calchash(): work around broken RTTI.
authorAlexei Sheplyakov <varg@metalica.kh.ua>
Mon, 23 Feb 2009 12:08:42 +0000 (14:08 +0200)
committerJens Vollinga <jensv@nikhef.nl>
Wed, 25 Feb 2009 11:44:20 +0000 (12:44 +0100)
Due to the strange (although permitted by the standard) behaviour of C++
RTTI on woe32 calchash() returns different hash values for equal objects.
As a result automatic evaluation gets spectacularly broken:

examining clifford objects.....({1+t,2+x,3+y,4+z}) - ({1+t,2+x,3+y,4+z}) erroneously returned -{1+t,2+x,3+y,4+z}+{1+t,2+x,3+y,4+z} instead of 0
({1+t,2+x,3+y,4+z}) - ({1+t,2+x,3+y,4+z}) erroneously returned -{1+t,2+x,3+y,4+z}+{1+t,2+x,3+y,4+z} instead of 0
.({1+t,2+x,3+y,4+z}) - ({1+t,2+x,3+y,4+z}) erroneously returned -{1+t,2+x,3+y,4+z}+{1+t,2+x,3+y,4+z} instead of 0
({1+t,2+x,3+y,4+z}) - ({1+t,2+x,3+y,4+z}) erroneously returned {1+t,2+x,3+y,4+z}-{1+t,2+x,3+y,4+z} instead of 0
[skipped]
.......FAIL: exam_clifford.exe

This patch works around `features' of woe32 RTTI, so calchash() works
properly.

ginac/Makefile.am
ginac/basic.cpp
ginac/crc32.h [new file with mode: 0644]
ginac/expairseq.cpp
ginac/function.pl
ginac/hash_seed.h [new file with mode: 0644]
ginac/idx.cpp
ginac/relational.cpp
ginac/symbol.cpp
ginac/symmetry.cpp
ginac/wildcard.cpp

index bf091b4..bf20afc 100644 (file)
@@ -9,7 +9,7 @@ libginac_la_SOURCES = add.cpp archive.cpp basic.cpp clifford.cpp color.cpp \
   operators.cpp power.cpp registrar.cpp relational.cpp remember.cpp \
   pseries.cpp print.cpp symbol.cpp symmetry.cpp tensor.cpp \
   utils.cpp wildcard.cpp \
-  remember.h tostring.h utils.h compiler.h \
+  remember.h tostring.h utils.h crc32.h hash_seed.h compiler.h \
   parser/parse_binop_rhs.cpp \
   parser/parser.cpp \
   parser/parse_context.cpp \
index ff1f7a0..f9f18f5 100644 (file)
@@ -33,6 +33,7 @@
 #include "wildcard.h"
 #include "archive.h"
 #include "utils.h"
+#include "hash_seed.h"
 #include "inifcns.h"
 
