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| Purpose |
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Copy the current basis into arrays.
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| Synopsis |
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int QSget_basis_array (QSprob p, char *cstat, char *rstat)
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| Arguments |
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p |
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a handle to an initialized problem. |
cstat |
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returns an array specifying the status of each column (variable) in the basis; this field can be NULL, if it is not NULL it should point to an array of length at least ncols, the number of columns in the problem. |
rstat |
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returns an array specifying the status of each row (constraint) in the basis; this field can be NULL, if it is not NULL it should point to an array of length at least nrows, the number of rows in the problem. |
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| Returns |
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A zero value if the function terminated correctly, and a non-zero value if an error occurred.
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| Description |
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The status of the columns (variables) in the basis are specified in the array cstat. Each entry in the cstat array is one of the following four values | Value | | Constant | | Meaning | | 0 | | QS_COL_BSTAT_LOWER | | Variable is non-basic, at lower bound | | 1 | | QS_COL_BSTAT_BASIC | | Variable is basic | | 2 | | QS_COL_BSTAT_UPPER | | Variable is non-basic, at upper bound | | 3 | | QS_COL_BSTAT_FREE | | Variable is non-basic and free |
Similarly, the status of the rows (constraints) in the basis (that is, the status of the logical variables [either slack variables or artificial variables] corresponding to the rows) are specified in the array rstat. Each entry in the rstat array is one of the following two values | Value | | Constant | | Meaning | | 0 | | QS_ROW_BSTAT_LOWER | | Logical variable is non-basic, at lower bound | | 1 | | QS_ROW_BSTAT_BASIC | | Logical variable is basic | | 2 | | QS_ROW_BSTAT_UPPER | | Logical variable is non-basic, at upper bound |
Note that a logical variable has an associated upper bound only if it corresponds to a range constraint.
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| Example |
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/* p is an initialized QSprob, a handle to an existing LP problem */
int rval, ncols, nrows;
char *cstat, *rstat;
ncols = QSget_colcount (p);
nrows = QSget_rowcount (p);
cstat = (char *) malloc (ncols * sizeof (char));
rstat = (char *) malloc (nrows * sizeof (char));
rval = QSget_basis_array (p, cstat, rstat);
if (rval) {
fprintf (stderr, "Could not get the basis, error code %d\n", rval);
} else {
/* The basis information is stored in the arrays. */
}
free (cstat);
free (rstat);
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