Dangers of Array Padding

• Compiler will automatically pad local data
• -O3 optimization will automatically pad common blocks
• Padding of common blocks is safe as long as the Fortran standard is not violated:
• Fix violation or do not to use this optimization either by compiling with lower optimization or using explicit compiler flag:
  • -OPT:reorg_common=off

SUBROUTINE SUB

COMMON // A(512,512), B(512,512)

DO I=1, 2*512*512

A(I) = 0.0

END

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