clean up jacobian.c

jacobian/jacobian.c

-#include <math.h>  /* log */
 #include <pari/pari.h>
 
-#include "algsmall.h"
 #include "finite-fields.h"
-#include "matsmall.h"
 
 #include "addflip-chain.h"
 #include "curve.h"
@@ -25,60 +22,29 @@
   and we need to know  \Gamma(X,{\cal L}_0^i)  for  i <= 9.
 */
 
-static GEN
-jacobian_V (GEN X) {
-  switch (jacobian_type (X)) {
+static long
+jacobian_power(GEN J) {
+  switch (jacobian_type(J)) {
   case JACOBIAN_TYPE_MEDIUM:
     /* For the medium model,  V = \Gamma(X,{\cal L}_0^2).  */
-    return jacobian_V_0_2 (X);
+    return 2;
   case JACOBIAN_TYPE_LARGE:
     /* For the large model,  V = \Gamma(X,{\cal L}_0^3).  */
-    return jacobian_V_0_3 (X);
+    return 3;
   default:
-    pari_err (e_MISC, "invalid type for the Jacobian");
-    return NULL;
+    pari_err(e_MISC, "invalid type for the Jacobian");
+    return 0;
   }
 }
 
 static GEN
-jacobian_IGS_V (GEN X) {
-  switch (jacobian_type (X)) {
-  case JACOBIAN_TYPE_MEDIUM:
-    return curve_IGS_V (X, 2);
-  case JACOBIAN_TYPE_LARGE:
-    return curve_IGS_V (X, 3);
-  default:
-    pari_err (e_MISC, "invalid type for the Jacobian");
-    return NULL;
-  }
+jacobian_V(GEN J) {
+  return curve_V(J, jacobian_power(J));
 }
 
-static int
-jacobian_deg_L (GEN X) {
-  switch (jacobian_type (X)) {
-  case JACOBIAN_TYPE_MEDIUM:
-    /* For the medium model,  {\cal L} = {\cal L}_0^2.  */
-    return 2 * jacobian_deg_L_0 (X);
-  case JACOBIAN_TYPE_LARGE:
-    /* For the large model,  {\cal L} = {\cal L}_0^3.  */
-    return 3 * jacobian_deg_L_0 (X);
-  default:
-    pari_err (e_MISC, "invalid type for the Jacobian");
-    return 0;
-  }
-}
-
-static int
-jacobian_dim_V_2 (GEN X) {
-  switch (jacobian_type (X)) {
-  case JACOBIAN_TYPE_MEDIUM:
-    return lg (curve_V (X, 4)) - 1;
-  case JACOBIAN_TYPE_LARGE:
-    return lg (curve_V (X, 6)) - 1;
-  default:
-    pari_err (e_MISC, "invalid type for the Jacobian");
-    return 0;
-  }
+static GEN
+jacobian_IGS_V(GEN J) {
+  return curve_IGS_V(J, jacobian_power(J));
 }
 
 /*
@@ -89,25 +55,7 @@ jacobian_dim_V_2 (GEN X) {
 */
 GEN
 jacobian_deflate (GEN X, GEN W_D) {
-  unsigned long p = curve_base_field_characteristic (X);
-  GEN T = curve_base_field_polynomial (X);
-  GEN V = jacobian_V (X);
-  int degree_D = jacobian_divisor_deg (X, W_D);
-  int dim_W_2_D = jacobian_dim_V_2 (X) - degree_D;
-  const float alpha = 0.9;
-  int h = 1 + ceil (log ((jacobian_deg_L (X) - degree_D) / alpha)
-		    / log_ffsize (p, T));
-  GEN IGS, IGS_V;
-  pari_sp av = avma;
-
-  if (lg(W_D) < 4)
-    return gcopy(W_D);
-  do {
-    avma = av;
-    IGS = matsmall_random_subspace(W_D, h, 0, p, T);
-    IGS_V = curve_multiply_subspaces(X, IGS, V);
-  } while (lg (IGS_V) - 1 < dim_W_2_D);
-  return gerepileupto(av, IGS);
+  return curve_divisor_IGS(X, W_D, jacobian_power(X));
 }
 
 /*
@@ -118,18 +66,7 @@ GEN
 jacobian_inflate (GEN X, GEN IGS_D) {
   GEN V = jacobian_V (X);
   pari_sp av = avma;
-  int i;
-  switch (jacobian_type(X)) {
-  case JACOBIAN_TYPE_MEDIUM:
-    i = 2;
-    break;
-  case JACOBIAN_TYPE_LARGE:
-    i = 3;
-    break;
-  default:
-    pari_err (e_MISC, "invalid type for the Jacobian");
-    return NULL;
-  }
+  long i = jacobian_power(X);
   return gerepileupto(av, curve_divide_subspaces
 		      (X, curve_multiply_subspaces(X, IGS_D, V), 2 * i,
 		       jacobian_IGS_V(X), i));
@@ -146,18 +83,7 @@ GEN
 jacobian_flip (GEN X, GEN W_D, GEN s) {
   GEN V = jacobian_V (X);
   pari_sp av = avma;
-  int i;
-  switch (jacobian_type (X)) {
-  case JACOBIAN_TYPE_MEDIUM:
-    i = 2;
-    break;
-  case JACOBIAN_TYPE_LARGE:
-    i = 3;
-    break;
-  default:
-    pari_err (e_MISC, "invalid type for the Jacobian");
-    return NULL;
-  }
+  long i = jacobian_power(X);
   return gerepileupto (av, curve_divide_subspaces
 		       (X, curve_multiply_section_subspace(X, s, V), 2*i,
 			jacobian_deflate (X, W_D), i));
@@ -603,18 +529,9 @@ jacobian_count_points (GEN J) {
 
 GEN
 jacobian_random_point (GEN J) {
-  /*
-    We need to find a random divisor of degree  d.
-    In the case of the large model, the choice below means that
-    we pick a small divisor.
-  */
-  long d = curve_degree (J);
-  if (jacobian_type (J) == JACOBIAN_TYPE_MEDIUM)
-    return curve_random_divisor (J, d, 2);
-  if (jacobian_type (J) == JACOBIAN_TYPE_LARGE)
-    return curve_random_divisor (J, d, 3);
-  pari_err (e_MISC, "invalid type for the Jacobian");
-  return NULL;
+  /* In the case of the large model, we pick a small divisor.  */
+  return curve_random_divisor(J, curve_degree(J),
+			      jacobian_power(J));
 }
 
 GEN