 #include <iostream>
@@ -780,8 +781,7 @@ return_type_t basic::return_type_tinfo() const
  *  would all end up with the same hashvalue. */
 unsigned basic::calchash() const
 {
-       const void* this_tinfo = (const void*)typeid(*this).name();
-       unsigned v = golden_ratio_hash((p_int)this_tinfo);
+       unsigned v = make_hash_seed(typeid(*this));
        for (size_t i=0; i<nops(); i++) {
                v = rotate_left(v);
                v ^= this->op(i).gethash();
diff --git a/ginac/crc32.h b/ginac/crc32.h
new file mode 100644 (file)
index 0000000..6edd5c6
--- /dev/null
@@ -0,0 +1,74 @@
+#ifndef GINAC_CRC32_H
+#define GINAC_CRC32_H
+/**
+ * CRC32 hash function. Shamelessly stolen from GNU coreutils (cksum.c)
+ */
+namespace GiNaC
+{
+static unsigned const crctab[256] =
+{
+  0x00000000,
+  0x04c11db7, 0x09823b6e, 0x0d4326d9, 0x130476dc, 0x17c56b6b,
+  0x1a864db2, 0x1e475005, 0x2608edb8, 0x22c9f00f, 0x2f8ad6d6,
+  0x2b4bcb61, 0x350c9b64, 0x31cd86d3, 0x3c8ea00a, 0x384fbdbd,
+  0x4c11db70, 0x48d0c6c7, 0x4593e01e, 0x4152fda9, 0x5f15adac,
+  0x5bd4b01b, 0x569796c2, 0x52568b75, 0x6a1936c8, 0x6ed82b7f,
+  0x639b0da6, 0x675a1011, 0x791d4014, 0x7ddc5da3, 0x709f7b7a,
+  0x745e66cd, 0x9823b6e0, 0x9ce2ab57, 0x91a18d8e, 0x95609039,
+  0x8b27c03c, 0x8fe6dd8b, 0x82a5fb52, 0x8664e6e5, 0xbe2b5b58,
+  0xbaea46ef, 0xb7a96036, 0xb3687d81, 0xad2f2d84, 0xa9ee3033,
+  0xa4ad16ea, 0xa06c0b5d, 0xd4326d90, 0xd0f37027, 0xddb056fe,
+  0xd9714b49, 0xc7361b4c, 0xc3f706fb, 0xceb42022, 0xca753d95,
+  0xf23a8028, 0xf6fb9d9f, 0xfbb8bb46, 0xff79a6f1, 0xe13ef6f4,
+  0xe5ffeb43, 0xe8bccd9a, 0xec7dd02d, 0x34867077, 0x30476dc0,
+  0x3d044b19, 0x39c556ae, 0x278206ab, 0x23431b1c, 0x2e003dc5,
+  0x2ac12072, 0x128e9dcf, 0x164f8078, 0x1b0ca6a1, 0x1fcdbb16,
+  0x018aeb13, 0x054bf6a4, 0x0808d07d, 0x0cc9cdca, 0x7897ab07,
+  0x7c56b6b0, 0x71159069, 0x75d48dde, 0x6b93dddb, 0x6f52c06c,
+  0x6211e6b5, 0x66d0fb02, 0x5e9f46bf, 0x5a5e5b08, 0x571d7dd1,
+  0x53dc6066, 0x4d9b3063, 0x495a2dd4, 0x44190b0d, 0x40d816ba,
+  0xaca5c697, 0xa864db20, 0xa527fdf9, 0xa1e6e04e, 0xbfa1b04b,
+  0xbb60adfc, 0xb6238b25, 0xb2e29692, 0x8aad2b2f, 0x8e6c3698,
+  0x832f1041, 0x87ee0df6, 0x99a95df3, 0x9d684044, 0x902b669d,
+  0x94ea7b2a, 0xe0b41de7, 0xe4750050, 0xe9362689, 0xedf73b3e,
+  0xf3b06b3b, 0xf771768c, 0xfa325055, 0xfef34de2, 0xc6bcf05f,
+  0xc27dede8, 0xcf3ecb31, 0xcbffd686, 0xd5b88683, 0xd1799b34,
+  0xdc3abded, 0xd8fba05a, 0x690ce0ee, 0x6dcdfd59, 0x608edb80,
+  0x644fc637, 0x7a089632, 0x7ec98b85, 0x738aad5c, 0x774bb0eb,
+  0x4f040d56, 0x4bc510e1, 0x46863638, 0x42472b8f, 0x5c007b8a,
+  0x58c1663d, 0x558240e4, 0x51435d53, 0x251d3b9e, 0x21dc2629,
+  0x2c9f00f0, 0x285e1d47, 0x36194d42, 0x32d850f5, 0x3f9b762c,
+  0x3b5a6b9b, 0x0315d626, 0x07d4cb91, 0x0a97ed48, 0x0e56f0ff,
+  0x1011a0fa, 0x14d0bd4d, 0x19939b94, 0x1d528623, 0xf12f560e,
+  0xf5ee4bb9, 0xf8ad6d60, 0xfc6c70d7, 0xe22b20d2, 0xe6ea3d65,
+  0xeba91bbc, 0xef68060b, 0xd727bbb6, 0xd3e6a601, 0xdea580d8,
+  0xda649d6f, 0xc423cd6a, 0xc0e2d0dd, 0xcda1f604, 0xc960ebb3,
+  0xbd3e8d7e, 0xb9ff90c9, 0xb4bcb610, 0xb07daba7, 0xae3afba2,
+  0xaafbe615, 0xa7b8c0cc, 0xa379dd7b, 0x9b3660c6, 0x9ff77d71,
+  0x92b45ba8, 0x9675461f, 0x8832161a, 0x8cf30bad, 0x81b02d74,
+  0x857130c3, 0x5d8a9099, 0x594b8d2e, 0x5408abf7, 0x50c9b640,
+  0x4e8ee645, 0x4a4ffbf2, 0x470cdd2b, 0x43cdc09c, 0x7b827d21,
+  0x7f436096, 0x7200464f, 0x76c15bf8, 0x68860bfd, 0x6c47164a,
+  0x61043093, 0x65c52d24, 0x119b4be9, 0x155a565e, 0x18197087,
+  0x1cd86d30, 0x029f3d35, 0x065e2082, 0x0b1d065b, 0x0fdc1bec,
+  0x3793a651, 0x3352bbe6, 0x3e119d3f, 0x3ad08088, 0x2497d08d,
+  0x2056cd3a, 0x2d15ebe3, 0x29d4f654, 0xc5a92679, 0xc1683bce,
+  0xcc2b1d17, 0xc8ea00a0, 0xd6ad50a5, 0xd26c4d12, 0xdf2f6bcb,
+  0xdbee767c, 0xe3a1cbc1, 0xe760d676, 0xea23f0af, 0xeee2ed18,
+  0xf0a5bd1d, 0xf464a0aa, 0xf9278673, 0xfde69bc4, 0x89b8fd09,
+  0x8d79e0be, 0x803ac667, 0x84fbdbd0, 0x9abc8bd5, 0x9e7d9662,
+  0x933eb0bb, 0x97ffad0c, 0xafb010b1, 0xab710d06, 0xa6322bdf,
+  0xa2f33668, 0xbcb4666d, 0xb8757bda, 0xb5365d03, 0xb1f740b4
+};
+
+static unsigned crc32(const char* c, const unsigned len, const unsigned crcinit)
+{
+       unsigned crc = crcinit ^ 0xFFFFFFFFU;
+       for (unsigned i = 0; i < len; ++i)
+               crc = (crc << 8) ^ crctab[((crc >> 24) ^ c[i]) & 0xFF];
+       crc = ~crc & 0xFFFFFFFFU;
+       return crc;
+}
+} // namespace GiNaC
+#endif /* GINAC_CRC32_H */
+
index 7284836..1bf6345 100644 (file)
@@ -30,6 +30,7 @@
 #include "archive.h"
 #include "operators.h"
 #include "utils.h"
+#include "hash_seed.h"
 #include "indexed.h"
 
