insufficient algorithm
From: Sameh Halabi (smabeer_at_yahoo.com)
Date: 08/01/04
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Date: 1 Aug 2004 07:04:20 -0700
Hello .
I'm trying to create a 12 digit number which will be as much unique as
possible . for that I created 2 algorithms , the first one (which I
bring here first ) gave a max 11 digit number with output numbers
repeating themselves of about 20 times for a million tries .
then I created another algorithm which gave me an exact 12 digit
number with numbers repeating themselves of 0 times for a million
tries , but the problem with it was that it was about 6 times slower
than the first . performance is important for me . do anybody have any
idea how to make the 2nd algorithm more sufficient or to reduce
duplicates in the 1st one :
first algorithm :
=================
#define SEQ_L 9
#define FTRCD_C_L 6
#define DATE_C_L 8
int Mpgn_gt_hash_seq (unsigned long i_soc_seq_no,
char * i_feature_code,
char * i_eff_date,
unsigned long *o_calculated_seq)
{
char sKey[SEQ_L+FTRCD_C_L+DATE_C_L+1];
char* sKeyPtr;
double nHash=0;
double maxNum=999999999999;
memset(sKey,0,SEQ_L+FTRCD_C_L+DATE_C_L+1);
/* Make sure i_feature_code is padded with trailing spaces
to ensure consistency */
for (int i=0; i<FTRCD_C_L ; i++)
if (i_feature_code[i]<'!' || i_feature_code[i]>'z')
i_feature_code[i]=' ';
/* Format sKey - copy input params as strings*/
sprintf (sKey,"%.9d%.6s%.8s",i_soc_seq_no, i_feature_code,
i_eff_date);
/* Hash Algorithm */
nHash=*sKey;
sKeyPtr=sKey;
while (*sKeyPtr++)
{
nHash=((unsigned long)nHash<<7) + nHash + *sKeyPtr;
/* Ensure 12 digit value */
if (nHash>maxNum)
{
nHash=nHash-(maxNum*(unsigned long)(nHash/maxNum));
}
}
*o_calculated_seq=(long)nHash;
return SUCCESS;
}
in this algorithm I had also a problem with compilation getting
warnings for line << if (nHash>maxNum) >> , that variable exceeds max
size of C .
second algorithm :
==================
#define SEQ_L 9
#define FTRCD_C_L 6
#define DATE_C_L 8
int Mpgn_gt_hash_seq (unsigned long i_soc_seq_no,
char * i_feature_code,
char * i_eff_date,
unsigned long *o_calculated_seq)
{
char sKey[SEQ_L+FTRCD_C_L+DATE_C_L+1];
char* sKeyPtr;
double nHash=0;
char strNum[SEQ_L+FTRCD_C_L+DATE_C_L];
int len=0;
memset(sKey,0,SEQ_L+FTRCD_C_L+DATE_C_L+1);
/* Make sure i_feature_code is padded with trailing spaces
to ensure consistency */
for (int i=0; i<FTRCD_C_L ; i++)
if (i_feature_code[i]<'!' || i_feature_code[i]>'z')
i_feature_code[i]=' ';
/* Format sKey - copy input params as strings */
sprintf (sKey,"%.9d%.6s%.8s",i_soc_seq_no,i_feature_code,i_eff_date);
/* Hash Algorithm */
nHash=*sKey;
sKeyPtr=sKey;
sprintf(strNum,"%.0f\0",nHash);
while (*sKeyPtr++)
{
nHash=((unsigned long)nHash<<7) + nHash + *sKeyPtr;
sprintf(strNum,"%.0f\0",nHash);
/* Ensure 12 digit value */
len = strlen(strNum);
if (len>12)
{
strncpy(strNum,&strNum[len-12-1],12);
}
nHash = atof(strNum);
}
*o_calculated_seq=(long)nHash;
return SUCCESS;
}
as I said , this algorithm worked fine , but it was much slower than
the first .
please your assistance .
Thank you very much
Sameh .
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