Support reading SDPA files with multiple LP blocks - #25
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August 30, 2026 14:24
Multiple LP blocks (indicated by negative block sizes) are supported by the SDPA file format but not the reader. This change modifies the reader such that multiple LP blocks are read as if they were a single block: each element "v b i j x" is interpreted as "v b (i + blockoffsets[b]) (j + blockoffsets[b]) x" where "blockoffsets[b]" is the sum of the block sizes of all preceding LP blocks. This effectively reads LP blocks (i.e. diagonal block) as one single diagonal block.
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Thank you. This is great! Since I cannot write to this pull request, I created a copy #26 . There I added two tests for block indices outside of the range (in order to make the unit test |
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Some SDPA files (generated by other tools) may contain multiple LP blocks, but SCIP-SDP only allows for a single LP block. Converting such instances by merging the multiple blocks into a single block is tedious, so this change modifies the reader such that multiple blocks are supported.
The basic changes are as follows:
blockoffsetsandnewblockidxare added to the data struct,idxlinconsblockis removedblockoffsets[b]contains the offset of LP-blockb. This equals the sum of the sizes of all preceding LP blocks. An element at(row, col)of blockbis then interpreted as(row + blockoffsets[b], col + blockoffsets[b])of the single (merged) LP block.newblockidx[b]contains the new block index of each SDP blockb. This equals the old index minus the number of the preceding LP blocks (formerly the index shift was implemented w.r.t. the single LP block, now there may be several LP blocks). For an LP blocknewblockidx[b] == -1(this is how LP blocks are recognized).