* mul::expand() (mul.cpp): When multiplying two sums, be careful not to

  allocate too much.

diff --git a/ginac/mul.cpp b/ginac/mul.cpp
index 80f48571ac01fcb36be91cfa80467bc267570341..7ca04ef36ecb09696bc7b8affe89c60dfa1942c8 100644 (file)
--- a/ginac/mul.cpp
+++ b/ginac/mul.cpp
@@ -686,20 +686,75 @@ ex mul::expand(unsigned options) const
                        (cit->coeff.is_equal(_ex1))) {
                        ++number_of_adds;
                        if (is_ex_exactly_of_type(last_expanded, add)) {
+#if 1
+                               // Expand a product of two sums, simple and robust version.
                                const add & add1 = ex_to<add>(last_expanded);
                                const add & add2 = ex_to<add>(cit->rest);
-                               int n1 = add1.nops();
-                               int n2 = add2.nops();
+                               const int n1 = add1.nops();
+                               const int n2 = add2.nops();
+                               ex tmp_accu;
                                exvector distrseq;
-                               distrseq.reserve(n1*n2);
+                               distrseq.reserve(n2);
                                for (int i1=0; i1<n1; ++i1) {
                                        // cache the first operand (for efficiency):
                                        const ex op1 = add1.op(i1);
                                        for (int i2=0; i2<n2; ++i2)
                                                distrseq.push_back(op1 * add2.op(i2));
+                                       tmp_accu += (new add(distrseq))->
+                                                    setflag(status_flags::dynallocated);
+                                       distrseq.clear();
                                }
-                               last_expanded = (new add(distrseq))->
-                                                setflag(status_flags::dynallocated | (options == 0 ? status_flags::expanded : 0));
+                               last_expanded = tmp_accu;
+#else
+                               // Expand a product of two sums, aggressive version.
+                               // Caring for the overall coefficients in separate loops can give
+                               // a performance gain of up to 20%!
+                               const add & add1 = ex_to<add>(last_expanded);
+                               const add & add2 = ex_to<add>(cit->rest);
+                               const epvector::const_iterator add1begin = add1.seq.begin();
+                               const epvector::const_iterator add1end   = add1.seq.end();
+                               const epvector::const_iterator add2begin = add2.seq.begin();
+                               const epvector::const_iterator add2end   = add2.seq.end();
+                               epvector distrseq;
+                               distrseq.reserve(add1.seq.size()+add2.seq.size());
+                               // Multiply add2 with the overall coefficient of add1 and append it to distrseq:
+                               if (!add1.overall_coeff.is_zero()) {
+                                       if (add1.overall_coeff.is_equal(_ex1))
+                                               distrseq.insert(distrseq.end(),add2begin,add2end);
+                                       else
+                                               for (epvector::const_iterator i=add2begin; i!=add2end; ++i)
+                                                       distrseq.push_back(expair(i->rest, ex_to<numeric>(i->coeff).mul_dyn(ex_to<numeric>(add1.overall_coeff))));
+                               }
+                               // Multiply add1 with the overall coefficient of add2 and append it to distrseq:
+                               if (!add2.overall_coeff.is_zero()) {
+                                       if (add2.overall_coeff.is_equal(_ex1))
+                                               distrseq.insert(distrseq.end(),add1begin,add1end);
+                                       else
+                                               for (epvector::const_iterator i=add1begin; i!=add1end; ++i)
+                                                       distrseq.push_back(expair(i->rest, ex_to<numeric>(i->coeff).mul_dyn(ex_to<numeric>(add2.overall_coeff))));
+                               }
+                               // Compute the new overall coefficient and put it together:
+                               ex tmp_accu = (new add(distrseq, ex_to<numeric>(add1.overall_coeff).mul(ex_to<numeric>(add2.overall_coeff))))->
+                                              setflag(status_flags::dynallocated);
+                               // Multiply explicitly all non-numeric terms of add1 and add2:
+                               for (epvector::const_iterator i1=add1begin; i1!=add1end; ++i1) {
+                                       // We really have to combine terms here in order to compactify
+                                       // the result.  Otherwise it would become waayy tooo bigg.
+                                       numeric oc;
+                                       distrseq.clear();
+                                       for (epvector::const_iterator i2=add2begin; i2!=add2end; ++i2) {
+                                               // Don't push_back expairs which might have a rest that evaluates to a numeric,
+                                               // since that would violate an invariant of expairseq:
+                                               const ex rest = (new mul(i1->rest, i2->rest))->setflag(status_flags::dynallocated);
+                                               if (is_ex_exactly_of_type(rest, numeric))
+                                                       oc *= ex_to<numeric>(rest).mul_dyn(ex_to<numeric>(i1->coeff).mul_dyn(ex_to<numeric>(i2->coeff)));
+                                               else
+                                                       distrseq.push_back(expair(rest, ex_to<numeric>(i1->coeff).mul_dyn(ex_to<numeric>(i2->coeff))));
+                                       }
+                                       tmp_accu += (new add(distrseq, oc))->setflag(status_flags::dynallocated);
+                               }
+                               last_expanded = tmp_accu;
+#endif
                        } else {
                                non_adds.push_back(split_ex_to_pair(last_expanded));
                                last_expanded = cit->rest;