mirror of
https://github.com/levinsv/pgadmin3.git
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138 lines
3.4 KiB
C++
138 lines
3.4 KiB
C++
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/*
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* M_APM - mapm_log.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 the LOG and LOG10 functions.
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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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/****************************************************************************/
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/*
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Calls the LOG function. The formula used is :
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log10(x) = A * log(x) where A = log (e) [0.43429448190325...]
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10
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*/
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void m_apm_log10(M_APM rr, int places, M_APM aa)
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{
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int dplaces;
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M_APM tmp8, tmp9;
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tmp8 = M_get_stack_var();
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tmp9 = M_get_stack_var();
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dplaces = places + 4;
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M_check_log_places(dplaces + 45);
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m_apm_log(tmp9, dplaces, aa);
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m_apm_multiply(tmp8, tmp9, MM_lc_log10R);
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m_apm_round(rr, places, tmp8);
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M_restore_stack(2); /* restore the 2 locals we used here */
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}
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/****************************************************************************/
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void m_apm_log(M_APM r, int places, M_APM a)
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{
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M_APM tmp0, tmp1, tmp2;
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int mexp, dplaces;
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if (a->m_apm_sign <= 0)
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{
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M_apm_log_error_msg(M_APM_RETURN, "\'m_apm_log\', Negative argument");
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M_set_to_zero(r);
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return;
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}
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tmp0 = M_get_stack_var();
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tmp1 = M_get_stack_var();
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tmp2 = M_get_stack_var();
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dplaces = places + 8;
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/*
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* if the input is real close to 1, use the series expansion
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* to compute the log.
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*
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* 0.9999 < a < 1.0001
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*/
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mexp = a->m_apm_exponent;
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if (mexp == 0 || mexp == 1)
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{
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m_apm_subtract(tmp0, a, MM_One);
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if (tmp0->m_apm_sign == 0) /* is input exactly 1 ?? */
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{
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/* if so, result is 0 */
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M_set_to_zero(r);
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M_restore_stack(3);
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return;
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}
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if (tmp0->m_apm_exponent <= -4)
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{
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M_log_near_1(r, places, tmp0);
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M_restore_stack(3);
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return;
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}
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}
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/* make sure our log(10) is accurate enough for this calculation */
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/* (and log(2) which is called from M_log_basic_iteration) */
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M_check_log_places(dplaces + 25);
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if (abs(mexp) <= 3)
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{
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M_log_basic_iteration(r, places, a);
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}
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else
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{
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/*
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* use log (x * y) = log(x) + log(y)
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*
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* here we use y = exponent of our base 10 number.
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*
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* let 'C' = log(10) = 2.3025850929940....
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*
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* then log(x * y) = log(x) + ( C * base_10_exponent )
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*/
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m_apm_copy(tmp2, a);
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mexp = tmp2->m_apm_exponent - 2;
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tmp2->m_apm_exponent = 2; /* force number between 10 & 100 */
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M_log_basic_iteration(tmp0, dplaces, tmp2);
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m_apm_set_long(tmp1, (long)mexp);
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m_apm_multiply(tmp2, tmp1, MM_lc_log10);
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m_apm_add(tmp1, tmp2, tmp0);
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m_apm_round(r, places, tmp1);
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}
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M_restore_stack(3); /* restore the 3 locals we used here */
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}
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/****************************************************************************/
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