[37] | 1 | ///////////////////////////////////////////////////////////////////////////////// |
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| 2 | //// |
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| 3 | //// CRS sparse matrices manipulation routines |
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| 4 | //// Copyright (C) 2004 Manolis Lourakis (lourakis@ics.forth.gr) |
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| 5 | //// Institute of Computer Science, Foundation for Research & Technology - Hellas |
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| 6 | //// Heraklion, Crete, Greece. |
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| 7 | //// |
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| 8 | //// This program is free software; you can redistribute it and/or modify |
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| 9 | //// it under the terms of the GNU General Public License as published by |
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| 10 | //// the Free Software Foundation; either version 2 of the License, or |
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| 11 | //// (at your option) any later version. |
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| 12 | //// |
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| 13 | //// This program is distributed in the hope that it will be useful, |
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| 14 | //// but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 15 | //// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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| 16 | //// GNU General Public License for more details. |
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| 17 | //// |
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| 18 | /////////////////////////////////////////////////////////////////////////////////// |
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| 19 | |
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| 20 | #include <stdio.h> |
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| 21 | #include <stdlib.h> |
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| 22 | |
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| 23 | #include "sba.h" |
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| 24 | |
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| 25 | static void sba_crsm_print(struct sba_crsm *sm, FILE *fp); |
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| 26 | static void sba_crsm_build(struct sba_crsm *sm, int *m, int nr, int nc); |
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| 27 | |
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| 28 | /* allocate a sparse CRS matrix */ |
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| 29 | void sba_crsm_alloc(struct sba_crsm *sm, int nr, int nc, int nnz) |
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| 30 | { |
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| 31 | int msz; |
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| 32 | |
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| 33 | sm->nr=nr; |
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| 34 | sm->nc=nc; |
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| 35 | sm->nnz=nnz; |
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| 36 | msz=2*nnz+nr+1; |
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| 37 | sm->val=(int *)malloc(msz*sizeof(int)); /* required memory is allocated in a single step */ |
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| 38 | if(!sm->val){ |
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| 39 | fprintf(stderr, "memory allocation request failed in sba_crsm_alloc() [nr=%d, nc=%d, nnz=%d]\n", nr, nc, nnz); |
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| 40 | exit(1); |
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| 41 | } |
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| 42 | sm->colidx=sm->val+nnz; |
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| 43 | sm->rowptr=sm->colidx+nnz; |
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| 44 | } |
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| 45 | |
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| 46 | /* free a sparse CRS matrix */ |
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| 47 | void sba_crsm_free(struct sba_crsm *sm) |
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| 48 | { |
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| 49 | sm->nr=sm->nc=sm->nnz=-1; |
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| 50 | free(sm->val); |
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| 51 | sm->val=sm->colidx=sm->rowptr=NULL; |
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| 52 | } |
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| 53 | |
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| 54 | static void sba_crsm_print(struct sba_crsm *sm, FILE *fp) |
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| 55 | { |
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| 56 | register int i; |
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| 57 | |
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| 58 | fprintf(fp, "matrix is %dx%d, %d non-zeros\nval: ", sm->nr, sm->nc, sm->nnz); |
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| 59 | for(i=0; i<sm->nnz; ++i) |
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| 60 | fprintf(fp, "%d ", sm->val[i]); |
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| 61 | fprintf(fp, "\ncolidx: "); |
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| 62 | for(i=0; i<sm->nnz; ++i) |
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| 63 | fprintf(fp, "%d ", sm->colidx[i]); |
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| 64 | fprintf(fp, "\nrowptr: "); |
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| 65 | for(i=0; i<=sm->nr; ++i) |
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| 66 | fprintf(fp, "%d ", sm->rowptr[i]); |
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| 67 | fprintf(fp, "\n"); |
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| 68 | } |
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| 69 | |
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| 70 | /* build a sparse CRS matrix from a dense one. intended to serve as an example for sm creation */ |
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| 71 | static void sba_crsm_build(struct sba_crsm *sm, int *m, int nr, int nc) |
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| 72 | { |
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| 73 | int nnz; |
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| 74 | register int i, j, k; |
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| 75 | |
