[tmva] MLP codegen threadsafety

[pseyfert]

as it turnes out the ...class.C files generated by the TMVA MLP are not thread safe (fWeights is a constant array of contant pointers to beginnings of double arrays, and the contents therein vary at runtime inside the GetMvaValue__ method)

So the quick hack here is to replace the class member of dynamically allocated arrays by fixed sized arrays in the function scope.

QUASICODE OLD

class mlp {
  private:
    double *fweights[3]
    mlp() {
      fweights[0] = new double[5];
      fweights[1] = new double[10];
      fweights[2] = new double[1];
    }
    ~mlp() {
      delete fweights[0];
      delete fweights[1];
      delete fweights[2];
    }
    getmvavalue( std::vector<double> input) const {
       fweights[0] = input;
       fweights[1]  = some_function(fweights[0]);
       fweights[2] = some_other_function(fweights[1]);
       return fweights[2][0];
    }

QUASICODE NEW

class mlp {
  private:
    mlp() {
    }
    ~mlp() {
    }
    getmvavalue( std::vector<double> input) const {

      double fweights0[5];
      double fweights1[10];
      double fweights2[1];
       fweights0 = input;
       fweights1  = some_function(fweights0);
       fweights2 = some_other_function(fweights1);
       return fweights2[0];
    }

[phsft-bot]

Can one of the admins verify this patch?

[pseyfert]

NB: opened the PR to make the draft public and open the discussion thread. no need to let jenkins run haven't tested the output of the codegen yet.

[pseyfert]

• root builds
• formatting applied
• ran tutorials/tmva/TMVAClassification.C (produces .class.C files)
• class.C files compile
• checked consistency with master branch with rapidcheck link

from my side good to merge.

NB: in the rapidcheck repo you can also see how my change changes the generated code by comparing the class.C files.

[gganis]

@phsft-bot build!

[phsft-bot]

Starting build on gcc49/centos7, native/mac1012, gcc49/slc6, gcc62/slc6, native/ubuntu14 with CMake flags -Dvc=OFF -Dimt=ON -Dccache=ON

[phsft-bot]

Build failed on mac1012/native.
See console output.

Warnings:

• include/TMVA/DNN/Architectures/Cpu/CpuMatrix.h:62:50: warning: instantiation of variable 'TMVA::DNN::TCpuMatrix<double>::fOnes' required here, but no definition is available [-Wundefined-var-template]
• include/TMVA/DNN/Architectures/Cpu/CpuMatrix.h:144:4: warning: instantiation of variable 'TMVA::DNN::TCpuMatrix<double>::fPool' required here, but no definition is available [-Wundefined-var-template]
• include/TMVA/DNN/Architectures/Cpu/CpuMatrix.h:62:50: warning: instantiation of variable 'TMVA::DNN::TCpuMatrix<float>::fOnes' required here, but no definition is available [-Wundefined-var-template]
• include/TMVA/DNN/Architectures/Cpu/CpuMatrix.h:144:4: warning: instantiation of variable 'TMVA::DNN::TCpuMatrix<float>::fPool' required here, but no definition is available [-Wundefined-var-template]

[vgvassilev]

@phsft-bot build!