[petsc-users] PETSc binary write format

[Smith, Barry F.]

   You saved a Vec to the file, not a Mat.



> On Dec 3, 2018, at 1:38 PM, Sajid Ali via petsc-users <petsc-users at mcs.anl.gov> wrote:
> 
> Hi,
> 
> I ran ex10 from /vec/examples/tutorials and saved the matrix in binary format.
> 
> Looking at the matrix in binary using xxd, I see
> 
> [sajid at xrm temp]$ xxd -b vector.dat
> 0000000: 00000000 00010010 01111011 01001110 00000000 00000000  ..{N..
> 0000006: 00000000 00010100 00000000 00000000 00000000 00000000  ......
> 000000c: 00000000 00000000 00000000 00000000 00111111 11110000  ....?.
> 0000012: 00000000 00000000 00000000 00000000 00000000 00000000  ......
> 0000018: 01000000 00000000 00000000 00000000 00000000 00000000  @.....
> 000001e: 00000000 00000000 01000000 00001000 00000000 00000000  .. at ...
> 0000024: 00000000 00000000 00000000 00000000 01000000 00010000  .... at .
> 000002a: 00000000 00000000 00000000 00000000 00000000 00000000  ......
> 0000030: 01000000 00010100 00000000 00000000 00000000 00000000  @.....
> 0000036: 00000000 00000000 01000000 00011000 00000000 00000000  .. at ...
> 000003c: 00000000 00000000 00000000 00000000 01000000 00011100  .... at .
> 0000042: 00000000 00000000 00000000 00000000 00000000 00000000  ......
> 0000048: 01000000 00100000 00000000 00000000 00000000 00000000  @ ....
> 000004e: 00000000 00000000 01000000 00100010 00000000 00000000  ..@"..
> 0000054: 00000000 00000000 00000000 00000000 01000000 00100100  ....@$
> 000005a: 00000000 00000000 00000000 00000000 00000000 00000000  ......
> 0000060: 01000000 00100110 00000000 00000000 00000000 00000000  @&....
> 0000066: 00000000 00000000 01000000 00101000 00000000 00000000  ..@(..
> 000006c: 00000000 00000000 00000000 00000000 01000000 00101010  ....@*
> 0000072: 00000000 00000000 00000000 00000000 00000000 00000000  ......
> 0000078: 01000000 00101100 00000000 00000000 00000000 00000000  @,....
> 000007e: 00000000 00000000 01000000 00101110 00000000 00000000  .. at ...
> 0000084: 00000000 00000000 00000000 00000000 01000000 00110000  .... at 0
> 000008a: 00000000 00000000 00000000 00000000 00000000 00000000  ......
> 0000090: 01000000 00110001 00000000 00000000 00000000 00000000  @1....
> 0000096: 00000000 00000000 01000000 00110010 00000000 00000000  .. at 2..
> 000009c: 00000000 00000000 00000000 00000000 01000000 00110011  .... at 3
> 00000a2: 00000000 00000000 00000000 00000000 00000000 00000000  ......
> 
> 
> The format of the binary file is supposed to be 
> MAT_FILE_CLASSID, num_rows, num_cols, -1 followed by data. 
> 
> Converting the first 4 bytes (32 bits) of binary to int, the number 
> 00000000000100100111101101001110 becomes 1211214, but the value of MAT_FILE_CLASSID according to the header file petscmat.h is 1211216 (petsc at 3.10.2.1 built without complex support). What causes this discrepancy ? 
> 
> Also, what are the special characters at the end of every line ? Am i not reading the binary file correctly ?
> 
> 
> Thank You, 
> Sajid Ali
> Applied Physics
> Northwestern University