> On the other hand, Eigen didn't claim to be faster than any BLAS during my interaction with informational side of their website. It claims to be faster than

> On the other hand, Eigen didn't claim to be faster than any BLAS during my interaction with informational side of their website. It claims to be faster than any free BLAS in the FAQ (but talks about ATLAS and GotoBLAS there). Given how close GotoBLAS in the guise of OpenBLAS gets to peak performance for GEMM, that would be dubious without measuring 2/3 of OB DGEMM performance. I assume claims of speed are for when BLAS is actually providing it. (I'm too experienced to be susceptible to appeals to authority of HEP software!) Thanks for explaining the memory thing. I'd hope HPC code wouldn't be subject to SEGVs due to memory allocation failing (for two reasons), but you typically want arrays on the stack and otherwise large pages to minimize TLB misses (per Goto). I'm not intending to bash Eigen, happy if people can use performant free software.