Filtering directory lookups in CMPs

Coherence protocols consume an important fraction of power to determine which coherence action should take place. In this paper we focus on CMPs with a shared cache and a directory-based coherence protocol implemented as a duplicate of local caches tags. We observe that a big fraction of directory lookups produce a miss since the block looked up is not cached in any local cache. We propose to add a filter before the directory lookup in order to reduce the number of lookups to this structure. The filter identifies whether the current block was last accessed as a data or as an instruction. With this information, looking up the whole directory can be avoided for most accesses. We evaluate the filter in a CMP with 8 in-order processors with 4 threads each and a memory hierarchy with a shared L2 cache.We show that a filter with a size of 3% of the tag array of the shared cache can avoid more than 70% of all comparisons performed by directory lookups with a performance loss of just 0.2% for SPLASH2 and 1.5% for Specweb2005. On average, the number of 15-bit comparisons avoided per cycle is 54 out of 77 for SPLASH2 and 29 out of 41 for Specweb2005. In both cases, the filter requires less than one read of 1 bit per cycle.Postprint (published version

Effects of different feeding frequencies on growth, feed utilisation, digestive enzyme activities and plasma biochemistry of gilthead sea bream (Sparus aurata) fed with different fishmeal and fish oil dietary levels

In the context of Mediterranean aquaculture little attention has been paid to the manipulation of feeding frequency at the on-growing phase. The effects of different feeding frequencies: one meal per day, two meals per day, three meals per day on growth, digestive enzyme activity, feed digestibility and plasma biochemistry were studied in gilthead sea bream (Sparus aurata, L. 1758) fed with high and low fishmeal and fish oil levels. Isonitrogenous and isolipidic extruded diets were fed to triplicate fish groups by a fixed ration over 109 days. No significant effects of feeding frequency on overall performance, feed efficiency and feed digestibility during the on-growing of gilthead sea bream fed high or low fishmeal and fish oil dietary level were observed. Pepsin activity showed an apparent decrease in fish receiving more than one meal a day which was not compensated by an increased production of alkaline proteases particularly in fish fed on low FM. Although there were no effects on growth and feed utilisation at increasing feeding frequency, trypsin decreased significantly with an increasing number of meals only under low FMFO diet. Thus, it seemed that consecutive meals could have amplified the potential trypsin inhibitor effect of the vegetable meal-based diet adopted. Results of the plasma parameters related to nutritional and physiological conditions were not affected by feeding frequency. The higher level of plasma creatinine detected in fish fed a single daily meal with high FMFO level seems to be within physiological values in relation to the higher protein efficiency observed with this diet. According to the results, gilthead sea bream seems able to maximise feed utilisation regardless of the number of meals, and this could be a useful indicator for planning feeding activity at farm level to optimise growth of fish and costs of feeding procedures

Interaction Between Dietary Lipid Level and Seasonal Temperature Changes in Gilthead Sea Bream Sparus aurata: Effects on Growth, Fat Deposition, Plasma Biochemistry, Digestive Enzyme Activity, and Gut Bacterial Community

A 121-day feeding trial was undertaken to test the effects of two dietary lipid levels (16 and 21% L16, L21) in triplicated gilthead sea bream groups (initial weight: 67.5 g) reared at two different water temperatures (high, H 23°C and low, L 17°C) in the same recirculation system but exposed to a switch in temperature after 58 days. Fish kept at H were transferred to L (HL transition, autumn shift), and the fish kept at L were exposed to H (LH transition, summer shift), while continuing to receive the same diet to apparent satiation in each group. At the end of the trial, no significant diet effect on specific growth rate (SGR), feed intake (FI), and feed conversion rate (FCR) were detected in fish exposed to HL transition compared with those exposed to LH transition, while gross lipid efficiency (GLE) and lipid efficiency ratio (LER) were higher in L16. After temperature changes, L16 displayed higher SGR, FI, GLE, and LER, while mesenteric fat index was reduced. After temperature changes, the combined effects of low lipid diet and low temperature conditions resulted in higher pepsin activity, while trypsin, chymotrypsin, and lipase activities were generally higher at high lipid content. The combined effect of diet and temperature did not alter the metabolic plasma profile, except for the observed final higher aspartate aminotransferase (AST) and alkaline phosphatase (ALP) values when combining high dietary lipid (L21) and temperature changes. Different diets showed a significantly different gut microbiome layout, only at high temperature with L16 diet resulting in a higher load of Lactobacillus. On the contrary, no dietary impact on ecosystem diversity was observed, independently from the temperature. In addition, L16 diet in the HL transition favored an increase in Weissella and Bradyrhizobium genera in the gut microbiome, while in the final condition of LH transition, L21 diet favored a significant increase in Streptococcus and Bacillus. According to the results, the utilization of 16% dietary lipid levels in gilthead sea bream should be preferred during seasonal temperature changes in order to optimize feed utilization and gut health

The Atlantic Bonito ( Sarda sarda,Bloch 1793) Transcriptome and Detection of Differential Expression during Larvae Development

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Analogue micropower FET techniques review

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The thyroid gland and thyroid hormones in Senegalese sole (Solea senegalensis) during early development and metamorphosis

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Fish larval nutrition and feed formulation – knowledge gaps and bottlenecks for advances in larval rearing (a larvanet review)

The requirements of most of the nutrients in fish larvae are unknown, due to difficulties in making the graded, stable and easily bio-available diets needed in dose response experiments. Instead, researchers have tried to find indirect methods to measure the nutrient requirements. One method is to analyze the nutrient profile of the main natural diet, copepods, assuming that these organisms cover the requirements. Another is to extrapolate the requirements in fish to the larval stage. Other methods based on nutrient composition and utilization of the yolk and the uptake and metabolism of radiolabelled nutrients have also been applied. An important aspect is the definition of the requirement, e.g. the requirement for pigmentation and immune function may be different from that for optimal growth and survival. Furthermore, requirements may differ between species and with environmental conditions. In the present review, we look at some requirement estimates according to the present knowledge and compare them to the nutrient composition of live feeds. The protein requirement, extrapolated from juveniles in Atlantic cod and Atlantic halibut, appears to be higher than the protein content of their feed organisms, rotifers and Artemia, respectively. There are two experiments which measure quantitatively the requirements for phospholipids (PL) in fish larvae (ex. Cahu et al., 2003) and which indicate requirements of more that 45% of the lipid. This is higher than the PL content of rotifers and Artemia. The enrichment of rotifers with protein and PL is limited by the volume of their digestive tract, since these nutrients cannot be stored in excess in the rotifer tissues. Rotifers, but not always Artemia, can be enriched to contain enough n-3 fatty acids to cover the requirements in cold water species. Rotifers can occasionally drop below fish requirement levels in certain micronutrients, but enrichment can easily be obtained according to linear dose response models for most of these nutrients. There are thus many gaps in the knowledge before we can claim to feed fish larvae according to their nutrient requirements. First of all, the requirements must be determined. In order to do the proper dose response experiments one will need an experimental diet. The technology for both formulated feeds and for enrichment of live feeds is steadily improving, and some of the nutrients can be studied with the presently available tools. However, further improvement of formulated diets for fish larvae is necessary, both from a scientific and producers point of view. Acknowledgement: This work was financed by Cost Action FA0801-Larvane