- ...COMM_WORLD
- It has been pointed out that
if multiple MPI threads are allowed in the same Java VM, the default
communicator cannot be obtained from a static variable. The final version
of the API may change this convention.
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- ...data
- A better protocol would be to eagerly send data for short
messages in the header, assuming some fixed-size buffer
is preallocated at the receiving end. The two-message protocol
would be reserved for long messages. This marginally complicates the
implementation but does not essentially change the rest of the discussion
or the benchmark results presented below, since the latter concentrate on the
asymptotic case. We are grateful to one of the anonymous referees for
raising this point.
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- ...elements
- We note that there some debate about whether the
Java model of multidimensional arrays is the most appropriate one
for high performance computing. There are various proposals for
for optimized HPC array class libraries [15]. See section
6 for some further discussion.
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- ...T[N][N]
- Our timing
model assumed the values of these parameters is independent of the
element type. This is only approximately true, and the values quoted in
the table and used in the plotted curves are averages.
Separately measured values for byte arrays were smaller than
these averages, and for int and float arrays they were
larger.
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- ...elements
- Defined to be arrays of objects, each element being
an array of primitive type of the same type and length.
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- ...process
- It can also introduce some unexpected
behaviour. Our version subtly alters the semantics of serialization,
because it does not detect of aliasing of rows (either with other rows
of the same two-dimensional array, or with one-dimensional primitive
arrays elsewhere in the stream). Hence the reconstructed object graph
at the receiving end will not reproduce such aliasing. Whether this is
a serious problem is unclear.
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