X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=ryg_rans%2Fmain.cpp;fp=ryg_rans%2Fmain.cpp;h=a9b9a6eaceca81c6866446b0f8422bd079793f02;hb=2225f774d8f17f45e93a37f627c5ed450401d06d;hp=0000000000000000000000000000000000000000;hpb=76fd9c6939007519b84264b0721e031551ba464e;p=narabu

diff --git a/ryg_rans/main.cpp b/ryg_rans/main.cpp
new file mode 100644
index 0000000..a9b9a6e
--- /dev/null
+++ b/ryg_rans/main.cpp
@@ -0,0 +1,297 @@
+#include "platform.h"
+#include <stdio.h>
+#include <stdarg.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <assert.h>
+
+#include "rans_byte.h"
+
+// This is just the sample program. All the meat is in rans_byte.h.
+
+static void panic(const char *fmt, ...)
+{
+    va_list arg;
+
+    va_start(arg, fmt);
+    fputs("Error: ", stderr);
+    vfprintf(stderr, fmt, arg);
+    va_end(arg);
+    fputs("\n", stderr);
+
+    exit(1);
+}
+
+static uint8_t* read_file(char const* filename, size_t* out_size)
+{
+    FILE* f = fopen(filename, "rb");
+    if (!f)
+        panic("file not found: %s\n", filename);
+
+    fseek(f, 0, SEEK_END);
+    size_t size = ftell(f);
+    fseek(f, 0, SEEK_SET);
+
+    uint8_t* buf = new uint8_t[size];
+    if (fread(buf, size, 1, f) != 1)
+        panic("read failed\n");
+
+    fclose(f);
+    if (out_size)
+        *out_size = size;
+
+    return buf;
+}
+
+// ---- Stats
+
+struct SymbolStats
+{
+    uint32_t freqs[256];
+    uint32_t cum_freqs[257];
+
+    void count_freqs(uint8_t const* in, size_t nbytes);
+    void calc_cum_freqs();
+    void normalize_freqs(uint32_t target_total);
+};
+
+void SymbolStats::count_freqs(uint8_t const* in, size_t nbytes)
+{
+    for (int i=0; i < 256; i++)
+        freqs[i] = 0;
+
+    for (size_t i=0; i < nbytes; i++)
+        freqs[in[i]]++;
+}
+
+void SymbolStats::calc_cum_freqs()
+{
+    cum_freqs[0] = 0;
+    for (int i=0; i < 256; i++)
+        cum_freqs[i+1] = cum_freqs[i] + freqs[i];
+}
+
+void SymbolStats::normalize_freqs(uint32_t target_total)
+{
+    assert(target_total >= 256);
+    
+    calc_cum_freqs();
+    uint32_t cur_total = cum_freqs[256];
+    
+    // resample distribution based on cumulative freqs
+    for (int i = 1; i <= 256; i++)
+        cum_freqs[i] = ((uint64_t)target_total * cum_freqs[i])/cur_total;
+
+    // if we nuked any non-0 frequency symbol to 0, we need to steal
+    // the range to make the frequency nonzero from elsewhere.
+    //
+    // this is not at all optimal, i'm just doing the first thing that comes to mind.
+    for (int i=0; i < 256; i++) {
+        if (freqs[i] && cum_freqs[i+1] == cum_freqs[i]) {
+            // symbol i was set to zero freq
+
+            // find best symbol to steal frequency from (try to steal from low-freq ones)
+            uint32_t best_freq = ~0u;
+            int best_steal = -1;
+            for (int j=0; j < 256; j++) {
+                uint32_t freq = cum_freqs[j+1] - cum_freqs[j];
+                if (freq > 1 && freq < best_freq) {
+                    best_freq = freq;
+                    best_steal = j;
+                }
+            }
+            assert(best_steal != -1);
+
+            // and steal from it!