 #include <algorithm>
@@ -611,8 +612,7 @@ unsigned expairseq::return_type() const
 
 unsigned expairseq::calchash() const
 {
-       const void* this_tinfo = (const void*)typeid(*this).name();
-       unsigned v = golden_ratio_hash((p_int)this_tinfo);
+       unsigned v = make_hash_seed(typeid(*this));
        epvector::const_iterator i = seq.begin();
        const epvector::const_iterator end = seq.end();
        while (i != end) {
index 31f8ba5..e1533be 100644 (file)
@@ -603,6 +603,7 @@ $implementation=<<END_OF_IMPLEMENTATION;
 #include "inifcns.h"
 #include "tostring.h"
 #include "utils.h"
+#include "hash_seed.h"
 #include "remember.h"
 
 #include <iostream>
@@ -1062,8 +1063,7 @@ ex function::eval_ncmul(const exvector & v) const
 
 unsigned function::calchash() const
 {
-       const void* this_tinfo = (const void*)typeid(*this).name();
-       unsigned v = golden_ratio_hash(golden_ratio_hash((p_int)this_tinfo) ^ serial);
+       unsigned v = golden_ratio_hash(make_hash_seed(typeid(*this)) ^ serial);
        for (size_t i=0; i<nops(); i++) {
                v = rotate_left(v);
                v ^= this->op(i).gethash();
diff --git a/ginac/hash_seed.h b/ginac/hash_seed.h
new file mode 100644 (file)
index 0000000..32b057f
--- /dev/null
@@ -0,0 +1,45 @@
+#ifndef GINAC_HASH_SEED_H
+#define GINAC_HASH_SEED_H
+/**
+ * We need a hash function which gives different values for objects of
+ * different types. Hence we need some unique integer for each type.
+ * Fortunately, standard C++ RTTI class `type_info' stores a pointer to
+ * mangled type name. Normally this pointer is the same for all objects
+ * of the same type (although it changes from run to run), so it can be
+ * used for computing hashes. However, on some platforms (such as woe32)
+ * the pointer returned by type_info::name() might be different even for
+ * objects of the same type! Hence we need to resort to comparing string
+ * representation of the (mangled) type names. This is quite expensive,
+ * so we compare crc32 hashes of those strings. We might got more hash
+ * collisions (and slower evaluation as a result), but being a bit slower
+ * is much better than being wrong.
+ */
+#include <typeinfo>
+#include <cstring>
+#include "crc32.h"
+#include "utils.h"
+#ifdef _WIN32
+#define GINAC_HASH_USE_MANGLED_NAME 1
+#endif
+namespace GiNaC
+{
+#ifndef GINAC_HASH_USE_MANGLED_NAME
+static inline unsigned make_hash_seed(const std::type_info& tinfo)
+{
+       // this pointer is the same for all objects of the same type.
+       // Hence we can use that pointer 
+       const void* mangled_name_ptr = (const void*)tinfo.name();
+       unsigned v = golden_ratio_hash((p_int)mangled_name_ptr);
+       return v;
+}
+#else
+static unsigned make_hash_seed(const std::type_info& tinfo)
+{
+       const char* mangled_name = tinfo.name();
+       return crc32(mangled_name, std::strlen(mangled_name), 0);
+}
+#endif
+} // namespace GiNaC
+#endif /* GINAC_HASH_SEED_H */
+
+
index c2565ca..d1a9c49 100644 (file)
@@ -27,6 +27,7 @@
 #include "operators.h"
 #include "archive.h"
 #include "utils.h"
+#include "hash_seed.h"
 
