Re^2: exp() bignum issue

This problem is solved, not because I got the function to run more quickly but because I was getting that huge number because of a mistake in my regression equation. :-/

It's still true, however, that Windows calculator does e ^ 15863.8668285308 in the blink of an eye. I wonder why it's so much faster...

Comment on Re^2: exp() bignum issue

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Re^3: exp() bignum issue by syphilis (Archbishop) on Aug 31, 2020 at 00:29 UTC
... Windows calculator does e ^ 15863.8668285308 in the blink of an eye. I wonder why it's so much faster It's so much faster because it uses an executable that was built from optimized C (and perhaps also assembly) routines. The pure perl Math::BigFloat can't compete with that. <plug> In perl, use Math::MPFR in order to get the same (perhaps even better) performance compared to the Windows calculator. </plug> # 53 bit precision, rounding to nearest C:\>perl -MMath::MPFR -le "print exp(Math::MPFR->new('15863.8668285308 +'))" 3.8888865970333893e6889 # 64 bit precision, rounding to nearest C:\>perl -MMath::MPFR=":mpfr" -le "Rmpfr_set_default_prec(64);print ex +p(Math::MPFR->new('15863.8668285308'))" 3.88888659703546523928e6889 # 113 bit precision, rounding to nearest C:\>perl -MMath::MPFR=":mpfr" -le "Rmpfr_set_default_prec(113);print e +xp(Math::MPFR->new('15863.8668285308'))" 3.88888659703546395686515111487812115e6889 [download] You can, of course, additionally do the inversion in one step: `C:\>perl -MMath::MPFR -le "print 1 / exp(Math::MPFR->new('15863.866828 +5308'))" 2.5714300868604479e-6890` [download] NOTE: Math::MPFR requires both the gmp and mpfr libraries. You could also do the same arithmetic (without the fine grained control over precision) using Math::GMPf - which requires the gmp library only. However, the gmp project recommends mpfr over the floating point gmp routines. Cheers, Rob	[reply] [d/l] [select]

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Re^3: exp() bignum issue
by syphilis (Archbishop) on Aug 31, 2020 at 00:29 UTC

... Windows calculator does e ^ 15863.8668285308 in the blink of an eye. I wonder why it's so much faster

# 53 bit precision, rounding to nearest
C:\>perl -MMath::MPFR -le "print exp(Math::MPFR->new('15863.8668285308
+'))"
3.8888865970333893e6889

# 64 bit precision, rounding to nearest
C:\>perl -MMath::MPFR=":mpfr" -le "Rmpfr_set_default_prec(64);print ex
+p(Math::MPFR->new('15863.8668285308'))"
3.88888659703546523928e6889

# 113 bit precision, rounding to nearest
C:\>perl -MMath::MPFR=":mpfr" -le "Rmpfr_set_default_prec(113);print e
+xp(Math::MPFR->new('15863.8668285308'))"
3.88888659703546395686515111487812115e6889
[download]

C:\>perl -MMath::MPFR -le "print 1 / exp(Math::MPFR->new('15863.866828
+5308'))"
2.5714300868604479e-6890
[download]

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