrames; ++i) {
// some pseudo filter code..
y0 = *(in)++ + b1 * y1 + b2 * y2;
*(out)++ = a0 * y0 + a1 * y1 + a2 * y2;
}

private:
double *in, *out;
};

curiously if I do:
Filter.Process( filtIn, FiltOut, inNumFrames);
to call:
void Process(double *in, double *out, UInt32 inNumFrames) {//etc };
and omitt
private: double *in, *out;
then all is fine.
Stephen

Could it be because you are dereferenceing un-initialized data (the arrays)?
Let's test something. In your FilterSynth() constructor:

FilterSynth(){
for( int i(0); i < 10; ++i ){
std::cout<< filtIn[ i ] <<'\n';
} // for(i)
} // Ctor

What's your output from that? (I got garbage (UB)).
Also, please indent your code for posting (using spaces, not tabs).

--
Bob R
POVrookie

[stephen b]

On 14 Oct, 19:56, "BobR" <removeBadB...@ worldnet.att.ne twrote:

stephen b wrote in message...

I am using arrays instead of vector<doublebe cause I found the
initialisation of many vector<double>s caused brief CPU spikes each
time an object is created.

I'm curious. How did you initialize the vectors?

Arrays seemed less troublesome which is
important for real-time DSP stuff.

I think it's the opposite. :-}

really? right, I think I initialised my vectors like this:
vector<doubleve c (8192, 0.); so I guess maybe filling the array
with zeros was causing some overhead. I also found arrays to be
slightly more efficient in use although it's probably negligible even
though I'll be using 20 or so per synth.

Could it be because you are dereferenceing un-initialized data (the arrays)?
Let's test something. In your FilterSynth() constructor:

FilterSynth(){
for( int i(0); i < 10; ++i ){
std::cout<< filtIn[ i ] <<'\n';
} // for(i)
} // Ctor

What's your output from that? (I got garbage (UB)).

well with the filter example I fill the array with zeros first but
otherwise just garbage.

Stephen.

[stephen b]

void Process(UInt32 inNumFrames) {

>
for (UInt32 i=0; i<inNumFrames; ++i) {
// some pseudo filter code..
y0 = *(in)++ + b1 * y1 + b2 * y2;
*(out)++ = a0 * y0 + a1 * y1 + a2 * y2;
}

private:
double *in, *out;

forgot to clarify: the reason my code is crashing is because I'm
incrementing the pointers into the arrays and calling Process
potentially hundreds of times a second. so I need to reset the
pointers to the start of the array.. if such a thing is possible? I'm
quite surprised I didn't notice that. or I could just continue
passing the pointers via the Process function.

Stephen