76 lines
1.0 KiB
C++
76 lines
1.0 KiB
C++
// Bignum square root
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#include "stdafx.h"
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#include "defs.h"
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#if 0 // not used anymore
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unsigned int *
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msqrt(unsigned int *n)
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{
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int i, k, kk;
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unsigned int m, *x, *y;
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if (MLENGTH(n) == 1 && n[0] == 0) {
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x = mint(0);
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return x;
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}
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// count number of bits
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k = 32 * (MLENGTH(n) - 1);
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m = n[MLENGTH(n) - 1];
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while (m) {
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m >>= 1;
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k++;
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}
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k = (k - 1) / 2;
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// initial guess
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kk = k / 32 + 1;
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x = mnew(kk);
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MSIGN(x) = 1;
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MLENGTH(x) = kk;
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for (i = 0; i < kk; i++)
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x[i] = 0;
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mp_set_bit(x, k);
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while (--k >= 0) {
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mp_set_bit(x, k);
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y = mmul(x, x);
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if (mcmp(y, n) == 1)
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mp_clr_bit(x, k);
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mfree(y);
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}
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return x;
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}
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void
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test_msqrt(void)
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{
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int i;
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unsigned int *n, *x, *y;
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logout("testing msqrt\n");
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for (i = 0; i < 1000000; i++) {
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n = mint(i);
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x = msqrt(n);
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y = mint((int) (sqrt((double) i) + 1e-10));
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if (mcmp(x, y) != 0) {
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sprintf(logbuf, "failed for %d got %u\n", i, x[0]);
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logout(logbuf);
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errout();
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}
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mfree(n);
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mfree(x);
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mfree(y);
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}
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logout("ok\n");
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}
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#endif
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