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allow number of exponent bits to be adjustable

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This commit is contained in:
Jeff Wang 2019-05-01 01:37:14 -04:00
parent 4b87ad27c8
commit 58a162fe4d
4 changed files with 62 additions and 21 deletions
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4
src/calc.c
View File

@ -25,7 +25,7 @@ static void pop(){
StackPtr++; //adjust pointer StackPtr++; //adjust pointer
} }
void push_decn(const char* signif_str, int8_t exponent, uint8_t no_lift){ void push_decn(const char* signif_str, exp_t exponent, uint8_t no_lift){
if (!no_lift){ if (!no_lift){
StackPtr--; StackPtr--;
} }
@ -36,7 +36,7 @@ void clear_x(void){
set_dec80_zero(&stack(STACK_X)); set_dec80_zero(&stack(STACK_X));
} }
void set_x(const char* signif_str, int8_t exponent){ void set_x(const char* signif_str, exp_t exponent){
build_dec80(&stack(STACK_X), signif_str, exponent); build_dec80(&stack(STACK_X), signif_str, exponent);
} }

4
src/calc.h
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@ -16,10 +16,10 @@ extern "C" {
void process_cmd(char cmd); void process_cmd(char cmd);
void push_decn(const char* signif_str, int8_t exponent, uint8_t no_lift); void push_decn(const char* signif_str, exp_t exponent, uint8_t no_lift);
void clear_x(void); void clear_x(void);
void set_x(const char* signif_str, int8_t exponent); void set_x(const char* signif_str, exp_t exponent);
__xdata dec80* get_x(void); __xdata dec80* get_x(void);
__xdata dec80* get_y(void); __xdata dec80* get_y(void);

