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https://github.com/levinsv/pgadmin3.git
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131 lines
3 KiB
C++
131 lines
3 KiB
C++
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/*
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* M_APM - mapm_mul.c
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*
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* Copyright (C) 1999 - 2007 Michael C. Ring
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*
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* Permission to use, copy, and distribute this software and its
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* documentation for any purpose with or without fee is hereby granted,
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* provided that the above copyright notice appear in all copies and
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* that both that copyright notice and this permission notice appear
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* in supporting documentation.
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*
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* Permission to modify the software is granted. Permission to distribute
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* the modified code is granted. Modifications are to be distributed by
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* using the file 'license.txt' as a template to modify the file header.
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* 'license.txt' is available in the official MAPM distribution.
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*
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* This software is provided "as is" without express or implied warranty.
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*/
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/*
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*
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* This file contains basic multiplication function.
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*
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*/
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#include "pgAdmin3.h"
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#include "pgscript/utilities/mapm-lib/m_apm_lc.h"
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extern void M_fast_multiply(M_APM, M_APM, M_APM);
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/****************************************************************************/
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void m_apm_multiply(M_APM r, M_APM a, M_APM b)
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{
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int ai, itmp, sign, nexp, ii, jj, indexa, indexb, index0, numdigits;
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UCHAR *cp, *cpr, *cp_div, *cp_rem;
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void *vp;
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sign = a->m_apm_sign * b->m_apm_sign;
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nexp = a->m_apm_exponent + b->m_apm_exponent;
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if (sign == 0) /* one number is zero, result is zero */
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{
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M_set_to_zero(r);
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return;
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}
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numdigits = a->m_apm_datalength + b->m_apm_datalength;
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indexa = (a->m_apm_datalength + 1) >> 1;
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indexb = (b->m_apm_datalength + 1) >> 1;
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/*
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* If we are multiplying 2 'big' numbers, use the fast algorithm.
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*
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* This is a **very** approx break even point between this algorithm
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* and the FFT multiply. Note that different CPU's, operating systems,
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* and compiler's may yield a different break even point. This point
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* (~96 decimal digits) is how the test came out on the author's system.
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*/
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if (indexa >= 48 && indexb >= 48)
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{
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M_fast_multiply(r, a, b);
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return;
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}
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ii = (numdigits + 1) >> 1; /* required size of result, in bytes */
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if (ii > r->m_apm_malloclength)
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{
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if ((vp = MAPM_REALLOC(r->m_apm_data, (ii + 32))) == NULL)
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{
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/* fatal, this does not return */
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M_apm_log_error_msg(M_APM_FATAL, "\'m_apm_multiply\', Out of memory");
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}
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r->m_apm_malloclength = ii + 28;
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r->m_apm_data = (UCHAR *)vp;
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}
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M_get_div_rem_addr(&cp_div, &cp_rem);
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index0 = indexa + indexb;
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cp = r->m_apm_data;
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memset(cp, 0, index0);
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ii = indexa;
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while (TRUE)
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{
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index0--;
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cpr = cp + index0;
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jj = indexb;
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ai = (int)a->m_apm_data[--ii];
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while (TRUE)
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{
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itmp = ai * b->m_apm_data[--jj];
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*(cpr - 1) += cp_div[itmp];
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*cpr += cp_rem[itmp];
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if (*cpr >= 100)
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{
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*cpr -= 100;
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*(cpr - 1) += 1;
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}
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cpr--;
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if (*cpr >= 100)
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{
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*cpr -= 100;
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*(cpr - 1) += 1;
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}
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if (jj == 0)
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break;
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}
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if (ii == 0)
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break;
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}
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r->m_apm_sign = sign;
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r->m_apm_exponent = nexp;
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r->m_apm_datalength = numdigits;
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M_apm_normalize(r);
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}
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/****************************************************************************/
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