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do not require BDecn to be preserved (frees up some xdata and code space)

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This commit is contained in:
Jeff Wang 2019-05-02 03:49:21 -04:00
parent 0049f3df98
commit 52ddf7dd96
2 changed files with 45 additions and 48 deletions
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91
src/decn/decn.c
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@ -44,7 +44,7 @@ static const uint8_t num_digits_display = 16;
#endif
__idata dec80 AccDecn, BDecn;
__idata dec80 TmpDecn;
__xdata char Buf[DECN_BUF_SIZE];
@ -518,7 +518,7 @@ static void sub_mag(dec80* acc, const dec80* x){
_incr_exp(&tmp, get_exponent(acc));
}
#ifdef DEBUG_ADD
decn_to_str_complete(Buf, &tmp);
decn_to_str_complete(&tmp);
printf(" incr_exp tmp: %s\n", Buf);
#endif
//do subtraction
@ -538,7 +538,6 @@ static void sub_mag(dec80* acc, const dec80* x){
}
void add_decn(void){
static __xdata dec80 tmp;
int8_t rel;
uint8_t carry = 0;
int8_t i;
@ -564,9 +563,9 @@ void add_decn(void){
#ifdef DEBUG_ADD
printf("|-acc| < |+x|\n");
#endif
copy_decn(&tmp, &BDecn);
sub_mag(&tmp, &AccDecn);
copy_decn(&AccDecn, &tmp);
copy_decn(&TmpDecn, &BDecn);
sub_mag(&TmpDecn, &AccDecn);
copy_decn(&AccDecn, &TmpDecn);
return;
} else { //equal
#ifdef DEBUG_ADD
@ -588,9 +587,9 @@ void add_decn(void){
#ifdef DEBUG_ADD
printf("|+acc| < |-x|\n");
#endif
copy_decn(&tmp, &BDecn);
sub_mag(&tmp, &AccDecn);
copy_decn(&AccDecn, &tmp);
copy_decn(&TmpDecn, &BDecn);
sub_mag(&TmpDecn, &AccDecn);
copy_decn(&AccDecn, &TmpDecn);
return;
} else { //equal
#ifdef DEBUG_ADD
@ -601,34 +600,33 @@ void add_decn(void){
}
}
//signs must now be the same, begin adding
copy_decn(&tmp, &BDecn);
//normalize
remove_leading_zeros(&AccDecn);
remove_leading_zeros(&tmp);
remove_leading_zeros(&BDecn);
#ifdef DEBUG_ADD
decn_to_str_complete(Buf, &AccDecn);
decn_to_str_complete(&AccDecn);
printf(" rem_leading_zeros acc: %s\n", Buf);
decn_to_str_complete(Buf, &tmp);
decn_to_str_complete(&BDecn);
printf(" rem_leading_zeros tmp: %s\n", Buf);
#endif
if (get_exponent(&AccDecn) > get_exponent(&tmp)){
_incr_exp(&tmp, get_exponent(&AccDecn));
} else if (get_exponent(&AccDecn) < get_exponent(&tmp)){
if (get_exponent(&AccDecn) > get_exponent(&BDecn)){
_incr_exp(&BDecn, get_exponent(&AccDecn));
} else if (get_exponent(&AccDecn) < get_exponent(&BDecn)){
//shift significand and adjust exponent to match
for (i = 0; i < get_exponent(&tmp) - get_exponent(&AccDecn); i++){
for (i = 0; i < get_exponent(&BDecn) - get_exponent(&AccDecn); i++){
shift_right(&AccDecn);
}
set_exponent(&AccDecn, get_exponent(&tmp), (AccDecn.exponent < 0));
set_exponent(&AccDecn, get_exponent(&BDecn), (AccDecn.exponent < 0));
}
#ifdef DEBUG_ADD
decn_to_str_complete(Buf, &AccDecn);
decn_to_str_complete(&AccDecn);
printf(" incr_exp acc: %s\n", Buf);
decn_to_str_complete(Buf, &tmp);
decn_to_str_complete(&BDecn);
printf(" incr_exp tmp: %s\n", Buf);
#endif
//do addition
for (i = DEC80_NUM_LSU - 1; i >= 0; i--){
uint8_t digit100 = AccDecn.lsu[i] + tmp.lsu[i] + carry;
uint8_t digit100 = AccDecn.lsu[i] + BDecn.lsu[i] + carry;
AccDecn.lsu[i] = digit100 % 100;
carry = digit100 / 100;
assert(carry < 100);
@ -657,30 +655,27 @@ void add_decn(void){
}
void mult_decn(void){
static __xdata dec80 tmp; //copy of x
static __xdata dec80 acc_tmp; //holds sum
int8_t i, j;
uint8_t carry = 0;
uint8_t is_neg;
exp_t new_exponent;
//initialize values
copy_decn(&tmp, &BDecn);
set_dec80_zero(&acc_tmp);
set_dec80_zero(&TmpDecn);
//normalize
remove_leading_zeros(&AccDecn);
remove_leading_zeros(&tmp);
remove_leading_zeros(&BDecn);
//store new sign
#ifdef EXP16
if ((AccDecn.exponent & 0x8000) ^ (tmp.exponent & 0x8000)){ //signs differ
