Make COMB_BLOCKS and COMB_TEETH configurable, and test in Travis

Author: sipa

.travis.yml

@@ -11,7 +11,7 @@ cache:
   - src/java/guava/
 env:
   global:
-    - FIELD=auto  BIGNUM=auto  SCALAR=auto  ENDOMORPHISM=no  STATICPRECOMPUTATION=yes  ECMULTGENPRECISION=auto  ASM=no  BUILD=check  EXTRAFLAGS=  HOST=  ECDH=no  RECOVERY=no  EXPERIMENTAL=no  JNI=no
+    - FIELD=auto  BIGNUM=auto  SCALAR=auto  ENDOMORPHISM=no  STATICPRECOMPUTATION=yes  ECMULTGENBLOCKS=auto  ECMULTGENTEETH=auto  ASM=no  BUILD=check  EXTRAFLAGS=  HOST=  ECDH=no  RECOVERY=no  EXPERIMENTAL=no  JNI=no
     - GUAVA_URL=https://search.maven.org/remotecontent?filepath=com/google/guava/guava/18.0/guava-18.0.jar GUAVA_JAR=src/java/guava/guava-18.0.jar
   matrix:
     - SCALAR=32bit    RECOVERY=yes
@@ -30,8 +30,9 @@ env:
     - EXTRAFLAGS=CPPFLAGS=-DDETERMINISTIC
     - EXTRAFLAGS=CFLAGS=-O0
     - BUILD=check-java JNI=yes ECDH=yes EXPERIMENTAL=yes
-    - ECMULTGENPRECISION=2
-    - ECMULTGENPRECISION=8
+    - ECMULTGENBLOCKS=256 ECMULTGENTEETH=1
+    - ECMULTGENBLOCKS=43 ECMULTGENTEETH=6
+    - ECMULTGENBLOCKS=1 ECMULTGENTEETH=1
 matrix:
   fast_finish: true
   include:

configure.ac

@@ -165,13 +165,21 @@ AC_ARG_WITH([ecmult-window], [AS_HELP_STRING([--with-ecmult-window=SIZE|auto],
 )],
 [req_ecmult_window=$withval], [req_ecmult_window=auto])
 
-AC_ARG_WITH([ecmult-gen-precision], [AS_HELP_STRING([--with-ecmult-gen-precision=2|4|8|auto],
-[Precision bits to tune the precomputed table size for signing.]
-[The size of the table is 32kB for 2 bits, 64kB for 4 bits, 512kB for 8 bits of precision.]
-[A larger table size usually results in possible faster signing.]
+AC_ARG_WITH([ecmult-gen-blocks], [AS_HELP_STRING([--with-ecmult-gen-blocks=BLOCKS|auto],
+[The number of blocks to use in the multi-comb multiplication algorithm, in the range [1..256].]
+[Larger values result in possibly better performance at the cost of a linearly larger precomputed table.]
+[There must exist a multiple of BLOCKS*TEETH that is between 256 and 288, inclusive.]
 ["auto" is a reasonable setting for desktop machines (currently 4). [default=auto]]
 )],
-[req_ecmult_gen_precision=$withval], [req_ecmult_gen_precision=auto])
+[req_ecmult_gen_blocks=$withval], [req_ecmult_gen_blocks=auto])
+
+AC_ARG_WITH([ecmult-gen-teeth], [AS_HELP_STRING([--with-ecmult-gen-blocks=TEETH|auto],
+[The number of teeth to use in the multi-comb multiplication algorithm, in the range [1..8].]
+[Larger values result in possibly better performance at the cost of an exponentially larger precomputed table.]
+[There must exist a multiple of BLOCKS*TEETH that is between 256 and 288, inclusive.]
+["auto" is a reasonable setting for desktop machines (currently 5). [default=auto]]
+)],
+[req_ecmult_gen_teeth=$withval], [req_ecmult_gen_teeth=auto])
 
 AC_CHECK_TYPES([__int128])
 