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| 76 | /* count nonzeros */ |
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| 77 | for(i=nnz=0; i<nr; ++i) |
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| 78 | for(j=0; j<nc; ++j) |
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| 79 | if(m[i*nc+j]!=0) ++nnz; |
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| 80 | |
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| 81 | sba_crsm_alloc(sm, nr, nc, nnz); |
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| 82 | |
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| 83 | /* fill up the sm structure */ |
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| 84 | for(i=k=0; i<nr; ++i){ |
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| 85 | sm->rowptr[i]=k; |
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| 86 | for(j=0; j<nc; ++j) |
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| 87 | if(m[i*nc+j]!=0){ |
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| 88 | sm->val[k]=m[i*nc+j]; |
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| 89 | sm->colidx[k++]=j; |
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| 90 | } |
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| 91 | } |
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| 92 | sm->rowptr[nr]=nnz; |
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| 93 | } |
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| 94 | |
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| 95 | /* returns the index of the (i, j) element. No bounds checking! */ |
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| 96 | int sba_crsm_elmidx(struct sba_crsm *sm, int i, int j) |
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| 97 | { |
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| 98 | register int low, high, mid; |
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| 99 | |
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| 100 | low=sm->rowptr[i]; |
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| 101 | high=sm->rowptr[i+1]-1; |
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| 102 | |
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| 103 | /* binary search for finding the element at column j */ |
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| 104 | while(low<=high){ |
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| 105 | if(j<sm->colidx[low] || j>sm->colidx[high]) return -1; /* not found */ |
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| 106 | |
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| 107 | mid=(low+high)>>1; //(low+high)/2; |
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| 108 | if(j<sm->colidx[mid]) |
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| 109 | high=mid-1; |
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| 110 | else if(j>sm->colidx[mid]) |
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| 111 | low=mid+1; |
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| 112 | else |
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| 113 | return mid; |
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| 114 | } |
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| 115 | |
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| 116 | return -1; /* not found */ |
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| 117 | } |
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| 118 | |
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| 119 | /* returns the number of nonzero elements in row i and |
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| 120 | * fills up the vidxs and jidxs arrays with the val and column |
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| 121 | * indexes of the elements found, respectively. |
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| 122 | * vidxs and jidxs are assumed preallocated and of max. size sm->nc |
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| 123 | */ |
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| 124 | int sba_crsm_row_elmidxs(struct sba_crsm *sm, int i, int *vidxs, int *jidxs) |
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| 125 | { |
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| 126 | register int j, k; |
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| 127 | |
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| 128 | for(j=sm->rowptr[i], k=0; j<sm->rowptr[i+1]; ++j, ++k){ |
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| 129 | vidxs[k]=j; |
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| 130 | jidxs[k]=sm->colidx[j]; |
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| 131 | } |
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| 132 | |
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| 133 | return k; |
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| 134 | } |
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| 135 | |
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| 136 | /* returns the number of nonzero elements in col j and |
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| 137 | * fills up the vidxs and iidxs arrays with the val and row |
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| 138 | * indexes of the elements found, respectively. |
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| 139 | * vidxs and iidxs are assumed preallocated and of max. size sm->nr |
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| 140 | */ |
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| 141 | int sba_crsm_col_elmidxs(struct sba_crsm *sm, int j, int *vidxs, int *iidxs) |
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| 142 | { |
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| 143 | register int *nextrowptr=sm->rowptr+1; |
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| 144 | register int i, l; |
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| 145 | register int low, high, mid; |
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| 146 | |
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| 147 | for(i=l=0; i<sm->nr; ++i){ |
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| 148 | low=sm->rowptr[i]; |
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| 149 | high=nextrowptr[i]-1; |
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| 150 | |
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| 151 | /* binary search attempting to find an element at column j */ |
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| 152 | while(low<=high){ |
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| 153 | if(j<sm->colidx[low] || j>sm->colidx[high]) break; /* not found */ |
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| 154 | |
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| 155 | mid=(low+high)>>1; //(low+high)/2; |
