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  1. #include <stdio.h>
  2. #include <limits.h>
  3.  
  4. #if UINT_MAX >= 0xFFFFFFFF
  5. typedef unsigned myfloat;
  6. #else
  7. typedef unsigned long myfloat;
  8. #endif
  9.  
  10. #define MF_EXP_BIAS 0x80
  11.  
  12. myfloat mfadd(myfloat a, myfloat b)
  13. {
  14.   unsigned ea = a >> 16, eb = b >> 16;
  15.   if (ea > eb)
  16.   {
  17.     a &= 0xFFFF;
  18.     b = (b & 0xFFFF) >> (ea - eb);
  19.     if ((a += b) > 0xFFFF)
  20.       a >>= 1, ++ea;
  21.     return a | ((myfloat)ea << 16);
  22.   }
  23.   else if (eb > ea)
  24.   {
  25.     b &= 0xFFFF;
  26.     a = (a & 0xFFFF) >> (eb - ea);
  27.     if ((b += a) > 0xFFFF)
  28.       b >>= 1, ++eb;
  29.     return b | ((myfloat)eb << 16);
  30.   }
  31.   else
  32.   {
  33.     return (((a & 0xFFFF) + (b & 0xFFFF)) >> 1) | ((myfloat)++ea << 16);
  34.   }
  35. }
  36.  
  37. myfloat mfmul(myfloat a, myfloat b)
  38. {
  39.   unsigned ea = a >> 16, eb = b >> 16, e = ea + eb - MF_EXP_BIAS;
  40.   myfloat p = ((a & 0xFFFF) * (b & 0xFFFF)) >> 16;
  41.   return p | ((myfloat)e << 16);
  42. }
  43.  
  44. myfloat double2mf(double x)
  45. {
  46.   myfloat f;
  47.   unsigned e = MF_EXP_BIAS + 16;
  48.   if (x <= 0)
  49.     return 0;
  50.   while (x < 0x8000)
  51.     x *= 2, --e;
  52.   while (x >= 0x10000)
  53.     x /= 2, ++e;
  54.   f = x;
  55.   return f | ((myfloat)e << 16);
  56. }
  57.  
  58. double mf2double(myfloat f)
  59. {
  60.   double x;
  61.   unsigned e = (f >> 16) - 16;
  62.   if ((f & 0xFFFF) == 0)
  63.     return 0;
  64.   x = f & 0xFFFF;
  65.   while (e > MF_EXP_BIAS)
  66.     x *= 2, --e;
  67.   while (e < MF_EXP_BIAS)
  68.     x /= 2, ++e;
  69.   return x;
  70. }
  71.  
  72. int main(void)
  73. {
  74.   double testConvData[] = { 1e-18, .25, 0.3333333, .5, 1, 2, 3.141593, 1e18 };
  75.   unsigned i;
  76.   for (i = 0; i < sizeof(testConvData) / sizeof(testConvData[0]); i++)
  77.     printf("%e -> 0x%06lX -> %e\n",
  78.            testConvData[i],
  79.            (unsigned long)double2mf(testConvData[i]),
  80.            mf2double(double2mf(testConvData[i])));
  81.  
  82.   printf("300 * 5 = %e\n", mf2double(mfmul(double2mf(300),double2mf(5))));
  83.   printf("500 + 3 = %e\n", mf2double(mfadd(double2mf(500),double2mf(3))));
  84.   printf("1e18 * 1e-18 = %e\n", mf2double(mfmul(double2mf(1e18),double2mf(1e-18))));
  85.   printf("1e-18 + 2e-18 = %e\n", mf2double(mfadd(double2mf(1e-18),double2mf(2e-18))));
  86.   printf("1e-16 + 1e-18 = %e\n", mf2double(mfadd(double2mf(1e-16),double2mf(1e-18))));
  87.  
  88.   return 0;
  89. }
  90.  
Success #stdin #stdout 0s 1832KB
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stdin
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Standard input is empty
stdout
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1.000000e-18 -> 0x459392 -> 9.999753e-19
2.500000e-01 -> 0x7F8000 -> 2.500000e-01
3.333333e-01 -> 0x7FAAAA -> 3.333282e-01
5.000000e-01 -> 0x808000 -> 5.000000e-01
1.000000e+00 -> 0x818000 -> 1.000000e+00
2.000000e+00 -> 0x828000 -> 2.000000e+00
3.141593e+00 -> 0x82C90F -> 3.141541e+00
1.000000e+18 -> 0xBCDE0B -> 9.999926e+17
300 * 5 = 1.500000e+03
500 + 3 = 5.030000e+02
1e18 * 1e-18 = 9.999390e-01
1e-18 + 2e-18 = 2.999926e-18
1e-16 + 1e-18 = 1.009985e-16
https://ideone.com/HhRmUR
language:
C99 (gcc 8.3)
created:
12 years ago
visibility:
public

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