[Help-gsl] strange 'data' pointers using more than one submatrix simultaneously

[Matthias Sitte]

Hi,

I've got mixed results on different platforms when using more than one 
submatrix simultaneously.

Setup (code is attached):

Create two 2N-by-2N matrices A and B whose elements are given by:
   A(i,j) = i*N + j
   B(i,j) = i + j*N
Suppose we want to operate on A_ul and B_lr, the upper-left N-by-N 
submatrix of A and the lower-right N-by-N submatrix of B, respectively, 
and suppose we want to use submatrices instead of writing some loop-like 
code.

On one machine (CentOS 6) I get the following:

=== BEGIN ===
address@hidden gsl-matrix-view-test]$ gcc gsl-matrix-view-test.c 
-I /u7/matthias/opt/include -L /u7/matthias/opt/lib -lgsl -lgslcblas
address@hidden gsl-matrix-view-test]$ ldd a.out
        linux-vdso.so.1 =>  (0x00007fff8799b000)
        libgsl.so.0 => /u7/matthias/opt/lib/libgsl.so.0 (0x00007f00c2810000)
	libgslcblas.so.0 => /u7/matthias/opt/lib/libgslcblas.so.0 
(0x00007f00c25d6000)
        libc.so.6 => /lib64/libc.so.6 (0x000000309d600000)
        libm.so.6 => /lib64/libm.so.6 (0x000000309da00000)
        /lib64/ld-linux-x86-64.so.2 (0x000000309d200000)
address@hidden gsl-matrix-view-test]$ ./a.out
GSL version: 1.16

A = 0x17c6010
A->data = 0x17c6070
A->nrows = 40
A->ncols = 40

B = 0x17c9280
B->data = 0x17c92e0
B->nrows = 40
B->ncols = 40

A_ul = 0x7fffdb7bad70
A_ul->data = 0x17cac80
A_ul->nrows = 20
A_ul->ncols = 20

B_lr = 0x7fffdb7bad70
B_lr->data = 0x17cac80
B_lr->nrows = 20
B_lr->ncols = 20
=== END ===

So, the 'data' pointer of both A_ul and B_lr are the same??

If I run the same code on a Mac, I get something different:

=== BEGIN ===
wireless-10-145-113-144:gsl-matrix-view-test matthias$ gcc -lgsl 
-lgslcblas gsl-matrix-view-test.c -I /opt/local/include/ -L /opt/local/lib
wireless-10-145-113-144:gsl-matrix-view-test matthias$ otool -L a.out
a.out:
  /opt/local/lib/libgsl.0.dylib (compatibility version 18.0.0, current 
version 18.0.0)
  /opt/local/lib/libgslcblas.0.dylib (compatibility version 1.0.0, 
current version 1.0.0)
  /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current 
version 1213.0.0)
wireless-10-145-113-144:gsl-matrix-view-test matthias$ ./a.out
GSL version: 1.16

A = 0x7fb6ca404b80
A->data = 0x7fb6ca803200
A->nrows = 40
A->ncols = 40

B = 0x7fb6ca404bc0
B->data = 0x7fb6ca806400
B->nrows = 40
B->ncols = 40

A_ul = 0x7fff5d212ad0
A_ul->data = 0x7fb6ca803200
A_ul->nrows = 20
A_ul->ncols = 20

B_lr = 0x7fff5d212aa0
B_lr->data = 0x7fb6ca807da0
B_lr->nrows = 20
B_lr->ncols = 20
=== END ===

So, here the 'data' pointer is correct and differs for both submatrices.

I'm really puzzled... Any ideas what might be going on here??

MS

--
Dr. Matthias Sitte
The University of Texas at Austin
Department of Physics
2515 Speedway, C1600
Austin, TX 78712-1192

gsl-matrix-view-test.c
Description: Text Data

guysborough.txt
Description: Text document

mac.txt
Description: Text document