SparseMat multiplication

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I am doing an image retrieval using Bag of Words. I've constructed the inverted file which is represented by SparseMat. Now I need to multiply the inverted file with the vector of the visual words of the query to get the scores however I'm not really sure how to do it and I didn't find any documentation about it. I've tried to represent the query vector as SparseMat or Mat, but it always says: no operator "*" matches these operands. Does anyone know hot to multiply a SparsaMat without converting it to the dense form? Thanks!