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Remove per-pixel atomics and dynamic scheduling from RTC _normalizeRtcArea (#341) #355

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Remove per-pixel atomics and dynamic scheduling from RTC _normalizeRtcArea (#341) #355

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18 changes: 8 additions & 10 deletions cxx/isce3/geometry/RTC.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -270,18 +270,16 @@ void _normalizeRtcArea(isce3::core::Matrix<float>& numerator_array,
pyre::journal::info_t& info)
{
info << "normalizing gamma-naught area..." << pyre::journal::endl;
_Pragma("omp parallel for schedule(dynamic) collapse(2)")
for (int i = 0; i < numerator_array.length(); ++i)
// Each (i, j) is read and written by exactly one iteration, so no
// atomics are required. Row-wise static scheduling avoids per-pixel
// dynamic dispatch overhead.
_Pragma("omp parallel for")
for (int i = 0; i < numerator_array.length(); ++i)
for (int j = 0; j < numerator_array.width(); ++j) {
const float denominator_value = denominator_array(i, j);
if (denominator_value == 0) {
_Pragma("omp atomic write")
numerator_array(i, j) =
std::numeric_limits<float>::quiet_NaN();
continue;
}
_Pragma("omp atomic update")
numerator_array(i, j) /= denominator_value;
numerator_array(i, j) = denominator_value == 0
? std::numeric_limits<float>::quiet_NaN()
: numerator_array(i, j) / denominator_value;
}
}

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