- matrix::inverse(): Added a shortcut for sparse cases.
authorRichard Kreckel <Richard.Kreckel@uni-mainz.de>
Mon, 18 Sep 2000 22:31:26 +0000 (22:31 +0000)
committerRichard Kreckel <Richard.Kreckel@uni-mainz.de>
Mon, 18 Sep 2000 22:31:26 +0000 (22:31 +0000)
ginac/matrix.cpp

index d72104a4589fbd93e85bb81cfc6ea2b932eb9b41..763024c35dbb841e71269c207d9b6308806b703f 100644 (file)
@@ -647,7 +647,7 @@ matrix matrix::inverse(void) const
                throw (std::logic_error("matrix::inverse(): matrix not square"));
        
        // NOTE: the Gauss-Jordan elimination used here can in principle be
-       // replaced this by two clever calls to gauss_elimination() and some to
+       // replaced by two clever calls to gauss_elimination() and some to
        // transpose().  Wouldn't be more efficient (maybe less?), just more
        // orthogonal.
        matrix tmp(row,col);
@@ -673,14 +673,17 @@ matrix matrix::inverse(void) const
                }
                for (unsigned r2=0; r2<row; ++r2) {
                        if (r2 != r1) {
-                               ex a2 = cpy.m[r2*col+r1];
-                               for (unsigned c=0; c<col; ++c) {
-                                       cpy.m[r2*col+c] -= a2 * cpy.m[r1*col+c];
-                                       if (!cpy.m[r2*col+c].info(info_flags::numeric))
-                                               cpy.m[r2*col+c] = cpy.m[r2*col+c].normal();
-                                       tmp.m[r2*col+c] -= a2 * tmp.m[r1*col+c];
-                                       if (!tmp.m[r2*col+c].info(info_flags::numeric))
-                                               tmp.m[r2*col+c] = tmp.m[r2*col+c].normal();
+                               if (!cpy.m[r2*col+r1].is_zero()) {
+                                       ex a2 = cpy.m[r2*col+r1];
+                                       // yes, there is something to do in this column
+                                       for (unsigned c=0; c<col; ++c) {
+                                               cpy.m[r2*col+c] -= a2 * cpy.m[r1*col+c];
+                                               if (!cpy.m[r2*col+c].info(info_flags::numeric))
+                                                       cpy.m[r2*col+c] = cpy.m[r2*col+c].normal();
+                                               tmp.m[r2*col+c] -= a2 * tmp.m[r1*col+c];
+                                               if (!tmp.m[r2*col+c].info(info_flags::numeric))
+                                                       tmp.m[r2*col+c] = tmp.m[r2*col+c].normal();
+                                       }
                                }
                        }
                }
@@ -945,7 +948,7 @@ int matrix::gauss_elimination(const bool det)
                                sign = -sign;
                        for (unsigned r2=r0+1; r2<m; ++r2) {
                                if (!this->m[r2*n+r1].is_zero()) {
-                                       // there is something to do in this row
+                                       // yes, there is something to do in this row
                                        ex piv = this->m[r2*n+r1] / this->m[r0*n+r1];
                                        for (unsigned c=r1+1; c<n; ++c) {
                                                this->m[r2*n+c] -= piv * this->m[r0*n+c];
@@ -1189,7 +1192,7 @@ int matrix::pivot(unsigned ro, unsigned co, bool symbolic)
        // matrix needs pivoting, so swap rows k and ro
        ensure_if_modifiable();
        for (unsigned c=0; c<col; ++c)
-               m[k*col+c].swap(m[ro*col+c]);
+               this->m[k*col+c].swap(this->m[ro*col+c]);
        
        return k;
 }