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On Mon, 26 Mar 2018 02:37:44 +0100, bartc wrote: > Calling a function that sets up C using 'C = 288714...' on one line, and > that then calculates D=C+C, takes 0.12 seconds to call 1000000 times. > > To do D=C*C, takes 2.2 seconds (I've subtracted the function call > overhead of 0.25 seconds; there might not be any function call). Bart, this is a contrived example that really proves nothing. This is literally the sort of premature optimization that Knuth etc so frequently warn about. In *almost any* real program, you're not going to be calculating C+C over and over and over and over again, millions of times in a row, while doing *literally* nothing else. If your point is that, *hypothetically*, there could be some amazingly unlikely set of circumstances where that's exactly what I will need to do, then fine, I'll deal with those circumstances when it happens and not a moment before. And I'll probably deal with it by calculating C+C in Python, then hard- coding D= that number, reducing the runtime cost of the addition to zero. > If I instead initialise C using 'C = int("288712...")', then timings > increase as follows: Given that the original number given had 397 digits and has a bit length of 1318, I must admit to some curiosity as to how exactly you managed to cast it to a C int (32 bits on most platforms). It is too big for an int, a long (64 bits), a long-long (128 bits) or even a long-long-long-long-long-long-long-long-long-long-long-long-long- long-long-long (1024 bits), if such a thing even exists. So what exactly did you do? -- Steve

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