makedesc.cpp

密码学界牛人Victor Shoup用C++编写数论类库。 NTL is a high-performance, portable C++ library providing data struct

   while (tval) {
      tval <<= 1;
      touch_size_t(&tval);
      bpt++;
   }


   /*
    * check if bpl and bpi are not too small --- any standard conforming
    * platform should pass this test.
    */

   if (bpi < 16) {
      fprintf(stderr, "BAD NEWS: int type too short.\n");
      return 1;
   }

   if (bpl < 32) {
      fprintf(stderr, "BAD NEWS: long type too short.\n");
      return 1;
   }




   /*
    * check that bpl is a multiple of 8.
    */

   if (bpl % 8 != 0) {
      fprintf(stderr, "BAD NEWS: word size must be multiple of 8 bits.\n");
      return 1;
   }




   /*
    * check if width of signed versions of int and long agree with that of
    * the unsigned versions, and that negative numbers are represented
    * using 2's compliment.
    *
    * The C99 standard, at least, is very precise about the possible
    * representations of unsigned and signed integer types, and so if
    * the following tests pass, we can be sure that the desired
    * properties hold.  NTL relies implicitly and crucially on 
    * these properties.
    *
    * I know of no machines for which these properties do not hold.
    */

   if (((unsigned int) val_int(INT_MIN)) != val_uint(1U << (bpi-1))) {
      fprintf(stderr, "BAD NEWS: machine must be 2's compliment.\n");
      return 1;
   }

   if (((unsigned int) val_int(INT_MAX)) != val_uint((1U << (bpi-1)) - 1U)) {
      fprintf(stderr, "BAD NEWS: machine must be 2's compliment.\n");
      return 1;
   }

   if (((unsigned long) val_long(LONG_MIN)) != val_ulong(1UL << (bpl-1))) {
      fprintf(stderr, "BAD NEWS: machine must be 2's compliment.\n");
      return 1;
   }

   if (((unsigned long) val_long(LONG_MAX)) != val_ulong((1UL<<(bpl-1))-1UL)) {
      fprintf(stderr, "BAD NEWS: machine must be 2's compliment.\n");
      return 1;
   }



   /*
    * check that floating point to integer conversions truncates toward zero
    * --- any standard conforming platform should pass this test.
    */

   if (((long) val_double(1.75)) != 1L) {
      fprintf(stderr, 
         "BAD NEWS: machine must truncate floating point toward zero.\n");
      return 1;
   }

   if (((long) val_double(-1.75)) != -1L) {
      fprintf(stderr, 
         "BAD NEWS: machine must truncate floating point toward zero.\n");
      return 1;
   }



   /*
    * Test if right shift is arithemtic or not.  According to the
    * standards, the result of right-shifting a negative number is
    * "implementation defined", which almost surely means the right shift
    * is *always* arithmetic or *always* logical.  However, this cannot
    * be guaranteed, and so this test is *not* 100% portable --- but I
    * know of no machine for which this test does not correctly
    * predict the general behavior.  One should set the NTL_CLEAN_INT
    * flag if one wants to avoid such machine dependencies.
    */

   slval = val_long(-1);
   if ((slval >> 1) == slval)
      rs_arith = 1;
   else
      rs_arith = 0;



   /*
    * Next, we check some properties of floating point arithmetic.
    * An implementation should conform to the IEEE floating
    * point standard --- essentially all modern platforms do,
    * except for a few very old Cray's.  There is no easy way
    * to check this, so we simply make a few simple sanity checks,
    * calculate the precision, and if the platform performs
    * double precision arithemtic in extended double precision registers.
    * The last property is one that the IEE standard allows, and which
    * some important platforms (like x86) have --- this is quite
    * unfortunate, as it really makes many of the other properties
    * of the IEEE standard unusable.
    */

   /*
    * First, we simply check that we are using a machine with radix 2.
    */

   if (FLT_RADIX != 2) {
      fprintf(stderr, "BAD NEWS: machine must use IEEE floating point.\n");
      return 1;
   }

