d99fa58ced
Review URL: http://webrtc-codereview.appspot.com/42001 git-svn-id: http://webrtc.googlecode.com/svn/trunk@95 4adac7df-926f-26a2-2b94-8c16560cd09d
39 lines
1.3 KiB
C
39 lines
1.3 KiB
C
/*
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* Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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/*
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* This file contains the function WebRtcSpl_Sqrt().
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* The description header can be found in signal_processing_library.h
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*
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*/
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#include "signal_processing_library.h"
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#define iter1(N) \
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try1 = root + (1 << (N)); \
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if (value >= try1 << (N)) \
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{ \
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value -= try1 << (N); \
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root |= 2 << (N); \
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}
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// (out) Square root of input parameter
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WebRtc_Word32 WebRtcSpl_Sqrt(WebRtc_Word32 value) {
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// new routine for performance, 4 cycles/bit in ARM
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// output precision is 16 bits
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WebRtc_Word32 root = 0, try1;
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iter1 (15); iter1 (14); iter1 (13); iter1 (12);
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iter1 (11); iter1 (10); iter1 ( 9); iter1 ( 8);
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iter1 ( 7); iter1 ( 6); iter1 ( 5); iter1 ( 4);
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iter1 ( 3); iter1 ( 2); iter1 ( 1); iter1 ( 0);
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return root >> 1;
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}
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