Vector growth factor in languages

Growth factor is the factor by which the new size of a C++ STL vector is computed when we need to insert beyond its current capacity. There are dynamic arrays similar to the STL vector in other languages. It is quite interesting to see what factors were chosen in those implementations.

• C++: The last time I looked into this (see this post), VC++ vector had a growth factor of 1.5 and GCC vector had a growth factor of 2.

• Java: ArrayList seems to have a growth factor of 1.5:

int newCapacity = oldCapacity + (oldCapacity >> 1);

• Julia: Array seems to have a growth factor of 2:

size_t newmaxsize = reqmaxsize >= a->maxsize * 2
    ? (reqmaxsize < 4 ? 4 : reqmaxsize)
    : a->maxsize * 2;

• Python: List in the CPython implementation seems to have a growth factor of 1.125:

new_allocated = ((size_t)newsize + (newsize >> 3) + 6) & ~(size_t)3;