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79 lines
1.6 KiB
79 lines
1.6 KiB
/*++
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Copyright (c) 1998 Microsoft Corporation
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Module Name:
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decayacc.cpp
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Abstract:
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SIS Groveler decaying accumulator
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Authors:
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John Douceur, 1998
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Environment:
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User Mode
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Revision History:
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--*/
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#include "all.hxx"
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DecayingAccumulator::DecayingAccumulator(
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unsigned int time_constant)
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{
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ASSERT(this != 0);
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this->time_constant = double(time_constant);
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ASSERT(this->time_constant >= 0.0);
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decaying_accumulation = 0.0;
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update_time = GET_TICK_COUNT();
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}
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void
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DecayingAccumulator::increment(
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int increase)
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{
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ASSERT(this != 0);
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ASSERT(time_constant >= 0.0);
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ASSERT(decaying_accumulation >= 0.0);
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ASSERT(increase >= 0);
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unsigned int current_time = GET_TICK_COUNT();
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unsigned int elapsed_time = current_time - update_time;
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ASSERT(signed(elapsed_time) >= 0);
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double coefficient = 0.0;
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if (time_constant > 0.0)
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{
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coefficient = exp(-double(elapsed_time)/time_constant);
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}
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ASSERT(coefficient >= 0.0);
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ASSERT(coefficient <= 1.0);
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decaying_accumulation =
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coefficient * decaying_accumulation + double(increase);
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ASSERT(decaying_accumulation >= 0.0);
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update_time = current_time;
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}
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double
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DecayingAccumulator::retrieve_value() const
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{
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ASSERT(this != 0);
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ASSERT(time_constant >= 0.0);
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ASSERT(decaying_accumulation >= 0.0);
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unsigned int current_time = GET_TICK_COUNT();
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unsigned int elapsed_time = current_time - update_time;
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ASSERT(signed(elapsed_time) >= 0);
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double coefficient = 0.0;
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if (time_constant > 0.0)
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{
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coefficient = exp(-double(elapsed_time)/time_constant);
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}
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ASSERT(coefficient >= 0.0);
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ASSERT(coefficient <= 1.0);
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return coefficient * decaying_accumulation;
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}
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