   /*
    * Next, we calculate the precision of "in memory" doubles,
    * and check that it is at least 53.
    */

   dp = DoublePrecision();

   if (dp < 53) {
      fprintf(stderr, "BAD NEWS: machine must use IEEE floating point (*).\n");
      return 1;
   }

   /*
    * Next, we check that the *range* of doubles is sufficiently large.
    * Specifically, we require that DBL_MAX > 2^{7*max(bpl, dp)} 
    * and 1/DBL_MIN > 2^{7*max(bpl, dp)}.  
    * On IEEE floating point compliant machines, this
    * will hold, and the following test will pass, if bpl is at most 128, which
    * should be true for the foreseeable future.
    */

   if (log(DBL_MAX)/log(2.0) < 7.01*bpl ||  log(DBL_MAX)/log(2.0) < 7.01*dp ||
      -log(DBL_MIN)/log(2.0) < 7.01*bpl || -log(DBL_MIN)/log(2.0) < 7.01*dp) {
      fprintf(stderr, "BAD NEWS: range of doubles too small.\n");
      return 1;
   }

   

   /*
    * Next, we check if the machine has wider "in-register" doubles or not.
    * This test almost always yields the correct result --- if not,
    * you will have to set the NTL_EXT_DOUBLE in "mach_desc.h"
    * by hand.
    * 
    * The test effectively proves that in-register doubles are wide
    * if dp1 > dp || dr.
    */


   dp1 = DoublePrecision1();
   dr = DoubleRounding(dp);


   /*
    * Set nbits --- the default radix size for NTL's "built in"
    * long integer arithmetic.
    *
    *  Given the minimum size of blp and dp, the smallest possible
    *  value of nbits is 30.
    */


   if (bpl-2 < dp-3)
      nbits = bpl-2;
   else
      nbits = dp-3;

   if (nbits % 2 != 0) nbits--;


   /* 
    * We next test if the NTL_SINGLE_MUL option is valid.  This test is
    * inherently DIRTY (i.e., the behavior of the test itself is not well
    * defined according to the standard), but in practice should not cause any
    * bad behavior, especially if the NTL_SINGLE_MUL option is never used.
    * This option is anyway considered fairly obsolete, and if desired, one may
    * change the following "if 1" to "if 0" and avoid performing this test
    * altogether.
    */

#if 1
   single_mul_ok = RepTest();
#else
   single_mul_ok = 0;
#endif


   /*
    * That's it!  All tests have passed.
    */

   fprintf(stderr, "GOOD NEWS: compatible machine.\n");
   fprintf(stderr, "summary of machine characteristics:\n");
   fprintf(stderr, "bits per long = %ld\n", bpl);
   fprintf(stderr, "bits per int = %ld\n", bpi);
   fprintf(stderr, "bits per size_t = %ld\n", bpt);
   fprintf(stderr, "arith right shift = %s\n", yn_vec[rs_arith]);
   fprintf(stderr, "double precision = %ld\n", dp);
   fprintf(stderr, "NBITS (maximum) = %ld\n", nbits);
   fprintf(stderr, "single mul ok = %s\n", yn_vec[single_mul_ok != 0]);
   fprintf(stderr, "register double precision = %ld\n", dp1);
   fprintf(stderr, "double rounding detected = %s\n", yn_vec[dr]);  

   if (((dp1 > dp) || dr) && AutoFix)
      fprintf(stderr, "-- auto x86 fix\n");

   if (dp != 53) {
      warnings = 1;

      fprintf(stderr, "\n\nWARNING:\n\n"); 
      fprintf(stderr, "Nonstandard floating point precision.\n");
      fprintf(stderr, "IEEE standard is 53 bits.\n"); 
   }

