Problems with comments in F14Table

[leventov]

First is from here: #1142 (comment)

folly/folly/container/detail/F14Table.h

Lines 2021 to 2022 in 9feea21

	// Returns true iff a rehash was performed
	void reserveForInsert(size_t incoming = 1) {

doesn't seem that this function returns anything now

Second:

folly/folly/container/detail/F14Table.h

Lines 1788 to 1802 in 9feea21

	FOLLY_NOINLINE void reserveForInsertImpl(
	std::size_t capacityMinusOne,
	std::size_t origChunkCount,
	std::size_t origCapacityScale,
	std::size_t origCapacity) {
	FOLLY_SAFE_DCHECK(capacityMinusOne >= size(), "");
	std::size_t capacity = capacityMinusOne + 1;
	// we want to grow by between 2^0.5 and 2^1.5 ending at a "good"
	// size, so we grow by 2^0.5 and then round up
	// 1.01101_2 = 1.40625
	std::size_t minGrowth = origCapacity + (origCapacity >> 2) +
	(origCapacity >> 3) + (origCapacity >> 5);
	capacity = std::max<std::size_t>(capacity, minGrowth);

I cannot make sense of the comment (why would growing by 2^1.5 ~= 2.8 be optimal, when the chunk array's size is always a power of two?), it might be a typo where 2^1.0 was actually intended, but not sure.

[yfeldblum]

@nbronson for the growth strategy.