kernel: optimize LcmInt for small inputs

This gives a tiny speed boost, but more importantly, avoids unnecessary allocation of temporary memory Before: gap> for i in [1..10000000] do LcmInt(2^50*13, 2^50*17); od; time; 2605 After: gap> for i in [1..10000000] do LcmInt(2^50*13, 2^50*17); od; time; 2427
gap-system · Feb 5, 2018 · 67f753d · 67f753d
1 parent ea95324
commit 67f753d
Showing 1 changed file with 9 additions and 0 deletions.
diff --git a/src/integer.c b/src/integer.c
@@ -2202,6 +2202,15 @@ Obj LcmInt(Obj opL, Obj opR)
  sizeL = SIZE_INT_OR_INTOBJ(opL);
  sizeR = SIZE_INT_OR_INTOBJ(opR);
 
+ if (sizeL == 1 || sizeR == 1) {
+ if (sizeR != 1) {
+ SWAP(Obj, opL, opR);
+ }
+ Obj gcd = GcdInt(opL, opR);
+ opR = QuoInt(opR, gcd);
+ return AbsInt(ProdInt(opL, opR));
+ }
+
  NEW_FAKEMPZ(mpzResult, sizeL + sizeR);
  FAKEMPZ_GMPorINTOBJ(mpzL, opL);
  FAKEMPZ_GMPorINTOBJ(mpzR, opR);