1: #include <petsc/private/drawimpl.h>

  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:  */
  8: PetscErrorCode PetscADefLabel(PetscReal val, PetscReal sep, char **p)
  9: {
 10:   static char buf[40];

 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: }

 29: /* Finds "nice" locations for the ticks */
 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;

 35:   PetscFunctionBegin;
 36:   PetscCall(PetscAGetBase(low, high, num, &base, &power));
 37:   PetscCall(PetscAGetNice(low, base, -1, &x));

 39:   /* Values are of the form j * base */
 40:   /* Find the starting value */
 41:   if (x < low) x += base;

 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:   if (i) tickloc[i - 1] = PetscMin(tickloc[i - 1], high);
 51:   if (i < 2 && num < 10) PetscCall(PetscADefTicks(low, high, num + 1, ntick, tickloc, maxtick));
 52:   PetscFunctionReturn(PETSC_SUCCESS);
 53: }

 55: #define EPS 1.e-6

 57: static PetscErrorCode PetscExp10(PetscReal d, PetscReal *result)
 58: {
 59:   PetscFunctionBegin;
 60:   *result = PetscPowReal((PetscReal)10.0, d);
 61:   PetscFunctionReturn(PETSC_SUCCESS);
 62: }

 64: static PetscErrorCode PetscMod(PetscReal x, PetscReal y, PetscReal *result)
 65: {
 66:   int i;

 68:   PetscFunctionBegin;
 69:   if (y == 1) {
 70:     *result = 0.0;
 71:     PetscFunctionReturn(PETSC_SUCCESS);
 72:   }
 73:   i = ((int)x) / ((int)y);
 74:   x = x - ((PetscReal)i) * y;
 75:   while (x > y) x -= y;
 76:   *result = x;
 77:   PetscFunctionReturn(PETSC_SUCCESS);
 78: }

 80: static PetscErrorCode PetscCopysign(PetscReal a, PetscReal b, PetscReal *result)
 81: {
 82:   PetscFunctionBegin;
 83:   if (b >= 0) *result = a;
 84:   else *result = -a;
 85:   PetscFunctionReturn(PETSC_SUCCESS);
 86: }

 88: /*
 89:     Given a value "in" and a "base", return a nice value.
 90:     based on "sign", extend up (+1) or down (-1)
 91:  */
 92: PetscErrorCode PetscAGetNice(PetscReal in, PetscReal base, int sign, PetscReal *result)
 93: {
 94:   PetscReal etmp, s, s2, m;

 96:   PetscFunctionBegin;
 97:   PetscCall(PetscCopysign(0.5, (double)sign, &s));
 98:   etmp = in / base + 0.5 + s;
 99:   PetscCall(PetscCopysign(0.5, etmp, &s));
100:   PetscCall(PetscCopysign(EPS * etmp, (double)sign, &s2));
101:   etmp = etmp - 0.5 + s - s2;
102:   PetscCall(PetscMod(etmp, 1.0, &m));
103:   etmp    = base * (etmp - m);
104:   *result = etmp;
105:   PetscFunctionReturn(PETSC_SUCCESS);
106: }

108: PetscErrorCode PetscAGetBase(PetscReal vmin, PetscReal vmax, int num, PetscReal *Base, int *power)
109: {
110:   PetscReal        base, ftemp, e10;
111:   static PetscReal base_try[5] = {10.0, 5.0, 2.0, 1.0, 0.5};
112:   int              i;

114:   PetscFunctionBegin;
115:   /* labels of the form n * BASE */
116:   /* get an approximate value for BASE */
117:   base = (vmax - vmin) / (double)(num + 1);

119:   /* make it of form   m x 10^power,  m in [1.0, 10) */
120:   if (base <= 0.0) {
121:     base = PetscAbsReal(vmin);
122:     if (base < 1.0) base = 1.0;
123:   }
124:   ftemp = PetscLog10Real((1.0 + EPS) * base);
125:   if (ftemp < 0.0) ftemp -= 1.0;
126:   *power = (int)ftemp;
127:   PetscCall(PetscExp10((double)-*power, &e10));
128:   base = base * e10;
129:   if (base < 1.0) base = 1.0;
130:   /* now reduce it to one of 1, 2, or 5 */
131:   for (i = 1; i < 5; i++) {
132:     if (base >= base_try[i]) {
133:       PetscCall(PetscExp10((double)*power, &e10));
134:       base = base_try[i - 1] * e10;
135:       if (i == 1) *power = *power + 1;
136:       break;
137:     }
138:   }
139:   *Base = base;
140:   PetscFunctionReturn(PETSC_SUCCESS);
141: }