NVQParameters.idStringFor throws MissingFormatArgumentException #779

CompressorParameters.NVQParameters.idStringFor (jvector-examples, util/CompressorParameters.java, line 89) formats "NVQ_%s_%d_%s" with only two arguments (ds.getName() and nSubVectors), so every call throws MissingFormatArgumentException.

NVQParameters.supportsCaching() returns true, so Grid.getCompressor calls idStringFor whenever an NVQParameters is used as a build or search compressor. Nothing constructs NVQParameters today, so the bug can't currently be triggered. It will fail as soon as NVQ is offered as a compressor option.

The bug has been there since e8d5c3c (#374). Fix: drop the trailing _%s.