Last change
on this file since 403 was 337, checked in by coas-nagasima, 6 years ago |
ASP3版ECNLを追加
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Property svn:eol-style
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Property svn:mime-type
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File size:
485 bytes
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1 | #include "libm.h"
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2 |
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3 | /* k is such that k*ln2 has minimal relative error and x - kln2 > log(DBL_MIN) */
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4 | static const int k = 2043;
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5 | static const double kln2 = 0x1.62066151add8bp+10;
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6 |
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7 | /* exp(x)/2 for x >= log(DBL_MAX), slightly better than 0.5*exp(x/2)*exp(x/2) */
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8 | double __expo2(double x)
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9 | {
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10 | double scale;
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11 |
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12 | /* note that k is odd and scale*scale overflows */
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13 | INSERT_WORDS(scale, (uint32_t)(0x3ff + k/2) << 20, 0);
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14 | /* exp(x - k ln2) * 2**(k-1) */
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15 | return exp(x - kln2) * scale * scale;
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16 | }
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