[Help]The following code failed

[Help]The following code failed

Wed Oct 14, 2009 3:42 pm

I'm using Eigen 2.0.6 with sse2 . The compiler is icc 10.1 for windows.
There is an exception throwed:
Access violation reading location 0xcdcdcdd1
when D* dd = new D;
So what's wrong with the code below?

Code: Select all

typedef Eigen::Transform<float,3> transform_t;
using namespace Eigen;
struct C{
   EIGEN_MAKE_ALIGNED_OPERATOR_NEW

   char a;
   transform_t b;
};
struct D{
   EIGEN_MAKE_ALIGNED_OPERATOR_NEW
   C x;
   char c;
};
void test(){
   C* cc = new C;
   cc->b.setIdentity();
   
   D* dd = new D;
   dd->x.b.setIdentity();
   cc->b = dd->x.b;
   delete dd;
   delete cc;
}




I'm using Eigen 2.0.6 with sse2 . The compiler is icc 10.1 for windows.
There is an exception throwed:
Access violation reading location 0xcdcdcdd1
when D* dd = new D;
So what's wrong with the code below?
[code]
typedef Eigen::Transform<float,3> transform_t;
using namespace Eigen;
struct C{
EIGEN_MAKE_ALIGNED_OPERATOR_NEW

char a;
transform_t b;
};
struct D{
EIGEN_MAKE_ALIGNED_OPERATOR_NEW
C x;
char c;
};
void test(){
C* cc = new C;
cc->b.setIdentity();

D* dd = new D;
dd->x.b.setIdentity();
cc->b = dd->x.b;
delete dd;
delete cc;
}


[/code]

Last edited by lastsnow on Wed Oct 14, 2009 3:56 pm, edited 1 time in total.

[bjacob]

Re: [Help]The following code failed

Wed Oct 14, 2009 3:51 pm

I can't reproduce your issue, i even checked that all objects are created at aligned locations. Please provide a readily compilable program and specify your compiler version. Please also paste a full back-trace.

I can't reproduce your issue, i even checked that all objects are created at aligned locations. Please provide a readily compilable program and specify your compiler version. Please also paste a full back-trace.

[ggael]

Re: [Help]The following code failed

Wed Oct 14, 2009 3:57 pm

your code looks ok, and since here I cannot reproduce your issue we'll need more information: Can you run your test under a debugger and post a complete backtrace ? and/or if you are running linux try to run it with valgrind. What happens if you disable SSE, or if you try with a different compiler ?

your code looks ok, and since here I cannot reproduce your issue we'll need more information: Can you run your test under a debugger and post a complete backtrace ? and/or if you are running linux try to run it with valgrind. What happens if you disable SSE, or if you try with a different compiler ?

Re: [Help]The following code failed

Wed Oct 14, 2009 5:00 pm

Thanks for your reply.
I just tried gcc 4.4 under linux.It seems ok.
The code will have problem when using intel compiler(10.1.013 ) under windows.It's weired that I cannot always reproduce the problem(memory not aligned ?).
I will try it under different circumtance to find out what's going on.
I will capture more data if I encounter this problem again.

Thanks for your reply.
I just tried gcc 4.4 under linux.It seems ok.
The code will have problem when using intel compiler(10.1.013 ) under windows.It's weired that I cannot always reproduce the problem(memory not aligned ?).
I will try it under different circumtance to find out what's going on.
I will capture more data if I encounter this problem again.

Re: [Help]The following code failed

Wed Oct 14, 2009 5:18 pm

BTW, this is really inconvenient for struct D to use the macro EIGEN_MAKE_ALIGNED_OPERATOR_NEW, if other class or struct wrap a D member,the macro must write there.This intrusive way makes me uncomfortable.

What about do something like this in matrixstorage.h, I have tried it.
But the cost is obvious: extra 16 bytes storage.