#if (defined(__sparc__) && !defined(__sparc_v8__))

   warnings = 1;

   fprintf(stderr, "\n\nWARNING:\n\n");
   fprintf(stderr, "If this Sparc is a Sparc-10 or later (so it has\n");
   fprintf(stderr, "a hardware integer multiply instruction) you\n");
   fprintf(stderr, "should specify the -mv8 option in the makefile\n"); 
   fprintf(stderr, "to obtain more efficient code.\n");

#endif

   if (((dp1 > dp) || dr) && !AutoFix) {
      warnings = 1;
      fprintf(stderr, "\n\nWARNING:\n\n");
      fprintf(stderr, "This platform has extended double precision registers.\n");
      fprintf(stderr, "While that may sound like a good thing, it actually is not.\n");
      fprintf(stderr, "If this is a Pentium or other x86 and your compiler\n");
      fprintf(stderr, "is g++ or supports GNU 'asm' constructs, it is recommended\n");
      fprintf(stderr, "to compile NTL with the NTL_X86_FIX flag to get true IEEE floating point.\n");
      fprintf(stderr, "Set this flag by editing the file config.h.\n");
      fprintf(stderr, "The code should still work even if you don't set\n");
      fprintf(stderr, "this flag.  See quad_float.txt for details.\n\n");
   }


#if 0

   /* better not to be interactive */

   if (warnings) {
      int c;

      fprintf(stderr, "Do you want to continue anyway[y/n]? ");
      c = getchar();
      if (c == 'n' || c == 'N') {
         fprintf(stderr, "Make the necessary changes to the makefile and/or config.h,\n");
         fprintf(stderr, "then type 'make clobber' and then 'make'.\n\n\n");
         return 1;
      }
   }

#endif

   f = fopen("mach_desc.h", "w");
   if (!f) {
      fprintf(stderr, "can't open mach_desc.h for writing\n");
      return 1;
   }

   fprintf(f, "#ifndef NTL_mach_desc__H\n");
   fprintf(f, "#define NTL_mach_desc__H\n\n\n");
   fprintf(f, "#define NTL_BITS_PER_LONG (%ld)\n", bpl);
   fprintf(f, "#define NTL_MAX_LONG (%ldL)\n", ((long) ((1UL<<(bpl-1))-1UL)));
   fprintf(f, "#define NTL_MAX_INT (%ld)\n", ((long) ((1UL<<(bpi-1))-1UL)));
   fprintf(f, "#define NTL_BITS_PER_INT (%ld)\n", bpi);
   fprintf(f, "#define NTL_BITS_PER_SIZE_T (%ld)\n", bpt);
   fprintf(f, "#define NTL_ARITH_RIGHT_SHIFT (%ld)\n", rs_arith);
   fprintf(f, "#define NTL_NBITS_MAX (%ld)\n", nbits);
   fprintf(f, "#define NTL_DOUBLE_PRECISION (%ld)\n", dp);
   fprintf(f, "#define NTL_FDOUBLE_PRECISION ");
   print2k(f, dp-1, bpl);
   fprintf(f, "\n");
   fprintf(f, "#define NTL_QUAD_FLOAT_SPLIT (");
   print2k(f, dp - (dp/2), bpl);
   fprintf(f, "+1.0)\n");
   fprintf(f, "#define NTL_EXT_DOUBLE (%d)\n", ((dp1 > dp) || dr));
   fprintf(f, "#define NTL_SINGLE_MUL_OK (%d)\n", single_mul_ok != 0);
   fprintf(f, "#define NTL_DOUBLES_LOW_HIGH (%d)\n\n\n", single_mul_ok < 0);
   print_BB_mul_code(f, bpl);
   print_BB_half_mul_code(f, bpl);
   print_BB_sqr_code(f, bpl);
   print_BB_rev_code(f, bpl);

   fprintf(f, "#define NTL_MIN_LONG (-NTL_MAX_LONG - 1L)\n");
   fprintf(f, "#define NTL_MIN_INT  (-NTL_MAX_INT - 1)\n");

   fprintf(f, "#endif\n\n");

   fclose(f);

   fprintf(stderr, "\n\n");
   
   return 0;
}