 #include <iostream>
 #include <sstream>
@@ -350,8 +351,7 @@ unsigned idx::calchash() const
        // hash keys. That is, the hash values must not depend on the index
        // dimensions or other attributes (variance etc.).
        // The compare_same_type() methods will take care of the rest.
-       const void* this_tinfo = (const void*)(typeid(*this).name());
-       unsigned v = golden_ratio_hash((p_int)this_tinfo);
+       unsigned v = make_hash_seed(typeid(*this));
        v = rotate_left(v);
        v ^= value.gethash();
 
index fc75e68..eff8e94 100644 (file)
@@ -25,6 +25,7 @@
 #include "numeric.h"
 #include "archive.h"
 #include "utils.h"
+#include "hash_seed.h"
 
 #include <iostream>
 #include <stdexcept>
@@ -259,8 +260,7 @@ return_type_t relational::return_type_tinfo() const
 
 unsigned relational::calchash() const
 {
-       const void* this_tinfo = (const void*)typeid(*this).name();
-       unsigned v = golden_ratio_hash((p_int)this_tinfo);
+       unsigned v = make_hash_seed(typeid(*this));
        unsigned lhash = lh.gethash();
        unsigned rhash = rh.gethash();
 
index cb33de7..a736088 100644 (file)
@@ -25,6 +25,7 @@
 #include "archive.h"
 #include "tostring.h"
 #include "utils.h"
+#include "hash_seed.h"
 #include "inifcns.h"
 
 #include <map>
@@ -253,8 +254,8 @@ bool symbol::is_equal_same_type(const basic & other) const
 
 unsigned symbol::calchash() const
 {
-       const void* this_tinfo = (const void*)typeid(*this).name();
-       hashvalue = golden_ratio_hash((p_int)this_tinfo ^ serial);
+       unsigned seed = make_hash_seed(typeid(*this));
+       hashvalue = golden_ratio_hash(seed ^ serial);
        setflag(status_flags::hash_calculated);
        return hashvalue;
 }
index 1de84e6..9e00a8c 100644 (file)
@@ -26,6 +26,7 @@
 #include "operators.h"
 #include "archive.h"
 #include "utils.h"
+#include "hash_seed.h"
 
 #include <functional>
 #include <iostream>
@@ -185,8 +186,7 @@ int symmetry::compare_same_type(const basic & other) const
 
 unsigned symmetry::calchash() const
 {
-       const void* this_tinfo = (const void*)typeid(*this).name();
-       unsigned v = golden_ratio_hash((p_int)this_tinfo);
+       unsigned v = make_hash_seed(typeid(*this));
 
        if (type == none) {
                v = rotate_left(v);
index 6f96a04..98ff880 100644 (file)
@@ -23,6 +23,7 @@
 #include "wildcard.h"
 #include "archive.h"
 #include "utils.h"
+#include "hash_seed.h"
 
 #include <iostream>
 
@@ -106,8 +107,8 @@ unsigned wildcard::calchash() const
        // this is where the schoolbook method
        // (golden_ratio_hash(typeid(*this).name()) ^ label)
        // is not good enough yet...
-       const void* this_tinfo = (const void*)typeid(*this).name();
-       hashvalue = golden_ratio_hash(golden_ratio_hash((p_int)this_tinfo) ^ label);
+       unsigned seed = make_hash_seed(typeid(*this));
+       hashvalue = golden_ratio_hash(seed ^ label);
        setflag(status_flags::hash_calculated);
        return hashvalue;
 }