Changeset 2880

Timestamp:

12/13/13 19:00:06 (10 years ago)

Author:

WataruKawasaki

Message:

New Development: No

JIRA Issue: No

Ready for Test: Yes

Interface Changes: No

What Interface Changed:

Test Programs:

Put in Release Notes: No

Module(s): sd

Description: modify algorithm to calculate Chebyshev polynomials with better accuracy.

File:

• trunk/src/Scantable.cpp (modified) (1 diff)

trunk/src/Scantable.cpp

@@ -3365 +3365 @@
     return x;
   } else {
-    double res = 0.0;
-    for (int m = 0; m <= n/2; ++m) {
-      double c = 1.0;
-      if (m > 0) {
-        for (int i = 1; i <= m; ++i) {
-          c *= (double)(n-2*m+i)/(double)i;
-        }
-      }
-      res += (m%2 == 0 ? 1.0 : -1.0)*(double)n/(double)(n-m)*pow(2.0*x, (double)(n-2*m))/2.0*c;
-    }
-    return res;
+    double res[n+1];
+    for (int i = 0; i < n+1; ++i) {
+      double res0 = 0.0;
+      if (i == 0) {
+        res0 = 1.0;
+      } else if (i == 1) {
+        res0 = x;
+      } else {
+        res0 = 2.0 * x * res[i-1] - res[i-2];
+      }
+      res[i] = res0;
+    }
+    return res[n];
   }
 }