Date: Fri, 1 Feb 2019 16:24:53 -0800 From: Steve Kargl <sgk@troutmask.apl.washington.edu> To: freebsd-numerics@freebsd.org Subject: cexp[f] patch Message-ID: <20190202002453.GA17741@troutmask.apl.washington.edu>
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The following patch utilizes sincos[f] in the computation of cexp[f]. For 20 million random z=x+Iy drawn in the box defined by x,y in [0,MAX_EXP*LN2], this amounts to a 8.7% and 11.4% speed improvement over computing sin[f] and cos[f] individually. Index: msun/src/s_cexp.c =================================================================== --- msun/src/s_cexp.c (revision 2135) +++ msun/src/s_cexp.c (working copy) @@ -41,7 +41,7 @@ double complex cexp(double complex z) { - double x, y, exp_x; + double c, exp_x, s, x, y; uint32_t hx, hy, lx, ly; x = creal(z); @@ -55,8 +55,10 @@ return (CMPLX(exp(x), y)); EXTRACT_WORDS(hx, lx, x); /* cexp(0 + I y) = cos(y) + I sin(y) */ - if (((hx & 0x7fffffff) | lx) == 0) - return (CMPLX(cos(y), sin(y))); + if (((hx & 0x7fffffff) | lx) == 0) { + sincos(y, &s, &c); + return (CMPLX(c, s)); + } if (hy >= 0x7ff00000) { if (lx != 0 || (hx & 0x7fffffff) != 0x7ff00000) { @@ -86,6 +88,7 @@ * - x = NaN (spurious inexact exception from y) */ exp_x = exp(x); - return (CMPLX(exp_x * cos(y), exp_x * sin(y))); + sincos(y, &s, &c); + return (CMPLX(exp_x * c, exp_x * s)); } } Index: msun/src/s_cexpf.c =================================================================== --- msun/src/s_cexpf.c (revision 2135) +++ msun/src/s_cexpf.c (working copy) @@ -41,7 +41,7 @@ float complex cexpf(float complex z) { - float x, y, exp_x; + float c, exp_x, s, x, y; uint32_t hx, hy; x = crealf(z); @@ -55,8 +55,10 @@ return (CMPLXF(expf(x), y)); GET_FLOAT_WORD(hx, x); /* cexp(0 + I y) = cos(y) + I sin(y) */ - if ((hx & 0x7fffffff) == 0) - return (CMPLXF(cosf(y), sinf(y))); + if ((hx & 0x7fffffff) == 0) { + sincosf(y, &s, &c); + return (CMPLXF(c, s)); + } if (hy >= 0x7f800000) { if ((hx & 0x7fffffff) != 0x7f800000) { @@ -86,6 +88,7 @@ * - x = NaN (spurious inexact exception from y) */ exp_x = expf(x); - return (CMPLXF(exp_x * cosf(y), exp_x * sinf(y))); + sincosf(y, &s, &c); + return (CMPLXF(exp_x * c, exp_x * s)); } } -- Steve
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