code: @Override
      public int iamax(INDArray arr) {
          if (arr.isSparse()) {
              return Nd4j.getSparseBlasWrapper().level1().iamax(arr);
          }
          if (Nd4j.getExecutioner().getProfilingMode() == OpExecutioner.ProfilingMode.ALL)
              OpProfiler.getInstance().processBlasCall(false, arr);
  
          if (arr.data().dataType() == DataType.DOUBLE) {
              DefaultOpExecutioner.validateDataType(DataType.DOUBLE, arr);
              return idamax(arr.length(), arr, BlasBufferUtil.getBlasStride(arr));
          } else {
              DefaultOpExecutioner.validateDataType(DataType.FLOAT, arr);
              return isamax(arr.length(), arr, BlasBufferUtil.getBlasStride(arr));
          }
      }
docs: finds the element of a
  vector that has the largest absolute value.
  
  @param arr
  @return