Which packages optimize performance parameters during build?

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So it's really only `ntl` and `atlas` that doing any build parameter performance testing?

You will have to look at the output of the various packages (check `SAGE_ROOT/logs/install.log`). I suspect r might be also doing some tuning. In fact, almost all compiled packages _should_ be doing some tuning, at least for the compilation flags, so that it is specific to your architecture. If you want to force some compile time optimization, you can define the `CFLAGS` before compiling: $ export CFLAGS="-march=native -pipe" $ export CXXFLAGS="${CFLAGS}" You can read up on `-march=native` from your gcc manual. You can check what it enables by comparing the output of the following two commands $ gcc -Q -march=native --help=target $ gcc -Q --help=target