From 5ab8a5088b729a9953b8dff1b2a985dc8fb2098b Mon Sep 17 00:00:00 2001
From: mzuenni <michi.zuendorf@gmail.com>
Date: Mon, 27 Jun 2022 17:19:28 +0200
Subject: updated tcr

---
 math/transforms/fftPerm.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)
 create mode 100644 math/transforms/fftPerm.cpp

(limited to 'math/transforms/fftPerm.cpp')

diff --git a/math/transforms/fftPerm.cpp b/math/transforms/fftPerm.cpp
new file mode 100644
index 0000000..2b6fb10
--- /dev/null
+++ b/math/transforms/fftPerm.cpp
@@ -0,0 +1,8 @@
+int perm[MAXN]; //perm[i] = j in Zeile 10
+void genPerm(int n){
+	ull mask = ~0ull << (__lg(n) - 1);
+	for (int i = 0, j = 0; i < n; i++) {
+		perm[i] = j; //if (i < j) swap(a[i], a[j]);
+		ull y = mask >> __builtin_ctz(~i);
+		j ^= y & (n - 1);
+}}
-- 
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