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| 156 | if(j<sm->colidx[mid]) |
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| 157 | high=mid-1; |
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| 158 | else if(j>sm->colidx[mid]) |
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| 159 | low=mid+1; |
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| 160 | else{ /* found */ |
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| 161 | vidxs[l]=mid; |
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| 162 | iidxs[l++]=i; |
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| 163 | break; |
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| 164 | } |
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| 165 | } |
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| 166 | } |
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| 167 | |
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| 168 | return l; |
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| 169 | } |
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| 170 | |
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| 171 | /* a more straighforward (but slower) implementation of the above function */ |
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| 172 | /*** |
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| 173 | int sba_crsm_col_elmidxs(struct sba_crsm *sm, int j, int *vidxs, int *iidxs) |
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| 174 | { |
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| 175 | register int i, k, l; |
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| 176 | |
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| 177 | for(i=l=0; i<sm->nr; ++i) |
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| 178 | for(k=sm->rowptr[i]; k<sm->rowptr[i+1]; ++k) |
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| 179 | if(sm->colidx[k]==j){ |
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| 180 | vidxs[l]=k; |
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| 181 | iidxs[l++]=i; |
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| 182 | } |
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| 183 | |
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| 184 | return l; |
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| 185 | } |
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| 186 | ***/ |
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| 187 | |
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| 188 | #if 0 |
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| 189 | |
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| 190 | /* sample code using the above routines */ |
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| 191 | |
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| 192 | main() |
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| 193 | { |
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| 194 | int mat[7][6]={ |
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| 195 | {10, 0, 0, 0, -2, 0}, |
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| 196 | {3, 9, 0, 0, 0, 3}, |
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| 197 | {0, 7, 8, 7, 0, 0}, |
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| 198 | {3, 0, 8, 7, 5, 0}, |
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| 199 | {0, 8, 0, 9, 9, 13}, |
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| 200 | {0, 4, 0, 0, 2, -1}, |
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| 201 | {3, 7, 0, 9, 2, 0} |
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| 202 | }; |
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| 203 | |
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| 204 | struct sba_crsm sm; |
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| 205 | int i, j, k, l; |
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| 206 | int vidxs[7], /* max(6, 7) */ |
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| 207 | jidxs[6], iidxs[7]; |
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| 208 | |
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| 209 | |
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| 210 | sba_crsm_build(&sm, mat[0], 7, 6); |
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| 211 | sba_crsm_print(&sm, stdout); |
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| 212 | |
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| 213 | for(i=0; i<7; ++i){ |
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| 214 | for(j=0; j<6; ++j) |
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| 215 | printf("%3d ", ((k=sba_crsm_elmidx(&sm, i, j))!=-1)? sm.val[k] : 0); |
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| 216 | printf("\n"); |
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| 217 | } |
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| 218 | |
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| 219 | for(i=0; i<7; ++i){ |
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| 220 | k=sba_crsm_row_elmidxs(&sm, i, vidxs, jidxs); |
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| 221 | printf("row %d\n", i); |
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| 222 | for(l=0; l<k; ++l){ |
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| 223 | j=jidxs[l]; |
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| 224 | printf("%d %d ", j, sm.val[vidxs[l]]); |
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| 225 | } |
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| 226 | printf("\n"); |
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| 227 | } |
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| 228 | |
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| 229 | for(j=0; j<6; ++j){ |
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| 230 | k=sba_crsm_col_elmidxs(&sm, j, vidxs, iidxs); |
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| 231 | printf("col %d\n", j); |
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| 232 | for(l=0; l<k; ++l){ |
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| 233 | i=iidxs[l]; |
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| 234 | printf("%d %d ", i, sm.val[vidxs[l]]); |
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| 235 | } |
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| 236 | printf("\n"); |
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| 237 | } |
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| 238 | |
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| 239 | sba_crsm_free(&sm); |
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| 240 | } |
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| 241 | #endif |
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