+            if (best_steal < i) {
+                for (int j = best_steal + 1; j <= i; j++)
+                    cum_freqs[j]--;
+            } else {
+                assert(best_steal > i);
+                for (int j = i + 1; j <= best_steal; j++)
+                    cum_freqs[j]++;
+            }
+        }
+    }
+
+    // calculate updated freqs and make sure we didn't screw anything up
+    assert(cum_freqs[0] == 0 && cum_freqs[256] == target_total);
+    for (int i=0; i < 256; i++) {
+        if (freqs[i] == 0)
+            assert(cum_freqs[i+1] == cum_freqs[i]);
+        else
+            assert(cum_freqs[i+1] > cum_freqs[i]);
+
+        // calc updated freq
+        freqs[i] = cum_freqs[i+1] - cum_freqs[i];
+    }
+}
+
+int main()
+{
+    size_t in_size;
+    uint8_t* in_bytes = read_file("book1", &in_size);
+
+    static const uint32_t prob_bits = 14;
+    static const uint32_t prob_scale = 1 << prob_bits;
+
+    SymbolStats stats;
+    stats.count_freqs(in_bytes, in_size);
+    stats.normalize_freqs(prob_scale);
+
+    // cumlative->symbol table
+    // this is super brute force
+    uint8_t cum2sym[prob_scale];
+    for (int s=0; s < 256; s++)
+        for (uint32_t i=stats.cum_freqs[s]; i < stats.cum_freqs[s+1]; i++)
+            cum2sym[i] = s;
+
+    static size_t out_max_size = 32<<20; // 32MB
+    uint8_t* out_buf = new uint8_t[out_max_size];
+    uint8_t* dec_bytes = new uint8_t[in_size];
+
+    // try rANS encode
+    uint8_t *rans_begin;
+    RansEncSymbol esyms[256];
+    RansDecSymbol dsyms[256];
+
+    for (int i=0; i < 256; i++) {
+        RansEncSymbolInit(&esyms[i], stats.cum_freqs[i], stats.freqs[i], prob_bits);
+        RansDecSymbolInit(&dsyms[i], stats.cum_freqs[i], stats.freqs[i]);
+    }
+
+    // ---- regular rANS encode/decode. Typical usage.
+
+    memset(dec_bytes, 0xcc, in_size);
+
+    printf("rANS encode:\n");
+    for (int run=0; run < 5; run++) {
+        double start_time = timer();
+        uint64_t enc_start_time = __rdtsc();
+
+        RansState rans;
+        RansEncInit(&rans);
+
+        uint8_t* ptr = out_buf + out_max_size; // *end* of output buffer
+        for (size_t i=in_size; i > 0; i--) { // NB: working in reverse!
+            int s = in_bytes[i-1];
+            RansEncPutSymbol(&rans, &ptr, &esyms[s]);
+        }
+        RansEncFlush(&rans, &ptr);
+        rans_begin = ptr;
+
+        uint64_t enc_clocks = __rdtsc() - enc_start_time;
+        double enc_time = timer() - start_time;
+        printf("%"PRIu64" clocks, %.1f clocks/symbol (%5.1fMiB/s)\n", enc_clocks, 1.0 * enc_clocks / in_size, 1.0 * in_size / (enc_time * 1048576.0));
+    }
+    printf("rANS: %d bytes\n", (int) (out_buf + out_max_size - rans_begin));
+
+    // try rANS decode
+    for (int run=0; run < 5; run++) {
+        double start_time = timer();
+        uint64_t dec_start_time = __rdtsc();
+
+        RansState rans;
+        uint8_t* ptr = rans_begin;
+        RansDecInit(&rans, &ptr);
+
+        for (size_t i=0; i < in_size; i++) {
+            uint32_t s = cum2sym[RansDecGet(&rans, prob_bits)];
+            dec_bytes[i] = (uint8_t) s;
+            RansDecAdvanceSymbol(&rans, &ptr, &dsyms[s], prob_bits);
+        }
+
+        uint64_t dec_clocks = __rdtsc() - dec_start_time;
+        double dec_time = timer() - start_time;
+        printf("%"PRIu64" clocks, %.1f clocks/symbol (%5.1fMiB/s)\n", dec_clocks, 1.0 * dec_clocks / in_size, 1.0 * in_size / (dec_time * 1048576.0));
+    }
+
+    // check decode results
+    if (memcmp(in_bytes, dec_bytes, in_size) == 0)
+        printf("decode ok!\n");
+    else
+        printf("ERROR: bad decoder!\n");
+
+    // ---- interleaved rANS encode/decode. This is the kind of thing you might do to optimize critical paths.
