Unaligned data warnings with Intel compiler

[jacobwilliams]

Commit 0066f7d (where a SEQUENCE attribute was added to json_value type) is causing unaligned data warnings to be issued by the Intel fortran compiler (v2015). A fix is in the works.

[jacobwilliams]

Should be fixed now.

[szaghi]

Hi all,

I am not sure why you used "sequence" attribute (I read your developments,
but I miss this specific issue; maybe "sequence" is necessary for C
interoprrability or other peculiar situations), anyhow I would like to
highligth that declaring sequence attribute for derived type components can
compromise the optimizations of the campiler that is prevented to modify
the memory "shape". In some circumstances, the compiler optimizer greatly
improves the memory handling if it is allowed to modify the derived type
components, but the sequence can prevent this.

This is just a reminder, in many case this is not relevant, but I was not
sure that you have evaluated this aspect and I would like to help you, this
project being beatiful!

See you soon.

Il giorno 03:07 gio 08/gen/2015 Jacob Williams notifications@github.com
ha scritto:

Closed #34 #34.

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#34 (comment).

[jacobwilliams]

The SEQUENCE was because I'm using it an argument in a DLL subroutine. See: https://software.intel.com/en-us/forums/topic/538073 . I'll do some speed tests to see if it is causing a significant performance penalty.

[zbeekman]

I think that if the memory alignment warnings issued by ifort have been addressed this shouldn't be a big issue.

[szaghi]

I am not sure, but I think it is more complicated.

For example there are situations where the components of a derived type should be not aligned for memory optimization, thus the compiler use memory padding to optimize the derived type memory handling (for caching/prefetching and similar obscure nerd-details :-) ). Sequence prevent memory padding...

I think that in this case the use of sequence has not relevant consequences on performances, but if there is the time to check it, this is a plus. This is just a remainder due to my paranoiac nature.

See you soon.