+ int ipow(int base, int exp)
+ {
+ int result = 1;
+ while (exp)
+ {
+ if (exp & 1)
+ result *= base;
+ exp >>= 1;
+ base *= base;
+ }
+
+ return result;
+ }
+
+ prestore::prestore(unsigned int _max2j)
+ {
+ max2j = _max2j;
+ cgcdata = new double[ipow(max2j+1,6)];
+
+ for (int factor1_2j=0; factor1_2j<=max2j; factor1_2j++)
+ for (int factor1_mp=0; factor1_mp<=max2j; factor1_mp++)
+ for (int factor2_2j=0; factor2_2j<=max2j; factor2_2j++)
+ for (int factor2_mp=0; factor2_mp<=max2j; factor2_mp++)
+ for (int irrep_2j=0; irrep_2j<=max2j; irrep_2j++)
+ for (int irrep_mp=0; irrep_mp<=max2j; irrep_mp++)
+ {
+ cgcdata[ factor1_2j*ipow(max2j+1,5) + factor1_mp*ipow(max2j+1,4) +
+ factor2_2j*ipow(max2j+1,3) + factor2_mp*ipow(max2j+1,2) +
+ irrep_2j*(max2j+1) + irrep_mp ]
+ =
+ cgc( factor1_2j, 2*factor1_mp-max2j, factor2_2j, 2*factor2_mp-max2j,
+ irrep_2j, 2*irrep_mp-max2j );
+ }
+ }
+
+ bool stateValid(int state_2j, int state_2m)
+ {
+ if ( abs(state_2m) > state_2j || (state_2j + state_2m) % 2 != 0 )
+ return false;
+ else
+ return true;
+ }
+
+ double cgc (int factor1_2j, int factor1_2m, int factor2_2j, int factor2_2m,
+ int irrep_2j, int irrep_2m, const prestore& Prestore)
+ {
+ if ( ! ( stateValid(factor1_2j, factor1_2m) && stateValid(factor2_2j, factor2_2m) && stateValid(irrep_2j, irrep_2m) ) )
+ return 0.0;
+
+ if ( factor1_2j > Prestore.max2j || factor2_2j > Prestore.max2j || irrep_2j > Prestore.max2j )
+ return cgc(factor1_2j, factor1_2m, factor2_2j, factor2_2m, irrep_2j, irrep_2m);
+
+ return Prestore.cgcdata[ factor1_2j*ipow(Prestore.max2j+1,5) +
+ (factor1_2m+Prestore.max2j)/2 *ipow(Prestore.max2j+1,4) +
+ factor2_2j*ipow(Prestore.max2j+1,3) +
+ (factor2_2m+Prestore.max2j)/2 *ipow(Prestore.max2j+1,2) +
+ irrep_2j*(Prestore.max2j+1) +
+ (irrep_2m+Prestore.max2j)/2 ];
+ }