#6375: Because of COMMON, the alignment of object is inconsistent with its type

[Gabriele_B_]

Hi,

I saw this topic for the visual Fortran compiler for Windows, I get the same warning on OSX for a code that I didn't write.

#6375: Because of COMMON, the alignment of object is inconsistent with its type

https://software.intel.com/en-us/forums/intel-visual-fortran-compiler-for-windows/topic/296523

What does it mean? what are the "potential performance impact"?

Thanks

GB

[TimP]

For example, you might have an odd number of 32 bit data followed by 64 bit data.  That could result in a data access requiring references to 2 cache lines and the hardware piecing the 2 together or splitting them, which may be slow even though you probably have a hardware platform which supports it. 

[Gabriele_B_]

Thanks Tim,

So the only risk is that my code slows down, am I right? My results shouldn't be affected.

[TimP]

Yes, it's ok, as long as you don't set a nonstandard padding option and use it inconsistently.

[jayb]

Isn't there a preferred practice, when using COMMON, to list variables largest first, e.g., 64-bit, then in decreasing order of size?  Of course, you need to change all references to the common block.

j
 

[Gabriele_B_]

I didn't know about it.

[Gabriele_B_]

Jayb is your question an answer?or are you wondering about it like me?