45 lines
841 B
C
45 lines
841 B
C
#include <assert.h>
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#include <math.h>
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#include <limits.h>
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/* Access bit-level representation of floating-point number */
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typedef unsigned float_bits;
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/* computs 0.5*f. If f is NaN, then return f. */
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float_bits float_half(float_bits uf) {
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float_bits s = uf & 0x80000000U, f = uf & 0x007FFFFF, e = (uf >> 23) & 0xFF;
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if (e == 0xFFU) {
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return uf;
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}
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if (e > 1) {
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e = e - 1;
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return s | (e << 23) | f;
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}
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if (e == 1) {
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f = f | (1 << 23);
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e = 0;
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}
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int t = f;
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f = f >> 1;
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if (t & f & 1) {
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f = f + 1;
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}
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return s | (e << 23) | f;
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}
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int main() {
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for (float_bits x = 0; ; x = x + 1) {
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float *a = (float*) &x;
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float b = 0.5 * *a;
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float_bits c = float_half(x);
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float *d = (float*) &c;
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assert(b == *d || (isnan(b) && isnan(*d)));
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if (x == UINT_MAX) {
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break;
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}
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}
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} |