{
"Find a Strahlkorper using a 'fast flow' method.\n"
"Based on Gundlach, PRD 57, 863 (1998).\n"
"Expands the surface in terms of spherical harmonics Y_lm up to a given\n"
"l_surface, and varies the coefficients S_lm where 0<=l<=l_surface to\n"
"minimize the residual of the apparent horizon equation. Also keeps\n"
"another representation of the surface that is expanded up to\n"
"l_mesh > l_surface. Let R_{Y_lm} be the residual computed using the\n"
"surface represented up to l_surface; this residual can in principle be\n"
"lowered to machine roundoff by enough iterations. Let R_{mesh} be the\n"
"residual computed using the surface represented up to l_mesh; this\n"
"residual represents the truncation error, since l_mesh>l_surface and\n"
"since coefficients S_lm with l>l_surface are not modified in the\n"
"iteration.\n\n"
"Convergence is achieved if R_{Y_lm}< TruncationTol*R_{mesh}, or if\n"
"R_{Y_lm}<AbsTol, where TruncationTol and AbsTol are input parameters.\n"
"If instead |R_{mesh}|_i > DivergenceTol * min_{j}(|R_{mesh}|_j) where\n"
"i is the iteration index and j runs from 0 to i-DivergenceIter, then\n"
"FastFlow exits with Status::DivergenceError. Here DivergenceIter and\n"
"DivergenceTol are input parameters."}