POD version of TPCFastSpaceChargeCorrection

Created from the TPCFastTransform using:
std::vector<char> buff; // can be also pmr::vector from DPL make(..) const o2::gpu::TPCFastTransformPOD& pod = o2::gpu::TPCFastTransformPOD::create(buff, tpc_fast_transform);

The buff vector will be expanded during creation and can be sent over DPL. On the receiving side, it should be cast as:
const auto& podTransform = o2::gpu::TPCFastTransformPOD::get(pc.inputs().get<gsl::span<char>>(ref));

No initialization is needed, the transform methods (at the moment all methods of TPCFastSpaceChargeCorrection are implemented) can be directly queried from the object received over sh.memory.

GPU/TPCFastTransformation/CMakeLists.txt

@@ -25,6 +25,7 @@ set(SRCS
     TPCFastSpaceChargeCorrection.cxx
     TPCFastSpaceChargeCorrectionMap.cxx
     TPCFastTransform.cxx
+    TPCFastTransformPOD.cxx
     CorrectionMapsHelper.cxx
 )
 

GPU/TPCFastTransformation/TPCFastSpaceChargeCorrection.h

@@ -37,6 +37,8 @@ namespace gpu
 ///
 class TPCFastSpaceChargeCorrection : public FlatObject
 {
+  friend class TPCFastTransformPOD;
+
  public:
   ///
   /// \brief The struct contains necessary info for TPC padrow

