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authorAndroid Build Coastguard Worker <android-build-coastguard-worker@google.com>2023-07-07 05:07:20 +0000
committerAndroid Build Coastguard Worker <android-build-coastguard-worker@google.com>2023-07-07 05:07:20 +0000
commit70bf985bf12dfa02e9d634a433858320aa2f29dd (patch)
treeb6182e391304fb3a42c51d482dcf671f540f2363 /pl/math/tools/v_erfc.sollya
parenta57d1a3f7aaf52c6cc32e264be96a14ed1cec5a0 (diff)
parent172d24a7ae67ee7bae413d5a8618f1b5edc002be (diff)
downloadarm-optimized-routines-android14-mainline-sdkext-release.tar.gz
Change-Id: I215e72558ed58a0414b9cabba3e9c567d0895c17
Diffstat (limited to 'pl/math/tools/v_erfc.sollya')
-rw-r--r--pl/math/tools/v_erfc.sollya46
1 files changed, 46 insertions, 0 deletions
diff --git a/pl/math/tools/v_erfc.sollya b/pl/math/tools/v_erfc.sollya
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+++ b/pl/math/tools/v_erfc.sollya
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+// polynomial for approximating erfc(x)*exp(x*x)
+//
+// Copyright (c) 2022-2023, Arm Limited.
+// SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
+
+deg = 12; // poly degree
+
+itv = parse(__argv[0]);
+
+bounds = [|3.725290298461914e-9,
+ 0.18920711500272103,
+ 0.41421356237309515,
+ 0.681792830507429,
+ 1,
+ 1.378414230005442,
+ 1.8284271247461903,
+ 2.363585661014858,
+ 3,
+ 3.756828460010884,
+ 4.656854249492381,
+ 5.727171322029716,
+ 7,
+ 8.513656920021768,
+ 10.313708498984761,
+ 12.454342644059432,
+ 15,
+ 18.027313840043536,
+ 21.627416997969522,
+ 25.908685288118864,
+ 31|];
+
+a = bounds[itv];
+b = bounds[itv + 1];
+
+f = proc(y) {
+ t = y + a;
+ return erfc(t) * exp(t*t);
+};
+
+poly = fpminimax(f(x), deg, [|double ...|], [0;b-a]);
+
+display = hexadecimal;
+print("rel error:", accurateinfnorm(1-poly(x)/f(x), [a;b], 30));
+print("in [",a,b,"]");
+print("coeffs:");
+for i from 0 to deg do coeff(poly, i);