libdivide

Fast prime counting function implementations

libdivide allows you to replace expensive integer divides with comparatively cheap multiplication and bitshifts. Compilers usually do this, but only when the divisor is known at compile time. libdivide allows you to take advantage of it at runtime. The result is that integer division can become faster - a lot faster. Furthermore, libdivide allows you to divide SIMD vectors by runtime constants, which is especially nice because SIMD typically lacks integer division. See also: https://github.com/ridiculousfish/libdivide/