57
src/decn/decn.c
View File

@ -53,21 +53,37 @@ void copy_decn(dec80* dest, const dec80* src){
} }
} }
int8_t get_exponent(const dec80* x){ exp_t get_exponent(const dec80* x){
int8_t exponent = x->exponent; exp_t exponent = x->exponent;
#ifdef EXP16
if (exponent & 0x4000){ //negative
return exponent | 0x8000;
} else { //positive
return exponent & 0x7fff;
}
#else
if (exponent & 0x40){ //negative if (exponent & 0x40){ //negative
return exponent | 0x80; return exponent | 0x80;
} else { //positive } else { //positive
return exponent & 0x7f; return exponent & 0x7f;
} }
#endif
} }
void set_exponent(dec80* acc, int8_t exponent, uint8_t num_is_neg){ static void set_exponent(dec80* acc, exp_t exponent, uint8_t num_is_neg){
#ifdef EXP16
if (num_is_neg){
exponent |= 0x8000;
} else {
exponent &= 0x7fff;
}
#else
if (num_is_neg){ if (num_is_neg){
exponent |= 0x80; exponent |= 0x80;
} else { } else {
exponent &= 0x7f; exponent &= 0x7f;
} }
#endif
acc->exponent = exponent; acc->exponent = exponent;
} }
@ -103,7 +119,7 @@ static void shift_left(dec80* x){
static void remove_leading_zeros(dec80* x){ static void remove_leading_zeros(dec80* x){
uint8_t digit100; uint8_t digit100;
uint8_t is_negative = (x->exponent < 0); uint8_t is_negative = (x->exponent < 0);
int8_t exponent = get_exponent(x); exp_t exponent = get_exponent(x);
//find first non-zero digit100 //find first non-zero digit100
for (digit100 = 0; digit100 < DEC80_NUM_LSU; digit100++){ for (digit100 = 0; digit100 < DEC80_NUM_LSU; digit100++){
@ -133,7 +149,7 @@ static void remove_leading_zeros(dec80* x){
set_exponent(x, exponent, is_negative); set_exponent(x, exponent, is_negative);
} }
void build_dec80(dec80* dest, const char* signif_str, int8_t exponent){ void build_dec80(dec80* dest, const char* signif_str, exp_t exponent){
enum { enum {
SIGN_ZERO, SIGN_ZERO,
SIGN_ZERO_SEEN_POINT, SIGN_ZERO_SEEN_POINT,
@ -341,7 +357,11 @@ static uint8_t decn_is_zero(const dec80* x){
uint8_t decn_is_nan(const dec80* x){ uint8_t decn_is_nan(const dec80* x){
uint8_t i; uint8_t i;
if (x->exponent & 0x7f != DEC80_NAN_EXP){ #ifdef EXP16
if ((x->exponent & 0x7fff) != DEC80_NAN_EXP){
#else
if ((x->exponent & 0x7f) != DEC80_NAN_EXP){
#endif
return 0; return 0;
} }
for (i = 0; i < DEC80_NUM_LSU; i++){ for (i = 0; i < DEC80_NUM_LSU; i++){
@ -366,13 +386,17 @@ void set_dec80_NaN(dec80* dest){
#endif #endif
void negate_decn(dec80* x){ void negate_decn(dec80* x){
static const int8_t xor_val = -(0x7f) - 1; #ifdef EXP16
static const exp_t xor_val = -(0x7fff) - 1;
#else
static const exp_t xor_val = -(0x7f) - 1;
#endif
(x->exponent) ^= xor_val; (x->exponent) ^= xor_val;
} }
int8_t compare_magn(const dec80* a, const dec80* b){ //a<b: -1, a==b: 0, a>b: 1 int8_t compare_magn(const dec80* a, const dec80* b){ //a<b: -1, a==b: 0, a>b: 1
uint8_t a_i, b_i; uint8_t a_i, b_i;
int8_t a_exp=0, b_exp=0; exp_t a_exp=0, b_exp=0;
int8_t a_signif_b = 0; //a<b: -1, a==b: 0, a>b: 1 int8_t a_signif_b = 0; //a<b: -1, a==b: 0, a>b: 1
static __xdata dec80 a_tmp, b_tmp; static __xdata dec80 a_tmp, b_tmp;
//copy //copy
@ -460,8 +484,8 @@ int8_t compare_decn(const dec80* a, const dec80* b){ //a<b: -1, a==b: 0, a>b: 1
//acc and the number from which exponent was taken MUST be stripped of leading 0s first //acc and the number from which exponent was taken MUST be stripped of leading 0s first
//rescales acc up to exponent (increase exponent of acc, while shifting right) //rescales acc up to exponent (increase exponent of acc, while shifting right)
//the actual value of acc->exponent remains unchanged //the actual value of acc->exponent remains unchanged
static void _incr_exp(dec80* acc, int8_t exponent){ static void _incr_exp(dec80* acc, exp_t exponent){
int8_t curr_exp = get_exponent(acc); exp_t curr_exp = get_exponent(acc);
#ifdef DEBUG_ADD #ifdef DEBUG_ADD
uint8_t is_neg = (acc->exponent < 0); uint8_t is_neg = (acc->exponent < 0);
printf(" (is_neg,curr_exp,exponent)=(%d,%d,%d)\n", printf(" (is_neg,curr_exp,exponent)=(%d,%d,%d)\n",
@ -612,7 +636,7 @@ void add_decn(dec80* acc, const dec80* x){
} }
//may need to rescale number //may need to rescale number
if (carry > 0){ if (carry > 0){
int8_t curr_exp = get_exponent(acc); exp_t curr_exp = get_exponent(acc);
rel = (acc->exponent < 0); //is_neg? rel = (acc->exponent < 0); //is_neg?
#ifdef DEBUG_ADD #ifdef DEBUG_ADD
printf(" carry out: %d", carry); printf(" carry out: %d", carry);
@ -639,7 +663,7 @@ void mult_decn(dec80* acc, const dec80* x){
int8_t i, j; int8_t i, j;
uint8_t carry = 0; uint8_t carry = 0;
uint8_t is_neg; uint8_t is_neg;
int8_t new_exponent; exp_t new_exponent;
//initialize values //initialize values
copy_decn(&tmp, x); copy_decn(&tmp, x);
set_dec80_zero(&acc_tmp); set_dec80_zero(&acc_tmp);
@ -647,7 +671,11 @@ void mult_decn(dec80* acc, const dec80* x){
remove_leading_zeros(acc); remove_leading_zeros(acc);
remove_leading_zeros(&tmp); remove_leading_zeros(&tmp);
//store new sign //store new sign
#ifdef EXP16
if ((acc->exponent & 0x8000) ^ (tmp.exponent & 0x8000)){ //signs differ
#else
if ((acc->exponent & 0x80) ^ (tmp.exponent & 0x80)){ //signs differ if ((acc->exponent & 0x80) ^ (tmp.exponent & 0x80)){ //signs differ
#endif
is_neg = 1; is_neg = 1;
} else { } else {
is_neg = 0; is_neg = 0;
@ -726,7 +754,7 @@ void div_decn(dec80* acc, const dec80* x){
static __xdata dec80 tmp; //copy of x, holds current 1/x estimate static __xdata dec80 tmp; //copy of x, holds current 1/x estimate
static __xdata dec80 acc_copy; //holds copy of original acc static __xdata dec80 acc_copy; //holds copy of original acc
uint8_t i; uint8_t i;
int8_t initial_exp; exp_t initial_exp;
//check divide by zero //check divide by zero
#ifdef EXTRA_CHECKS #ifdef EXTRA_CHECKS
if (decn_is_zero(x)){ if (decn_is_zero(x)){
@ -800,7 +828,7 @@ int8_t decn_to_str(char* buf, const dec80* x){
#define INSERT_DOT() buf[i++]='.' #define INSERT_DOT() buf[i++]='.'
uint8_t i = 0; uint8_t i = 0;
uint8_t digit100; uint8_t digit100;
int8_t exponent = 0; exp_t exponent = 0;
uint8_t trailing_zeros = 0; uint8_t trailing_zeros = 0;
uint8_t use_sci = 0; uint8_t use_sci = 0;
static __xdata dec80 tmp; static __xdata dec80 tmp;
@ -923,6 +951,7 @@ int8_t decn_to_str(char* buf, const dec80* x){
#endif #endif
//print exponent //print exponent
if (use_sci){ if (use_sci){
//check for overflow
if (exponent > DEC80_MAX_EXP || exponent < DEC80_MIN_EXP){ if (exponent > DEC80_MAX_EXP || exponent < DEC80_MIN_EXP){
set_str_error(buf); set_str_error(buf);
return 0; return 0;