GPU/TPCFastTransformation/TPCFastTransformPOD.cxx

@@ -0,0 +1,138 @@
+// Copyright 2019-2020 CERN and copyright holders of ALICE O2.
+// See https://alice-o2.web.cern.ch/copyright for details of the copyright holders.
+// All rights not expressly granted are reserved.
+//
+// This software is distributed under the terms of the GNU General Public
+// License v3 (GPL Version 3), copied verbatim in the file "COPYING".
+//
+// In applying this license CERN does not waive the privileges and immunities
+// granted to it by virtue of its status as an Intergovernmental Organization
+// or submit itself to any jurisdiction.
+
+/// \file  TPCFastTransformPOD.cxx
+/// \brief Implementation of POD correction map
+///
+/// \author  [email protected]
+
+#include "TPCFastTransformPOD.h"
+
+namespace GPUCA_NAMESPACE
+{
+namespace gpu
+{
+#if !defined(GPUCA_GPUCODE)
+
+size_t TPCFastTransformPOD::estimateSize(const TPCFastTransform& src)
+{
+  // estimate size of own buffer
+  const auto& origCorr = src.getCorrection();
+  const size_t selfSizeFix = sizeof(TPCFastTransformPOD);
+  size_t nextDynOffs = alignOffset(selfSizeFix);
+  nextDynOffs = alignOffset(nextDynOffs + origCorr.mNumberOfScenarios * sizeof(size_t)); // spline scenarios start here
+  // space for splines
+  for (int isc = 0; isc < origCorr.mNumberOfScenarios; isc++) {
+    const auto& spline = origCorr.mScenarioPtr[isc];
+    nextDynOffs = alignOffset(nextDynOffs + sizeof(spline));
+  }
+  // space for splines data
+  for (int is = 0; is < 3; is++) {
+    for (int slice = 0; slice < origCorr.mGeo.getNumberOfSlices(); slice++) {
+      for (int row = 0; row < NROWS; row++) {
+        const auto& spline = origCorr.getSpline(slice, row);
+        int nPar = spline.getNumberOfParameters();
+        if (is == 1) {
+          nPar = nPar / 3;
+        }
+        if (is == 2) {
+          nPar = nPar * 2 / 3;
+        }
+        nextDynOffs += nPar * sizeof(float);
+      }
+    }
+  }
+  nextDynOffs = alignOffset(nextDynOffs);
+  return nextDynOffs;
+}
+
+const TPCFastTransformPOD& TPCFastTransformPOD::create(char* buff, size_t buffSize, const TPCFastTransform& src)
+{
+  // instantiate objec to already created buffer of the right size
+  assert(buffSize > sizeof(TPCFastTransformPOD));
+  const auto& origCorr = src.getCorrection();
+  auto& podMap = getNonConst(buff);
+
+  // copy fixed size data --- start
+  podMap.mNumberOfScenarios = origCorr.mNumberOfScenarios;
+  std::memcpy(&podMap.mGeo, &origCorr.mGeo, sizeof(TPCFastTransformGeo)); // copy geometry (fixed size)
+  for (int row = 0; row < NROWS; row++) {
+    podMap.mRowInfo[row] = origCorr.getRowInfo(row); // dataOffsetBytes will be modified later
+  }
+  for (int slice = 0; slice < TPCFastTransformGeo::getNumberOfSlices(); slice++) {
+    podMap.mSliceInfo[slice] = origCorr.getSliceInfo(slice);
+    for (int row = 0; row < NROWS; row++) {
+      podMap.mSliceRowInfo[NROWS * slice + row] = origCorr.getSliceRowInfo(slice, row);
+    }
+  }
+  podMap.mInterpolationSafetyMargin = origCorr.fInterpolationSafetyMargin;
+  podMap.mTimeStamp = origCorr.mTimeStamp;
+  // copy fixed size data --- end
+
+  size_t nextDynOffs = alignOffset(sizeof(TPCFastTransformPOD));
+  // copy slice scenarios
+  podMap.mOffsScenariosOffsets = nextDynOffs; // spline scenarios offsets start here
+  LOGP(debug, "Set mOffsScenariosOffsets = {}", podMap.mOffsScenariosOffsets);
+  nextDynOffs = alignOffset(nextDynOffs + podMap.mNumberOfScenarios * sizeof(size_t)); // spline scenarios start here
+
+  // copy spline objects
+  size_t* scenOffs = reinterpret_cast<size_t*>(buff + podMap.mOffsScenariosOffsets);
+  for (int isc = 0; isc < origCorr.mNumberOfScenarios; isc++) {
+    scenOffs[isc] = nextDynOffs;
+    const auto& spline = origCorr.mScenarioPtr[isc];
+    if (buffSize < nextDynOffs + sizeof(spline)) {
+      throw std::runtime_error(fmt::format("attempt to copy {} bytes for spline for scenario {} to {}, overflowing the buffer of size {}", sizeof(spline), isc, nextDynOffs + sizeof(spline), buffSize));
+    }
+    std::memcpy(buff + scenOffs[isc], &spline, sizeof(spline));
+    nextDynOffs = alignOffset(nextDynOffs + sizeof(spline));
+    LOGP(debug, "Copy {} bytes for spline scenario {} (ptr:{}) to offsset {}", sizeof(spline), isc, (void*)&spline, scenOffs[isc]);
+  }
+
+  // copy splines data
+  for (int is = 0; is < 3; is++) {
+    float* data = reinterpret_cast<float*>(buff + nextDynOffs);
+    LOGP(debug, "splinID={} start offset {} -> {}", is, nextDynOffs, (void*)data);
+    for (int slice = 0; slice < origCorr.mGeo.getNumberOfSlices(); slice++) {
+      podMap.mSplineDataOffsets[slice][is] = nextDynOffs;
+      size_t rowDataOffs = 0;
+      for (int row = 0; row < NROWS; row++) {
+        const auto& spline = origCorr.getSpline(slice, row);
+        const float* dataOr = origCorr.getSplineData(slice, row, is);
+        int nPar = spline.getNumberOfParameters();
+        if (is == 1) {
+          nPar = nPar / 3;
+        }
+        if (is == 2) {
+          nPar = nPar * 2 / 3;
+        }
+        LOGP(debug, "Copying {} floats for spline{} of slice:{} row:{} to offset {}", nPar, is, slice, row, nextDynOffs);
+        size_t nbcopy = nPar * sizeof(float);
+        if (buffSize < nextDynOffs + nbcopy) {
+          throw std::runtime_error(fmt::format("attempt to copy {} bytes of data for spline{} of slice{}/row{} to {}, overflowing the buffer of size {}", nbcopy, is, slice, row, nextDynOffs, buffSize));
+        }
+        std::memcpy(data, dataOr, nbcopy);
+        podMap.getRowInfo(row).dataOffsetBytes[is] = rowDataOffs;
+        rowDataOffs += nbcopy;
+        data += nPar;
+        nextDynOffs += nbcopy;
+      }
+    }
+  }
+  podMap.mTotalSize = alignOffset(nextDynOffs);
+  if (buffSize != podMap.mTotalSize) {
+    throw std::runtime_error(fmt::format("Estimated buffer size {} differs from filled one {}", buffSize, podMap.mTotalSize));
+  }
+  return podMap;
+}
+#endif
+
+} // namespace gpu
+} // namespace GPUCA_NAMESPACE