In-Datacenter Performance Analysis of a Tensor Processing Unit

Many architects believe that major improvements in cost-energy-performance must now come from domain-specific hardware. This paper evaluates a custom ASIC---called a Tensor Processing Unit (TPU)---deployed in datacenters since 2015 that accelerates the inference phase of neural networks (NN). The heart of the TPU is a 65,536 8-bit MAC matrix multiply unit that offers a peak throughput of 92 TeraOps/second (TOPS) and a large (28 MiB) software-managed on-chip memory. The TPU's deterministic execution model is a better match to the 99th-percentile response-time requirement of our NN applications than are the time-varying optimizations of CPUs and GPUs (caches, out-of-order execution, multithreading, multiprocessing, prefetching, ...) that help average throughput more than guaranteed latency. The lack of such features helps explain why, despite having myriad MACs and a big memory, the TPU is relatively small and low power. We compare the TPU to a server-class Intel Haswell CPU and an Nvidia K80 GPU, which are contemporaries deployed in the same datacenters. Our workload, written in the high-level TensorFlow framework, uses production NN applications (MLPs, CNNs, and LSTMs) that represent 95% of our datacenters' NN inference demand. Despite low utilization for some applications, the TPU is on average about 15X - 30X faster than its contemporary GPU or CPU, with TOPS/Watt about 30X - 80X higher. Moreover, using the GPU's GDDR5 memory in the TPU would triple achieved TOPS and raise TOPS/Watt to nearly 70X the GPU and 200X the CPU.Comment: 17 pages, 11 figures, 8 tables. To appear at the 44th International Symposium on Computer Architecture (ISCA), Toronto, Canada, June 24-28, 201

Genomic investigations of unexplained acute hepatitis in children

Since its first identification in Scotland, over 1,000 cases of unexplained paediatric hepatitis in children have been reported worldwide, including 278 cases in the UK1. Here we report an investigation of 38 cases, 66 age-matched immunocompetent controls and 21 immunocompromised comparator participants, using a combination of genomic, transcriptomic, proteomic and immunohistochemical methods. We detected high levels of adeno-associated virus 2 (AAV2) DNA in the liver, blood, plasma or stool from 27 of 28 cases. We found low levels of adenovirus (HAdV) and human herpesvirus 6B (HHV-6B) in 23 of 31 and 16 of 23, respectively, of the cases tested. By contrast, AAV2 was infrequently detected and at low titre in the blood or the liver from control children with HAdV, even when profoundly immunosuppressed. AAV2, HAdV and HHV-6 phylogeny excluded the emergence of novel strains in cases. Histological analyses of explanted livers showed enrichment for T cells and B lineage cells. Proteomic comparison of liver tissue from cases and healthy controls identified increased expression of HLA class 2, immunoglobulin variable regions and complement proteins. HAdV and AAV2 proteins were not detected in the livers. Instead, we identified AAV2 DNA complexes reflecting both HAdV-mediated and HHV-6B-mediated replication. We hypothesize that high levels of abnormal AAV2 replication products aided by HAdV and, in severe cases, HHV-6B may have triggered immune-mediated hepatic disease in genetically and immunologically predisposed children

Bilateral near-infrared spectroscopy for detecting traumatic vascular injury

Extremity wounds account for most battlefield injuries. Clinical examination may be unreliable by medics or first responders, and continuous assessment by experienced practitioners may not be possible on the frontline or during transport. Near-infrared spectroscopy (NIRS) provides continuous, noninvasive monitoring of tissue oxygen saturation (StO2), but its use is limited by inter-patient and intra-patient variability. We tested the hypothesis that bilateral NIRS partially addresses the variability problem and can reliably identify vascular injury after extremity trauma. This prospective study consisted of 30 subjects: 20 trauma patients with extremity injury and 10 healthy volunteers. Bilateral StO2 tissue sensors were placed on the thenar eminence or medial plantar surface. Injured and non-injured extremities within the same patient (ΔStO2) were compared using Wilcoxon signed ranks test. Receiver operating characteristic curves were generated and areas under the curve (AUCs) were calculated for ΔStO2 of 6, 10, and 15. Values are expressed as median (interquartile range). Trauma patients were age 31 y (23 y), 85% male, with injury severity score of 9 (5). There were seven arterial and three venous injuries. Most involved the lower extremity (n = 16; 80%) and resulted from a penetrating mechanism (n = 14; 70%). ΔStO2 between limbs was 20.4 (10.4) versus 2.4 (3.0) (P < 0.001) for all patients with vascular injury versus patients and volunteers with no vascular injury. ΔStO2 reliably identified any vascular injury (AUC, 0.975; P < 0.001), whereas pulse examination alone or in combination with Doppler exam could detect only arterial injury. A ΔStO2 of 6 had the greatest sensitivity and specificity (AUC, 0.900; P < 0.001). Continuous monitoring of bilateral limbs with NIRS detects changes in perfusion resulting from arterial or venous injury and may offer advantages over serial manual measurements of pulses or Doppler signals. This technique may be most relevant in military and disaster scenarios or during transport, in which the ability to monitor limb perfusion is difficult or experienced clinical judgment is unavailable

