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55 lines
2.1 KiB
C++
55 lines
2.1 KiB
C++
// Copyright 2023 Google LLC
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// SPDX-License-Identifier: Apache-2.0
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef HIGHWAY_HWY_TIMER_H_
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#define HIGHWAY_HWY_TIMER_H_
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// Platform-specific timer functions. Provides Now() and functions for
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// interpreting and converting the timer-inl.h Ticks.
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#include <stdint.h>
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#include "hwy/highway_export.h"
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namespace hwy {
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namespace platform {
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// Returns current timestamp [in seconds] relative to an unspecified origin.
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// Features: monotonic (no negative elapsed time), steady (unaffected by system
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// time changes), high-resolution (on the order of microseconds).
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// Uses InvariantTicksPerSecond and the baseline version of timer::Start().
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HWY_DLLEXPORT double Now();
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// Functions for use with timer-inl.h:
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// Returns whether it is safe to call timer::Stop without executing an illegal
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// instruction; if false, fills cpu100 (a pointer to a 100 character buffer)
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// with the CPU brand string or an empty string if unknown.
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HWY_DLLEXPORT bool HaveTimerStop(char* cpu100);
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// Returns tick rate, useful for converting timer::Ticks to seconds. Invariant
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// means the tick counter frequency is independent of CPU throttling or sleep.
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// This call may be expensive, callers should cache the result.
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HWY_DLLEXPORT double InvariantTicksPerSecond();
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// Returns ticks elapsed in back to back timer calls, i.e. a function of the
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// timer resolution (minimum measurable difference) and overhead.
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// This call is expensive, callers should cache the result.
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HWY_DLLEXPORT uint64_t TimerResolution();
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} // namespace platform
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} // namespace hwy
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#endif // HIGHWAY_HWY_TIMER_H_
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