hashmap for quick var and dim retrieval -- nc3 files #238
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The var struct has a 'dim' field which was not being used Instead, the dimids field would always search for the dim with the matching dimid. For db with large numbers of dims, this could be a significant time sync. Modified code to always set var-dim[i] when var->dimids[i] was set (if the dim existed at that point). Then use the var->dim field instead of var->dimids and search whenever requested. All var->dim accesses are protected by asserts that verify non-null and that the var->dim[]->dimid == var->dimids[].
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Looks good; managing merge now, thanks very much @gsjaardema ! |
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Thanks. I am working on a similar patch for nc4 files... |
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Added a hashmap that hashes the var/dim name and returns the var/dim id which can then be used for O(1) lookup of the actual var/dim object for nc3 files. This eliminates walking a doubly-linked list with strcmp calls that was previously needed to retrieve a var/dim when given a name.
Removed the old hash stored in the var/dim which was used to eliminate many strcmp calls.
Results in significant speedup for files with large numbers of vars and dims; prototype for applying a similar concept to nc4 and possibly nc5 (pnetcdf-based) files.