From 0ac466e55ded15d3b00ad4b776a0c15c11042eba Mon Sep 17 00:00:00 2001
From: Ewan Barr <ewanbarr@krpc74.mpifr-bonn.mpg.de>
Date: Tue, 11 Dec 2018 13:15:42 +0100
Subject: [PATCH] changed offset and scaling calculation
---
psrdada_cpp/effelsberg/edd/FftSpectrometer.cuh | 3 +--
.../effelsberg/edd/detail/FftSpectrometer.cu | 13 ++++++++-----
.../effelsberg/edd/src/fft_spectrometer_cli.cu | 11 +++++------
.../edd/test/src/FftSpectrometerTester.cu | 2 +-
4 files changed, 15 insertions(+), 14 deletions(-)
diff --git a/psrdada_cpp/effelsberg/edd/FftSpectrometer.cuh b/psrdada_cpp/effelsberg/edd/FftSpectrometer.cuh
index 75202028..ca3a6862 100644
--- a/psrdada_cpp/effelsberg/edd/FftSpectrometer.cuh
+++ b/psrdada_cpp/effelsberg/edd/FftSpectrometer.cuh
@@ -63,8 +63,7 @@ private:
std::size_t _fft_length;
std::size_t _naccumulate;
std::size_t _nbits;
- float _scaling;
- float _offset;
+ float _input_level;
HandlerType& _handler;
cufftHandle _fft_plan;
int _nchans;
diff --git a/psrdada_cpp/effelsberg/edd/detail/FftSpectrometer.cu b/psrdada_cpp/effelsberg/edd/detail/FftSpectrometer.cu
index edce0e13..33d464a9 100644
--- a/psrdada_cpp/effelsberg/edd/detail/FftSpectrometer.cu
+++ b/psrdada_cpp/effelsberg/edd/detail/FftSpectrometer.cu
@@ -14,15 +14,13 @@ FftSpectrometer<HandlerType>::FftSpectrometer(
std::size_t fft_length,
std::size_t naccumulate,
std::size_t nbits,
- float scaling,
- float offset,
+ float input_level,
HandlerType& handler)
: _buffer_bytes(buffer_bytes)
, _fft_length(fft_length)
, _naccumulate(naccumulate)
, _nbits(nbits)
- , _scaling(scaling)
- , _offset(offset)
+ , _input_level(input_level)
, _handler(handler)
, _fft_plan(0)
, _call_count(0)
@@ -38,6 +36,11 @@ FftSpectrometer<HandlerType>::FftSpectrometer(
std::size_t n64bit_words = buffer_bytes / sizeof(uint64_t);
_nchans = _fft_length / 2 + 1;
int batch = nsamps_per_buffer/_fft_length;
+ BOOST_LOG_TRIVIAL(debug) << "Calculating scales and offsets";
+ float dof = 2 * _naccumulate;
+ float scale = (_input_level * np.sqrt(_nchans))**2;
+ float offset = scale * dof;
+ float scaling = scale * std::sqrt(2 * dof);
BOOST_LOG_TRIVIAL(debug) << "Generating FFT plan";
int n[] = {static_cast<int>(_fft_length)};
CUFFT_ERROR_CHECK(cufftPlanMany(&_fft_plan, 1, n, NULL, 1, _fft_length,
@@ -55,7 +58,7 @@ FftSpectrometer<HandlerType>::FftSpectrometer(
CUFFT_ERROR_CHECK(cufftSetStream(_fft_plan, _proc_stream));
_unpacker.reset(new Unpacker(_proc_stream));
_detector.reset(new DetectorAccumulator(_nchans, _naccumulate,
- _scaling, _offset, _proc_stream));
+ scaling, offset, _proc_stream));
}
template <class HandlerType>
diff --git a/psrdada_cpp/effelsberg/edd/src/fft_spectrometer_cli.cu b/psrdada_cpp/effelsberg/edd/src/fft_spectrometer_cli.cu
index 537108e8..f929813a 100644
--- a/psrdada_cpp/effelsberg/edd/src/fft_spectrometer_cli.cu
+++ b/psrdada_cpp/effelsberg/edd/src/fft_spectrometer_cli.cu
@@ -30,8 +30,7 @@ int main(int argc, char** argv)
int nsamps_per_block;
int naccumulate;
int nbits;
- float scaling;
- float offset;
+ float input_level;
std::time_t now = std::time(NULL);
std::tm * ptm = std::localtime(&now);
char buffer[32];
@@ -62,8 +61,8 @@ int main(int argc, char** argv)
("nbits,b", po::value<int>(&nbits)->required(),
"The number of bits per sample in the packetiser output (8 or 12)")
- ("scaling", po::value<float>(&scaling)->required(),
- "The power scaling for data produced by the spectrometer (used for conversion back to 8-bit)")
+ ("input_level", po::value<float>(&input_level)->required(),
+ "The input power level (standard deviation, used for 8-bit conversion)")
("offset", po::value<float>(&offset)->required(),
"The power offset for data produced by the spectrometer (used for conversion back to 8-bit)")
@@ -86,7 +85,7 @@ int main(int argc, char** argv)
po::store(po::parse_command_line(argc, argv, desc), vm);
if ( vm.count("help") )
{
- std::cout << "EDDFFT -- Read EDD data from a DADA buffer and perform a simple FFT spectrometer"
+ std::cout << "FftSpectrometer -- Read EDD data from a DADA buffer and perform a simple FFT spectrometer"
<< std::endl << desc << std::endl;
return SUCCESS;
}
@@ -106,7 +105,7 @@ int main(int argc, char** argv)
std::size_t buffer_bytes = client.data_buffer_size()
SimpleFileWriter sink(filename);
//NullSink sink;
- effelsberg::edd::FftSpectrometer<decltype(sink)> spectrometer(buffer_bytes, fft_length, naccumulate, nbits, scaling, offset, sink);
+ effelsberg::edd::FftSpectrometer<decltype(sink)> spectrometer(buffer_bytes, fft_length, naccumulate, nbits, input_level, sink);
DadaInputStream<decltype(spectrometer)> istream(input_key, log, spectrometer);
istream.start();
/**
diff --git a/psrdada_cpp/effelsberg/edd/test/src/FftSpectrometerTester.cu b/psrdada_cpp/effelsberg/edd/test/src/FftSpectrometerTester.cu
index 15929fae..efb8b709 100644
--- a/psrdada_cpp/effelsberg/edd/test/src/FftSpectrometerTester.cu
+++ b/psrdada_cpp/effelsberg/edd/test/src/FftSpectrometerTester.cu
@@ -42,7 +42,7 @@ void FftSpectrometerTester::performance_test(
std::vector<char> header_block(4096);
RawBytes header_raw_bytes(header_block.data(), 4096, 4096);
NullSink null_sink;
- FftSpectrometer<NullSink> spectrometer(input_block_bytes, fft_length, tscrunch, nbits, 1.0f, 0.0f, null_sink);
+ FftSpectrometer<NullSink> spectrometer(input_block_bytes, fft_length, tscrunch, nbits, 16.0f, null_sink);
spectrometer.init(header_raw_bytes);
for (int ii = 0; ii < 100; ++ii)
{
--
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