Code: Select all

template <typename T, int Size, int MatrixOptions,
bool Align = (MatrixOptions&AutoAlign) && (((Size*sizeof(T))&0xf)==0)
> struct ei_matrix_array
{
   EIGEN_ALIGN_128 T data[Size]; //make extra room for it
   char x[16];
template<typename U> inline U* align_up(U* p, size_t a) {return (U*)(((size_t)p + (a-1)) & -(int)a);}
   ei_matrix_array()
   {
      x[15] = (char)align_up(data,0x10)- (char)data;
#ifndef EIGEN_DISABLE_UNALIGNED_ARRAY_ASSERT
      ei_assert((reinterpret_cast<size_t>(array()) & 0xf) == 0
         && "this assertion is explained here: http://eigen.tuxfamily.org/dox/UnalignedArrayAssert.html  **** READ THIS WEB PAGE !!! ****");
#endif
   }

   ei_matrix_array(ei_constructor_without_unaligned_array_assert) {
      x[15] = (char)align_up(data,0x10)- (char)data;
   }
   T* array(){return (T*)((size_t)data+(size_t)x[15]);}
   const T* array()const{return (T*)((size_t)data+(size_t)x[15]);}
};




BTW, this is really inconvenient for struct D to use the macro EIGEN_MAKE_ALIGNED_OPERATOR_NEW, if other class or struct wrap a D member,the macro must write there.This intrusive way makes me uncomfortable.

What about do something like this in matrixstorage.h, I have tried it.
But the cost is obvious: extra 16 bytes storage.
[code]
template <typename T, int Size, int MatrixOptions,
bool Align = (MatrixOptions&AutoAlign) && (((Size*sizeof(T))&0xf)==0)
> struct ei_matrix_array
{
EIGEN_ALIGN_128 T data[Size]; //make extra room for it
char x[16];
template<typename U> inline U* align_up(U* p, size_t a) {return (U*)(((size_t)p + (a-1)) & -(int)a);}
ei_matrix_array()
{
x[15] = (char)align_up(data,0x10)- (char)data;
#ifndef EIGEN_DISABLE_UNALIGNED_ARRAY_ASSERT
ei_assert((reinterpret_cast<size_t>(array()) & 0xf) == 0
&& "this assertion is explained here: http://eigen.tuxfamily.org/dox/UnalignedArrayAssert.html **** READ THIS WEB PAGE !!! ****");
#endif
}

ei_matrix_array(ei_constructor_without_unaligned_array_assert) {
x[15] = (char)align_up(data,0x10)- (char)data;
}
T* array(){return (T*)((size_t)data+(size_t)x[15]);}
const T* array()const{return (T*)((size_t)data+(size_t)x[15]);}
};


[/code]

[bjacob]

Re: [Help]The following code failed

Wed Oct 14, 2009 5:37 pm

But the cost is obvious: extra 16 bytes storage.

And also a runtime computation. Two good reasons why we can't do that.

If you don't like that you can:
- disable vectorization/alignment (define EIGEN_DONT_ALIGN)
or
- wait for the next C++ standard which finally provides good alignment support.

[quote]But the cost is obvious: extra 16 bytes storage.[/quote]
And also a runtime computation. Two good reasons why we can't do that.

If you don't like that you can:
- disable vectorization/alignment (define EIGEN_DONT_ALIGN)
or
- wait for the next C++ standard which finally provides good alignment support.

Re: [Help]The following code failed

Fri Oct 16, 2009 12:05 pm

Is the alignment enabled by default ?

vs2005 compile the following code without define EIGEN_DONT_ALIGN

std::vector<transform_t> v;

will generate this error:

error C2719: '_Val': formal parameter with __declspec(align('16')) won't be aligned

I think no alignment should be the default option.

Is the alignment enabled by default ?

vs2005 compile the following code without define EIGEN_DONT_ALIGN

std::vector<transform_t> v;

will generate this error:

error C2719: '_Val': formal parameter with __declspec(align('16')) won't be aligned

I think no alignment should be the default option.

[bjacob]

Re: [Help]The following code failed

Fri Oct 16, 2009 12:09 pm

On VS 2005, we don't vectorize. So alignment is useless indeed. But, if we want to preserve ABI compatibility, we still need to align. If you are sure that VS 2005 doesn't have the same C++ ABI as VS 2008 anyway, then I'm OK to disable alignment on VS 2005.

On VS 2005, we don't vectorize. So alignment is useless indeed. But, if we want to preserve ABI compatibility, we still need to align. If you are sure that VS 2005 doesn't have the same C++ ABI as VS 2008 anyway, then I'm OK to disable alignment on VS 2005.