Impact of definitions on trauma center mortality rates and performance

Trauma center performance depends on quality metrics, such as mortality rates, but there have been few studies on how an exact definition of death can influence these statistics. The purpose of this study was to test the hypothesis that the mortality rate at one trauma center could be influenced by the interpretation of "dead on arrival." Personal communication suggests that this definition is applied variably throughout our state. All deaths at our Level I trauma center from January 2009 to April 2011 were reviewed. There were 11,121 trauma admissions, predominantly male (75%), with mean +/- SD of 39 +/- 20, 72% blunt, 22% penetrating, and 7% burn injuries. There were 661 deaths, of which 582 were "hospital deaths" and an additional 79 were classified as "dead on arrival," defined as patients arriving with no vital signs and receiving no hospital intervention. However, 23% (n = 136) of the hospital deaths also arrived with no vital signs but received some lifesaving intervention, for example, tube thoracostomy (n = 95, 70%), thoracotomy (n = 48, 35%), and/or central venous catheter (n = 21, 15%). The state-reported mortality rate each month was 5.3 +/- 1.4%. If those who arrived with no vital signs were excluded, the mortality rate each month was 4.0 +/- 1.2% (p < 0.001). At this trauma center, approximately one fourth of the deaths reported to the state were patients who arrived with no vital signs. If any lifesaving intervention is attempted in these moribund patients, even if it is futile, it is termed "hospital death," rather than "dead on arrival." State regulations exclude patients who received any intervention from being classified as dead on arrival, but compliance with this definition is not audited. Therefore, unless there is strict compliance and standardized definitions, any comparison of trauma center quality based on mortality could be questioned. Epidemiologic study, level III

Persistence of hypercoagulable state after resection of intra-abdominal malignancies

The hypercoagulable state associated with cancer imparts considerable risk for venous thromboembolism. Surgical resection of malignancies should theoretically reverse tumor-induced hypercoagulability. However, coagulation changes in cancer patients postresection have not been described thoroughly. Conventional coagulation tests are unable to detect hypercoagulable states. In contrast, rotational thromboelastography (ROTEM) can detect hypo- or hypercoagulable conditions. We hypothesized that the cancer-induced hypercoagulable state would improve after surgical resection. After informed consent, blood samples of patients undergoing surgical resection for curative intent were analyzed with serial ROTEM. Thirty-five patients (mean ± SD age 66 ± 17 years; 67% male) had cancers involving the pancreas (n = 12 [34%]), esophagus (n = 10 [29%]), stomach (n = 7 [20%]), bile ducts (n = 3 [9%]), and duodenum (n = 3 [9%]). Preoperative ROTEM identified 14 (40%) who were hypercoagulable. After surgical resection, patients became progressively hypercoagulable with more rapid clot formation time (low clot formation time, high alpha) and higher maximum clot firmness. By week one, 86% (n = 30) had abnormal ROTEM values, including 17 of 21 (81%) who had normal coagulation profiles preoperatively. Most (n = 30 [86%]) remained hypercoagulable at 3 to 4 weeks. Rotational thromboelastography identifies baseline hypercoagulability in more than one third of patients with intra-abdominal malignancies. This is among the first studies to demonstrate progressive hypercoagulability that persists for at least 1 month after resection. These data support postdischarge thromboprophylaxis regimens in high-risk cancer patients

Pre-existing hypercoagulability in patients undergoing potentially curative cancer resection

Rotational thromboelastometry (ROTEM) is a new point-of-care test that allows a rapid and comprehensive evaluation of coagulation. We were among the first to show that ROTEM identifies baseline hypercoagulability in 40% of patients with intra-abdominal malignancies and that hypercoagulability persists for ≥1 month after resection. The purpose of this follow-up study was to confirm and extend these observations to a larger population in outpatient preoperative clinics. The hypothesis is that pre-existing hypercoagulability is present in patients undergoing surgery for malignant disease and that coagulation status varies by tumor type. After informed consent, preoperative blood samples were drawn from patients undergoing exploratory laparotomies for intra-abdominal malignancies and analyzed with ROTEM. Eighty-two patients were enrolled, including 72 with a confirmed pathologic diagnosis and 10 age-matched controls with benign disease. The most common cancers involved the pancreas (n = 23; 32%), esophagus (n = 19; 26%), liver (n = 12; 17%), stomach (n = 7; 10%), and bile ducts (n = 5; 7%). Preoperative hypercoagulability was detected in 31% (n = 22); these patients were more likely to have lymphovascular invasion (88% vs 50%; P = .011), perineural invasion (77% vs 36%; P = .007), and stage III/IV disease (80% vs 62%; P = .039). More patients with pancreatic tumors (9/23, 39%) were hypercoagulable than with esophageal (3/19, 16%) or liver (2/13, 15%, P = .034) tumors. When only resectable malignancies were considered, clot formation was more rapid (low clot formation time, high alpha) with enhanced maximum clot strength (high maximum clot firmness) in pancreatic versus esophageal or liver cancers and in all cancers versus those with benign disease. Preoperative hypercoagulability can be identified with ROTEM and is associated with lymphovascular/perineural invasion and advanced-staged disease in cancer. Compared with other tumor types, pancreatic adenocarcinomas have the greatest risk for hypercoagulability