18
src/decn/decn.h
View File

@ -16,15 +16,27 @@ extern "C" {
#define DEC80_NUM_LSU 9 #define DEC80_NUM_LSU 9
//#define EXP16
#ifdef EXP16
typedef int16_t exp_t;
//allow full range, but reserve -16384 for special numbers
#define DEC80_MIN_EXP (-16383)
#define DEC80_MAX_EXP 16383
#define DEC80_NAN_EXP (-16383 - 1)
#else
typedef int8_t exp_t;
//allow full range, but reserve -128 for special numbers //allow full range, but reserve -128 for special numbers
#define DEC80_MIN_EXP (-63) #define DEC80_MIN_EXP (-63)
#define DEC80_MAX_EXP 63 #define DEC80_MAX_EXP 63
#define DEC80_NAN_EXP (-63 - 1) //-64 #define DEC80_NAN_EXP (-63 - 1) //-64
#endif
//decimal80 unpacked into 80 bits //decimal80 unpacked into 80 bits
// for computation // for computation
typedef struct { typedef struct {
int8_t exponent; //MSBit is sign of dec80 number, bottom 15 bits are 2's Compl exponent exp_t exponent; //MSBit is sign of dec80 number, bottom 15 or 7 bits are 2's Compl exponent
uint8_t lsu[DEC80_NUM_LSU]; //lsu[0] holds most-significant 2 digits (base 100) uint8_t lsu[DEC80_NUM_LSU]; //lsu[0] holds most-significant 2 digits (base 100)
//implicit decimal point between (lsu[0]/10) and (lsu[0]%10) //implicit decimal point between (lsu[0]/10) and (lsu[0]%10)
} dec80; } dec80;
@ -36,13 +48,13 @@ static const dec80 DECN_1 = {
}; };
//remove sign bit, and return 15 bit exponent sign-extended to 16 bits //remove sign bit, and return 15 bit exponent sign-extended to 16 bits
int8_t get_exponent(const dec80* x); exp_t get_exponent(const dec80* x);
//void dec64to80(dec80* dest, const dec64* src); //void dec64to80(dec80* dest, const dec64* src);
void copy_decn(dec80* dest, const dec80* src); void copy_decn(dec80* dest, const dec80* src);
void build_dec80(dec80* dest, const char* signif_str, int8_t exponent); void build_dec80(dec80* dest, const char* signif_str, exp_t exponent);
void set_dec80_zero(dec80* dest); void set_dec80_zero(dec80* dest);
void set_dec80_NaN(dec80* dest); void set_dec80_NaN(dec80* dest);