forked from szvictdb/sqlite
-
Notifications
You must be signed in to change notification settings - Fork 1
Expand file tree
/
Copy pathlogest.c
More file actions
170 lines (164 loc) · 4.77 KB
/
logest.c
File metadata and controls
170 lines (164 loc) · 4.77 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
/*
** 2013-06-10
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains a simple command-line utility for converting from
** integers and LogEst values and back again and for doing simple
** arithmetic operations (multiple and add) on LogEst values.
**
** Usage:
**
** ./LogEst ARGS
**
** See the showHelp() routine for a description of valid arguments.
** Examples:
**
** To convert 123 from LogEst to integer:
**
** ./LogEst ^123
**
** To convert 123456 from integer to LogEst:
**
** ./LogEst 123456
**
*/
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <assert.h>
#include <string.h>
#include "sqlite3.h"
typedef short int LogEst; /* 10 times log2() */
LogEst logEstMultiply(LogEst a, LogEst b){ return a+b; }
LogEst logEstAdd(LogEst a, LogEst b){
static const unsigned char x[] = {
10, 10, /* 0,1 */
9, 9, /* 2,3 */
8, 8, /* 4,5 */
7, 7, 7, /* 6,7,8 */
6, 6, 6, /* 9,10,11 */
5, 5, 5, /* 12-14 */
4, 4, 4, 4, /* 15-18 */
3, 3, 3, 3, 3, 3, /* 19-24 */
2, 2, 2, 2, 2, 2, 2, /* 25-31 */
};
if( a<b ){ LogEst t = a; a = b; b = t; }
if( a>b+49 ) return a;
if( a>b+31 ) return a+1;
return a+x[a-b];
}
LogEst logEstFromInteger(sqlite3_uint64 x){
static LogEst a[] = { 0, 2, 3, 5, 6, 7, 8, 9 };
LogEst y = 40;
if( x<8 ){
if( x<2 ) return 0;
while( x<8 ){ y -= 10; x <<= 1; }
}else{
while( x>255 ){ y += 40; x >>= 4; }
while( x>15 ){ y += 10; x >>= 1; }
}
return a[x&7] + y - 10;
}
static sqlite3_uint64 logEstToInt(LogEst x){
sqlite3_uint64 n;
if( x<10 ) return 1;
n = x%10;
x /= 10;
if( n>=5 ) n -= 2;
else if( n>=1 ) n -= 1;
if( x>=3 ) return (n+8)<<(x-3);
return (n+8)>>(3-x);
}
static LogEst logEstFromDouble(double x){
sqlite3_uint64 a;
LogEst e;
assert( sizeof(x)==8 && sizeof(a)==8 );
if( x<=0.0 ) return -32768;
if( x<0.01 ) return -logEstFromDouble(1.0/x);
if( x<1.0 ) return logEstFromDouble(100.0*x) - 66;
if( x<1024.0 ) return logEstFromInteger((sqlite3_uint64)(1024.0*x)) - 100;
if( x<=2000000000.0 ) return logEstFromInteger((sqlite3_uint64)x);
memcpy(&a, &x, 8);
e = (a>>52) - 1022;
return e*10;
}
int isInteger(const char *z){
while( z[0]>='0' && z[0]<='9' ) z++;
return z[0]==0;
}
int isFloat(const char *z){
char c;
while( ((c=z[0])>='0' && c<='9') || c=='.' || c=='E' || c=='e'
|| c=='+' || c=='-' ) z++;
return z[0]==0;
}
static void showHelp(const char *zArgv0){
printf("Usage: %s ARGS...\n", zArgv0);
printf("Arguments:\n"
" NUM Convert NUM from integer to LogEst and push onto the stack\n"
" ^NUM Interpret NUM as a LogEst and push onto stack\n"
" x Multiple the top two elements of the stack\n"
" + Add the top two elements of the stack\n"
" dup Dupliate the top element on the stack\n"
" inv Take the reciprocal of the top of stack. N = 1/N.\n"
" log Find the LogEst of the number on top of stack\n"
" nlogn Compute NlogN where N is the top of stack\n"
);
exit(1);
}
int main(int argc, char **argv){
int i;
int n = 0;
LogEst a[100];
for(i=1; i<argc; i++){
const char *z = argv[i];
if( strcmp(z,"+")==0 ){
if( n>=2 ){
a[n-2] = logEstAdd(a[n-2],a[n-1]);
n--;
}
}else if( strcmp(z,"x")==0 ){
if( n>=2 ){
a[n-2] = logEstMultiply(a[n-2],a[n-1]);
n--;
}
}else if( strcmp(z,"dup")==0 ){
if( n>0 ){
a[n] = a[n-1];
n++;
}
}else if( strcmp(z,"log")==0 ){
if( n>0 ) a[n-1] = logEstFromInteger(a[n-1]) - 33;
}else if( strcmp(z,"nlogn")==0 ){
if( n>0 ) a[n-1] += logEstFromInteger(a[n-1]) - 33;
}else if( strcmp(z,"inv")==0 ){
if( n>0 ) a[n-1] = -a[n-1];
}else if( z[0]=='^' ){
a[n++] = (LogEst)atoi(z+1);
}else if( isInteger(z) ){
a[n++] = logEstFromInteger(atoi(z));
}else if( isFloat(z) && z[0]!='-' ){
a[n++] = logEstFromDouble(atof(z));
}else{
showHelp(argv[0]);
}
}
for(i=n-1; i>=0; i--){
if( a[i]<-40 ){
printf("%5d (%f)\n", a[i], 1.0/(double)logEstToInt(-a[i]));
}else if( a[i]<10 ){
printf("%5d (%f)\n", a[i], logEstToInt(a[i]+100)/1024.0);
}else{
sqlite3_uint64 x = logEstToInt(a[i]+100)*100/1024;
printf("%5d (%lld.%02lld)\n", a[i], x/100, x%100);
}
}
return 0;
}