From d54358b5338495bc7b90dc1fcac5f2c9734e9e89 Mon Sep 17 00:00:00 2001
From: tomsmeding <tom.smeding@gmail.com>
Date: Sat, 20 Apr 2019 16:56:35 +0200
Subject: Use 'init' in max_root_norm in futhark

---
 aberth/aberth_kernel.fut | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

(limited to 'aberth')

diff --git a/aberth/aberth_kernel.fut b/aberth/aberth_kernel.fut
index e1e7aa3..79d7cfa 100644
--- a/aberth/aberth_kernel.fut
+++ b/aberth/aberth_kernel.fut
@@ -29,11 +29,11 @@ let evaln_d (p: poly) (nterms: i32) (pt: f32): f32 =
 let eval_d (p: poly) (pt: f32): f32 = evaln_d p (length p) pt
 
 let derivative (p: poly): *poly = 
-    map (\(i, v) -> f32.i32 i * v) (zip (1..<PolyN) (drop 1 p)) ++ [0]
+    map (\(i, v) -> f32.i32 i * v) (zip (1..<PolyN) (tail p)) ++ [0]
 
 -- Cauchy's bound: https://en.wikipedia.org/wiki/Geometrical_properties_of_polynomial_roots#Lagrange's_and_Cauchy's_bounds
 let max_root_norm (p: poly): f32 =
-    1 + f32.maximum (map (\coef -> f32.abs (coef / p[PolyN-1])) p)
+    1 + f32.maximum (map (\coef -> f32.abs (coef / p[PolyN-1])) (init p))
 
 module aberth = {
     type approx = [N]complex
-- 
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