78 lines
1.6 KiB
C
78 lines
1.6 KiB
C
/*
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* This file is part of the UCB release of Plan 9. It is subject to the license
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* terms in the LICENSE file found in the top-level directory of this
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* distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No
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* part of the UCB release of Plan 9, including this file, may be copied,
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* modified, propagated, or distributed except according to the terms contained
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* in the LICENSE file.
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*/
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/*
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C program for floating point sin/cos.
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Calls modf.
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There are no error exits.
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Coefficients are #3370 from Hart & Cheney (18.80D).
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*/
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#include <u.h>
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#include <libc.h>
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#define p0 .1357884097877375669092680e8
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#define p1 -.4942908100902844161158627e7
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#define p2 .4401030535375266501944918e6
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#define p3 -.1384727249982452873054457e5
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#define p4 .1459688406665768722226959e3
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#define q0 .8644558652922534429915149e7
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#define q1 .4081792252343299749395779e6
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#define q2 .9463096101538208180571257e4
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#define q3 .1326534908786136358911494e3
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static
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double
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sinus(double arg, int quad)
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{
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double e, f, ysq, x, y, temp1, temp2;
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int k;
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x = arg;
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if(x < 0) {
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x = -x;
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quad += 2;
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}
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x *= 1/PIO2; /* underflow? */
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if(x > 32764) {
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y = jehanne_modf(x, &e);
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e += quad;
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jehanne_modf(0.25*e, &f);
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quad = e - 4*f;
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} else {
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k = x;
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y = x - k;
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quad += k;
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quad &= 3;
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}
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if(quad & 1)
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y = 1-y;
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if(quad > 1)
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y = -y;
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ysq = y*y;
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temp1 = ((((p4*ysq+p3)*ysq+p2)*ysq+p1)*ysq+p0)*y;
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temp2 = ((((ysq+q3)*ysq+q2)*ysq+q1)*ysq+q0);
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return temp1/temp2;
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}
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double
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jehanne_cos(double arg)
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{
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if(arg < 0)
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arg = -arg;
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return sinus(arg, 1);
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}
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double
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jehanne_sin(double arg)
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{
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return sinus(arg, 0);
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}
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