1 #include <petsc/private/drawimpl.h> /*I "petscdraw.h" I*/
2
3 /*
4 val is the label value. sep is the separation to the next (or previous)
5 label; this is useful in determining how many significant figures to
6 keep.
7 */
PetscADefLabel(PetscReal val,PetscReal sep,char ** p)8 PetscErrorCode PetscADefLabel(PetscReal val, PetscReal sep, char **p)
9 {
10 static char buf[40];
11
12 PetscFunctionBegin;
13 /* Find the string */
14 if (PetscAbsReal(val) / sep < 1.e-4) {
15 buf[0] = '0';
16 buf[1] = 0;
17 } else {
18 PetscCall(PetscSNPrintf(buf, PETSC_STATIC_ARRAY_LENGTH(buf), "%0.1e", (double)val));
19 PetscCall(PetscStripZerosPlus(buf));
20 PetscCall(PetscStripe0(buf));
21 PetscCall(PetscStripInitialZero(buf));
22 PetscCall(PetscStripAllZeros(buf));
23 PetscCall(PetscStripTrailingZeros(buf));
24 }
25 *p = buf;
26 PetscFunctionReturn(PETSC_SUCCESS);
27 }
28
29 /* Finds "nice" locations for the ticks */
PetscADefTicks(PetscReal low,PetscReal high,int num,int * ntick,PetscReal * tickloc,int maxtick)30 PetscErrorCode PetscADefTicks(PetscReal low, PetscReal high, int num, int *ntick, PetscReal *tickloc, int maxtick)
31 {
32 int i, power;
33 PetscReal x = 0.0, base = 0.0, eps;
34
35 PetscFunctionBegin;
36 PetscCall(PetscAGetBase(low, high, num, &base, &power));
37 PetscCall(PetscAGetNice(low, base, -1, &x));
38
39 /* Values are of the form j * base */
40 /* Find the starting value */
41 if (x < low) x += base;
42
43 i = 0;
44 eps = base / 10;
45 while (i < maxtick && x <= high + eps) {
46 tickloc[i++] = x;
47 x += base;
48 }
49 *ntick = i;
50 tickloc[i - 1] = PetscMin(tickloc[i - 1], high);
51
52 if (i < 2 && num < 10) PetscCall(PetscADefTicks(low, high, num + 1, ntick, tickloc, maxtick));
53 PetscFunctionReturn(PETSC_SUCCESS);
54 }
55
56 #define EPS 1.e-6
57
PetscExp10(PetscReal d,PetscReal * result)58 static PetscErrorCode PetscExp10(PetscReal d, PetscReal *result)
59 {
60 PetscFunctionBegin;
61 *result = PetscPowReal((PetscReal)10.0, d);
62 PetscFunctionReturn(PETSC_SUCCESS);
63 }
64
PetscMod(PetscReal x,PetscReal y,PetscReal * result)65 static PetscErrorCode PetscMod(PetscReal x, PetscReal y, PetscReal *result)
66 {
67 int i;
68
69 PetscFunctionBegin;
70 if (y == 1) {
71 *result = 0.0;
72 PetscFunctionReturn(PETSC_SUCCESS);
73 }
74 i = ((int)x) / ((int)y);
75 x = x - ((PetscReal)i) * y;
76 while (x > y) x -= y;
77 *result = x;
78 PetscFunctionReturn(PETSC_SUCCESS);
79 }
80
PetscCopysign(PetscReal a,PetscReal b,PetscReal * result)81 static PetscErrorCode PetscCopysign(PetscReal a, PetscReal b, PetscReal *result)
82 {
83 PetscFunctionBegin;
84 if (b >= 0) *result = a;
85 else *result = -a;
86 PetscFunctionReturn(PETSC_SUCCESS);
87 }
88
89 /*
90 Given a value "in" and a "base", return a nice value.
91 based on "sign", extend up (+1) or down (-1)
92 */
PetscAGetNice(PetscReal in,PetscReal base,int sign,PetscReal * result)93 PetscErrorCode PetscAGetNice(PetscReal in, PetscReal base, int sign, PetscReal *result)
94 {
95 PetscReal etmp, s, s2, m;
96
97 PetscFunctionBegin;
98 PetscCall(PetscCopysign(0.5, (double)sign, &s));
99 etmp = in / base + 0.5 + s;
100 PetscCall(PetscCopysign(0.5, etmp, &s));
101 PetscCall(PetscCopysign(EPS * etmp, (double)sign, &s2));
102 etmp = etmp - 0.5 + s - s2;
103 PetscCall(PetscMod(etmp, 1.0, &m));
104 etmp = base * (etmp - m);
105 *result = etmp;
106 PetscFunctionReturn(PETSC_SUCCESS);
107 }
108
PetscAGetBase(PetscReal vmin,PetscReal vmax,int num,PetscReal * Base,int * power)109 PetscErrorCode PetscAGetBase(PetscReal vmin, PetscReal vmax, int num, PetscReal *Base, int *power)
110 {
111 PetscReal base, ftemp, e10;
112 static PetscReal base_try[5] = {10.0, 5.0, 2.0, 1.0, 0.5};
113 int i;
114
115 PetscFunctionBegin;
116 /* labels of the form n * BASE */
117 /* get an approximate value for BASE */
118 base = (vmax - vmin) / (double)(num + 1);
119
120 /* make it of form m x 10^power, m in [1.0, 10) */
121 if (base <= 0.0) {
122 base = PetscAbsReal(vmin);
123 if (base < 1.0) base = 1.0;
124 }
125 ftemp = PetscLog10Real((1.0 + EPS) * base);
126 if (ftemp < 0.0) ftemp -= 1.0;
127 *power = (int)ftemp;
128 PetscCall(PetscExp10((double)-*power, &e10));
129 base = base * e10;
130 if (base < 1.0) base = 1.0;
131 /* now reduce it to one of 1, 2, or 5 */
132 for (i = 1; i < 5; i++) {
133 if (base >= base_try[i]) {
134 PetscCall(PetscExp10((double)*power, &e10));
135 base = base_try[i - 1] * e10;
136 if (i == 1) *power = *power + 1;
137 break;
138 }
139 }
140 *Base = base;
141 PetscFunctionReturn(PETSC_SUCCESS);
142 }
143