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-rw-r--r--src/math/j0f.c171
1 files changed, 70 insertions, 101 deletions
diff --git a/src/math/j0f.c b/src/math/j0f.c
index 2ee2824b..79bab62a 100644
--- a/src/math/j0f.c
+++ b/src/math/j0f.c
@@ -18,10 +18,39 @@
static float pzerof(float), qzerof(float);
static const float
-huge = 1e30,
invsqrtpi = 5.6418961287e-01, /* 0x3f106ebb */
-tpi = 6.3661974669e-01, /* 0x3f22f983 */
+tpi = 6.3661974669e-01; /* 0x3f22f983 */
+
+static float common(uint32_t ix, float x, int y0)
+{
+ float z,s,c,ss,cc;
+ /*
+ * j0(x) = 1/sqrt(pi) * (P(0,x)*cc - Q(0,x)*ss) / sqrt(x)
+ * y0(x) = 1/sqrt(pi) * (P(0,x)*ss + Q(0,x)*cc) / sqrt(x)
+ */
+ s = sinf(x);
+ c = cosf(x);
+ if (y0)
+ c = -c;
+ cc = s+c;
+ if (ix < 0x7f000000) {
+ ss = s-c;
+ z = -cosf(2*x);
+ if (s*c < 0)
+ cc = z/ss;
+ else
+ ss = z/cc;
+ if (ix < 0x58800000) {
+ if (y0)
+ ss = -ss;
+ cc = pzerof(x)*cc-qzerof(x)*ss;
+ }
+ }
+ return invsqrtpi*cc/sqrtf(x);
+}
+
/* R0/S0 on [0, 2.00] */
+static const float
R02 = 1.5625000000e-02, /* 0x3c800000 */
R03 = -1.8997929874e-04, /* 0xb947352e */
R04 = 1.8295404516e-06, /* 0x35f58e88 */
@@ -33,56 +62,29 @@ S04 = 1.1661400734e-09; /* 0x30a045e8 */
float j0f(float x)
{
- float z, s,c,ss,cc,r,u,v;
- int32_t hx,ix;
+ float z,r,s;
+ uint32_t ix;
- GET_FLOAT_WORD(hx, x);
- ix = hx & 0x7fffffff;
+ GET_FLOAT_WORD(ix, x);
+ ix &= 0x7fffffff;
if (ix >= 0x7f800000)
- return 1.0f/(x*x);
+ return 1/(x*x);
x = fabsf(x);
- if (ix >= 0x40000000) { /* |x| >= 2.0 */
- s = sinf(x);
- c = cosf(x);
- ss = s-c;
- cc = s+c;
- if (ix < 0x7f000000) { /* make sure x+x does not overflow */
- z = -cosf(x+x);
- if (s*c < 0.0f)
- cc = z/ss;
- else
- ss = z/cc;
- }
- /*
- * j0(x) = 1/sqrt(pi) * (P(0,x)*cc - Q(0,x)*ss) / sqrt(x)
- * y0(x) = 1/sqrt(pi) * (P(0,x)*ss + Q(0,x)*cc) / sqrt(x)
- */
- if (ix > 0x80000000)
- z = (invsqrtpi*cc)/sqrtf(x);
- else {
- u = pzerof(x);
- v = qzerof(x);
- z = invsqrtpi*(u*cc-v*ss)/sqrtf(x);
- }
- return z;
- }
- if (ix < 0x39000000) { /* |x| < 2**-13 */
- /* raise inexact if x != 0 */
- if (huge+x > 1.0f) {
- if (ix < 0x32000000) /* |x| < 2**-27 */
- return 1.0f;
- return 1.0f - 0.25f*x*x;
- }
+
+ if (ix >= 0x40000000) { /* |x| >= 2 */
+ /* large ulp error near zeros */
+ return common(ix, x, 0);
}
- z = x*x;
- r = z*(R02+z*(R03+z*(R04+z*R05)));
- s = 1.0f+z*(S01+z*(S02+z*(S03+z*S04)));
- if(ix < 0x3F800000) { /* |x| < 1.00 */
- return 1.0f + z*(-0.25f + (r/s));
- } else {
- u = 0.5f*x;
- return (1.0f+u)*(1.0f-u) + z*(r/s);
+ if (ix >= 0x3a000000) { /* |x| >= 2**-11 */
+ /* up to 4ulp error near 2 */
+ z = x*x;
+ r = z*(R02+z*(R03+z*(R04+z*R05)));
+ s = 1+z*(S01+z*(S02+z*(S03+z*S04)));
+ return (1+x/2)*(1-x/2) + z*(r/s);
}
+ if (ix >= 0x21800000) /* |x| >= 2**-60 */
+ x = 0.25f*x*x;
+ return 1 - x;
}
static const float
@@ -100,61 +102,28 @@ v04 = 4.4111031494e-10; /* 0x2ff280c2 */
float y0f(float x)
{
- float z,s,c,ss,cc,u,v;
- int32_t hx,ix;
+ float z,u,v;
+ uint32_t ix;
- GET_FLOAT_WORD(hx, x);
- ix = 0x7fffffff & hx;
- /* Y0(NaN) is NaN, y0(-inf) is Nan, y0(inf) is 0 */
+ GET_FLOAT_WORD(ix, x);
+ if ((ix & 0x7fffffff) == 0)
+ return -1/0.0f;
+ if (ix>>31)
+ return 0/0.0f;
if (ix >= 0x7f800000)
- return 1.0f/(x+x*x);
- if (ix == 0)
- return -1.0f/0.0f;
- if (hx < 0)
- return 0.0f/0.0f;
+ return 1/x;
if (ix >= 0x40000000) { /* |x| >= 2.0 */
- /* y0(x) = sqrt(2/(pi*x))*(p0(x)*sin(x0)+q0(x)*cos(x0))
- * where x0 = x-pi/4
- * Better formula:
- * cos(x0) = cos(x)cos(pi/4)+sin(x)sin(pi/4)
- * = 1/sqrt(2) * (sin(x) + cos(x))
- * sin(x0) = sin(x)cos(3pi/4)-cos(x)sin(3pi/4)
- * = 1/sqrt(2) * (sin(x) - cos(x))
- * To avoid cancellation, use
- * sin(x) +- cos(x) = -cos(2x)/(sin(x) -+ cos(x))
- * to compute the worse one.
