Actual source code: sortd.c

petsc-3.4.4 2014-03-13
  2: /*
  3:    This file contains routines for sorting doubles.  Values are sorted in place.
  4:    These are provided because the general sort routines incur a great deal
  5:    of overhead in calling the comparision routines.

  7:  */
  8: #include <petscsys.h>                /*I  "petscsys.h"  I*/

 10: #define SWAP(a,b,t) {t=a;a=b;b=t;}

 14: /* A simple version of quicksort; taken from Kernighan and Ritchie, page 87 */
 15: static PetscErrorCode PetscSortReal_Private(PetscReal *v,PetscInt right)
 16: {
 17:   PetscInt  i,last;
 18:   PetscReal vl,tmp;

 21:   if (right <= 1) {
 22:     if (right == 1) {
 23:       if (v[0] > v[1]) SWAP(v[0],v[1],tmp);
 24:     }
 25:     return(0);
 26:   }
 27:   SWAP(v[0],v[right/2],tmp);
 28:   vl   = v[0];
 29:   last = 0;
 30:   for (i=1; i<=right; i++) {
 31:     if (v[i] < vl) {last++; SWAP(v[last],v[i],tmp);}
 32:   }
 33:   SWAP(v[0],v[last],tmp);
 34:   PetscSortReal_Private(v,last-1);
 35:   PetscSortReal_Private(v+last+1,right-(last+1));
 36:   return(0);
 37: }

 41: /*@
 42:    PetscSortReal - Sorts an array of doubles in place in increasing order.

 44:    Not Collective

 46:    Input Parameters:
 47: +  n  - number of values
 48: -  v  - array of doubles

 50:    Level: intermediate

 52:    Concepts: sorting^doubles

 54: .seealso: PetscSortInt(), PetscSortRealWithPermutation()
 55: @*/
 56: PetscErrorCode  PetscSortReal(PetscInt n,PetscReal v[])
 57: {
 58:   PetscInt  j,k;
 59:   PetscReal tmp,vk;

 62:   if (n<8) {
 63:     for (k=0; k<n; k++) {
 64:       vk = v[k];
 65:       for (j=k+1; j<n; j++) {
 66:         if (vk > v[j]) {
 67:           SWAP(v[k],v[j],tmp);
 68:           vk = v[k];
 69:         }
 70:       }
 71:     }
 72:   } else PetscSortReal_Private(v,n-1);
 73:   return(0);
 74: }

 78: /*@
 79:    PetscSortSplit - Quick-sort split of an array of PetscScalars in place.

 81:    Not Collective

 83:    Input Parameters:
 84: +  ncut  - splitig index
 85: .  n     - number of values to sort
 86: .  a     - array of values
 87: -  idx   - index for array a

 89:    Output Parameters:
 90: +  a     - permuted array of values such that its elements satisfy:
 91:            abs(a[i]) >= abs(a[ncut-1]) for i < ncut and
 92:            abs(a[i]) <= abs(a[ncut-1]) for i >= ncut
 93: -  idx   - permuted index of array a

 95:    Level: intermediate

 97:    Concepts: sorting^doubles

 99: .seealso: PetscSortInt(), PetscSortRealWithPermutation()
100: @*/
101: PetscErrorCode  PetscSortSplit(PetscInt ncut,PetscInt n,PetscScalar a[],PetscInt idx[])
102: {
103:   PetscInt    i,mid,last,itmp,j,first;
104:   PetscScalar d,tmp;
105:   PetscReal   abskey;

108:   first = 0;
109:   last  = n-1;
110:   if (ncut < first || ncut > last) return(0);

112:   while (1) {
113:     mid    = first;
114:     abskey = (d = a[mid],PetscAbsScalar(d));
115:     i      = last;
116:     for (j = first + 1; j <= i; ++j) {
117:       if ((d = a[j],PetscAbsScalar(d)) >= abskey) {
118:         ++mid;
119:         /* interchange */
120:         tmp = a[mid];  itmp = idx[mid];
121:         a[mid] = a[j]; idx[mid] = idx[j];
122:         a[j] = tmp;    idx[j] = itmp;
123:       }
124:     }

126:     /* interchange */
127:     tmp = a[mid];      itmp = idx[mid];
128:     a[mid] = a[first]; idx[mid] = idx[first];
129:     a[first] = tmp;    idx[first] = itmp;

131:     /* test for while loop */
132:     if (mid == ncut) break;
133:     else if (mid > ncut) last = mid - 1;
134:     else first = mid + 1;
135:   }
136:   return(0);
137: }

141: /*@
142:    PetscSortSplitReal - Quick-sort split of an array of PetscReals in place.

144:    Not Collective

146:    Input Parameters:
147: +  ncut  - splitig index
148: .  n     - number of values to sort
149: .  a     - array of values in PetscReal
150: -  idx   - index for array a

152:    Output Parameters:
153: +  a     - permuted array of real values such that its elements satisfy:
154:            abs(a[i]) >= abs(a[ncut-1]) for i < ncut and
155:            abs(a[i]) <= abs(a[ncut-1]) for i >= ncut
156: -  idx   - permuted index of array a

158:    Level: intermediate

160:    Concepts: sorting^doubles

162: .seealso: PetscSortInt(), PetscSortRealWithPermutation()
163: @*/
164: PetscErrorCode  PetscSortSplitReal(PetscInt ncut,PetscInt n,PetscReal a[],PetscInt idx[])
165: {
166:   PetscInt  i,mid,last,itmp,j,first;
167:   PetscReal d,tmp;
168:   PetscReal abskey;

171:   first = 0;
172:   last  = n-1;
173:   if (ncut < first || ncut > last) return(0);

175:   while (1) {
176:     mid    = first;
177:     abskey = (d = a[mid],PetscAbsReal(d));
178:     i      = last;
179:     for (j = first + 1; j <= i; ++j) {
180:       if ((d = a[j],PetscAbsReal(d)) >= abskey) {
181:         ++mid;
182:         /* interchange */
183:         tmp = a[mid];  itmp = idx[mid];
184:         a[mid] = a[j]; idx[mid] = idx[j];
185:         a[j] = tmp;    idx[j] = itmp;
186:       }
187:     }

189:     /* interchange */
190:     tmp = a[mid];      itmp = idx[mid];
191:     a[mid] = a[first]; idx[mid] = idx[first];
192:     a[first] = tmp;    idx[first] = itmp;

194:     /* test for while loop */
195:     if (mid == ncut) break;
196:     else if (mid > ncut) last = mid - 1;
197:     else first = mid + 1;
198:   }
199:   return(0);
200: }