### Handcrafted memory layout: a case study in magic number mayhem

Observe, in the code snippet below, that no fewer than 27 subtly different aliases have been created for the same chunk of memory...

Semantics/Syntax: The @ sign instructs the compiler to have the variables named `varsc`

and `vars`

share storage much like C's `union`

construct. The `symbolic`

keyword acts like a macro definition.

dynamic complex(64) varsc[(nx+2)/2,ny,37] @ real(64) vars[ nx+2,ny,37] symbolic mic[i,j,l] = varsc[i,j,l] , rhoc[i,j] = varsc[i,j,4] , engyc[i,j] = varsc[i,j,5] , drho_dxic[i,j,l] = varsc[i,j,l+5] , dengy_dxic[i,j,l] = varsc[i,j,l+8] , dmi_dxic[i,j,l,m] = varsc[i,j,11+(l-1)*3+m] , rhsc[i,j,l,m] = varsc[i,j,25+(l-1)*3+m] , rhs_rhoc[i,j] = varsc[i,j,21] symbolic mi[i,j,l] = vars[i,j,l] , rho[i,j] = vars[i,j,4] , engy[i,j] = vars[i,j,5] , drho_dxi[i,j,l] = vars[i,j,l+5] , dengy_dxi[i,j,l] = vars[i,j,l+8] , dmi_dxi[i,j,l,m] = vars[i,j,11+(l-1)*3+m] , rhs_rho[i,j] = vars[i,j,21] , dui_dxi[i,j,l,m] = vars[i,j,11+(l-1)*3+m] , pres[i,j] = vars[i,j,22] , tmpt[i,j] = vars[i,j,23] , mu[i,j] = vars[i,j,24] , tau[i,j,l,m] = vars[i,j,25+(l-1)*3+m] , q1[i,j] = vars[i,j,9] , q3[i,j] = vars[i,j,11] , rhs[i,j,l,m] = vars[i,j,25+(l-1)*3+m] , dmu_dx2[i,j] = vars[i,j,6] , dtmpt_dx2[i,j] = vars[i,j,7] , d2tmpt_dx22[i,j] = vars[i,j,8] , d2ui_dx22[i,j,l] = vars[i,j,8+l]

## No comments:

Post a Comment