+
+    memset(dec_bytes, 0xcc, in_size);
+
+    // try interleaved rANS encode
+    printf("\ninterleaved rANS encode:\n");
+    for (int run=0; run < 5; run++) {
+        double start_time = timer();
+        uint64_t enc_start_time = __rdtsc();
+
+        RansState rans0, rans1;
+        RansEncInit(&rans0);
+        RansEncInit(&rans1);
+
+        uint8_t* ptr = out_buf + out_max_size; // *end* of output buffer
+
+        // odd number of bytes?
+        if (in_size & 1) {
+            int s = in_bytes[in_size - 1];
+            RansEncPutSymbol(&rans0, &ptr, &esyms[s]);
+        }
+
+        for (size_t i=(in_size & ~1); i > 0; i -= 2) { // NB: working in reverse!
+            int s1 = in_bytes[i-1];
+            int s0 = in_bytes[i-2];
+            RansEncPutSymbol(&rans1, &ptr, &esyms[s1]);
+            RansEncPutSymbol(&rans0, &ptr, &esyms[s0]);
+        }
+        RansEncFlush(&rans1, &ptr);
+        RansEncFlush(&rans0, &ptr);
+        rans_begin = ptr;
+
+        uint64_t enc_clocks = __rdtsc() - enc_start_time;
+        double enc_time = timer() - start_time;
+        printf("%"PRIu64" clocks, %.1f clocks/symbol (%5.1fMiB/s)\n", enc_clocks, 1.0 * enc_clocks / in_size, 1.0 * in_size / (enc_time * 1048576.0));
+    }
+    printf("interleaved rANS: %d bytes\n", (int) (out_buf + out_max_size - rans_begin));
+
+    // try interleaved rANS decode
+    for (int run=0; run < 5; run++) {
+        double start_time = timer();
+        uint64_t dec_start_time = __rdtsc();
+
+        RansState rans0, rans1;
+        uint8_t* ptr = rans_begin;
+        RansDecInit(&rans0, &ptr);
+        RansDecInit(&rans1, &ptr);
+
+        for (size_t i=0; i < (in_size & ~1); i += 2) {
+            uint32_t s0 = cum2sym[RansDecGet(&rans0, prob_bits)];
+            uint32_t s1 = cum2sym[RansDecGet(&rans1, prob_bits)];
+            dec_bytes[i+0] = (uint8_t) s0;
+            dec_bytes[i+1] = (uint8_t) s1;
+            RansDecAdvanceSymbolStep(&rans0, &dsyms[s0], prob_bits);
+            RansDecAdvanceSymbolStep(&rans1, &dsyms[s1], prob_bits);
+            RansDecRenorm(&rans0, &ptr);
+            RansDecRenorm(&rans1, &ptr);
+        }
+
+        // last byte, if number of bytes was odd
+        if (in_size & 1) {
+            uint32_t s0 = cum2sym[RansDecGet(&rans0, prob_bits)];
+            dec_bytes[in_size - 1] = (uint8_t) s0;
+            RansDecAdvanceSymbol(&rans0, &ptr, &dsyms[s0], prob_bits);
+        }
+
+        uint64_t dec_clocks = __rdtsc() - dec_start_time;
+        double dec_time = timer() - start_time;
+        printf("%"PRIu64" clocks, %.1f clocks/symbol (%5.1fMB/s)\n", dec_clocks, 1.0 * dec_clocks / in_size, 1.0 * in_size / (dec_time * 1048576.0));
+    }
+
+    // check decode results
+    if (memcmp(in_bytes, dec_bytes, in_size) == 0)
+        printf("decode ok!\n");
+    else
+        printf("ERROR: bad decoder!\n");
+
+    delete[] out_buf;
+    delete[] dec_bytes;
+    delete[] in_bytes;
+    return 0;
+}