@@ -431,19 +439,45 @@ case $set_ecmult_window in
   ;;
 esac
 
-#set ecmult gen precision
-if test x"$req_ecmult_gen_precision" = x"auto"; then
-  set_ecmult_gen_precision=4
+#set ecmult gen blocks
+if test x"$req_ecmult_gen_blocks" = x"auto"; then
+  set_ecmult_gen_blocks=4
 else
-  set_ecmult_gen_precision=$req_ecmult_gen_precision
+  set_ecmult_gen_blocks=$req_ecmult_gen_blocks
 fi
+error_gen_blocks=['option to --with-ecmult-gen-blocks not an integer in range [1..256] or "auto"']
+case $set_ecmult_gen_blocks in
+''|*[[!0-9]]*)
+  # no valid integer
+  AC_MSG_ERROR($error_gen_blocks)
+  ;;
+*)
+  if test "$set_ecmult_gen_blocks" -lt 1 -o "$set_ecmult_gen_blocks" -gt 256 ; then
+    # not in range
+    AC_MSG_ERROR($error_gen_blocks)
+  fi
+  AC_DEFINE_UNQUOTED(COMB_BLOCKS, $set_ecmult_gen_blocks, [Set number of blocks in ecmult_gen precomputation])
+  ;;
+esac
 
-case $set_ecmult_gen_precision in
-2|4|8)
-  AC_DEFINE_UNQUOTED(ECMULT_GEN_PREC_BITS, $set_ecmult_gen_precision, [Set ecmult gen precision bits])
+#set ecmult gen teeth
+if test x"$req_ecmult_gen_teeth" = x"auto"; then
+  set_ecmult_gen_teeth=5
+else
+  set_ecmult_gen_teeth=$req_ecmult_gen_teeth
+fi
+error_gen_teeth=['option to --with-ecmult-gen-teeth not an integer in range [1..8] or "auto"']
+case $set_ecmult_gen_teeth in
+''|*[[!0-9]]*)
+  # no valid integer
+  AC_MSG_ERROR($error_gen_teeth)
   ;;
 *)
-  AC_MSG_ERROR(['ecmult gen precision not 2, 4, 8 or "auto"'])
+  if test "$set_ecmult_gen_teeth" -lt 1 -o "$set_ecmult_gen_teeth" -gt 8 ; then
+    # not in range
+    AC_MSG_ERROR($error_gen_teeth)
+  fi
+  AC_DEFINE_UNQUOTED(COMB_TEETH, $set_ecmult_gen_teeth, [Set number of teeth in ecmult_gen precomputation])
   ;;
 esac
 
@@ -582,7 +616,8 @@ echo "  bignum                  = $set_bignum"
 echo "  field                   = $set_field"
 echo "  scalar                  = $set_scalar"
 echo "  ecmult window size      = $set_ecmult_window"
-echo "  ecmult gen prec. bits   = $set_ecmult_gen_precision"
+echo "  ecmult gen blocks       = $set_ecmult_gen_blocks"
+echo "  ecmult gen teeth        = $set_ecmult_gen_teeth"
 echo
 echo "  CC                      = $CC"
 echo "  CFLAGS                  = $CFLAGS"

src/ecmult_gen.h

@@ -10,11 +10,20 @@
 #include "scalar.h"
 #include "group.h"
 
+#if defined HAVE_CONFIG_H
+#include "libsecp256k1-config.h"
+#endif
+
 #if defined(EXHAUSTIVE_TEST_ORDER)
 
   /* We need to control these values for exhaustive tests because
    * the tables cannot have infinities in them (secp256k1_ge_storage
    * doesn't support infinities) */
+#undef COMB_BLOCKS
+#undef COMB_TEETH
+#undef COMB_SPACING
+#undef COMB_NEGATION
+
 #  if EXHAUSTIVE_TEST_ORDER > 32
 #    define COMB_BLOCKS 52
 #    define COMB_TEETH 5
@@ -42,10 +51,18 @@
    * comb will use negations so that only negative multiples need be precomputed. The resulting memory
    * usage for precomputation will be COMB_POINTS_TOTAL * sizeof(secp256k1_ge_storage).
    */
-  #define COMB_BLOCKS 4
-  #define COMB_TEETH 5
-  #define COMB_SPACING 13
-  #define COMB_NEGATION 1
+#ifndef COMB_BLOCKS
+#define COMB_BLOCKS 4
+#endif
+#ifndef COMB_TEETH
+#define COMB_TEETH 5
+#endif
+#ifndef COMB_SPACING
+#define COMB_SPACING ((COMB_BLOCKS * COMB_TEETH + 255) / (COMB_BLOCKS * COMB_TEETH))
+#endif
+#ifndef COMB_NEGATION
+#define COMB_NEGATION 1
+#endif
 
 #endif