Bug#776802: We need a bigger pari stack size

[Julien Puydt]

Package: lcalc
Version: 1.23+dfsg-3

the current debian package doesn't work as well as sagemath hopes it to:

jpuydt at cauchy:~$ lcalc -z 3 -e --a1 0 --a2 0 --a3 1 --a4 -1 --a6 0
   ***   Warning: new stack size = 1028928 (0.981 Mbytes).
   ***   Error in the PARI system. End of program.

whereas using sagemath's version (on another box) :
(sage-sh) jpuydt at localhost:sage-6.4.1$ lcalc -z 3 -e --a1 0 --a2 0 --a3 
1 --a4 -1 --a6 0
  0
  5.00317001401
  6.87039121695

indeed, one of sagemath's patches against lcalc is to use a larger pari 
stack -- it is named init_stack.patch and contains :
diff -ru src/include/Lcommandline.h b/include/Lcommandline.h
--- src/include/Lcommandline.h	2012-08-08 23:21:55.000000000 +0200
+++ b/include/Lcommandline.h	2014-01-06 14:04:55.981027532 +0100
@@ -40,12 +40,7 @@
  #include "Lcommandline_globals.h"      //command line global variables
  #ifdef INCLUDE_PARI
  #include "pari.h"          //for pari's elliptic curve functions
-#undef init                //pari has a '#define init pari_init' which
-                           //causes trouble with the stream.h init.
-                           //pari also causes trouble with things like abs.
-                           //we place the pari include first since 
otherwise it
-                           //messes up.
-
+#include "paripriv.h"      //for pari_init_stack()
  #endif //ifdef INCLUDE_PARI


diff -ru src/src/Lcommandline.cc b/src/Lcommandline.cc
--- src/src/Lcommandline.cc	2012-08-08 23:21:56.000000000 +0200
+++ b/src/Lcommandline.cc	2014-01-06 14:02:19.463388366 +0100
@@ -473,7 +473,9 @@

  #ifdef INCLUDE_PARI
          if(do_elliptic_curve){
-             allocatemoremem((int) N_terms*16+1000000); //XXXXXXXXX 
this should depend on whether we're double or long double or mpfr double
+             // Reallocate PARI stack
+             pari_init_stack((size_t)N_terms*16 + 1000000, top-bot); 
//XXXXXXXXX this should depend on whether we're double or long double or 
mpfr double
+
               if (my_verbose>0) cout << "Will precompute " << N_terms 
<< " elliptic L-function dirichlet coefficients..." << endl;
               initialize_new_L(a1,a2,a3,a4,a6,N_terms);
          }


This patch doesn't seem to apply cleanly, and even so the include needs 
a "pari/paripriv.h", but  it looks like something like this would help us.

I will work on this problem in debian-science's git, but I still wanted 
it clearly reported.

Snark on #debian-science