Matthias Boehm created SYSTEMML-1782:
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Summary: Extend parfor block indexing analysis
Key: SYSTEMML-1782
URL: https://issues.apache.org/jira/browse/SYSTEMML-1782
Project: SystemML
Issue Type: Task
Reporter: Matthias Boehm
This task aims to better support arbitrary block indexing in a parfor context,
for expressions as this example from SYSTEMML-1774:
{code}
parfor (j in 1:parallel_batches, log=DEBUG) {
# Get a mini-batch in this group
beg = ((j-1) * batch_size) %% nrow(X_group_batch) + 1
end = min(nrow(X_group_batch), beg + batch_size - 1)
X_batch = X_group_batch[beg:end,]
y_batch = y_group_batch[beg:end,]
{code}
Currently, we're unable to determine a constant size for X_batch and y_batch.
However, since the parfor body is anyway recompiled on parfor entry, we can
improve upon this as follows:
* Leverage known constants and index ranges to perform a limit analysis for
linear functions in indexing expressions. For example, the above expression for
beg and end would simplify to {{(j-1) * 32 + 1}} and {{beg + batch_size -1}}.
* Better handling of linear functions in right indexing HOPs - this would allow
us to determine batch_size as the number of rows in the output.
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