- */
- s = sinf(x);
- c = cosf(x);
- ss = s-c;
- cc = s+c;
- /*
- * j0(x) = 1/sqrt(pi) * (P(0,x)*cc - Q(0,x)*ss) / sqrt(x)
- * y0(x) = 1/sqrt(pi) * (P(0,x)*ss + Q(0,x)*cc) / sqrt(x)
- */
- if (ix < 0x7f000000) { /* make sure x+x not overflow */
- z = -cosf(x+x);
- if (s*c < 0.0f)
- cc = z/ss;
- else
- ss = z/cc;
- }
- if (ix > 0x80000000)
- z = (invsqrtpi*ss)/sqrtf(x);
- else {
- u = pzerof(x);
- v = qzerof(x);
- z = invsqrtpi*(u*ss+v*cc)/sqrtf(x);
- }
- return z;
+ /* large ulp error near zeros */
+ return common(ix,x,1);
}
- if (ix <= 0x32000000) { /* x < 2**-27 */
- return u00 + tpi*logf(x);
+ if (ix >= 0x39000000) { /* x >= 2**-13 */
+ /* large ulp error at x ~= 0.89 */
+ z = x*x;
+ u = u00+z*(u01+z*(u02+z*(u03+z*(u04+z*(u05+z*u06)))));
+ v = 1+z*(v01+z*(v02+z*(v03+z*v04)));
+ return u/v + tpi*(j0f(x)*logf(x));
}
- z = x*x;
- u = u00+z*(u01+z*(u02+z*(u03+z*(u04+z*(u05+z*u06)))));
- v = 1.0f+z*(v01+z*(v02+z*(v03+z*v04)));
- return u/v + tpi*(j0f(x)*logf(x));
+ return u00 + tpi*logf(x);
}
/* The asymptotic expansions of pzero is
@@ -233,14 +202,14 @@ static float pzerof(float x)
{
const float *p,*q;
float z,r,s;
- int32_t ix;
+ uint32_t ix;
GET_FLOAT_WORD(ix, x);
ix &= 0x7fffffff;
if (ix >= 0x41000000){p = pR8; q = pS8;}
else if (ix >= 0x40f71c58){p = pR5; q = pS5;}
else if (ix >= 0x4036db68){p = pR3; q = pS3;}
- else if (ix >= 0x40000000){p = pR2; q = pS2;}
+ else /*ix >= 0x40000000*/ {p = pR2; q = pS2;}
z = 1.0f/(x*x);
r = p[0]+z*(p[1]+z*(p[2]+z*(p[3]+z*(p[4]+z*p[5]))));
s = 1.0f+z*(q[0]+z*(q[1]+z*(q[2]+z*(q[3]+z*q[4]))));
@@ -329,14 +298,14 @@ static float qzerof(float x)
{
const float *p,*q;
float s,r,z;
- int32_t ix;
+ uint32_t ix;
GET_FLOAT_WORD(ix, x);
ix &= 0x7fffffff;
if (ix >= 0x41000000){p = qR8; q = qS8;}
else if (ix >= 0x40f71c58){p = qR5; q = qS5;}
else if (ix >= 0x4036db68){p = qR3; q = qS3;}
- else if (ix >= 0x40000000){p = qR2; q = qS2;}
+ else /*ix >= 0x40000000*/ {p = qR2; q = qS2;}
z = 1.0f/(x*x);
r = p[0]+z*(p[1]+z*(p[2]+z*(p[3]+z*(p[4]+z*p[5]))));
s = 1.0f+z*(q[0]+z*(q[1]+z*(q[2]+z*(q[3]+z*(q[4]+z*q[5])))));
generated by cgit v1.2.1 (git 2.18.0) at 2024-04-29 21:51:17 +0000