Actual source code: axis.c


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

  4: /*
  5:    val is the label value.  sep is the separation to the next (or previous)
  6:    label; this is useful in determining how many significant figures to
  7:    keep.
  8:  */
  9: PetscErrorCode PetscADefLabel(PetscReal val, PetscReal sep, char **p)
 10: {
 11:   static char buf[40];

 13:   PetscFunctionBegin;
 14:   /* Find the string */
 15:   if (PetscAbsReal(val) / sep < 1.e-4) {
 16:     buf[0] = '0';
 17:     buf[1] = 0;
 18:   } else {
 19:     PetscCall(PetscSNPrintf(buf, PETSC_STATIC_ARRAY_LENGTH(buf), "%0.1e", (double)val));
 20:     PetscCall(PetscStripZerosPlus(buf));
 21:     PetscCall(PetscStripe0(buf));
 22:     PetscCall(PetscStripInitialZero(buf));
 23:     PetscCall(PetscStripAllZeros(buf));
 24:     PetscCall(PetscStripTrailingZeros(buf));
 25:   }
 26:   *p = buf;
 27:   PetscFunctionReturn(PETSC_SUCCESS);
 28: }

 30: /* Finds "nice" locations for the ticks */
 31: PetscErrorCode PetscADefTicks(PetscReal low, PetscReal high, int num, int *ntick, PetscReal *tickloc, int maxtick)
 32: {
 33:   int       i, power;
 34:   PetscReal x = 0.0, base = 0.0, eps;

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

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

 44:   i   = 0;
 45:   eps = base / 10;
 46:   while (i < maxtick && x <= high + eps) {
 47:     tickloc[i++] = x;
 48:     x += base;
 49:   }
 50:   *ntick         = i;
 51:   tickloc[i - 1] = PetscMin(tickloc[i - 1], high);

 53:   if (i < 2 && num < 10) PetscCall(PetscADefTicks(low, high, num + 1, ntick, tickloc, maxtick));
 54:   PetscFunctionReturn(PETSC_SUCCESS);
 55: }

 57: #define EPS 1.e-6

 59: PetscErrorCode PetscExp10(PetscReal d, PetscReal *result)
 60: {
 61:   PetscFunctionBegin;
 62:   *result = PetscPowReal((PetscReal)10.0, d);
 63:   PetscFunctionReturn(PETSC_SUCCESS);
 64: }

 66: PetscErrorCode PetscMod(PetscReal x, PetscReal y, PetscReal *result)
 67: {
 68:   int i;

 70:   PetscFunctionBegin;
 71:   if (y == 1) {
 72:     *result = 0.0;
 73:     PetscFunctionReturn(PETSC_SUCCESS);
 74:   }
 75:   i = ((int)x) / ((int)y);
 76:   x = x - i * y;
 77:   while (x > y) x -= y;
 78:   *result = x;
 79:   PetscFunctionReturn(PETSC_SUCCESS);
 80: }

 82: PetscErrorCode PetscCopysign(PetscReal a, PetscReal b, PetscReal *result)
 83: {
 84:   PetscFunctionBegin;
 85:   if (b >= 0) *result = a;
 86:   else *result = -a;
 87:   PetscFunctionReturn(PETSC_SUCCESS);
 88: }

 90: /*
 91:     Given a value "in" and a "base", return a nice value.
 92:     based on "sign", extend up (+1) or down (-1)
 93:  */
 94: PetscErrorCode PetscAGetNice(PetscReal in, PetscReal base, int sign, PetscReal *result)
 95: {
 96:   PetscReal etmp, s, s2, m;

 98:   PetscFunctionBegin;
 99:   PetscCall(PetscCopysign(0.5, (double)sign, &s));
100:   etmp = in / base + 0.5 + s;
101:   PetscCall(PetscCopysign(0.5, etmp, &s));
102:   PetscCall(PetscCopysign(EPS * etmp, (double)sign, &s2));
103:   etmp = etmp - 0.5 + s - s2;
104:   PetscCall(PetscMod(etmp, 1.0, &m));
105:   etmp    = base * (etmp - m);
106:   *result = etmp;
107:   PetscFunctionReturn(PETSC_SUCCESS);
108: }

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

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

121:   /* make it of form   m x 10^power,  m in [1.0, 10) */
122:   if (base <= 0.0) {
123:     base = PetscAbsReal(vmin);
124:     if (base < 1.0) base = 1.0;
125:   }
126:   ftemp = PetscLog10Real((1.0 + EPS) * base);
127:   if (ftemp < 0.0) ftemp -= 1.0;
128:   *power = (int)ftemp;
129:   PetscCall(PetscExp10((double)-*power, &e10));
130:   base = base * e10;
131:   if (base < 1.0) base = 1.0;
132:   /* now reduce it to one of 1, 2, or 5 */
133:   for (i = 1; i < 5; i++) {
134:     if (base >= base_try[i]) {
135:       PetscCall(PetscExp10((double)*power, &e10));
136:       base = base_try[i - 1] * e10;
137:       if (i == 1) *power = *power + 1;
138:       break;
139:     }
140:   }
141:   *Base = base;
142:   PetscFunctionReturn(PETSC_SUCCESS);
143: }