Reduce MPI communication overhead #4414
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Re-order struct data members to reduce padding. New sizes in bytes: sizeof(Particle): 624 -> 592 sizeof(ParticleLocal): 48 -> 40 sizeof(ParticleProperties): 328 -> 304 sizeof(StoredParticleProperty): 24 -> 16
Since the size of Array and Vector objects is known at compile time, it doesn't have to be communicated. This spares an integer and a prefix code during MPI communication operations, thus reducing the serialization buffer size by 33% for Vector3i (from 24 to 16 bytes) and by 22% for Vector3d (from 36 to 28 bytes).
Change the Boost serialization object class info to elide two short ints (version for Utils::detail::Storage and Utils::Array), thus reducing the serialization buffer size by 25% for Vector3i (from 16 to 12 bytes) and by 14% for Vector3d (from 28 to 24 bytes).
Since Array and Vector objects are not communicated by pointers, it is not necessary for Boost to track double deserialization.
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Provide a mechanism to walk through a serialization tree recursively to check for a specific trait. Check that all fixed-length members of the Particle struct are statically serializable. The std::vector objects should be the only non-statically serializable members.
reinaual
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Mar 28, 2022
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reinaual
approved these changes
Mar 28, 2022
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Fixes #4415, fixes #3638
Description of changes:
Utils::Array,Utils::VectorandUtils::Quaternionas MPI datatypes and bitwise serializableUtils::VectorandParticleby removing tracking information and metadataParticlesubstructs are bitwise serializableFor a LJ fluid simulation, the speed-up is around 8% on maxset configuration and 3% on empty configuration.