Copyright R.A. van Engelen, FSU Department of Computer Science, 2000

 

Problem-Solving Environments

  • Supported by Center Of Excellence (Oceanography)
  • Scientific application prototyping and development
  • The CTADEL system is a translator of high-level model descriptions into efficient numerical (parallel) programs
  • CTADEL used to generate codes for HIRLAM numerical weather forecast system
  • Team members:

    • Gerard Cats (Royal Netherlands Meteorological Institute)
    Paul van der Mark
    Prof. van Engelen
    Prof. Dewar (Oceanography)
    Prof. Wolters (Leiden University)

 

Numerical Weather Forecast

  • HIRLAM (HIgh Resolution Limited Area Model)
  • Used in many European countries to predict weather
  • 3D grid with 110x100x16 (LONGxLATxVERT) points covers prediction area
  • Each grid point models local temperature, wind velocities and direction, humidity, etc.

 

Automatic Code Generation

  • Automatic code generation for weather forecast models involves the translation of model descriptions into (parallelized) Fortran programs
  • An example translation of the surface pressure equation to discretized form is shown below
Surface pressure field declaration
Surface pressure equation
Dimensional analysis
Discretization

 

Automatic Code Generation: Data Parallel Code

  • The HPF data parallel Fortran program generated:
      FORALL (j=1:nlat,i=1:nlon+1) t31(i,j) = 0
      DO k = 1,nlev-1
         FORALL (j=1:nlat,i=1:nlon+1) t31(i,j) = t31(i,j)+(p(i,j,k)
     .   +p(i-1,j,k)-p(i,j,k+1)-p(i-1,j,k+1))*(u(i-1,j,k)+u(i-1,j,k+1))
      ENDDO
      FORALL (j=1:nlat,i=1:nlon+1) t31(i,j) = -0.25*t31(i,j)
      FORALL (j=1:nlat+1,i=1:nlon) t35(i,j) = 0
      DO k = 1,nlev-1
         FORALL (j=1:nlat+1,i=1:nlon) t35(i,j) = t35(i,j)+(p(i,j,k)
     .   +p(i,j-1,k)-p(i,j,k+1)-p(i,j-1,k+1))*(v(i,j-1,k)+v(i,j-1,k+1))
      ENDDO
      FORALL (j=1:nlat+1,i=1:nlon) t35(i,j) = -0.25*t35(i,j)
      FORALL (j=1:nlat,i=1:nlon) pst(i,j) = -1.56961230576048E-7*(
     .  (1/dlam*(hyu(i,j)*t31(i+1,j)-hyu(i-1,j)*t31(i,j))+1/dtheta
     .  *(hxv(i,j)*t35(i,j+1)-hxv(i,j-1)*t35(i,j)))/(hxt(i,j)*hyt(i,j))
     .  )

 

Automatic Code Generation: Data Distribution for Message Passing Code

  • CTADEL can also generate Fortran with message passing code
  • The horizontal component of the data is distributed among the available processors
  • The Fortran code computes the forecast for each block in parallel
  • When the horizontal is split in four by four blocks, we get:
  • Each block has an overlap with neighboring blocks
  • The overlap is the data that needs to be communicated between the neighboring processors

 

Open Student Projects

  • Code generation for coupled ocean-atmosphere models