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author | upstream source tree <ports@midipix.org> | 2015-03-15 20:14:05 -0400 |
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committer | upstream source tree <ports@midipix.org> | 2015-03-15 20:14:05 -0400 |
commit | 554fd8c5195424bdbcabf5de30fdc183aba391bd (patch) | |
tree | 976dc5ab7fddf506dadce60ae936f43f58787092 /libquadmath/math/sqrtq.c | |
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Diffstat (limited to 'libquadmath/math/sqrtq.c')
-rw-r--r-- | libquadmath/math/sqrtq.c | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/libquadmath/math/sqrtq.c b/libquadmath/math/sqrtq.c new file mode 100644 index 000000000..6ed4605ed --- /dev/null +++ b/libquadmath/math/sqrtq.c @@ -0,0 +1,57 @@ +#include "quadmath-imp.h" +#include <math.h> +#include <float.h> + +__float128 +sqrtq (const __float128 x) +{ + __float128 y; + int exp; + + if (x == 0) + return x; + + if (isnanq (x)) + return x; + + if (x < 0) + return nanq (""); + + if (x <= DBL_MAX && x >= DBL_MIN) + { + /* Use double result as starting point. */ + y = sqrt ((double) x); + + /* Two Newton iterations. */ + y -= 0.5q * (y - x / y); + y -= 0.5q * (y - x / y); + return y; + } + +#ifdef HAVE_SQRTL + if (x <= LDBL_MAX && x >= LDBL_MIN) + { + /* Use long double result as starting point. */ + y = sqrtl ((long double) x); + + /* One Newton iteration. */ + y -= 0.5q * (y - x / y); + return y; + } +#endif + + /* If we're outside of the range of C types, we have to compute + the initial guess the hard way. */ + y = frexpq (x, &exp); + if (exp % 2) + y *= 2, exp--; + + y = sqrt (y); + y = scalbnq (y, exp / 2); + + /* Two Newton iterations. */ + y -= 0.5q * (y - x / y); + y -= 0.5q * (y - x / y); + return y; +} + |