XPRSbtran
XPRSbtran |
Purpose
Post-multiplies a (row) vector provided by the user by the inverse of the current basis.
Synopsis
int XPRS_CC XPRSbtran(XPRSprob prob, double vec[]);
Arguments
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prob
|
The current problem.
|
|
vec
|
Double array of length
ROWS containing the values by which the basis inverse is to be multiplied. The transformed values will also be returned in this array.
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Related controls
Double
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Tolerance on eta elements.
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Example
Get the (unscaled) tableau row
z of constraint number
irow, assuming that all arrays have been dimensioned.
/* Minimum size of arrays:
* y: nrow + ncol;
* mstart: 2;
* mrowind, dmatval: nrow.
*/
/* set up the unit vector y to pick out row irow */
for(i = 0; i < nrow; i++) y[i] = 0.0;
y[irow] = 1.0;
rc = XPRSbtran(prob,y); /* y = e*B^{-1} */
/* Form z = y * A */
for(j = 0; j < ncol, j++) {
rc = XPRSgetcols(prob, mstart, mrowind, dmatval,
nrow, &nelt, j, j);
for(d = 0.0, ielt = 0, ielt < nelt; ielt++)
d += y[mrowind[ielt]] * dmatval[ielt];
y[nrow + j] = d;
}
Further information
If the matrix is in a presolved state,
XPRSbtran works with the basis for the presolved problem.
Related topics