These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 1.12 s (backtrack: 0/20).

[ebuild  N     ] virtual/fortran-0-r1::gentoo  USE="openmp" 0 KiB
[ebuild  N     ] sci-libs/fftw-3.3.10-r1:3.0/3::gentoo  USE="openmp threads -doc -fortran -mpi -test (-zbus)" CPU_FLAGS_X86="avx avx2 fma3 sse sse2 -fma4" 4047 KiB
[ebuild  N     ] sci-libs/openblas-0.3.34::gentoo  USE="openmp -cpudetection -index64 -pthread -relapack -test" 24734 KiB
[ebuild  N     ] sci-libs/lapack-3.12.1-r2::gentoo  USE="deprecated flexiblas lapacke -doc -eselect-ldso -index64 -test" 7879 KiB
[ebuild  N     ] sci-libs/flexiblas-3.5.0::gentoo  USE="openblas openmp system-blas -blis -index64 -mkl -tbb -test" 80741 KiB
[ebuild  N     ] sci-libs/blas-lapack-aux-wrapper-6::gentoo  USE="-index64 -test" 10 KiB
[ebuild  N     ] virtual/blas-3.8-r1::gentoo  USE="flexiblas -eselect-ldso -index64" 0 KiB
[ebuild  N     ] virtual/lapack-3.10-r1::gentoo  USE="flexiblas -eselect-ldso -index64" 0 KiB
[ebuild  N     ] sci-libs/itpp-4.3.1-r2::gentoo  USE="-doc" 1260 KiB

Total: 9 packages (9 new), Size of downloads: 118668 KiB