I'll elaborate a bit on Barrie's point, which is correct, if disappointing.
The problem is that English spelling was not designed for Modern English. It was designed for Middle English, a very different language. When Middle English changed its pronunciation to become Modern English, English spelling did not change. Furthermore, English borrowed many thousands of words from other languages, which were of course pronounced differently, and spelled differently still.
The result is that one has to choose between two strategies in learning English words, however they are spelled -- this is not a problem confined to the letter I -- or else figure out some way to mix them.
Either you can actually learn the historical rules about pronunciation and learn to distinguish the different kinds of word each rule applies to -- which amounts to learning some basic linguistics,
Or you can do as Barrie suggested, and memorize 2 things about every word you learn -- (1) how it's spelled and (2) how it's pronounced (Kenyon and Knott is your friend here) -- and just ignore the possible but treacherous correspondences you might suspect between Middle English or foreign spellings and Modern English pronunciations.
The second option amounts to giving up all hope of making sense of English spelling. Most native English speakers do this, which is simpler for them, since they already know the pronunciation.
Since Anglophone education systems don't teach anything about English language, they never learn any different, and many still believe there should be a simple rule for pronouncing every letter.
In the context of iostreams, writers often will refer to << and >> as
the “put-to” or "stream insertion" and “get-from” or "stream
extraction" operators, respectively* .
If you are using << for output in C++ programming then I would just call it "put-to".
(Otherwise, that would also be used as the bitwise left shift in binary operations, but I doubt that is what you meant)
Best Answer
Native speakers of English typically do not reduce the th-s transition at all. The th sound, though famously difficult for people learning English as adults, usually poses no problem for people who learn to speak it as young children. To me it feels perfectly natural to go from th directly into s and I do it without a second thought.
If you have difficulty with th-s, you might just go ahead and pronounce "Smiths" as "Smits", which should be well enough understood by most people.