in reply to Re^13: Math::BigFloat to native double?
in thread Math::BigFloat to native double?

Thanks syphilis. That's beyond the call.

I'm still digesting Re^12: Math::BigFloat to native double?; but I took "But I'm pretty much out of ideas (and energy) if Math::MPFR is to be excluded. (Without it, there's just too many hoops for me)." at face value, so this is most unexpected :) Thank you.

"(I'll scrutinise it and test it over the next week or so.)" But, please don't expend more of your energies on this. It's just a background project for me; something I do whilst I'm waiting for other stuff to run; or when I hit a mental block in my current work and need a diversion to allow my brain to unencumber itself of the details.

Given where I started with the simple question in the OP, this thread's has gone way beyond anything I could have expected anyone else to give a damn about :)

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.
I'm with torvalds on this Agile (and TDD) debunked I told'em LLVM was the way to go. But did they listen!
  • Comment on Re^14: Math::BigFloat to native double?

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Re^15: Math::BigFloat to native double?
by syphilis (Archbishop) on Jul 16, 2015 at 11:10 UTC
    Thing is that, with re-charged batteries, I start thinking "Hang on, I *can* improve on that". (And there's still room for improvement.)

    Anyway - good luck, and enjoy the exercise. I find the doubledouble to be rather intriguing (not to mention a little exasperating), and I purchased the (second hand) PPC box for the sole purpose of looking more readily at it.
    You should be able to pick one up over there for next-to-nothing if you ever get the urge. I had one offered to me for free - it was a genuine offer, too, but would've required a trip to New York to pick it up.
    Being big-endian, the PPC box also provides a handy reference to that architecture, too.

    Cheers,
    Rob
[reply]
      I find the doubledouble to be rather intriguing (not to mention a little exasperating), and I purchased the (second hand) PPC box for the sole purpose of looking more readily at it.

      I'm gonna ask this again: are you sure that we are talking about the same thing with respect to doubledouble and PPC?

      When I google "PPC doubledouble" (and click past its annoying habit of trying to be helpful instead of searching for what I ask for), the *only* hits I get are those that also include (one of) your handles. Here, or on active state forums etc.

      But, when I look at the C code there, I see "long double"; which according to wikipedia: MS map to double; Intel map to 80-bit IEEE (hardware) extended precision; and gcc maps to 128-bit IEEE quad precision. None of which are the doubledouble I'm talking of.

      With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
      Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
      "Science is about questioning the status quo. Questioning authority".
      In the absence of evidence, opinion is indistinguishable from prejudice.
      I'm with torvalds on this Agile (and TDD) debunked I told'em LLVM was the way to go. But did they listen!
[reply]
        are you sure that we are talking about the same thing with respect to doubledouble and PPC

        Yes - though "being sure" doesn't guarantee that I'm right ;-)

        The wikipedia "long double" page mentions a number of ways of implementing long doubles, including the double double:

        "On some PowerPC and SPARCv9 machines, long double is implemented as a double-double arithmetic, where a long double value is regarded as the exact sum of two double-precision values, giving at least a 106-bit precision; with such a format, the long double type does not conform to the IEEE floating-point standard."

        Also this Wikipedia "double-double arithmetic" entry accurately describes the PPC double-double (and, I think, the double-double that you are wanting to implement).

        Cheers,
        Rob
[reply]

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