From 837db021f41e8b081b1531b2f0fe3085305c3a4b Mon Sep 17 00:00:00 2001
From: Ernst Hellbar <ernst.hellbar@cern.ch>
Date: Thu, 18 Jun 2026 14:02:05 +0200
Subject: [PATCH] TPC: fix initialization of FFTW arrays in aggregator-ft

---
 .../include/TPCCalibration/IDCFourierTransform.h     | 12 +++++-------
 .../TPC/calibration/src/IDCFourierTransform.cxx      |  2 ++
 .../test/testO2TPCIDCFourierTransform.cxx            |  2 ++
 .../TPCWorkflow/TPCFourierTransformAggregatorSpec.h  |  3 +++
 4 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/Detectors/TPC/calibration/include/TPCCalibration/IDCFourierTransform.h b/Detectors/TPC/calibration/include/TPCCalibration/IDCFourierTransform.h
index 8a27321e131f3..db79695ce9834 100644
--- a/Detectors/TPC/calibration/include/TPCCalibration/IDCFourierTransform.h
+++ b/Detectors/TPC/calibration/include/TPCCalibration/IDCFourierTransform.h
@@ -45,8 +45,7 @@ class IDCFourierTransform : public IDCFourierTransformBase<Type>
   template <bool IsEnabled = true, typename std::enable_if<(IsEnabled && (std::is_same<Type, IDCFourierTransformBaseAggregator>::value)), int>::type = 0>
   IDCFourierTransform(const unsigned int rangeIDC = 200, const unsigned int nFourierCoefficientsStore = 200 + 2) : IDCFourierTransformAggregator(rangeIDC), mFourierCoefficients{1, nFourierCoefficientsStore}, mVal1DIDCs(sNThreads), mCoefficients(sNThreads)
   {
-    initFFTW3Members();
-  };
+  }
 
   /// constructor for  EPN type
   /// \param rangeIDC number of IDCs for each interval which will be used to calculate the fourier coefficients
@@ -54,8 +53,7 @@ class IDCFourierTransform : public IDCFourierTransformBase<Type>
   template <bool IsEnabled = true, typename std::enable_if<(IsEnabled && (std::is_same<Type, IDCFourierTransformBaseEPN>::value)), int>::type = 0>
   IDCFourierTransform(const unsigned int rangeIDC = 200, const unsigned int nFourierCoefficientsStore = 200 + 2) : IDCFourierTransformEPN(rangeIDC), mFourierCoefficients{1, nFourierCoefficientsStore}, mVal1DIDCs(sNThreads), mCoefficients(sNThreads)
   {
-    initFFTW3Members();
-  };
+  }
 
   // Destructor
   ~IDCFourierTransform();
@@ -72,6 +70,9 @@ class IDCFourierTransform : public IDCFourierTransformBase<Type>
     sNThreads = nThreads;
   }
 
+  /// initalizing fftw members, e.g. when changing sNThreads via setNThreads after first initialization
+  void initFFTW3Members();
+
   /// calculate fourier coefficients for one TPC side
   template <bool IsEnabled = true, typename std::enable_if<(IsEnabled && (std::is_same<Type, IDCFourierTransformBaseAggregator>::value)), int>::type = 0>
   void calcFourierCoefficients(const unsigned int timeFrames = 2000)
@@ -155,9 +156,6 @@ class IDCFourierTransform : public IDCFourierTransformBase<Type>
   /// \return returns maximum numbers of stored real/imag fourier coeffiecients
   unsigned int getNMaxCoefficients() const { return this->mRangeIDC / 2 + 1; }
 
-  /// initalizing fftw members
-  void initFFTW3Members();
-
   /// performing of ft using FFTW
   void fftwLoop(const std::vector<float>& idcOneExpanded, const std::vector<unsigned int>& offsetIndex, const unsigned int interval, const unsigned int thread);
 
diff --git a/Detectors/TPC/calibration/src/IDCFourierTransform.cxx b/Detectors/TPC/calibration/src/IDCFourierTransform.cxx
index c4b92b57c17ab..437fa4b8f1991 100644
--- a/Detectors/TPC/calibration/src/IDCFourierTransform.cxx
+++ b/Detectors/TPC/calibration/src/IDCFourierTransform.cxx
@@ -35,6 +35,8 @@ o2::tpc::IDCFourierTransform<Type>::~IDCFourierTransform()
 template <class Type>
 void o2::tpc::IDCFourierTransform<Type>::initFFTW3Members()
 {
+  mVal1DIDCs.resize(sNThreads);
+  mCoefficients.resize(sNThreads);
   for (int thread = 0; thread < sNThreads; ++thread) {
     mVal1DIDCs[thread] = fftwf_alloc_real(this->mRangeIDC);
     mCoefficients[thread] = fftwf_alloc_complex(getNMaxCoefficients());
diff --git a/Detectors/TPC/calibration/test/testO2TPCIDCFourierTransform.cxx b/Detectors/TPC/calibration/test/testO2TPCIDCFourierTransform.cxx
index c71889bfd2d08..874206ddf8add 100644
--- a/Detectors/TPC/calibration/test/testO2TPCIDCFourierTransform.cxx
+++ b/Detectors/TPC/calibration/test/testO2TPCIDCFourierTransform.cxx
@@ -67,6 +67,7 @@ BOOST_AUTO_TEST_CASE(IDCFourierTransformAggregator_test)
     FtType::setNThreads(2);
 
     FtType idcFourierTransform{rangeIDC, nFourierCoeff};
+    idcFourierTransform.initFFTW3Members();
     const auto intervalsPerTF = getIntegrationIntervalsPerTF(integrationIntervals, tfs);
     idcFourierTransform.setIDCs(get1DIDCs(intervalsPerTF), intervalsPerTF);
     idcFourierTransform.setIDCs(get1DIDCs(intervalsPerTF), intervalsPerTF);
@@ -105,6 +106,7 @@ BOOST_AUTO_TEST_CASE(IDCFourierTransformEPN_test)
       const bool fft = iType == 0 ? false : true;
       FtType::setFFT(fft);
       FtType idcFourierTransform{rangeIDC, nFourierCoeff};
+      idcFourierTransform.initFFTW3Members();
       const auto intervalsPerTF = getIntegrationIntervalsPerTF(integrationIntervals, tfs);
       idcFourierTransform.setIDCs(get1DIDCs(intervalsPerTF));
       idcFourierTransform.calcFourierCoefficients();
diff --git a/Detectors/TPC/workflow/include/TPCWorkflow/TPCFourierTransformAggregatorSpec.h b/Detectors/TPC/workflow/include/TPCWorkflow/TPCFourierTransformAggregatorSpec.h
index 7facee78fb3d6..9c64634b438d9 100644
--- a/Detectors/TPC/workflow/include/TPCWorkflow/TPCFourierTransformAggregatorSpec.h
+++ b/Detectors/TPC/workflow/include/TPCWorkflow/TPCFourierTransformAggregatorSpec.h
@@ -66,6 +66,9 @@ class TPCFourierTransformAggregatorSpec : public o2::framework::Task
     mEnableFFTCCDB = ic.options().get<bool>("enable-fft-CCDB");
     int nthreads = ic.options().get<int>("nthreads");
     TPCFourierTransformAggregatorSpec::IDCFType::setNThreads(nthreads);
+    for (auto& fourierTransform : mIDCFourierTransform) {
+      fourierTransform.initFFTW3Members();
+    }
     resizeBuffer(mInputLanes);
   }