Refactor the code handling the local vocabulary #820
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The LocalVocab used to be an alias for std::vector<std::string> (defined inside of the ResultTable class). New words were pushed to this vector without checking whether they were already in the vocabulary (exception: when a sequence of identical new words were encountered in a SPARQL expression result, the words was only added once per sequence). The basic data is still a std::vector<std::string>, but there is now a phase, started by LocalVocab::startConstructionPhase() and ended by LocalVocab::endConstrutionPhase(), where new words can be added and a words-to-ID map records which words have already been added. After that phase, the map is deleted and the local vocabulary is read-only. Check test/LocalVocabTest for how it works in prinicple. This is also used by the Values class in PR #793 (and I tested it already quite extensively and it works).
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joka921
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Nov 9, 2022
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Thank you very much.
With the split up functionality it is much easier to reason about how things should REALLY be.
Some of my suggestions are not "just do this" but rather "maybe there is stuff to discuss here",
So maybe first read them, and then contact me for further details.
In particular, there is no longer a "construction" phase now, at the cost of using a slower hash map (absl::node_hash_map), slightly more space (the hash map and a vector to the strings stored in the hash map), and an indirection when looking up the word for an index (we have to follow the pointer to the actual string stored in the hash map).
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joka921
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Nov 10, 2022
We should discuss: 1. Argument type taken by getIndexAndAddIfNotContained 2. Return type of getWord
joka921
reviewed
Nov 10, 2022
test/LocalVocabTest.cpp
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| ASSERT_EQ(localVocab.getIndexAndAddIfNotContained("bla"), makeIndex(0)); | ||
| ASSERT_EQ(localVocab.getIndexAndAddIfNotContained("blu"), makeIndex(1)); | ||
| ASSERT_EQ(localVocab.getIndexAndAddIfNotContained("bli"), makeIndex(2)); | ||
| ASSERT_EQ(localVocab.getIndexAndAddIfNotContained("bla"), makeIndex(0)); | ||
| ASSERT_EQ(localVocab.size(), 3); | ||
| ASSERT_EQ(localVocab.getWord(LocalVocabIndex::make(0)), "bla"); | ||
| ASSERT_EQ(localVocab.getWord(LocalVocabIndex::make(1)), "blu"); |
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To be sure, I would add some more words in a loop (100s or 1000s) and then check for the pointers.
The goal is to make this test fail with very high probability once somebody uses a hashMap implementation that is not pointer-stable for the Keys.
joka921
approved these changes
Nov 10, 2022
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The LocalVocab used to be an alias for std::vectorstd::string (defined inside of the ResultTable class). New words were pushed to this vector without checking whether they were already in the vocabulary (exception: when a sequence of identical new words were encountered in a SPARQL expression result, the words was only added once per sequence).
The basic data is still a std::vectorstd::string, but there is now a phase, started by LocalVocab::startConstructionPhase() and ended by LocalVocab::endConstrutionPhase(), where new words can be added and a words-to-ID map records which words have already been added. After that phase, the map is deleted and the local vocabulary is read-only. Check test/LocalVocabTest for how it works in prinicple.
This is also used by the Values class in PR #793 (and I tested it already quite extensively and it works).