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xschem
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compile option for 2nd order 3-point backward derivative calculation formulaes for graph expressions

This commit is contained in:
Stefan Frederik 2022-09-29 18:22:55 +02:00
parent 6b4ce14e7d
commit 6296bbc1c6
2 changed files with 71 additions and 2 deletions
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70
src/save.c
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@ -678,10 +678,13 @@ static double ravg_store(int what , int i, int p, int last, double integ)
#define DERIV0 -41 /* derivative to first sweep variable, regardless of specified sweep_idx */
#define NUMBER -60
#define ORDER_DERIV 2 /* 1 or 2: 1st order or 2nd order differentiation. 1st order is faster */
typedef struct {
int i;
double d;
double prevy;
double prevprevy;
double prev;
int prevp;
} Stack1;
@ -852,6 +855,7 @@ int plot_raw_custom_data(int sweep_idx, int first, int last, const char *expr)
}
stack2[stackptr2 - 1] = integ;
break;
#if ORDER_DERIV==1
case DERIV:
if( p == first ) {
deriv = 0;
@ -882,6 +886,72 @@ int plot_raw_custom_data(int sweep_idx, int first, int last, const char *expr)
}
stack2[stackptr2 - 1] = deriv;
break;
#else /* second order backward differentiation formulas */
case DERIV:
if( p == first ) {
deriv = 0;
stack1[i].prevy = stack2[stackptr2 - 1];
stack1[i].prev = 0;
} else if(p == first + 1) {
if((x[p] != x[p - 1]))
deriv = (stack2[stackptr2 - 1] - stack1[i].prevy) / (x[p] - x[p - 1]);
else
deriv = stack1[i].prev;
stack1[i].prevprevy = stack1[i].prevy;
stack1[i].prevy = stack2[stackptr2 - 1] ;
stack1[i].prev = deriv;
} else {
double a = x[p - 2] - x[p];
double c = x[p - 1] - x[p];
double b = a * a / 2.0;
double d = c * c / 2.0;
double b_on_d = b / d;
double fa = stack1[i].prevprevy;
double fb = stack1[i].prevy;
double fc = stack2[stackptr2 - 1];
if(a != 0.0)
deriv = (fa - b_on_d * fb - (1 - b_on_d) * fc ) / (a - c * b_on_d);
else
deriv = stack1[i].prev;
stack1[i].prevprevy = stack1[i].prevy;
stack1[i].prevy = stack2[stackptr2 - 1] ;
stack1[i].prev = deriv;
}
stack2[stackptr2 - 1] = deriv;
break;
case DERIV0:
if( p == first ) {
deriv = 0;
stack1[i].prevy = stack2[stackptr2 - 1];
stack1[i].prev = 0;
} else if(p == first + 1) {
if((sweepx[p] != sweepx[p - 1]))
deriv = (stack2[stackptr2 - 1] - stack1[i].prevy) / (sweepx[p] - sweepx[p - 1]);
else
deriv = stack1[i].prev;
stack1[i].prevprevy = stack1[i].prevy;
stack1[i].prevy = stack2[stackptr2 - 1] ;
stack1[i].prev = deriv;
} else {
double a = sweepx[p - 2] - sweepx[p];
double c = sweepx[p - 1] - sweepx[p];
double b = a * a / 2.0;
double d = c * c / 2.0;
double b_on_d = b / d;
double fa = stack1[i].prevprevy;
double fb = stack1[i].prevy;
double fc = stack2[stackptr2 - 1];
if(a != 0.0)
deriv = (fa - b_on_d * fb - (1 - b_on_d) * fc ) / (a - c * b_on_d);
else
deriv = stack1[i].prev;
stack1[i].prevprevy = stack1[i].prevy;
stack1[i].prevy = stack2[stackptr2 - 1] ;
stack1[i].prev = deriv;
}
stack2[stackptr2 - 1] = deriv;
break;
#endif
case SQRT:
stack2[stackptr2 - 1] = sqrt(stack2[stackptr2 - 1]);
break;

3
xschem_library/examples/cmos_example.sch
View File

@ -1517,8 +1517,7 @@ value=".temp 30
.control
save all
op
write cmos_example.raw
set appendwrite
write cmos_example_ngspice.raw
* tran 1n 300n
dc vplus 2.3 2.7 0.001
write cmos_example_ngspice.raw