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[204.195.112.199]) by smtp.gmail.com with ESMTPSA id a26-20020a62d41a000000b0050dc7628176sm11766091pfh.80.2022.05.25.13.31.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 May 2022 13:31:26 -0700 (PDT) From: Stephen Hemminger To: dev@dpdk.org Cc: Stephen Hemminger , =?UTF-8?q?Mattias=20R=C3=B6nnblom?= , Ray Kinsella Subject: [PATCH v4 1/3] random: add rte_drand() function Date: Wed, 25 May 2022 13:31:21 -0700 Message-Id: <20220525203123.277180-2-stephen@networkplumber.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220525203123.277180-1-stephen@networkplumber.org> References: <20220524184623.480646-1-stephen@networkplumber.org> <20220525203123.277180-1-stephen@networkplumber.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org The PIE code and other applications can benefit from having a fast way to get a random floating point value. This new function is equivalent to drand() in the standard library. Signed-off-by: Stephen Hemminger --- app/test/test_rand_perf.c | 7 +++++ doc/guides/rel_notes/release_22_07.rst | 5 ++++ lib/eal/common/rte_random.c | 41 ++++++++++++++++++++++++++ lib/eal/include/rte_random.h | 18 +++++++++++ lib/eal/meson.build | 3 ++ lib/eal/version.map | 1 + 6 files changed, 75 insertions(+) diff --git a/app/test/test_rand_perf.c b/app/test/test_rand_perf.c index fe797ebfa1ca..26fb1d9a586e 100644 --- a/app/test/test_rand_perf.c +++ b/app/test/test_rand_perf.c @@ -20,6 +20,7 @@ static volatile uint64_t vsum; enum rand_type { rand_type_64, + rand_type_float, rand_type_bounded_best_case, rand_type_bounded_worst_case }; @@ -30,6 +31,8 @@ rand_type_desc(enum rand_type rand_type) switch (rand_type) { case rand_type_64: return "Full 64-bit [rte_rand()]"; + case rand_type_float: + return "Floating point [rte_drand()]"; case rand_type_bounded_best_case: return "Bounded average best-case [rte_rand_max()]"; case rand_type_bounded_worst_case: @@ -55,6 +58,9 @@ test_rand_perf_type(enum rand_type rand_type) case rand_type_64: sum += rte_rand(); break; + case rand_type_float: + sum += 1000. * rte_drand(); + break; case rand_type_bounded_best_case: sum += rte_rand_max(BEST_CASE_BOUND); break; @@ -83,6 +89,7 @@ test_rand_perf(void) printf("Pseudo-random number generation latencies:\n"); test_rand_perf_type(rand_type_64); + test_rand_perf_type(rand_type_float); test_rand_perf_type(rand_type_bounded_best_case); test_rand_perf_type(rand_type_bounded_worst_case); diff --git a/doc/guides/rel_notes/release_22_07.rst b/doc/guides/rel_notes/release_22_07.rst index e49cacecefd4..b131ea577226 100644 --- a/doc/guides/rel_notes/release_22_07.rst +++ b/doc/guides/rel_notes/release_22_07.rst @@ -104,6 +104,11 @@ New Features * ``RTE_EVENT_QUEUE_ATTR_WEIGHT`` * ``RTE_EVENT_QUEUE_ATTR_AFFINITY`` +* ** Added function get random floating point number.** + + Added the function ``rte_drand()`` to provide a pseudo-random + floating point number. + Removed Items ------------- diff --git a/lib/eal/common/rte_random.c b/lib/eal/common/rte_random.c index 4535cc980cec..3dc3484ee655 100644 --- a/lib/eal/common/rte_random.c +++ b/lib/eal/common/rte_random.c @@ -6,6 +6,9 @@ #include #endif #include +#ifdef RTE_LIBEAL_USE_IEEE754 +#include +#endif #include #include @@ -173,6 +176,44 @@ rte_rand_max(uint64_t upper_bound) return res; } +double +rte_drand(void) +{ + struct rte_rand_state *state = __rte_rand_get_state(); + uint64_t rand64 = __rte_rand_lfsr258(state); +#ifdef RTE_LIBEAL_USE_IEEE754 + union ieee754_double u = { + .ieee = { + .negative = 0, + .exponent = IEEE754_DOUBLE_BIAS, + }, + }; + + /* Take 64 bit random value and put it into the mantissa + * This uses direct access to IEEE format to avoid doing + * any direct floating point math here. + */ + u.ieee.mantissa0 = rand64 >> 32; + u.ieee.mantissa1 = rand64; + + return u.d - 1.0; +#else + /* Slower method requiring floating point divide + * + * The double mantissa only has 53 bits, so we uniformly mask off the + * high 11 bits and then floating-point divide by 2^53 to achieve a + * result in [0, 1). + * + * We are not allowed to emit 1.0, so denom must be one greater than + * the possible range of the preceeding step. + */ + static const uint64_t denom = (uint64_t)1 << 53; + + rand64 &= denom - 1; + return (double)rand64 / denom; +#endif +} + static uint64_t __rte_random_initial_seed(void) { diff --git a/lib/eal/include/rte_random.h b/lib/eal/include/rte_random.h index 29f5f1325a30..f6541c2b0f08 100644 --- a/lib/eal/include/rte_random.h +++ b/lib/eal/include/rte_random.h @@ -65,6 +65,24 @@ rte_rand(void); uint64_t rte_rand_max(uint64_t upper_bound); +/** + * @warning + * @b EXPERIMENTAL: this API may change without prior notice + * + * Generates a pseudo-random floating point number. + * + * This function returns a nonnegative double-precision floating random + * number uniformly distributed over the interval [0.0, 1.0). + * + * The generator is not cryptographically secure. + * If called from lcore threads, this function is thread-safe. + * + * @return + * A pseudo-random value between 0 and 1.0. + */ +__rte_experimental +double rte_drand(void); + #ifdef __cplusplus } #endif diff --git a/lib/eal/meson.build b/lib/eal/meson.build index 056beb946119..e50524901c98 100644 --- a/lib/eal/meson.build +++ b/lib/eal/meson.build @@ -32,3 +32,6 @@ endif if cc.has_function('getentropy', prefix : '#include ') cflags += '-DRTE_LIBEAL_USE_GETENTROPY' endif +if cc.has_header_symbol('ieee754.h', 'union ieee754_double') + cflags += '-DRTE_LIBEAL_USE_IEEE754' +endif diff --git a/lib/eal/version.map b/lib/eal/version.map index d49e30bd042f..cfbade9a33e9 100644 --- a/lib/eal/version.map +++ b/lib/eal/version.map @@ -422,6 +422,7 @@ EXPERIMENTAL { rte_intr_type_set; # added in 22.07 + rte_drand; rte_thread_get_affinity_by_id; rte_thread_self; rte_thread_set_affinity_by_id; -- 2.35.1