Here I am computing the distance d between two points A and B and the derivatives of d towards the coordinates of A and B
import sympy as sp sp.init_printing() X_A=sp.symbols('X_A') Y_A=sp.symbols('Y_A') Z_A=sp.symbols('Z_A') X_B=sp.symbols('X_B') Y_B=sp.symbols('Y_B') Z_B=sp.symbols('Z_B') d=sp.sqrt((X_A-X_B)**2+(Y_A-Y_B)**2+(Z_A-Z_B)**2) Q=sp.Matrix([d]) R=sp.Matrix([X_A,Y_A,Z_A,X_B,Y_B,Z_B]) dQ_dR=Q.jacobian(R) J=sp.MatrixSymbol('J',1,6) print sp.fcode(dQ_dR,J) This yields the (valid) code: J(1, 1) = (X_A - X_B)/sqrt((X_A - X_B)**2 + (Y_A - Y_B)**2 + (Z_A @ - Z_B)**2) J(1, 2) = (Y_A - Y_B)/sqrt((X_A - X_B)**2 + (Y_A - Y_B)**2 + (Z_A @ - Z_B)**2) J(1, 3) = (Z_A - Z_B)/sqrt((X_A - X_B)**2 + (Y_A - Y_B)**2 + (Z_A @ - Z_B)**2) J(1, 4) = (-X_A + X_B)/sqrt((X_A - X_B)**2 + (Y_A - Y_B)**2 + (Z_A @ - Z_B)**2) J(1, 5) = (-Y_A + Y_B)/sqrt((X_A - X_B)**2 + (Y_A - Y_B)**2 + (Z_A @ - Z_B)**2) J(1, 6) = (-Z_A + Z_B)/sqrt((X_A - X_B)**2 + (Y_A - Y_B)**2 + (Z_A @ - Z_B)**2) unfortunately, this could have been written much more efficiently: overd=1.0/sqrt((X_A - X_B)**2 + (Y_A - Y_B)**2 + (Z_A @ - Z_B)**2) J(1, 1) = (X_A - X_B)*overd J(1, 2) = (Y_A - Y_B)*overd J(1, 3) = (Z_A - Z_B)*overd J(1, 4) = (-X_A + X_B)*overd J(1, 5) = (-Y_A + Y_B)*overd J(1, 6) = (-Z_A + Z_B)*overd or even J(1, 4) = -J(1,1) J(1, 5) = -J(1,2) J(1, 6) = -J(1,3) Is there any way to have sympy recognise the possible use of such "temporary variables", or if not, at least enforce when you specify them? Would you expect compiler optimisation to catch this? -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sympy+unsubscr...@googlegroups.com. To post to this group, send email to sympy@googlegroups.com. Visit this group at https://groups.google.com/group/sympy. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/dad1a633-99b6-48dc-8507-bf96231d00d1%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.