if ((AccDecn.exponent & 0x8000) ^ (BDecn.exponent & 0x8000)){ //signs differ
#else
if ((AccDecn.exponent & 0x80) ^ (tmp.exponent & 0x80)){ //signs differ
if ((AccDecn.exponent & 0x80) ^ (BDecn.exponent & 0x80)){ //signs differ
#endif
is_neg = 1;
} else {
is_neg = 0;
}
//calculate new exponent
new_exponent = get_exponent(&AccDecn) + get_exponent(&tmp);
new_exponent = get_exponent(&AccDecn) + get_exponent(&BDecn);
#ifdef DEBUG_MULT
printf("\n new exponent: %d:", new_exponent);
#endif
@ -688,8 +683,8 @@ void mult_decn(void){
for (i = DEC80_NUM_LSU - 1; i >= 0; i--){
//partial product
for (j = DEC80_NUM_LSU - 1; j >= 0; j--){
uint16_t digit100 = acc_tmp.lsu[j] + (tmp.lsu[i] * AccDecn.lsu[j]) + carry;
acc_tmp.lsu[j] = digit100 % 100;
uint16_t digit100 = TmpDecn.lsu[j] + (BDecn.lsu[i] * AccDecn.lsu[j]) + carry;
TmpDecn.lsu[j] = digit100 % 100;
carry = digit100 / 100;
assert(carry < 100);
}
@ -702,49 +697,49 @@ void mult_decn(void){
printf("\n x:");
for (j = 0; j < DEC80_NUM_LSU; j++){
if (j == i)
printf(" %3d", tmp.lsu[j]);
printf(" %3d", BDecn.lsu[j]);
else
printf(" ");
}
#endif
#ifdef DEBUG_MULT
printf("\n acc_tmp:");
printf("\n TmpDecn:");
for (j = 0; j < DEC80_NUM_LSU; j++){
printf(" %3d", acc_tmp.lsu[j]);
printf(" %3d", TmpDecn.lsu[j]);
}
printf("\ncarry:%d", carry);
#endif
if (i != 0){ //handle last carry separately later, no final shift
//shift
shift_right(&acc_tmp);
shift_right(&acc_tmp);
shift_right(&TmpDecn);
shift_right(&TmpDecn);
//add back carry to MSdigit100
acc_tmp.lsu[0] = carry; //was 0 from shift
TmpDecn.lsu[0] = carry; //was 0 from shift
}
}
//handle last carry
if (carry >= 10){
//shift
shift_right(&acc_tmp);
shift_right(&acc_tmp);
shift_right(&TmpDecn);
shift_right(&TmpDecn);
new_exponent += 1;
//add back carry to MSdigit100
acc_tmp.lsu[0] = carry; //was 0 from shift
TmpDecn.lsu[0] = carry; //was 0 from shift
} else if (carry > 0){
//shift
shift_right(&acc_tmp);
shift_right(&TmpDecn);
//add back carry to MSdigit in MSdigit100
acc_tmp.lsu[0] += carry*10;
TmpDecn.lsu[0] += carry*10;
}
//set new exponent, checking for over/underflow
if (new_exponent < DEC80_MAX_EXP && new_exponent > DEC80_MIN_EXP){
set_exponent(&acc_tmp, new_exponent, is_neg);
set_exponent(&TmpDecn, new_exponent, is_neg);
} else {
set_dec80_NaN(&AccDecn);
return;
}
//copy back to acc
copy_decn(&AccDecn, &acc_tmp);
copy_decn(&AccDecn, &TmpDecn);
//normalize
remove_leading_zeros(&AccDecn);
}
@ -788,26 +783,26 @@ void div_decn(void){
//do newton raphson iterations
for (i = 0; i < DEC80_NUM_LSU; i++){ //just fix number of iterations for now
#ifdef DEBUG_DIV
decn_to_str_complete(Buf, &curr_recip);
decn_to_str_complete(&curr_recip);
printf("%2d: %s\n", i, Buf);
#endif
copy_decn(&BDecn, &x_copy);
mult_decn();
#ifdef DEBUG_DIV
decn_to_str_complete(Buf, &AccDecn);
decn_to_str_complete(&AccDecn);
printf(" %20s: %s\n", "recip*x", Buf);
#endif
negate_decn(&AccDecn);
copy_decn(&BDecn, &DECN_1);
add_decn();
#ifdef DEBUG_DIV
decn_to_str_complete(Buf, &AccDecn);
decn_to_str_complete(&AccDecn);
printf(" %20s: %s\n", "(1-recip*x)", Buf);
#endif
copy_decn(&BDecn, &curr_recip);
mult_decn();
#ifdef DEBUG_DIV
decn_to_str_complete(Buf, &AccDecn);
decn_to_str_complete(&AccDecn);
printf(" %20s: %s\n", "recip * (1-recip*x)", Buf);
#endif
add_decn();

2
src/decn/decn_test.c
View File

@ -66,6 +66,7 @@ int main(void){
build_dec80("-92.3456789012345678", 1);
copy_decn(&BDecn, &AccDecn);
copy_decn(&AccDecn, &tmp_copy); //restore
copy_decn(&tmp_copy, &BDecn); //save
decn_to_str_complete(&BDecn);
printf(" b: %s\n", Buf);
@ -85,6 +86,7 @@ int main(void){
//new acc for acc - b test
decn_to_str_complete(&AccDecn);
printf("acc: %s\n", Buf);
copy_decn(&BDecn, &tmp_copy); //restore
negate_decn(&BDecn);
decn_to_str_complete(&BDecn);
printf(" -b: %s\n", Buf);